IL46344A - Process for removing ions from liquid containing at least one metal salt - Google Patents

Description

46344/2 t aa D*ai» nttsinV T» nn Process for removing ions from liquid containing at least one metal salt ROHM AND HAAS COMPANY C:- 44246 This invention concerns a process for removing ions from desalinating liquids containing metal salts. In the process thermally regenerable hybrid resins are used and these resins may be regenerated by elution with an aqueous liquid having a temperature greater than that of the treated liquid at the time of the absorption phase.

Desalination of waters containing metal salts by ion exchange is not novel. For ecological, reasons such desalination processes preferably use resins which are regenerated by other than chemical means. Frequently, however, processes that utilize these resins, such as for example thermally regenerable resins, exhibit low efficiencies caused by low thermal load capacity or high resin attrition rates. By thermal load capacity is meant the ability of a resin or resin system to absorb or elute an amount of metal salts at a specified pH, expressed in mille-equivalents of salt per milleliter of resin.

We have now found an attractive process for removing ions from liquids using resins which are thermally regenerable.

The" process is effective for removing salts of metals such as Na, Al, K, Mn, Ca, Zn, Mg, Fe and Cu in combination with such anions as Cl~, NOj, SO^ , HCO3 and C03 . It is therefore widely useful in the removal of ions from liquids. Nevertheless, without implying any limitation, for convenience we will describe the invention in terms of the desalination of brackish waters.

However obvious uses include the preparation of potable water, the treatment of surface or ground waters for industrial feed waters, home water conditioning and sugar -liquor purification.

The process of the invention is particularly useful for removing sodium chloride from liquids but it should be understood that the invention may be applied to the removal, of any metal salt from a liquid. It is however particularly useful in the removal of salts of monovalent metals. Preferred resins are those having a mixed crosslinking system such as DVB and diethylene-r glycoldivinylether as opposed to resins containing a single crosslinker such as DVB alone.

The process of the invention employs hybrid resins. Hybrid resins and methods for making them are described in our Israel Patent Specification No. 36,546.

In general, the hybrid resins useful in the practice of the invention may be prepared by filling a macroreticular copolymer, usually termed "host polymer" with a cross-linked copolymer of a different nature, termed a "guest polymer" or "filling polymer". This process results in the location of one type of polymer in the pores and another type of polymer in the framework of the hybrid intermediate polymer. In one embodiment the structure may be prepared by 1) stirring a macroreticular (MR) host polymer such as styrene-divinylbenzene (DVB) into a given quantity of water; 2) adding to the resulting mixture a different monomer mixture, for example, a methacrylate-benzoyl peroxide-DVB solution which causes the organic liquid to be taken up by the host copolymer by capillary action, thus filling the voids of the host copolymer and 3) . thermally polymerizing the added solution.

The resulting hybrid polymer will comprise two different types of copolymer occupying separate and discrete regions within the overall polymeric structure. This intermediate hybrid polymer may then be chloromethylated.

Basic aminolysis converts the chloromethyl. groups and hydrolyses the ester linkages. Subsequent neutralization provides a hybrid resin which has distinct regions of differing functionality.

Hybrid resins, are considerably different from so-called "snake cage resins" which contain closely associated acid and basic functionalities. "Snake-cage" resins have been used in the demineralization of sugar solutions and consist of amphoteric resins containing for example strong base groups such as quaternary ammonium groups or weak base group such as tertiary amine groups and nearby weak acid groups such as' carboxylic groups in an intimate association. They are also sometimes know as "ampholytes" and absorb salt which may subsequently be removed by elution with hot water. The ampholytes are prepared in general by impregnating an anion exchange resin with an acid monomer, which is then polymerized in situ to form long chains of linear polymer intertwined with anion exchange resin to form the so-called "snake cage" resin. However, because of the close proximity of the positively and negatively charged sites in such resins, there is a strong tendency towards self-neutralization of the ionic charges due to ion pair formation so that there are relatively few charged sites which are sufficiently fa apart for the absorption of salt to occur, resulting in a very low capacity of such resins. Furthermore, again because of the proximity of the exchange sites, it is necessary to have approximately equal parts of acid and basic sites, as a significant excess of one type of site will bring about repulsion of ions of the same charge entering the resin thus inhibiting the rate of salt uptake or elution. Hybrid resins avoid these disadvantages because of the greater distances between the different types of ionic functional groups after polymerization.

