Classifications

• • C—CHEMISTRY; METALLURGY
  • C05—FERTILISERS; MANUFACTURE THEREOF
  • C05D—INORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C; FERTILISERS PRODUCING CARBON DIOXIDE
  • C05D3/00—Calcareous fertilisers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
  • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
  • B09B1/00—Dumping solid waste
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F9/00—Multistage treatment of water, waste water or sewage
• • C—CHEMISTRY; METALLURGY
  • C05—FERTILISERS; MANUFACTURE THEREOF
  • C05D—INORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C; FERTILISERS PRODUCING CARBON DIOXIDE
  • C05D5/00—Fertilisers containing magnesium
• • C—CHEMISTRY; METALLURGY
  • C05—FERTILISERS; MANUFACTURE THEREOF
  • C05D—INORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C; FERTILISERS PRODUCING CARBON DIOXIDE
  • C05D9/00—Other inorganic fertilisers
  • C05D9/02—Other inorganic fertilisers containing trace elements
• • C—CHEMISTRY; METALLURGY
  • C05—FERTILISERS; MANUFACTURE THEREOF
  • C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
  • C05F11/00—Other organic fertilisers
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
  • C02F1/004—Processes for the treatment of water whereby the filtration technique is of importance using large scale industrial sized filters
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/02—Treatment of water, waste water, or sewage by heating
  • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
  • C02F1/048—Purification of waste water by evaporation
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/20—Treatment of water, waste water, or sewage by degassing, i.e. liberation of dissolved gases
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/28—Treatment of water, waste water, or sewage by sorption
  • C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/28—Treatment of water, waste water, or sewage by sorption
  • C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
  • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
  • C02F1/5245—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents using basic salts, e.g. of aluminium and iron
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F11/00—Treatment of sludge; Devices therefor
  • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F11/00—Treatment of sludge; Devices therefor
  • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
  • C02F11/13—Treatment of sludge; Devices therefor by de-watering, drying or thickening by heating
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
  • C02F2001/5218—Crystallization
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/16—Nitrogen compounds, e.g. ammonia
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/30—Organic compounds
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
  • C02F2103/06—Contaminated groundwater or leachate
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/40—Bio-organic fraction processing; Production of fertilisers from the organic fraction of waste or refuse

Definitions

• the present i nvention relates to a process for recovering h um ic substances from percolate originating from urban solid refuse dumps or the like, and a humic substance obtained by the process.
• Hum ic substances are complex organic substances of variable and stil l not com pletely defined structure (su pramolecu lar, macromolecu lar structure), consisting of branched chains of mainly but not exclusively mono and polycyclic, including heterocyclic, aromatics with mainly carboxyl, phenol and hydroxyl functional groups, but also ethers, esters, amino, etc.
• HA - humic acids
• sol u b il ity characteristics enable h u m ic su bstances to be extracted from carbonaceous minerals such as leonardite, lignite, peat and also, recently proposed, from compounds produced by transformation and stabil ization of organ ic refuse such as the organ ic fraction of sol id urban refuse (S.U.R) in controlled plants.
• Leonardite which forms in the slow decomposition of organic substances (in particular lignin) is the most recent surface oxidized phase of the geochemical transformation of vegetable organic substances in peat and lignite. It is particularly rich in humic substances, which are extracted in basic aqueous solution with potassium hydroxide (pH 9-12). These solutions, which can contain inorgan ic salts sol uble in basic water in variable q uantities, according to the zones of origin, are normally marketed, with various humic substance concentrations, in particular as soil improvers in agriculture. In this respect, humic substances modify the characteristics of soils and improve growth and health of the most varied agricultural crops both by soil treatment and by leaf application.
• humic substances improve:
• Hum ic substances are virtual ly non-biodegradable; they consist of macromol ecu l es of med iu m (FA) and h ig h mol ecu l ar weig ht (HA) with hydrophobic parts and hydrophilic functional groups which are partly acid, and in their sal ified forms with al kaline metals exhibit surfactant properties which enable them to be also used as surfactants in the washing of earth and soils for their decontam ination from hydrocarbons and/or heavy metals by also using their chelating properties on various heavy metals.
