WO1996038039A1

WO1996038039A1 - Controlled release of pesticides with activated carbon

Info

Publication number: WO1996038039A1
Application number: PCT/US1996/007693
Authority: WO
Inventors: Robert D. Sjogren; David R. Sjogren
Original assignee: Meridian, L.L.C.
Priority date: 1995-06-02
Filing date: 1996-05-30
Publication date: 1996-12-05
Also published as: AU5932396A

Abstract

An effective slow release pest control composition can use activated carbon as a primary release agent. Liquid pesticide is adsorbed into the interior mesopore and macropore space of the activated carbon. Upon contact with water, the pesticide is displaced from the carbon into the environment for appropriate control. The particulate can be used as is or can be combined with liquid or solid diluents. The particle can be formed into larger composites comprising a granule, a pellet, and an agglomerated particle, etc. A variety of pesticides can be used including insecticides, herbicides, fungicides, etc.

Description

CONTROLLED RELEASE OF PESTICIDES WITH ACTIVATED CARBON

FIELD OF INVENTION

The invention relates to a controlled release pesticide composition and means to achieve pest control which can be distributed throughout the environment to provide effective pest control and environmental management. The pest control means, when in contact with water, releases said pesticide materials at desired low level concentrations for prolonged time periods thus achieving economical and effective active ingredient concentrations required for pest control .

BACKGROUND OF INVENTION Controlled release technology is a multi-billion dollar industry involving many applications. Scientific advances in controlled release technology focused on agriculture in the 1970' s, and more recently to medicine and non-biological areas. Market forces are in place for a renaissance of controlled release in agriculture with appropriate breakthroughs in providing superior, more predictable, cost effective control over release ( ilkins, R. M. (Ed.) , (1990) , Controlled Delivery of Crop Protection Agents, 322 pp. New York: Taylor & Francis) .

About 720 million pounds of pesticides are applied yearly in the United States alone. This level of pesticide usage continues to be extremely vigorous since annual crop losses due to pests are still staggering (c.

$35 billion, 1994 estimate) . The usual practice in agriculture is to initially apply an excess concentration

(when compared to package directions) of active ingredient to be assured of having a lethal dose over a desired time period (Wilkins, 1990) . This excess can compensate for losses due to decomposition, volatilization and leaching.

The controlled release of pesticide agents offer significant advantages for the control of pests of economic importance with low environmental impact . Agricultural chemicals utilizing controlled release include the following: algaecides, fertilizers, fumigants, fungicides, growth regulators, herbicides, insecticides, nematicides, nutrients, pheromones and repellents. Advantages include: reduced active ingredient (A.I.) spike concentrations in the environment, insure stable controlled concentrations at the use locus, increased stability of the active ingredient in the presence of adjuvants or complimentary pesticides, improved handling safety, reduced contamination of the food supply, prolonged residual activity, improved safety to crops, potentially lower application rates, reduced loss of active ingredient due to environmental factors- volatilization, leaching, chemical or biological decomposition in soil, photolysis, reduced environmental contamination, e.g. ground water, reduced odor, and reduced labor and equipment requirements made possible by fewer applications each year (Wilkins, 1990) . In the 1970's and early 1980' s there was much publicity about controlled release being a panacea for problems with agrochemicals due to the benefits cited above. Commercial realization of these advantages has been, at best, narrowly successful and very limited. Many of the promises have been unfulfilled largely due to unrealistic and costly product design. Key advances in controlled release technology have more recently occurred in medical applications due to the capacity of the cost structure to support higher priced technology. Many attempts have been made to combat pest control problems using a variety of controlled release methods. Pesticides have been encapsulated in both macro and micro-encapsulation processes, in ceramic materials, biodegradable polymers, porous mineral supports, cellulosic derivatives, polyurea compounds, gypsum and other supports in order to protect the pesticide from the environment and to ensure a controlled release, attempting substantial control of pest populations. For the purposes of this specification an effective pest control concentration is defined as a concentration effective to kill a substantial fraction of at least one form or stage of the pest during its life cycle, or a concentration effective to prevent development or maturation of a form or stage of the pest during its life cycle. The pesticide should be released by the pest control means at an even rate such that significant amounts are not wasted. Further, the pesticide composition and means should comprise natural materials, be biodegradable, and be of low cost. Accordingly, a substantial need exists for a versatile controlled release means which can be employed in the variety of common environmental pesticide formulation means to inexpensively deliver effective controlling concentrations of pest and environmental management chemicals for short, intermediate or long time intervals, in the field. The technology described herein addresses the need for low cost controlled release technology affordable by agriculture.

BRIEF DISCUSSION OF THE INVENTION

We have found a composition comprising activated carbon and an adsorbed pesticide, or other chemical of economic value, to be an effective slow release agent for pesticides when uniformly distributed in the environment. The slow release carbon-based pesticide is free of other slow release matrices such as a plaster matrix or a protein matrix. The particulate carbon adsorbs the pesticide into the carbon structure to form a pesticide loaded carbon. The distribution of the loaded activated carbon or charcoal causes a smooth release of the pesticide into the environment. Activated carbon is of particular economic value due to its high surface area permitting high effective loadings of pesticide. The small particle size makes possible uniform particle distribution over large areas of the environment. The high carbon particle surface area to water exchange ratio results in effective pesticide active ingredient release rates of economic value. I have found the combination of activated carbon powder and each active ingredient type to have unique controlled release properties which are representative of each respective combination of active ingredient and activated carbon type. The controlled release pesticide can be used without a separate slow release matrix. For the purposes of the invention a slow release matrix comprises an organic or inorganic solid that can include a pesticide and can slowly release the pesticide into the environment . Such matrices release the pesticide through a controlled dissolution of the matrix or a controlled release of the pesticide from the matrix.

The novel controlled release combination requires only appropriate active ingredient (A.I.) impregnation procedures and uniform distribution of the active ingredient impregnated powder in the environment to achieve the controlled release and benefit of respective pesticidal materials in the field. Such pesticidal active ingredient is adsorbed into activated carbon by slowly spraying a low viscosity liquid form of the active ingredient onto a moving bed of activated carbon, in a sealed powder blender such as a ribbon blender, to distribute the active ingredient for purposes of uniformly adsorbing or absorbing the liquid into the carbon powder. Non-polar liquid active ingredient's are physically and chemically held on reactive sites on the activated carbon whose non-polar nature creates a strong affinity for such organic active ingredient's. At such time as the impregnated carbon particles are evenly distributed into the environment, both equilibrium conditions and contact with water, creating a weak solvent action resulting in a solvent force which competes with the activated carbon surface, resulting in a slow release or liberation of the active ingredient dissolved or dispersed into a water phase. The rate of release of non-polar organic active ingredient's from the surface and internal structure of the activated carbon powder particles is in proportion to the chemical nature of the active ingredient including its water solubility, activated carbon powder substrate selected, carbon powder loading level, and co-solvent nature where important, to name a few of the influencing factors .