Another prior art process is commonly referred to as the mixed bed process. Mixed bed resin systems, as used, originally featuring resin beads having diameters ranging from 300 to 1200 Jm, have been considered for use in thermal regeneration desalination systems. The resins composed of beads having such particle sizes suffer, from a rate of salt uptake much top slow to allow these resins to perform economically. It was discovered that adequate resin utilization at acceptable flow rates could only occur if the resin beads were reduced in particle sizes to diameters of 10 to 20 im. The reduced particle size reduces the diffusion path for protons between the acid and base adsorption sites. Unfortunately the reduced particle size although providing good kinetics causes severe mechanical problems. Due to the nature of the fine particle sized resin, the mechanical difficulties inherent in the handling and retention of the resin within the equipment have effectively precluded their utility in large scale commercial processes. Such fine absorbent beds not only create pressure drops, are prone to clogging and fouling, but they are extremely difficult to backwash effectively owing to the ease with which the fine particles become entrained with the backwashing liquor. These disadvantages become particularly apparent in continuous ion exchange processes where the liquor and the adsorbents must be intimately contacted at one stage but must otherwise be handled separately.

According to this invention there is provided a process for removing ions from liquid containing at least one metal salt which comprises: a) contacting the liquid with thermally re- generable hybrid resin (as hereinafter defined) to absorb metal salt, and b) regenerating the hybrid resin by contact elution with an aqueous fluid at a temperature greater than that of the treated liquid at the time of its contact with the resin.

For the purposes of this specification and Claims the term "hybrid resin" means a crosslinked macroreticular host polymer, the pores of which contain a separately formed crosslinked filling polymer.

A. preferred embodiment of the process utilizes influent concentrations of impurities of less than 1000 ppm. However, the process will perform satisfactorily over a wide range of influent concentrations. Different hybrid resins have different pH criteria for optimum thermal load capacity. The optimum operational pH and thermal load capacity of a hybrid resin is influenced by the ratio of filling levels of host polymer versus guest polymer. This can be seen from data in tables given late in this Specification. The skilled practitioner can prepare those hybrid resins best suited to the pH of .the liquid to be treated. Although the hybrid resins when exhausted may be eluted or regenerated with aqueous solutions having a temperature exceeding the temperature of the adsorption, stage, preferred temperatures of the regeneration stage, range between 80 - ' 110° C. Typically useful regenerant solutions include saline solutions and, of course, deionized water.

As mentioned above, the hybrid copolymers useful in the process of the invention may be prepared by adding polymerizable monomer, crosslinking agent,-, and free radical initiator to a stirred mixture of macroreticular. host copolymer and water.

However, there are numerous other techniques that can be used to prepare the hybrid resins, which term, incidentally;, has been coined to distinguish this sort of polymer from the gel and macroreticular polymers of the prior art. The "hybrid" terminology indicates that the resins may have some of the characteristics and/or properties of both gel and macroreticular copolymers arid resins but, more importantly, they represent a class of materials having distinct properties of their own. One general approach for preparing these copolymers is to a least partially fill the pores of a macroreticular copolymer or resin with guest copolymer utilizing varying percentages of crosslinking agent and introducing such guest copolymer, or guest copolymer-forming components, in varying amounts. Alternatively, the hybrid copolymers can be prepared by filling the pores of a macroreticular copolymer with additional macroreticular copolymer in varying amounts and with varying crossiinker contents or percentages or made with different amounts of phase extender. Alternatively, in the case of anion exchange . resins, the crosslinkages may be introduced during chloro-methylation which is one of the steps in the introduction of anion exchange groups onto the polymer matrix.

. The base or host copolymer possesses, a special porous structure which is referred to herein as macroreticular. Macroreticular copolymers possess a network of microscopic channels extending through the mass and. while these microscopic channels are obviously very small, they are large in comparison with the pores in conventional homogenous cross-linked gels, pores of the latter type not being, visible in electron photomicrographs and, as is well known, not being true pores at all (vide Kunin, "Ion Exchange Resins" page 45, et seq. John. Wiley, & Sons, Inc. 1958). Typically, MR polymers have a surface area of at least 1 sq. meter per gram, and more generally at least- 5 sq. meters per gram and have pores larger than about 15 to 20 Λ0 Units. It is conventional to produce these MR polymers in bead form, usually in an overall particle size of about 10 to 900 microns.

Further information on the preparation and structure of macroreticular polymers, which are known materials, may be obtained by referring to British Patents 932,125 and 932,126 and U.S. Patent Nos. 3,275,548 and 3,357,158.