• FA macromol ecu l es of med iu m
• HA weig ht
• the percolate from S.U .R. dumps can contain humic substance quantities (0.05-5 % by weight) considered interesting for industrial and commercial purposes; however their direct recovery from percolate by known methods does not enable a product to be obtained at competitive cost which is free from the various contaminants present in the percolate, with particular regard to nitrogenated and ammoniacal compounds, and consequently unsuitable for use similar to the humic substances obtained by previously described methods.
• the object of the present invention is to provide a process enabling humic substances of marketable quality to be obtained from the percolate of S.U.R. dumps and similar refuse, while achieving lesser consumption of reagents (acids, additives) and using simple technologies, which can be integrated and used with existing technologies, to achieve low investment and running costs.
• the humic substance concentration in the percolate changes with the time (age) of activity of the S.U.R. dump; the succession of biological degradation stages which take place on the organic component of refuse once dumped are known to be the following:
• acetogenic stage in which volatile short chain acids form by fermentation, these being further degraded by acetogenic bacteria to acetic acid, a substrate of methanogenic bacteria. Methane is produced, hydrogen and carbon dioxide decrease and the pH increases.
• the percolate presents a lesser metal and BOD 5 concentration than in the previous stage and an increase in humic substance and ammonia concentration;
• methanogenic stage in which methane is formed in large quantity by the prevalence of methanogenic, hydrogenophilic and above all acetophilic bacteria (responsible for the production of 70% of methane).
• This stage characterises the dump "maturity": the percolate presents neutral-alkaline pH (7-10); low volatile acid and dissolved solids concentrations (low BOD 5 ), low mobility of heavy metals (for example Fe, Zn), high ammonia concentration, maximum humic substance concentration'
• the percolate from a "mature" dump is in fact visually recognizable by its dark brown colour typical of humic substances (HA brown-black colour; FA yellow-brown colour).
• Studies conducted on the chemical and structural nature of humic substances obtained from the percolate of various S.U.R. dumps by chemico-physical analyses (spectroscopic, UV, FTIR, NMR, etc.) have shown that these are similar, but not equal, to those obtained by extraction from leonardite, peat, lignite, compost.
• the humic substances are mainly removed together with the hydroxides and the basic carbonates of heavy metals by precipitation/clariflocculation with aluminium and iron salts, calcium hydroxide, organic flocculants, etc. implemented by technologies with membranes (ultrafiltration, reverse osmosis) which are however easily clogged by the humic substances.
• the sludges produced by the percolate purification are usually recycled to the dump or otherwise disposed of, it not being economically convenient to recover humic substances of sufficient commercial quality.
• the "mature" percolate is already a basic humic substance solution and is normally classified, in accordance with Italian and European regulations, as "percolate refuse, special non-dangerous" (CER code 190703).
• CER code 190703 percolate refuse, special non-dangerous
• a possible initial filtration is also provided to ensure that any "suspended solids" are at low level, less than 500 mg/litre, it being well known that certain dangerous organic m icrocontam inants, such as polychlorodibenzodioxins and polychlorodibenzofurans, if present, are practically absorbed into the insoluble particulate (suspended solids).
• the object of the invention is to recover humic substances from this solution and to purify them of any contaminants present which render them unsuitable for each specific use.
• humic substance acid precipitation on the percolate concentrated by evaporation for example under vacuum
• humic substances precipitated from it of possible volatile contaminants, either organic (carboxylic acids, hydrocarbons, other aliphatic/aromatic organic substances, includ ing halogenated and n itrogenated) or inorgan ic (pri ma ri ly am mon ia ); th is facil itates the su bseq u ent h u m ic su bsta nce purification stage to obtain humic substances of commercial quality.
• stage of humic substance precipitation with acid can be carried out hot, at 50-100°C, at the temperature of the concentrated percolate d ischarge from the evaporator, without add itional energy costs, so improving the precipitate morphology and the efficiency of the subsequent stages of solid-liquid separation and purification by washing with water, possibly acidified with inorganic acid to pH ⁇ 7 to reduce impurities such as inorganic salts and water-soluble organic compounds.
• Another advantage of operating on the concentrated percolate is that during evaporation it undergoes thermal treatment with temperatures of 50- 1 30°C for a h ig h averag e res id ence ti me (2-7 hours) with consequent reduction of the initial bacterial load, which is also further reduced in the next stage of acidification to pH 2, obtaining a product virtually free of dangerous bacteria, such as Escherichia coli and salmonella.