This invention is in contrast to industrial uses of activated carbon wherein it is used to purify a compound during chemical manufacturing by adsorption from a processing solution followed by desorption of the compound from the activated carbon using a more adsorbable substance which drives out the desired material such as, steaming, change of pH, extraction using a solvent or mixtures of solvents, electrodialysis or chemical reaction. The herein described invention impregnates the activated carbon, to its carrying capacity, with a concentrated pesticidal active ingredient, followed by incorporation of said combination during formulation into a commercial product form suitable for application in the field. When such products are applied in the field and contact surface or interstitial water, the water serves as a weak solvent slowly liberating the active ingredient from the activated carbon bonding over time. The controlled release of pesticide agents offers significant advantages for the control of pests of economic importance with reduced environmental impact . These advantages include reduced active ingredient (A.I.) spike concentrations in the environment common with conventional pesticide formulations, which may adversely affect adjacent non-target organisms; reduced active ingredient dosage rates needed to accomplish pest control for the desired time interval; long term maintenance of threshold chemical concentrations needed to control to achieve the desired target effect; increased safety of toxic pesticide formulations improving occupational safety; and in some cases fewer annual applications resulting in lower material, labor and equipment costs. The chemical composition claimed in this invention is the use of activated carbon powder into which is adsorbed an active ingredient . The preparation of slow release formulations involves an active ingredient which is adsorbed into the activated carbon pores directly when an active ingredient is a low viscosity liquid. When the active ingredient is crystalline with a high melting temperature, or when the active ingredient is a viscous liquid which does not change to a low viscosity liquid upon heating to a reasonable working temperature (i.e. a temperature below that which degrades the pesticide and which is safe to use) , it is necessary to use a solvent to lower the viscosity of the active ingredient to achieve good adsorption into the activated carbon pores.

The above combinations of activated carbon impregnated with active ingredient can be formulated for use: (i) alone in the physical form of a carbon powder, (ii) carbon powder with a diluent powder, (iii) carbon powders suspended in aqueous solutions optionally using thickeners such as aqueous flowables, (iv) carbon powders suspended in non-aqueous liquids, (v) powders made into water dispersible granules, (vi) prilled powders, (vii) activated carbon granules (crushed activated charcoal particles) , shapes, extruded or compressed activated carbon pellets, briquettes or blocks optionally in combination with other active ingredient's, solvents and adjuvants, as well as other formulation methods of value. Further, this invention recognizes that carbon is an efficient sun screen and further that activated carbon loaded with an active ingredient is an effective and useful means of protecting active ingredients from the damaging effects of ultra violet light when such combinations are exposed in the environment before and during periods of active ingredient release from the carbon. Ultra violet light is widely known to be a significant cause of degradation of pesticides and other useful chemicals in the environment. Such degradation is one reason higher dosage rates of pesticides are conventionally required to overcome A. I. breakdown during the desired period of pest control. Spike release of active ingredients are common in commercial products, in the absence of effective means of control release, to deliver enough active ingredient to sustain the necessary chemical concentration to last the period of time for which control is needed. Such spike releases can be environmentally damaging through runoff and non-target contact, and costly in terms of quantity of material used. The slow release of the same chemical in only the amount needed to achieve the control of the target organism is recognized as a means to deliver the optimum controlling concentration of an active ingredient at least cost .

Further, activated carbon is recognized to serve a valuable function to increase the safety of handling toxic active ingredients, due to the deep impregnation of active ingredient into the interior pore spaces of the carbon, thus reducing the occupational hazard of toxic pesticides. The adsorption of active ingredient's onto the large interior surface area of active carbon serves to reversibly bond materials, significantly reducing their availability when impregnated carbons are handled manually.

DETAILED DISCUSSION OF THE INVENTION In accordance with the present invention, there is provided a controlled release pesticide composition consisting essentially of a powdered or particulate activated carbon and an adsorbed pesticide phase. The pesticide is adsorbed into activated carbon during product formulation. The relationships between each respective activated carbon, with it's respective surface area and activation level, pore size, particle size, pH, carbon source, and active ingredient with it's respective water solubility, molecular weight, viscosity and possible co- solvent must be considered. The invention includes the use of the pesticide composition as a powder, a powder comprising the pesticide and a solid diluent, a dispersion of the pesticide composition in a liquid medium, a pellet or other larger units. Carbon Activated carbon, is a micro crystalline, nongraphitic form of carbon, which has been processed to develop an extraordinary large internal surface area and pore volume. These unique characteristics combined with its surface area and functional groups which render its surface chemically reactive, are responsible for activated carbon's adsorptive properties. These properties are exploited in many different commercial liquid and gas- phase applications. Activated carbon is an exceptionally versatile adsorbent because the size and distribution of the pores can be controlled to meet the needs of current and emerging markets. Engineering requirements of specific applications are satisfied by producing activated carbons in the form of powders, granules, and shaped or extruded products. Through choice of precursor, method of application, and control of processing conditions, the adsorptive properties of products are tailored for applications as diverse as the purification of potable water to the control of gasoline emissions from motor vehicles (Kirk-Othmer Encyclopedia of Chemical Technology, 4th Edition 1992) . The basic mechanism through which activated carbon holds pesticides, and other chemicals of economic value, by surface attraction is referred to as physical adsorption. Physical adsorption is a phenomenon resulting from electrostatic forces of attraction (Van der Waals' Forces) between the chemical active ingredients and the internal surfaces of the activated carbon. This adsorption is a fundamental property of matter having its origin in the attractive forces between molecules. Adsorption generally is a combination of physical adsorption resulting from weak "Van der Waals" forces and chemisorption, based upon the formation of stronger chemical bonds. In chemisorption there is significant electron transfer, equivalent to the formation of a chemical bond between the sorbate and the solid surface, and is limited to monolayer coverage. Functional groups are formed during carbon activation by interaction of free radicals on the carbon surface with atoms such as oxygen and nitrogen. The functional groups thus render the surface of activated carbon chemically reactive and influence its adsorptive properties. The affinity of a chemical for the internal surface of the activated carbon will depend greatly upon its chemical nature and the adsorption process is governed by the equilibrium between adsorption and desorption reactions. Contrasting several parameters of physical adsorption and chemisorption, the heat of adsorption in the former is low, < 2 or 3 times latent heat of evaporation, whereas the latter is high, > 2 or 3 times latent heat of evaporation. Specificity is nonspecific in the former and specific in the latter. The nature of the adsorbed phase in physical adsorption is monolayer or multilayer, with no dissociation of adsorbed species, whereas chemisorption is only monolayer and may involve dissociation. Regarding temperature range, physical adsorption is only significant at relatively low temperatures, whereas chemisorption is possible over a wide range of temperature. Finally, as to reversibility, physical adsorption is rapid, nonactivated, reversible, and chemisorption is activated, and may be slow and reversible (Kirk-Othmer Encyclopedia of Chemical Technology Vol. 1, p 494.) . Adsorption on a nonpolar surface such as an unoxidized carbon is dominated by Van der Waals forces. The affinity sequence on such a surface generally follows the sequence of molecular weights since the polarizability, which is the main factor governing the magnitude of the Van der Waals interaction energy, is itself roughly proportional to the molecular weight. In liquid phase absorption, factors influencing the adsorption process include molecular size, solubility and concentration of the solute, carbon particle size, temperature and pH value. Activated Carbon Activation Level Activated carbon products are rated by activity level, which is usually expressed as total surface area per unit weight, in square meters per gram. A secondary indicator of activation level is methylene blue adsorption level expressed in g./lOO g. Total exposed surface area will typically be in the range of 500-2000 m²/g. This is possible for both powdered and granular activated carbons because their surface areas lie in their vast internal pore structures. At the high end of this range, one can visualize one pound of activated carbon, about a quart in volume, as containing a total surface area of 125 acres. Surface area is recognized as a important factor influencing the quantity of an active ingredient which can be loaded or chemisorbed into activated carbon. Accordingly, it is also a factor in the respective rate of release of a compound. Activated carbon adsorption capacity and rate of adsorption depend on the internal surface area and distribution of pore size and shape. These factors are also influenced by the surface chemistry of the activated carbon. The macroporosity of the carbon is important for the transfer of pesticide molecules to adsorption sites within the particle. Both activated carbon surface area and activation level are important factors which influences it's carrying capacity for pesticidal active ingredients. Since activated carbon surface area determines the amount of activated carbon needed to deliver the pesticide into the environment. The content of the insecticide which is in the liquid state at room temperature, or converted to the liquid state by heating or use of solvents, to impregnate the activated carbon, powder or granule, is generally 5% to 70% Weight/Weight of the carbon, preferably 10% to 50% depending on carbon activation level. For reasons of transferring the impregnated powders in manufacturing, it is advantageous to have an impregnated powder whose surface is sufficiently dry to not drag or pack, without adding the bulk of a diluent or drying agent. Depending on the nature of the pesticide impregnated and activated carbon used, and whether the impregnated carbon is subsequently heated, as the need arises, at a raised temperature of 30° to 80°C. which draws the A.I. deeper into the carbon, for best manufacturing transfer the pesticide content is usually held between 5% and 40%. Carbons with highest carrying capacity enable the highest pesticide payload to be delivered in the smallest total combined weight of activated carbon and pesticide, which may be of value in product formulation. Preferred activated carbons for use in this invention have surface areas of 500 to 1,000 m²/g. and methylene blue adsorption levels of 7 to 12 g/l00 g. More preferred activated carbons have surface areas of 800 to 1,000 m²/g. and methylene blue adsorption levels of 12 to 18 g/l00 g. Most preferred activated carbons can carry the highest pesticide payloads and have activated carbon surface areas of 1,000 to 1,500 m²/g. and methylene blue adsorption levels of 18 to 25 g/100 g.