Usually similar types of monomeric materials are used in preparing the host, and the filling polymer, while the preparation process is varied to impart different characteristics, especially different porosity, to the two types of polymer. Preferably, the backbone of both types of polymer will be a crosslinked copolymer of ( 1) a polyunsaturated monomer, containing a plurality of non-conjugated groups , which acts as a cross- linking agent and (2) a monoethylenically unsaturated monomer, either aromatic or aliphatic. If desired one may use as host polymer a polymer based on vinyl benzyl chloride crosslinked with divi ylbenzene rather than the more commonly known styrene-divinylbenzene MR polymer.

A procedure to prepare such a resin is exemplified later, in Procedure V.

Suitable polyunsaturated cross-linking agents include divinylbenzene , divinyltoluenes , divinylnaphth-alenes , diallyl phthalate, ethylene glycol diacrylate, ethylene glycol dimethacrylate , trimethylolpropane tri-methacrylate, neopentyl glycol dimethacrylate, bis-phenol -A dimethacrylate, pentaerythritol tetra and trimethacrylates , divinylxylene , divinylethylbenzene , divinylsulfone , di-vinylketone, divinylsulfiie , allyl acrylate, diallyl maleate, diallyl fumarate, diallyl succinate, diallyl carbonate, diallyl malonate, diallyl oxalate, diallyl adipate, diallyl sebacate, divinyl sebacate, diallyl tartrate, diallyl silicate, triallyl tricarballylate, triallyl aconitate, triallyl citrate, triallyl phosphate, ,N ' -me hylenediacrylamide , ,N ' -methylene dimethacrylamide , ,N ' -ethylenediacrylamide , trivinylbenzene , trivinylnaph-thalene,. polyvinylanthracenes and the polyallyl and polyvinyl ethers of glycol glycerol, pentaerythritoi , resorcinol and the monothio or dithio derivatives of glycols.

Preferred cross-linking monomers for both the host polymer and the guest include polyvinyl aromatic hydrocarbons ,. such as divinylbenzene and trivinylbenzene, glycol dimethacrylates and polymethacrylates , such as ethylene glycol dimethacrylate , trimethylolpropane tri-methacrylate, and polyvinyl ethers of polyhydric alcohols, such as divinoxyethane and trivinoxypropane . The amount of crosslinking agent or monomer can be varied widely.

Suitable monoethylenically unsaturated monomers for both the host polymer and guest polymer include esters of acrylic acid, such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, tert-butyl acrylate , ethylhexyl acrylate, cyclohexyl acrylate, isobornyl acrylate, benzyl acrylate, phenyl acrylate, alkylphenyl acrylate, ethpxymethyl acrylate, ethoxyethyl acrylate, ethoxypropyl acrylate, propoxymethyl acrylate, propbxyethyl acrylate, propoxypropyl acrylate, ethoxyphenyl acrylate, ethoxybenzyl acrylate, ethoxy-cyclohexyl acrylate, the corresponding esters of meth-acrylic acid, styrene, _o-, m- and £-methyl styrenes, and 0-, m-, and p-ethyi styrenes, dimethyl itaconate, vinyl naphthalene, vinyl toluene and vinylnaphthalene. A class of monomers of particular interest consists of vinyl aromatic monomers such as styrene and the esters of acrylic and methacrylic acid with aliphatic alcohol.

The polymerization reaction is generally carried out in the presence of a catalyst. Suitable catalysts which provide free radicals to function as reaction initiators include benzoylperoxide , _t-butyl hydroperoxide, lauroyl peroxide, cumene hydroperoxide, tetralin peroxide, acetyl peroxide, caproyl peroxide, j:-butyl perbenzoate, _t-butyl diperphthalate, methyl ethyl ketone peroxide.

The amount of peroxide catalyst required is roughly; proportional to the concentration of the mixture of monomers. The usual range is 0.01% to 5% by weight of catalyst with reference to the weight of the monomer mixture. The optimum amount of catalyst is determined in large part by the nature of the particular monomers selected, including the nature of the impurities which may accompany the monomers.

Another suitable class of free-radical generating, compounds which can be used as catalysts are the azo catalysts, including for example, azodiisobutyronitrile , azodiisobuty amide , azobis (α,α-dimethylvaleronitrile ) , azobis (oc-methyl-butyronitrile) , dimethyl, diethyl, or dibutyl azobis (methyl-valerate ) . These and other similar azo compounds, which serve as free radical initiators, contain an -N= - group attached to aliphatic carbon atoms,, at least one of which is tertiary. An amount of 0.01% to 2% of the weight of monomer or monomers is usually sufficient.