• This object is attained according to the invention by a process for recovering hum ic substances from percolate orig inating from urban sol id refuse dumps or the like as described in claim 1 .
• the percolate originating from a S.U .R. dump or the l ike in its "maturation" phase conta ins suspended sol ids, it is in itial ly filtered with su itable filters such as sand filters, m icrofilters, decanters, centrifuges to obta i n a "su s pend ed sol id s" con centration of l ess th a n 500 mg/l itre (determined by the I RSA-CNR 2090 method) to remove any contaminant organic substances such as polychlorodibenzodioxins and polychlorodibenzofurans which, if present, are known to be adsorbed in the suspended solid particulate.
• filters such as sand filters, m icrofilters, decanters, centrifuges to obta i n a "su s pend ed sol id s
• the particular percolate presents neutral or basic pH (pH 7-10), is brown in colour, contains more than 0.1 % of organic substances by weight determined as the difference between the dry residue at 1 05°C (R1 05) and the dry residue at 600°C (R600), determined by the IRSA Q64(2) 84 met.02 method , and i n particu lar more than 0.05% of h u m ic carbon by weig ht, determined by the DM 23-01 -91 S.O.G.U No. 29/91 method.
• the percolate is then subjected to a continuous evaporation stage u nd e r vacu u m at a press u re of 5-200 KPa, temperature of 50-130°C, preferably by a continuous multiple effect process, for an average residence time of 2-7 hours, until a l iquid residue is obtained with a reduced volume equal to 1 /5 - 1 /29 of the initial percolate volume, at basic pH 8-1 1 .
• the concentrated percolate contains all the humic substances in solution, in particular humic acids soluble in a basic environment, fulvic acids and inorganic salts, in particular chlorides, sulphates, phosphates, alkaline silicates (Na, K salts) and alkaline-earth silicates (Ca, Mg salts).
• the condensate water of the evaporation-concentration stage contains al l the volati le contam inants present in the starting percolate, such as ammonia, volatile organic substances, hydrocarbons, halogenated organic substances. These substances are eliminated from the condensate water in a subsequent stripping/absorption stage wh ich also enables an ammon ium sulphate solution to be recovered, usable in industry.
• the condensate water purified in this manner can be used in the crude humic substance acid wash stage or d ischarged i nto the pu bl ic sewer, su rface waters or soi l , after possible further purification by known processes, for example oxidation , adsorption on active carbon, ultrafiltration, reverse osmosis, etc., to attain the contamination limits allowable for discharge.
• the concentrated percolate is subjected to an acidification stage with the addition of an aqueous solution of organic acid, for example 37.5 wt% concentrated sulphuric acid, 37.5 wt% hydrochloric acid, 75 wt% phosphoric acid , at a tem peratu re between ambient and the boiling point of the concentrated percolate, under agitation, in a discontinuous or continuous precipitator, for example three-stage, with continuous line dispensing of acid, under pH control and under ag itation , for example by recycl ing with static mixers, until complete precipitation of a flocky humic substance solid at pH 1 - 3, preferably 2.0 stable (constant); the acid quantity required varies with the type of percolate and the type of acid : for example for a mature percolate, for 37.5 wt% sulphuric acid it can be about 10 vol% of the concentrated percolate volume.
• organic acid for example 37.5 wt% concentrated sulphuric acid, 37.5
• Humic substance precipitation commences at pH 4.5-4.0 with possible formation of foam wh ich can be reduced and control led by add ing smal l quantities of anti-foaming agent, for example of silicone type; the acidification and precipitation system is provided with agitation means, means for bleeding and treatment of vapou rs and uncondensables such as carbon d ioxide, hydrogen sulphide and weak inorgan ic and organic acid substances volatile under said pH and temperature cond itions; consequently th is stage also contributes to purification of humic substances from substances which would reduce their quality, for example dangerous sulphides of unpleasant odour.
• anti-foaming agent for example of silicone type
• the acidification and precipitation system is provided with agitation means, means for bleeding and treatment of vapou rs and uncondensables such as carbon d ioxide, hydrogen sulphide and weak inorgan ic and organic acid substances volatile under said pH and temperature cond itions; consequently th is stage also
• the humic substances are then subjected to a solid/liquid separation stage achieved by one or more known methods such as filtration, including vacuum filtration, centrifugation, decantation, floatation, etc.