Activated Carbon Pore Size Activated carbons used in liquid phase applications have a high proportion of their pore volume in the macropore range, which permits liquids to diffuse more rapidly into the mesopores and micropores. The larger pores also promote greater adsorption of large molecules in many liquid phase applications. Methods of testing adsorbency employ substances having a range of molecular sizes (Kirk-Othmer 4th edition 1992) . Similarly, a carbon's ability to adsorb effectively depends on its having pores of the proper size and in sufficient number to accept and hold adsorbate molecules. The more pores of a proper size, the better the carbon will perform (Norit Americas) . Some very high surface area activated carbons lack physical strength, and may contain a large proportion of very small pores, which renders them unsuitable for applications involving adsorption of large molecules . Thus the preferred activated carbon pore sizes for impregnating active ingredient's for controlled release applications predominate in the micropore range (<2nm diameter) , the more preferred are those which have most pore sizes in the mesopore (2-50nm diameter) and micropore range, and the most preferred activated carbons for controlled release are those which have most pore sizes in the mesopore range as well as a substantial proportion of their pore volume in the macropore (>50nm diameter) range which permits high molecular weight pesticide liquids to diffuse readily into the mesopores and micropores with a minimum of diffusional resistance. Examples of the latter are peat based active carbon, and some lignite based active carbons. Activated Carbon Particle Size Activated carbon particle sizes influence the rate of adsorption of liquids in active ingredient impregnation by spraying during blending, with small particles having the fastest rates of adsorption. Small activated carbon particle size, distributed evenly in the environment aid in achieving uniform dispersal and effective slow release of adsorbed active ingredients under terrestrial, and static water conditions. Further, activated carbon particles in the 5 to 150 μm range are necessary to provide the high water exchange ratios necessary for water to effectively elute active ingredients off the carbon at levels necessary to achieve desired active ingredient effects. Carbon particles in the 0.1 - 10mm, preferably 0.3 -3.0 mm, range include granular and shaped or pelleted activated carbon are useful in field applications in which flowing water provides the high water exchange required to sufficiently elute active ingredient's off the carbon surfaces. The preferred activated carbon powder particle mesh size range for controlled release applications is 80% through 100 mesh (i.e ≤150 microns) , and 50% through 325 mesh (≤45 microns) . The more preferred activated carbon particle size is 90% through 100 mesh (≤150 microns) , and 60% through 325 mesh (≤45 microns) . The most preferred activated carbon particle size for pesticidal impregnation and environmental release is 99% through 100 mesh (≤150 microns) , and 70% through 325 mesh (≤45 microns) . Carbon Adsorptive Pore Space Openings into the carbon structure may be of various shapes, the term pore, implying a cylindrical opening is widely used. A description of the minute distances between the walls of these pores, normally expressed as a function of the total surface area or total pore volume presented by pores of various diameters is the pore structure curve.

The pore size distribution, by percentage, of activated carbon pore volume in cm³/cm³ particles based on raw material sources has been reported (Kirk-Othmer Encyclopedia of Chemical Technology. Fourth Edition. 1991) as follows:

Pore Size Distribution (%) Activated Carbon Source

Coconut Anthracite Bituminous Peat Lignite Lignite Shell Coal 1 2

Micropore 52 53 37 29 20 23

Mesopore 25 36 33 26 49 37

Macropore 23 11 30 45 31 40

The preferred activated carbons having the highest percentage of absorptive pore space made up of mesopores suitable for holding high loadings of large molecule pesticides, and macropore space large enough to admit the large molecules and allow them to reach the mesopore space are made from Anthracite, Bituminous coal, Peat and Lignite. More preferred activated carbons having the above characteristics are Bituminous coal, Peat, and Lignite. The most preferred activated carbons for reasons of the highest percentage of absorptive pore space are Peat and Lignite.

Activated Carbon pH Many pesticidal active ingredients are degraded by contact with high pH. As a result of the manufacturing processes used to activate them, steam activated carbons are inherently alkaline, whereas chemically activated carbons are inherently acidic (Norit) . Activated carbon pH levels can be reduced by acid washing processes, such as that used to manufacture Norit SX carbons. Such acid washed activated carbon products are preferred for use with high pH sensitive active ingredients. In most cases, the most efficient adsorption and best results are obtained working with lower pH activated carbons. With some compounds there is an optimum pH for maximum adsorption. This optimum pH may be quite different in the case of even similar compounds. Altering the pH of a solution can have an indirect beneficial effect (Activated Carbon, The Modern Purifier) . The preferred activated carbon pH range (water extract) for controlled release applications is between 5 and 9, with the more preferred pH range between 5 and 7, and the most preferred pH level for controlled release applications is 5 and 6.

Activated Carbon Sources Activated carbon can be produced from various carbonaceous raw materials, each of which impart typical qualities to the finished product. For economic reasons, most commercial grades of liquid phase carbons or decolorizing carbons, are prepared from lignite, coal, bones, wood, peat, and paper mill waste (lignin) . Activation of the raw material is accomplished by two basic processes, depending on the starting raw material and whether a low or high density, powdered or granular carbon is desired: (1) Chemical activation depends upon the action of inorganic chemical compounds, either naturally present or added to the raw material to degrade or dehydrate the organic molecules during carbonization or calcination. (2) Gas activation depends upon selective oxidation of the carbonaceous matter with air at low temperature, or steam, carbon dioxide, or flue gas at high temperature. The oxidation is usually preceded by a primary carbonization of the raw material. Decolorizing carbons are coal- and lignite-based granules, or light fluffy powders derived from low density starting materials such as sawdust or peat. Many decolorizing carbons are prepared by chemical inactivation. Decolorizing carbons are usually prepared by admixing or impregnating the raw material with chemicals that yield oxidizing gases when heated or that degrade the organic molecules by dehydration. In some cases, the chemically activated carbon is given a second activation with steam to impart physical properties not developed by chemical activation (Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Edition 1978) .