In making the hybrid polymers a wide variety of polymerization conditions and processes well known in the art can be used. However, the preferred method is suspension polymerization in a liquid, such as water, which is not a solvent for the monomeric material. '■ This method produces the polymer directly in the form of small spheroids or beads, the size of which can be regulated and controlled. By adjustments in the composition of the suspending medium and in the rate of agitation during polymerization, the suspension polymerization process can be made to produce spheroids or beads of a wide range of effective particle sizes.

In preparing the host base macroreticular copolymer or resin, and likewise in preparing a macror-eticular guest polymer of different cross-linkage content, the polymerization reaction may be carried out in the presence of a precipitant which is a liquid (a) which acts as a solvent for the monomer mixture' and is chemically inert under the polymerization conditions and (b) which is present in such amount and which exerts so little solvating action on the product cross-linked copolymer that phase separation of the product copolymer takes place as evidenced by the fact that the product copolymer is no more than semi-transparent and is preferably opaque when associated with a liquid having a different refractive index. Such a process together with information regarding choice of precipitant liquids is discussed in detail in U.K. Patent Specification Number 932,126. It is also possible to use as solvent for the monomer mixture a liquid which swells the product copolymer provided that the cross-linker level is sufficiently high. Those of the hybrid ion-exchange resins useful in the process of the .present invention, in which the pores of the host polymer are filled with a lightly cross-linked guest gel polymer, do in fact combine the high capacity of the conventional gel resin with the stability of the MR resin.

Typically, the hybrid copolymer is prepared by. adding fresh monomer such as, for example, styrene, catalyst, and a suitable cross-linking agent such as divinylbenzene to a suspension of a MR copolymer and water. The monomer is adsorbed or imbibed into the pores of. the MR copolymer, and the imbibed monomer is polymerized within the MR copolymer beads by heating the mixture and thereafter ion exchange functional groups are introduced to the polymer complex thus formed. Not only do the resulting resins show a greater combination of capacity and stability than one obtains with a MR resin and a gel resin, but also there are significan improvements in leakage and pressure drop over the corresponding MR and gel type resins. The monomer which is to be sorbed or imbibed into the host copolymer, herein designated as the guest monomer merely for ease of reference, is deposited within the pores of the substrate, and no interaction with the substrate is sought although some interaction would not necessarily be harmful or undesirable. In, any event, the final ompositions are /' ■ ' still heterogeneous; Thus, while the possibility of some swelling of the host polymer cannot be excluded, no groups or treatments promoting grafting efficiency are generally provided or even deemed necessary. The hybrid resins may be considered heterogeneous products characterized by two. relatively independent phases which can cooperate in providing superior thermal capacity , and particle stability.

The relative amounts of guest polymer and MR host polymer can be varied oyer a wide range. It is desirable, however, to use at least 50 parts by weight of guest polymer per 100 parts by weight host polymer, with the maximum amount' being dictated by that amount which can be imbibed or retained in or on the host polymer structure. This maximum will generally be about 300 parts by weight of guest polymer per 100 parts by weight of host polymer, although higher amounts can also be used. Preferably, the amounts of guest polymer to MR host will be from 100 to 200 parts of guest copolymer per 100 parts of MR host polymer.

In the procedures which are set out below, parts and percentages are by weight, and all mesh measurements are U.S. Standard Sieve, unless otherwise stated. All chemicals used are of good commerical quality. In the case of divinylbenzene (DVB) a good commercial grade is used which contains about 56% active material, i.e., pure DVB, the balance being essentially all ethyl vinyl benzene. The copolymers are in bead form and are prepared by suspension or pearl polymerization technique Porosity is reported as per cent porosity or as the volume of pores per dry volume of resin, usually as milliliter per milliliter (ml. /ml.). Percent porosity can be obtained by multiplying this value by 100. All temperatures given in the examples are in °C. unless otherwise stated.

The quoted thermal load capacity evaluations are made using 15 ml., of wet resin packed in a .5" I.D. jacketed glass column. The loading temperature is maintained at room temperature (23 - 25°C.) while the regeneration temperature is maintained by feeding water to the jacketed column at 90 to 95°C. so that the water coming from the jacket was 80 to 85°C. The flow rate is maintained at 0.5 gal/minute/cu. ft. for both the loading and the regenerating portion of the cycle. The thermal load capacity is calculated in meq of salt per ml. of resin. Duplicating the experiments but varying the flow rates from 0.5 gal/min/cu. ft. to .2.0 gal/min cu. ft. shows that the thermal1- capacity was not affected by the flow rate.

An evaluation to determine the effect of varying the weak .acid to weak base ratio of the hybrid resins was conducted with the following results. Hybrid resin A is prepared according to the procedure of Process I (set out later) and resins B - J are analogous to resin A, differing only in amounts of guest polymer or cross-linker content thereof.