• a solid/liquid separation stage achieved by one or more known methods such as filtration, including vacuum filtration, centrifugation, decantation, floatation, etc.
• filtration including vacuum filtration, centrifugation, decantation, floatation, etc.
• small quantities g en era l ly l ess tha n 1 .0 vol %
• polymer floccu l ation ag ents su ch as polyacrylates, polyacrylamide based cationic polyelectrolytes, additives which in any event do not influence final product quality.
• the crude humic substances are then dissolved as soluble alkaline humates by adding an aqueous solution of al kal ine hydroxide, preferably potassium, to pH 5.0-10.0, preferably pH 7.0; an aqueous solution of crude humic substances results which, possibly diluted, can be used as a soil improver in agriculture after qualitatively and quantitatively verifying compliance with the analytical limits provided by current regulations for products of similar origin such as sludge from mun icipal effluent water purifiers and composts from the S.U.R. organic fraction.
• the crude humic substances are purified by washes with water, possibly deriving from purification of the condensates produced in the evaporation stages of the present process (Fig. 1 ), acidified to pH ⁇ 7 with inorganic acid, for example sulphuric acid and/or hydrochloric acid and/or phosphoric acid , al l by known methods with cycl ic or continuous washes.
• inorganic acid for example sulphuric acid and/or hydrochloric acid and/or phosphoric acid
• a suspen sion of pu rified h u m ic su bstances is obta ined with d ry residue at 105°C of 10-80 wt%, preferably 40%, at pH 5-7, and with low salinity expressed as dry residue at 600°C of less than 1 5 wt%, preferably 5 wt%.
• the aqueous solution of crude or purified humic substances solubilized as al kaline humates can be further purified by known treatment with sol id adsorbent prod ucts such as active carbons, kaol i n s , cl ay etc . to re move a n y org a n i c m icrocontaminants such as alkylphthalates, in particular 2-ethyl-hexylphthalate, nonyl- and octyl-phenols, bisphenol A.
• sol id adsorbent prod ucts such as active carbons, kaol i n s , cl ay etc .
• aqueous solution of crude or purified humic substances described above besides being used after possible dilution as a soil improver for crops in agriculture in compliance with qualitative and quantitative limits provided by regulations, can be variously transformed into the following forms similar to those existing on the humic substance market:
• Effervescence is initially observed with foam production which is reduced and controlled by adding silicone antifoaming agent (0.2 ml of 10% Dinapan 16WD solution). At about pH 4 a flocky brown precipitate begins to form , with the solution colour clearing towards yellow, effervescence and foaming cease, and sulphuric acid addition is continued .
• Tab.3. shows for the said sample (1p) the quantities, expressed in volume and weight, of 37.45 wt sulphuric acid added and the pH values obtained after each addition; at pH 2.21.97 g of pure sulphuric acid (20.1 mgmoles) were used per 100 ml of percolate as such.
• sample 1pc corresponding to 1100 ml of percolate as such
• pH is measured until complete humic substance precipitation, in the same manner and with the same observations as for the previously described sample 1p; after centrifugation 41.8 g of moist crude humic substances (sample HS1c) were obtained with the characteristics given in Tab.2.
• Tab.3 shows the volumes (ml) and weight (g) of sulphuric acid used against pH for:
• Tab.2 shows the differences between the chemical characteristics of the two samples, in particular the concentrated product (sample HS1c) shows a higher dry residue at 105°C, 23.50%, a good humic and fulvic carbon level, low levels of heavy metals, and a high level of soluble alkaline salts (sodium, potassium) possibly reducible by subsequent washes.