Preferred activated carbon sources for controlled release use neutral to low pH bituminous and lignite coals, peat and hardwood, the more preferred activated carbon sources are lignite, peat and hardwood, and the most preferred are the peat and lignite.

Active Ingredient The term active ingredient as employed here is intended to include any active material used for control of unwanted insects, plants, animals, microorganisms, such as agricultural insect pests, weeds, snails, including in particular insecticides, herbicides, biocides, and other control or environmental management materials. A great variety of pesticides can be used which are compatible with the activated carbon powder component of the invention. Representative of the pesticides which may be employed as starting materials in the invention are those disclosed in U.S. Pat. No. 4,225,693, which are expressly incorporated herein by reference. In general, exemplary pesticides compositions include triazole insecticides, arsenic based insecticides, sulfonyl carbamate insecticides, thiazine insecticides, benzonitrile insecticides, which are set forth in column 3, lines 21-70, columns 4, 5 and 6, lines 1-10, organophosphate, and pyrethroid insecticides. No list of useful pesticide can be complete since there are pesticides of which I am not aware of and new pesticides useful in this invention will be developed in the future. However, any pesticide, or environmental management material, having useful properties which are compatible with activated carbon can be used in the invention. Further examples of preferred insecticides for use in this invention are methyl parathion, carbofuran, ethoprop, aldicarb, acephate, fonofos, phorate, isofenphos, thiram, chlorpyrifos, diazinon, terbufos, trefluthrin, fipronyl, disulfoton, endosulfan, phenamiphos, isofenphos, bendiocarb. Many fungi can be controlled using the pest control means of this invention in a variety of environments, including agricultural, and industrial applications. In agricultural applications fungi can often harm the maturation of agricultural plants and animals, resulting in the loss of valuable commodities. Fungal agents which can be used in the pest control means include organic fungicides such as quinones, chlorinel, dichlone, imidazoline based fungicides and others. Herbicides that can be used effectively to control unwanted plants in agricultural and residential areas are well known chemical herbicides that kill growing plants or prevent seed germination and plant growth. Most useful herbicides belong to compound classes including the phenoxy alkanoic acid such as 2,4-D, 2,4,5-T, 2,4-DD, MCPA; the S- triazines, cymazines, detreazine, propyzene; the phenyl carbamates, IPC, CIPC, barban; the delapon, TCA; the phenylureas (fenuron, monuron, diruon) ; the dinitrobinzenes (DNBP, trifluralin, benefin) ; the benzoic acids, dichlobenil, amiben, 2,3,6-TBA; the dipyridyls

(paraquat, diquot) ; and the dithiocarbamats, EPTC, and vernolate. Further examples of preferred herbicides include alachlor, EPTC, metolachlor, molinate, dichlobenil, butylate, thiobencarb, napropamide, trifluralin, bebefin, ethalfuralin, triallate. Algaecides can also be incorporated into the slow release pest control means of the invention. A variety of both organic and inorganic algaecides are well known in the art . Since the polarizability, which is the main factor governing the magnitude of the Van der Waals energy, is roughly proportional to the molecular weight, absorption of active ingredients on activated carbon increases with rise in the number of carbon atoms or chain length and increase in compound molecular weight. The preferred types of active ingredients for controlled release applications are those which are slightly polar to highly nonpolar and have molecular weights of between 100 and 400. The more preferred active ingredients are those which are moderate to highly nonpolar, and have molecular weights of between 200 and 400. The most preferred active ingredients are those which are highly nonpolar, and have molecular weights of between 250 and 350. Other ways of ranking pesticides for preferred use in this invention are to consider value added or need, i.e. those which would benefit most from slower rates of release. Any active ingredient which could be enhanced by reducing the wasted spike release at application and smoothing the same amount of material over time, releasing it at biologically effective levels would be a preferred use application. Similarly, more polar pesticides with high water solubilities are most difficult to formulate with conventional means, and could benefit most by retarding their release rates. Conversely, highly nonpolar pesticides which have low water solubilities are held most tightly by the activated carbon and thus can be released for the longest time periods. Active Ingredient Solubility

Active ingredients possess differing inherent water solubilities. Such water solubility property reflects the respective affinities which exist between water and the active ingredient solute. This aqueous affinity acts to oppose the active ingredient carbon attraction or bond weakening the carbon holding capacity. Consequently, any change that increases active ingredient solubility may be accompanied by reduced carbon adsorption. Thus active ingredient polar groups (which are characterized by an affinity for water) usually facilitate the release of an active ingredient from activated carbon surfaces into aqueous solutions. Conversely, non polar or low polar active ingredient compounds, including most organics, are more strongly adsorbed onto activated carbon due in part to their relatively lower solubility in aqueous solutions. Active ingredient water solubility influences the strength of the active ingredient adsorption bond on activated carbon surfaces, but it is important to recognize that the true nature of the influence of an active ingredient's water solubility is that it reduces the hold of the activated carbon attachment sites once in the presence of water. High water solubility does not prevent the adsorption of substances which are attracted to activated carbon surfaces, it merely reduces the strength of the chemisorption by the surface of the activated carbon. The amount of liquid adsorbed at a given temperature and concentration depends on the nature of the adsorbent and of all the components of the solution (solutes and solvent) . Of foremost significance is the general rule of "the mutual affinity of substances with similar polarity" . From this rule it is to be expected that non-polar substances will absorb better on active carbon, a non¬ polar adsorbent, than polar ones. The adsorbed amount of a substance will, on the whole, increase as its solubility in water decreases. A further factor significantly influencing adsorption from solutions is the steric arrangement and chemical constitution of the molecule. On active carbon, absorbability increases with increase in molecular weight and is larger for molecules with straight chains than with branched chains. Similarly, for non¬ polar surface of a solid adsorbent, in a homologous series of compounds, the adsorbability regularly increases with an increase in the number of carbon atoms (Traube's rule) . However, with active carbons containing very narrow micropores, a reversal of Traube's rule may occur, as the higher members of a homologous series are adsorbed less than the lower ones due to the inaccessibility of the smallest micropores to large-size molecules (Active Carbon, Manufacture, Properties and Applications; M. Smisek and S. Cerny, Elsevier Publishing Company, Amsterdam, 1970) .

Active ingredients which are crystalline in their technical state, and which can be converted to low viscosity liquids at reasonable manufacturing temperatures for carbon impregnation, are often best impregnated alone into the activated carbon. Such process conserves the carbon activated sites for the loaded material, without competition from co-solvents or other additives. With such pesticides, and depending on the quantity of A.I. loaded into the carbon, the technical materials will to varying extent recrystallize within the carbon. In such cases, after the impregnated carbon cools to room temperature, the newly combined form may exhibit a loosely clumped form. In such cases, the impregnated carbon should be passed through a hammer mill or pin mill to break up the clumps and return the material to a fine particle size representative of the activated carbon before impregnation. The preferred solubility of active ingredient's to use in the invention are moderately polar materials which are highly water soluble, 100 to 1,000 parts per million (ppm) , and are conventional commercial agricultural products which release concentrations in excess of that required to achieve control of target pests. Such products are often applied at above needed dosage rates, to maintain the active ingredient presence for the desired duration of control . Such materials may employ co-solvents during impregnation to reduce release rates from activated carbon. More preferred active ingredient solubilities to use are non-polar materials which have intermediate water solubility, 20 to 100 ppm. Such materials may employ co-solvents during impregnation to modulate natural release rates from activated carbon. The most preferred active ingredients are those which are strongly non-polar, have low water solubility 0.1 to 20 ppm, are expensive to manufacture, have very high levels of biological activity at low concentrations, and high mammalian toxicity and associated occupational hazards of use.

Active Ingredient Viscosity Viscosity of active ingredient and solutions of active ingredient used to impregnate the activated carbon influence the rate and efficiency of adsorption by the carbon. High viscosities retard the rate of active ingredient diffusion into activated carbon. It thus reduces the opportunity of contact, slowing the rate of adsorption as well as total adsorption. The degree to which viscosity is an influence depends on the chemical nature of the active ingredient, and or active ingredient co-solvent combination. The influence of viscosity may be modified in various ways, a preferred method is to conduct the adsorption at higher temperatures to reduce active ingredient solution viscosity, a second is use a suitable solvent to impregnate the active ingredient into the activated carbon in a more dilute solution. Preferred active ingredient viscosities are those which are crystalline or viscous technicals which can be readily dissolved into non-polar solvents (with Kauri Butanol values of above 70) at low solvent levels, thereby creating minimum displacement of active ingredient from the activated carbon active sites. More preferred active ingredient viscosities are those technicals which have moderate to high viscosities of 45 to 90 SUS @ 100°F (37.78°C) , whose viscosities can be lowered by heating during activated carbon impregnation. Most preferred active ingredient's are those which have very low viscosities of 30 to 45 SUS @ 100°F (37.7°C) , and which when sprayed on moving activated carbon powder beds, they readily and rapidly sorb deep into the carbon pores . Active Ingredient Solvent

When a solvent must be used to liquefy a crystalline technical active ingredient, or lower the viscosity of a liquid active ingredient, to effectively impregnate the activated charcoal, the competing role of the solvent must be considered. Both solute and solvent compete for the activated sites on the carbon surface. When a large amount of solvent must be used to achieve a required viscosity level, the solvent may occupy most of the carbon activated internal surface area, and prevent adsorption of the desired quantity dissolved active ingredient. Beside competing for the carbon surface, polar solvents may weaken the adsorption of the active ingredient on the activated carbon surface, altering the solubility of the active ingredient and hence result in the premature

(rapid) release of the active ingredient from the carbon surface. Conversely, non-polar solvents may be used to retard active ingredient release rates from activated carbon into water. Research on impregnation solvents has shown that the rates of active ingredient release are influenced by the solvent flash point, minimum and maximum boiling points, distillation range and evaporation rate.

With an increase in the values of these properties there is a tendency for slower release rates . A relative efficiency index was developed as follows:.

REI= FP • IBP (EP-IBP) X 10^"5 where REI is the relative efficiency index, FP is the flash point, IBP is the initial boiling point and EP is the end point (Mulla and Axelrod, 1960, "Efficiency of Granulated Insecticides Influenced by Solvents Used for Impregnation" Journal of Economic Entomology.) While chemical structure and composition of candidate solvents influence performance properties, the above solvent characteristics can be used as a guide to select co- solvents to use with active ingredient's to secondarily modulate the activated carbon release profile when impregnating activated carbon during formulation. As an example, a solvent with a high flash point, high minimum and maximum boiling range, and low evaporation rate can be used, at different W/W% levels, with a highly soluble active ingredient in formulation to retard the rate of release of the active ingredient from activated carbon. Thus, solvents may slow the inherent release rate of highly water soluble active ingredient's impregnated into activated carbon. Solvents are selected by comparative trials, based on the above solvent characteristics and the desired performance specifications of the finished product. Solvents, or additives therein, which may emulsify the impregnated pesticides are not preferred. Representative of the solvents which may be employed in the invention are those disclosed in An Overview - Solvents for Agricultural Chemicals (Pesticide Formulations and Application Systems: 8th Volume, ASTM STP 980, D. A. Hovde and G. B. Beestman, Eds. American Society for Testing and Materials, Philadelphia, 1988) , which is expressly incorporated herein by reference. Preferred co- solvents to used with active ingredient's are those which have REI values of 20 to 80, and more preferred solvents are those which have REI values of 40 to 80, whereas the most preferred solvents are those having REI values of 60 to 80, which most effectively retard the release of highly water soluble pesticides at the lowest W/W % levels of use.

Active Ingredient Diluent Use As pesticides impregnated into suitable activated carbons are typically in concentrated form, resulting in a concentrated pesticide in a small volume, a means of uniformly distributing the combination in the environment is needed. Inert diluents are used for this purpose. Diluents used in the pesticide industry for both conventional and controlled release formulations are of two types, liquid and solid.

The most common liquid diluent used is water. The quantity of water used to deliver the pesticide uniformly in the environment can vary widely, and needs only to be sufficient to deliver the well mixed active ingredient evenly over the area to be treated, without evaporating or drifting off target. Water based flowable formulations may be made by dissolving thickeners in water to raise the solution viscosity sufficient to suspend particulate powders, thus making an aqueous flowable formulation from a dry powder. Prior to spraying, flowable concentrate formulations are diluted further with water. Less commonly, small quantities of low volatile liquids are used (3 to 128 ounces of liquid/acre) to deliver pesticides. Examples of such liquid diluents are vegetable oils, petroleum oils and polypropylene glycols.

Solid diluents are commonly of two types. Dry powders of 5 to 100 microns and granules of 6 to 60 mesh size. Diluent powders are used to reduce technical powder A.I.s concentrations during manufacture of end use products. Liquid technical pesticides are also sprayed upon powders to transform them to a solid for formulating or handling as were applied by aerial "crop dusters". Examples of low bulk density powders are calcium silicate, diatomaceous earth, Fullers Earth, hydrated alumina and silica gel. High bulk density powders include calcium carbonate, some clays, pyrophyllite and talc. The most common solid diluents used to distribute pesticides in the environment are 6 to 40 mesh particles, i.e. granules. They are termed carriers because they carry or distribute the particle with pesticide in the environment . Large diluents such as sand, limestone and corn cob particles may be coated with a pesticide film. Particulate materials known for their absorptive capacity and high surface area, such as plant fiber granules, diatomaceous earth, and clays can absorb and hold liquid pesticides for application. Activated carbon powder may be blended with plant fiber slurries before prilling, later to be impregnated with a pesticide. Similarly, activated carbon may be prilled on the outside of absorptive conventional carriers during manufacture, and subsequently impregnated during pesticide formulation. The latter two uses provide partial control over pesticide release rate, with that portion of pesticide absorbed into a conventional absorptive carrier being released rapidly, and that portion adsorbed into the activated carbon released slowly over time.

Pesticides formulated on powder diluents may be formed into agglomerated balls, granules or pellets, without a core. Powders containing pesticide may be formed into rapidly dissolving granules called Water Dispersible Granules, for addition to water which will be sprayed. Finally, pesticide containing powders may be extruded with or without other inert ingredients into pellets, or molded into briquettes, balls and numerous other shapes.