• sample 1 p the percolate as such (sample 1 p) and of the relative concentrate (sample 1 pc) by dangerous organic compounds, the following were also sought in these samples by normal analytical methods of adequate sensitivity and specificity:
• PCB polychlorobiphenyls
• aromatic polycyclic hydrocarbons (naphthalene, benzo(e)pyrene, acenaphthylene, acenaphthene, fluorine, phenanthrene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indeno(123cd)pyrene, dibenzo(ah)anthracene, benzo(ghi)perylene, dibenzo(al)pyrene, dibenzo(ae)pyrene, dibenzo(ai)pyrene, dibenzo(ae)pyrene);
• chloromethane dichloromethane, chloroform, vinyl chloride, 1 ,2-dichloroethane, 1,1- dichloroethylene, trichloroethylene, tetrachloroethylene
• chloromethane dichloromethane, chloroform, vinyl chloride
• 1 ,2-dichloroethane 1,1- dichloroethylene
• trichloroethylene tetrachloroethylene
• chlorinated aromatic compounds chlorobenzene, 1 ,2-dichlorobenzene, 1,4- dichlorobenzene, 1 ,2,4-trichlorobenzene
• aromatic organic solvents benzene, toluene, ethyl benzene, styrene, xylenes, isopropylbenzene.
• Example 2 2000 ml of "mature" dump percolate (A) as in Example 1) were concentrated in the laboratory with the same method, temperature and pressure as in Example 1) to obtain 166 ml of 12 times concentrated percolate (sample 2pc).
• the humic substance precipitation commences, as in Example 1), at pH 4.4 and finishes at pH 2.3; the phosphoric acid used is 143 mgmoles per 100 ml of concentrated percolate and 11.48 mgmoles per 100 ml of percolate as such.
• phosphoric acid enables humic substances containing phosphates to be obtained, usually used as fertilisers in agriculture, hence enabling the raw materials used in the present invention to be upvalued.
• Example 3 An industrial concentrated percolate was used obtained by thermal evaporation under vacuum at a plant operating in a "mature" dump (B) having the following characteristics:
• Example 3pc 200 ml of said percolate (sample 3pc) were heated to 65°C, to simulate possible precipitation by acidification at the concentrator exit temperature, then while maintaining the sample heated, progressive quantities of 37.45 wt% sulphuric acid were added in the same manner as in Example 1), while continuously measuring pH, which at the end of precipitation was pH: 2.2; 22 ml of sulphuric acid were required (equal to 11 vol% of the concentrated percolate).
• Tab 5 shows the quantities, expressed in volume and weight, of 37.45 wt% sulphuric acid added to 100 ml of concentrated percolate (sample 3pc) and the pH values obtained after each addition; 53.8 mgmoles/1 OOml of concentrated percolate were required in total, a value very similar to that found in Example 1) of 58.2 mgmoles/1 OOml of a different concentrated percolate.
• Tab. 6 shows the analytical results, from which it can be observed that:
• the quantities extracted reduce by about 50 wt% for each wash on a 1/1 wt ratio wash basis; after the 4th wash, the values of the determinations made are reduced to about 10% of the initial value, indicating a satisfactory capacity for extracting the soluble salts;
• Example 1 20 ml of the silicone antifoaming solution used in Example 1) were added under agitation to 25 kg of industrial concentrated percolate (sample 4pc) originating from the plant operating at the same dump (B) as Example 3) but of a different period, with the following characteristics:
• a 10 g fraction of crude moist hum ic substances is withdrawn and washed with water acidified to pH 1 with sulphuric acid in a 1 /1 v/v ration of crude humic substances/water followed by centrifugation and separation of the precipitate; a total of four washes were carried out in successive steps for pu rification from the water-soluble salts.
• a sam ple of pu rified h u m ic substances is obtained (sample HS4).
• the results of the analysis of sample HS4 expressed in wt% on the dry residue at 105°C, and the methods used are given in Tab. 7.
• the high dry residue at 600°C can be observed together with high calcium (Ca) content (9.5 wt%) and high sulphate (SO4) content (30.5 wt%), in a molar ratio (0.7:1 ) such as to assume the presence of most of the sulphate ion (SO4) as calcium sulphate (CaSO4).
• CaSO4 and colloidal silica (SiO2) are also used as soil improvers and soil pH correctors in agriculture (calcium sulphate); consequently from calcium-rich percolates, by using the same tech nology, prod uct m ixtu res can be obta ined wh ich can perform several useful functions in agriculture.
• sample HS4 was dried in an oven in air at 105°C to constant weight, for two hours; about 0.6 g were used mixed with about 200 mg of potassium bromide (KBr) and a tablet produced by compression; on this latter an FT-IR spectrum was obtained compared with the spectra of KBr tablets produced by the same method from a commercial humic substance sample extracted from leonardite (COM2) and of standard calcium sulphate.