All of the above means employ diluents of one type or another. Activated carbon powder impregnated with pesticide described in this invention can be used as part or all of the diluent in the above-described roles. Thus activated carbon can be used as an adsorptive, and absorptive substrate in place of conventional diluents, or in combination with such diluents in pesticidal formulations. Such diluents serve a valuable function as a means to evenly distribute pesticides in the environment.

Finally, pesticides may be adsorbed into activated carbon granules of different particulate sizes, and used alone and without use of another diluent, as a means of active ingredient distribution in the environment.

FORMULATIONS

As has been demonstrated in U.S. Patent No.

4,732,762, March 22, 1988 by Sjogren, a pesticide in the form of a briquette or agglomerated spheres in combination with high compressive strength gypsum plaster can release pesticide into the environment at a controlled rate sufficient to control a pest population for a prolonged duration. A commercial briquette with an activated carbon UV screen, uses this technology to provide effective mosquito control for 150 days. The uses of activated carbon has also been demonstrated in U. S. Patent No. 4,971,796, November 20, 1990 by Sjogren, such pesticide in the form of a granule in combination with a proteinaceous material layer can release pesticide into the environment at a controlled rate sufficient to control a pest population for a prolonged duration. Commercial granular products using this technology and a carbon UV screen provide effective controlled release of active ingredient's for periods of 30 and 70 days, respectively. The significance of this invention is in the use of activated carbon as the primary control release agent. The value of the present composition, which requires only activated carbon and an active ingredient, and with some active ingredients a solvent, is the greater economy, simplicity, and variety of types of commercially useful controlled release formulations which this technology can employ.

EXAMPLES

Example 1

Insecticide Impregnated Activated Carbon Powder Formulated as a Water Dispersible Granule

This sustained release use application demonstrates the preparation of an insecticide formulation which consists of an agricultural insecticide impregnated into an acid washed activated carbon powder in a closed blender. This impregnated powder is then formulated into a water dispersible granule (WDG) similar to the method of Deming and Surgant, "Water-Dispersable Granules and Process for the Preparation Thereof", U.S. Patent No. 5,354,742.

The W/W% formulation ingredients to prepare a Disulfoton 40% active ingredient impregnated activated carbon powder to be used to make the WDG similar to the method discussed in U.S. Patent No. 5,354,742, substituting the impregnated carbon powder for the individual spherical microcapsules are :

Ingredient W/W%

Disulfoton, 99% technical 40.40

Norit SX2 activated powder 59.60

To prepare the Disulfoton impregnated activated carbon powder, place the Disulfoton, 99% technical in a pressure spray tank and pressurize the tank at 40 PSI. Next place the Norit SX2 carbon powder into a sealed high efficiency dry powder blender, such as a ribbon, or V blender, and spray the Disulfoton insecticide on the activated carbon powder during blending. To insure uniform pesticide impregnation into the activated carbon powder, spray the Disulfoton technical liquid with 80 degree flat fan nozzles, such as Spray Systems 800067, which will permit the slow delivery of the pesticide in a fine spray over a 20 to 30 minute period, followed by mixing for 30 minutes post spray. The impregnated activated carbon powder is then discharged and stored in labeled clean lined containers until used in formulating the WDG.

Example 2

Insecticide Impregnated Activated Carbon Powder Formulated as a Flowable Suspension

This controlled release use application demonstrates the impregnation of an agricultural insecticide into an acid washed activated carbon powder by spraying in a powder blender at room temperature followed by the preparation of a water based flowable suspension which typically eliminate hydrocarbon solvent use, solvent odor when used in dwellings, solvent phytotoxicity, reduce cost, occupational dust, and often increase product field effectiveness. The W/W% formulation ingredients to prepare a Chlorpyrifos 30% active ingredient impregnated activated carbon powder to make an aqueous flowable suspension in accordance with the methods discussed in Flowable Pesticide Formulations: Development, Process and the Need for Standard Testing Procedures, Pesticide Formulations and Application Systems: Second Conference, ASTM STP 795, K. G. Seymour, Ed. American Society for Testing and Materials, 1983, pp.45-52.

Ingredient W/W%

Chlorpyrifos, 99% technical 30.30

Tetrahydrofurfuryl alcohol 9.70

Norit SX2 60.00

To prepare the Chlorpyrifos impregnated activated carbon powder, dissolve the crystalline technical Chlorpyrifos by placing the technical crystals in a heat jacketed paddle mixing pressure spray tank and adding the Tetrahydrofurfuryl Alcohol solvent. Then slowly heat the combined materials slowly until all Chlorpyrifos dissolves, and pressurize the tank at 40 PSI. Next, place the Norit SX2 carbon powder into a sealed high efficiency dry powder blender, such as a ribbon, or V blender, and spray the Chlorpyrifos insecticide solution on the activated carbon powder during blending. To insure uniform pesticide impregnation into the activated carbon powder, spray the Chlorpyrifos liquid with 80 degree flat fan nozzles, such as Spray Systems 800067, which will permit the slow delivery of the pesticide in a fine spray over a 20 to 30 minute period. Then mix the powder for 30 minutes post spray to insure uniform distribution of the active ingredient. The impregnated activated carbon powder is then discharged and stored in labeled clean lined containers until used to formulate the water based flowable suspension. Example 3

Insecticide Impregnated Activated Carbon Powder Formulated as a Wettable Powder This example of controlled release demonstrates the impregnation of two co-blended liquid insecticides into acid washed activated carbon powder by spraying in a sealed powder blender followed by elevation of the impregnated powder to a temperature of 145°F (62.78°C) . to facilitate the penetration of the insecticides into the micro porous carbon particles, followed by cooling and the preparation of a wettable powder formulation by common wettable powder manufacturing methods, with or without additional milling to product necessary particle sizes and achieve appropriate suspension, similar to that of David A. Pearce, "Concentrated Carbamate Pesticide Wettable Powder Formulations", U.S. Patent No. 3,629,436, with necessary modifications.

The W/W% formulation ingredients to prepare an Ethoprop 15%, and Phorate 15% impregnated activated carbon powder to be used to make a wettable powder similar to the method discussed in U.S. Patent No. 3,629,436, with necessary modifications, substituting the impregnated carbon powder for the usual dry finely divided diluents normally used in formulating wettable posers such as talc, perlite, pyrophyllite, kaolin, and colloidal silica are:

Ingredient W/W%

Ethoprop, 96% technical 15.60

Phorate, 92% technical 16.30 _L_ Norit SX2, activated carbon powder 68.10

To prepare the Ethoprop/Phorate impregnated activated carbon powder, place the technical insecticides in a paddle mixing pressure spray tank and pressurize the tank at 40 PSI. Next, place the Norit SX2 carbon powder into a sealed high efficiency dry powder blender, such as a ribbon, or V blender, and spray the Ethoprop/Phorate insecticide solution on the activated carbon powder during blending. To insure uniform pesticide impregnation into the activated carbon powder, spray the Ethoprop/Phorate technical liquid with 80 degree flat fan nozzles, such as Spray Systems 800067, which will permit the slow delivery of the pesticide in a fine spray over a 20 to 30 minute period, followed by mixing for 30 minutes post spray, during which time the powder temperature is elevated to 140°F (60°C) , to facilitate the penetration of the pesticide combination into the macro and meso pores of the carbon powder, and then returned to ambient temperature. The impregnated activated carbon powder is then discharged and stored in labeled clean lined containers until used to formulate the wettable powder.

Example 4

Insecticide Impregnated Activated Carbon Powder Formulated as an Agglomerated Prill

This technology application demonstrates the controlled release of an insecticide impregnated into acid washed activated carbon powder by spraying in a sealed powder blender at 70°F (21.11°C) . temperature followed by the preparation of 20/40 mesh agglomerated prills using a pan agglomerator to produce a high pesticide payload granular formulation which reduces product weight and end user dust exposure.

The W/W% formulation ingredients to prepare an Acephate 30% impregnated activated carbon powder in accordance with commercial insecticide pan agglomeration methods are:

Ingredient W/W%

Acephate, 75% soluble powder 40.00

Norit SX3 60.00 To prepare the acephate impregnated activated carbon powder, co-blend the very fine acephate 75% water soluble technical powder with Norit SX3 activated carbon powder in a sealed powder blender. Next raise the temperature of the blended powders to 140°F (60°C) to melt the acephate technical crystals enabling them to absorb into the adjacent activated carbon powder, and continue to blend the powders for 30 minutes insure uniform distribution of the active ingredient while the powder temperature returns to ambient temperature. The impregnated activated carbon powder is then discharged and held for 24 hours for possible A.I. crystallization to occur, and passed through a hammer mill to insure separate particles of correct size range. It is then stored in labeled clean lined containers until used to formulate the agglomerated prill .

Example 5

Insecticide Impregnated Activated Carbon Powder Formulated in a Fly Bait

This insecticide controlled release use application demonstrates a low vapor pressure active ingredient impregnated into acid washed carbon powder by spraying in a powder blender followed by incorporation of said fly killing combination into a Synthetic Fly Attractants (SFA) media as developed by Mulla et. al. (1977) Jour. Econ. Ent. 70 (5) : 644-648.

The W/W% formulation ingredients for a Dichlorvos (DDVP) 30% insecticide impregnated activated carbon powder are:

Ingredient W/W%

Dichlorovos, 93% technical 32.26

Norit SX1, activated carbon powder 67.74 To prepare the Dichlorovos impregnated activated carbon powder, place the Dichlorovos technical liquid in a pressure spray tank at ambient temperature and pressurize to 40 PSI. Next, place the Norit SX1 carbon powder into a sealed high efficiency dry powder blender, and spray the Dichlorovos insecticide solution on the activated carbon powder during blending. To insure uniform pesticide impregnation into the activated carbon powder, spray the Dichlorovos liquid with 80 degree flat fan nozzles, such as Spray Systems 800067, which will permit the slow delivery of the pesticide in a fine spray over a 20 to 30 minute period. Then mix the powder for 30 minutes post spray to insure uniform distribution of the active ingredient. The impregnated activated carbon powder is then discharged and stored in labeled, sealed, clean lined containers until used to formulate the fly attractant bait.

Example 6 Aquatic Herbicide Impregnated Activated Carbon

Granule/Extruded Pellet

This controlled release use application demonstrates the impregnation of an end user aquatic herbicide product into activated carbon granules (or alternatively extruded pellets) by conventional spraying in a rotary blender (or alternatively dipping in a solution) . In this Example, the activated carbon granule herbicide impregnated product end use field application employs porous dispensers suspended from buoys to expose the slow release granule/pellet formulation to flow through water which bleeds out the active ingredient over time to control aquatic vegetation in irrigation canals.

The W/W% formulation ingredients to prepare 2,4-D Acid 20% impregnated activated carbon granules are:

Ingredient W/W%

2,4-D Acid, 95% technical 21.05

Tetrahydrofurfuryl alcohol 20.00

CG6/AW activated carbon granules 58.95

The 2,4-D Acid 20% impregnated activated carbon granules are prepared by placing the 2,4-D Acid -

Tetrahydrofurfuryl Alcohol liquid in a pressure spray tank and pressurizing it to 40 PSI. Next the Darco 8 x 20 (Norit America) lignite acid washed activated carbon granules are placed in a rotary blender, such as a Munson, or Continental Rollo mixer, and the 2,4-D Acid liquid is sprayed on the activated carbon granules during blending. To insure uniform pesticide impregnation into the granules, spray the herbicide liquid with 80 degree flat fan nozzles, such as Spray Systems 800067, which will permit the slow delivery of the pesticide in a fine spray over a 10 to 15 minute period. The impregnated activated carbon granules are then discharged and stored in labeled, clean lined containers until loaded into the dispensers for field application.

Example 7 Insecticide/Acaracide Impregnated Activated Carbon Powder Formulated as a Cattle Pour On

This pesticide controlled release use application demonstrates both the controlled release and ultra violet (UV) light shielding value of the herein described technology by way of the impregnation by spraying of an insecticide effective for control of biting flies of cattle into an acid washed activated carbon powder in an enclosed blender followed by co-blending said powder with an inert high molecular weight paraffinic oil to prepare a 5% A.I. end use product which is used as a "pour on" to treat the backs of cattle on which the biting flies rest.

Active ingredients so employed are effectively protected from the severe degrading effects of UV light until slowly released from the interior of the carbon particles to the surface of said particles to contact and kill cattle ticks and biting flies.

The W/W% formulation ingredients for Diazinon 30% impregnated activated carbon powder are:

Ingredient W/W%

Diazinon, 95.6% technical 31.38

Darco S-51 activated carbon powder 68.62

To prepare the Diazinon impregnated activated carbon powder, place the Diazinon 95.6% technical in a pressure spray tank and pressurize the tank to 40 PSI. Next place the Darco S-51 (Norit) carbon powder into a sealed high efficiency dry powder blender, such as a ribbon, or V blender, and spray the Diazinon insecticide on the activated carbon powder during blending. To insure uniform pesticide impregnation into the activated carbon powder, spray the Diazinon technical liquid with 80 degree flat fan nozzles, such as Spray Systems 800067, which will permit the slow delivery of the pesticide in a fine spray over a 20 to 30 minute period, followed by mixing for 30 minutes post spray. The impregnated activated carbon powder is then discharged and stored in labeled clean lined containers until blended with high molecular weight paraffinic oil to make a 5% W/W pour on product.

Example 8

Systemic Insecticide Impregnated Activated Carbon Powder Formulated as a Seed Treatment

This controlled release use application illustrates the use of a systemic insecticide impregnated into activated carbon powder which is subsequently applied as an agricultural seed coating to inhibit early plant damage by sucking and chewing insects.

The W/W% formulation ingredients to prepare a Disulfoton 10% systemic insecticide seed treatment are:

Ingredient W/W%

Disulfoton, 99% technical 10.10

Norit SX4, activated carbon powder 89.90

To prepare the Disulfoton impregnated activated carbon powder, place the Disulfoton 99.0% technical in a pressure spray tank and pressurize the tank to 40 PSI. Next place the Norit SX4 carbon powder into a sealed high efficiency dry powder blender, such as a ribbon, or V blender, and spray the Disulfoton insecticide on the activated carbon powder during blending. To insure uniform pesticide impregnation into the activated carbon powder, spray the Disulfoton technical liquid with 80 degree flat fan nozzles, such as Spray Systems 800067, which will permit the slow delivery of the pesticide in a fine spray over a 20 to 30 minute period, followed by mixing for 30 minutes post spray. The impregnated activated carbon powder is then discharged and stored in labeled clean lined containers until applied to seed at the appropriate end use dosage rate using a conventional seed coating binder.