• the spectra comparison shows the simultaneous presence of absorption bands characteristic of commercial humic substances (COM2) and of calcium sulphate, confirming the presence of this latter in Samp/HS4.
• Tab.8 shows the hydrochloric acid volumes and weights (ml and g) against pH.
• Precipitation commences at pH: 4.3, as in the previous examples, of a dark brown flocky solid, and is completed at pH: 2.0.
• a crude moist humic substance solid was separated (sample HS5g) of 20.0 g, equal to 10% of (5pc) with dry residue at 105°C of 25wt%.
• a portion of HS5g was subjected to four successive washes with water acidified to pH approximately 1 with hydrochloric acid in the manner described in Example 4.
• a purified moist humic substance solid was recovered (sample HS5) with dry residue at 105°C of 36 wt%. When dried at 105°C the sample HS5 has a weight equal to 26% of the weight of HS5g dried at 105°C from which it was obtained.
• Tab.9 shows the characteristics of the samples HS5g and HS5.
• the sample (HS6) in solution contains a humic carbon quantity similar to the commercial sample in solution (COM1 ), the soluble inorganic salt quantities (residue at 600°C) are similar and consist of alkaline salts (potassium, sodium) of chlorides, sulphates, in particular the powder sample (COM2) shows high phosphate quantities, the heavy metals are low and virtual ly si m i lar between the th ree sam ples and with in the regulation limits for agricultural applications; the two commercial samples obtained by extraction from leonard ite show h igh quantities of iron , wh ich however is used as a soil improver in agriculture. Consequently it has been demonstrated that products of composition similar to that of the various different commercial products used in agriculture can be prepared from humic substances obtained by acid precipitation from concentrated percolate.
• the molecular weight distribution, Tab. 13, determined by gel permeation (LPLC), is similar for the two samples, with Sample HS6 showing a greater quantity of 1st and 3rd fraction, generally correlated with the degree of humic substance maturation and biological activity.
• Tab. 1 5 shows evaluations of biostimulant activity on 14 day maize seedlings
• the test which consists of a hydroponic cultivation of maize seedlings for 1 2 days with da ily replacement of the nutrient solution , fol lowed by a period of 48 hours in wh ich the seedlings are brought into contact with two concentrations (1 .0 ml and 0.5 ml per litre) of the two humic extract samples, showed that Sample HS6 gives a better and good growth of the seedling fresh weight.
• TAB.1 Percolate characteristics (Bellolampo, Sicily) as such (sample 1p) and concentrate sample 1pc) - Example 1 - TAB. 1 - (continued)
• TAB 3 - Humic Substance precipitation from percolate (A) - 37.45 wt% sulphuric acid quantity (d: 1 .28 Kg/dm 3 ) referred to 100mL of percolate as such. - mL H 2 SO 4 vs pH)
• TAB. 8 Precipitation HS from concentrated industrial percolate (B) - amount hydrochloric acid to 37.45% w / w (d: 1 ,186 Kg/dm3) referred to 100mL of concentrated percolate - (mL HCI vs pH)
• the humic extract HS6 presents una better division of the three fractions than the humic extract COM1 in that it shows a greater presence of 1st and 3rd fraction and a smaller presence of 2nd fraction.
• humic extract samples were compared, by bioassay, with increasing quantities of 3 indoleacetic acid and gibberellic acid (GA3) to determine, respectively, inhibition of radical development on watercress and stimulation of hypocotyl elongation on white Trieste chicory.
• GA3 gibberellic acid
• TAB 15 - Determination of biostimulant activity of (HS6) on maize plants compared with commercial product (COM1 ).
• the test consists of a hydroponic cultivation of maize seedlings for 12 days with daily replacement of the nutrient solution, followed by a period of 48 hours in which the seedlings are brought into contact with two concentrations (1 .0 ml and 0.5 ml per litre) of the different humic extracts.
• the determination showed that the humic extract sample HS6 gives an increase in the whole seedling fresh weight (about +15%) for both tested concentrations, with the most significant increases (+19%) in the hypogeous portion.
• the sample COM1 showed an averagely negative trend.

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