Example 9

Nematocide Impregnated Activated Carbon Powder Formulated as a 20/40 Granule

This example of controlled release demonstrates the impregnation of a liquid nematocide into acid washed activated carbon powder by spraying in a sealed powder blender followed by elevation of the impregnated powder to a temperature of 145°F (62.78°C) to facilitate the penetration of the insecticides into the porous carbon particles, followed by cooling and the preparation of a Nemacur 10% Granule on 20/40 sand using polyvinyl alcohol binder. The W/W% formulation ingredients to prepare a Nemacur 40% impregnated activated carbon powder are:

Ingredient W/W%

Nemacur, 92.3% technical 43.3

Aromatic 150 solvent 5.0

Norit SX2, activated carbon powder 51.7

To prepare the Nemacur impregnated activated carbon powder, place the crystalline technical nematocide in a heat jacketed paddle mixing pressure spray tank, add the

Aromatic 150 solvent and slowly heat the contents to 100°F (37.78°C) with gentle mixing, and when all crystalline technical has dissolved pressurize the tank at 40 PSI. Next, place the Norit SX2 carbon powder into a sealed high efficiency dry powder blender, such as a ribbon, or V blender, and spray the nematocide solution on the activated carbon powder during blending. To insure uniform pesticide impregnation into the activated carbon powder, spray the nematocide liquid with 80 degree flat fan nozzles, such as Spray Systems 800067, which will permit the slow delivery of the pesticide in a fine spray over a 20 to 30 minute period, followed by mixing for 30 minutes post spray. The impregnated activated carbon powder is then discharged and held for 24 hours for possible A.I. crystallization to occur, and passed through a hammer mill to insure separate particles of correct size range. It is then discharged and stored in labeled clean lined containers until used to formulate the granule.

To make the Nemacur 10% Granule, prill 25% W/W of the pesticide impregnated activated carbon on clean 20/40 silica sand in a rotary blender using a sticker such as a polyvinyl alcohol solution, and conventional granule prilling methods.

FIELD EFFICACY This description presents the results anticipated from the application of Nylar, an insect growth regulating pesticide. Nylar alone is applied directly to one field mosquito breeding site. An equivalent amount of the same pesticide absorbed into Norit SX3 powdered activated carbon to make a 30% by weight Nylar impregnated activated carbon is applied to a second mosquito breeding site of equal size.

Both field mosquito breeding sites contained equivalent mosquito larval populations at time of treatment. Test site 1 is treated uniformly over the water surface with a Nylar 10% emsulsifiable formulation in 2 gallons of water at the rate of 68.1 grams of active ingredient on day 1. Test site 2 is treated on the same day with 226.7 grams of 30% by weight Nylar impregnated activated carbon, containing 68.1 grams of active ingredient, by adding the impregnated carbon powder to a spray tank containing 2 gallons of water with 1% Triton X-100 surface tension reducing agent and shaking while spraying uniformly over the water surface. Weekly mosquito pupal collections made from each treated site can be expected to find the following levels of mosquito control. Percent Pupal Mortality

Days Post-Treatment Nylar E.C. Nylar With Activated Carbon

7 100 100

14 100 100

21 97 94

28 80 100

35 95 100

42 9 91

49 0 96

56 0 99

63 3 95

70 0 97

77 0 95

84 0 99

91 0 96

98 0 95

105 0 90

The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.

Claims

WE CLAIM :

1. A controlled release particulate pesticide composition, substantially free of a slow release plaster or protein matrix composition, the particulate pesticide comprising a particulate activated carbon and, adsorbed in the particulate, a liquid phase comprising a pesticide wherein the particulate pesticide when contacted with environmental water, releases an effective pesticidal amount of pesticide.

2. The pesticide of claim 1 wherein the pesticide comprises an insecticide.

3. The pesticide of claim 1 wherein the pesticide comprises a herbicide.

4. The pesticide of claim 1 wherein there are about 0.01 to 1.8 parts by weight of pesticide per each part of activated carbon.

5. The pesticide of claim 1 wherein there are about 0.2 to 1.2 parts by weight of pesticide per each part of activated carbon.

6. The pesticide of claim 4 wherein the carbon has a particle size less than about 100 μm.

7. The pesticide of claim 4 wherein the carbon has a particle size less than about 5-25 μm.

8. The pesticide of claim 1 wherein about 1 to 70% of the adsorptive pore space of the activated carbon is occupied by pesticide.

9. The pesticide of claim 1 wherein about 5 to 50% of the adsorptive mesopore and macropore space of the activated carbon is occupied by pesticide.

10. The pesticide of claim 1 wherein the liquid phase comprises a solvent and pesticide.

11. A particulate pesticide composition comprising about 0.05 to 0.5 parts by weight of the controlled release particulate pesticide composition of claim 1 per each part by weight of a diluent.

12. The particulate pesticide of claim 8 wherein the diluent comprises a calcium sulfate, a diatomaceous earth, plant fiber, an alumina, a silica or mixtures thereof.

13. A pumpable liquid pesticide composition comprising a liquid medium and dispersed in the liquid medium about 0.05 to 0.5 parts by weight of the controlled release particulate pesticide composition of claim 1 per each part by weight of a liquid diluent.

14. The liquid pesticide of claim 13 wherein the diluent comprises water.

15. A controlled release pesticide composite particle comprising at least about 50 milligrams of the controlled release particulate pesticide composition of claim 1.

16. The pesticide composite of claim 15 wherein the composite has a minimum dimension of about 200μm.

17. The pesticide composite of claim 15 wherein the composite is formed using a binder.

18. The composite pesticide of claim 15 wherein the composite is formed by compressing a plurality of the particulate pesticide composition.

19. A process for the manufacture of a controlled release particulate pesticide composition comprising the steps of contacting a plurality of particulate activated carbon particles with a liquid pesticide, permitting the liquid pesticide to be adsorbed into the adsorptive mesopore and macropore space of the activated carbon to form a solid flowable particulate pesticide.

20. The process of claim 19 wherein there are about 0.1 to 1.8 parts by weight of the pesticide per each part of the activated carbon.

21. The method of claim 19 wherein the carbon has a particle size less than about 100 μm.

22. The method of claim 19 wherein about 5-50% of the adsorptive mesopore and macropore space of the activated carbon is occupied by the pesticide.

23. The method of claim 19 wherein the liquid pesticide comprises a solvent and a pesticide.

24. A controlled release particulate pesticide composition, the particulate pesticide consisting essentially of particulate activated carbon and, adsorbed in the particulate, a liquid phase comprising a pesticide wherein the particulate pesticide when contacted with environmental water, releases an effective pesticidal amount of pesticide.

25. The pesticide of claim 24 wherein the pesticide comprises an insecticide.

26. The pesticide of claim 24 wherein the pesticide comprises a herbicide.

27. The pesticide of claim 24 wherein there are about 0.01 to 1.8 parts by weight of pesticide per each part of activated carbon.

28. The pesticide of claim 24 wherein there are about 0.2 to 1.2 parts by weight of pesticide per each part of activated carbon.

29. The pesticide of claim 24 wherein the carbon has a particle size less than about 100 μm.

30. The pesticide of claim 24 wherein the carbon has a particle size less than about 5-25 μm.

31. The pesticide of claim 24 wherein about 1 to 70% of the adsorptive pore space of the activated carbon is occupied by pesticide.

32. The pesticide of claim 24 wherein about 5 to 50% of the adsorptive mesopore and macropore space of the activated carbon is occupied by pesticide.

33. The pesticide of claim 24 wherein the liquid phase comprises a solvent and pesticide.