Table I Hybrid Resin Ratio Weak Acid Weak Base Thermal CEC/AEC Capacit Capacity. Capacity Capacity meq./q. meq./q. meq. /ml .

A 0.92 2.37 2.58 0.044 B 1.08 2.56 .2.36 0.088 C 1.21 ..3.18 2.63 0.071 D 2.32 4.57 1.97 . 0.078 F 4.10 5.37 .1.31 0.074 . An evaluation to determine the effects of percentage crosslinker in the guest polymer gave. the following results as shown in Table II.

Table II .

Thermal Hybrid Resin . % DVB Capacity meq. /ml.

G . 1 N 0.050 H 2 0.043 I 3 0.074 J ■ 4 · . 0.026 Although the process of the invention is best conducted with influent liquids having a pH ranging from 5 - 7, such a pH should not be considered a limiting factor. For example, pH's outside of this range may also desalinate liquids..

As is shown, the filling level of guest polymer liquid into the MR host polymer affects the capacity of the final resins and in general it should be understood that the higher the ratio of cation exchange capacity (CEC) to anion exchange capactiy (AEC) the more effective will be the performance at relatively low pH's. Similarly, a ratio of cation exchange to anion exchange capacity of 1 or lower will allow more effective desalination at relatively high pH's •Further illustration of t e relationship between thermal /load capacity and filling levels may be found in Table III.

The following procedures, illustrate four different preferred processes for preparing suitable hybrid resins.

Process V illustrates the preparation of a suitable vinyl- benzylchloride based hybrid resin.

Process I. - Synthesis of . Resin A A 3-necked round bottom flask equipped with stirrer, condenser and thermometer is- charged. with 600 g. of HjO and' 150 g. of macroreticular (HR) styrene - DVB copolymer (4% DVB) commercially available from Rohm and Haas Company as Amber- lite XE-305. To the stirred reaction mixture is then added over an 8 minute period, a solution containing 94.5 g. of methyl acrylate, 5.5 g. of 54.9% active DVB and 4 g. of benzoyl peroxide. The resultant mixture is stirred 30 minutes and then heated to 70° C. for 20 hours. After cooling and filtering the beads, the latter are washed 4 times with 500 cc of methanol and subsequently dried to yield 242.4 g. of white spherical hybrid beads. The dried beads are subsequently heated at 60°C. with 1250 cc of ethylene dichloride (EDO for 16 hours. The EDC is filtered off and the beads are washed once with 1 liter of EDC and twice with 500 cc of methanol.. After drying, the beads weigh 207.2 g. 50 g. of the EDC washed and dried resin from above is swelled with 120 cc of EDC and 94.2 g. of chloromethyl ether (CME) for 1 hour at room temperature in a 3-necked round bottom flask equipped with stirrer, thermometer, reflux HYBRID RESINS: CORRELATION OF FILLING LEVEL RATIO WITH THERMAL Resin Process Filling Ratio Thermal Load . Cation Weak T No. . of guest : host Salt Capacity Exchange Bas Procedure polyme meq/fal of resin Capacity Capac- itv . meq/g meq/g 1 IV 0.61 .012 2.58 2.8 2 IV 0.82 .023 2.77 2.83 : 3 I 0.92 .044 2.37 2.58 • 4 I 1.02 .052 3.69 2.10 (1) 5 II 1.29 .073 4.41 2.30. (11) 6 ' I 1.31 .065 4.70 1.88 7* I 1.54 .095 4.78 2.07 (111) 8 II 1.71 .100 (111) 9 II 1.71 .097 — — ' ■ 10 IV 1.82 .099 5.26 1.96 11 I 1.97 .070 6.11 1.45 12 IV 2.51 .019 6.38 0.78 (1) Extender at 40% by weight (II) Procedure of I including DEGDVE (III) Extender of 10% by weight • Resin 7 influent was tested with different influent concentrations and showed a 500 ppm influent resulted in a 6.6 ppm effluent; a 200 ppm influent resulted in a 19 ppm effluent and a 1200 ppm influent resulted in a 570 ppm effluent. condenser and drying tube. This slurry is then cooled to 0°C and a solution of 63.9 g. of Al Cl3 in.50.7 g. of CME is adde with agitation over a 2 hour period with the temperature maintained at 0°C. The resultant mixture is stirred at 0°C. for three hours and subsequently added to 300 ml of methanol at 5-10°C, slowly so the temperature of the methanol solution does not exceed 25°C. The methanol is siphoned from the beads and the beads washed three times with equal volumes of water. The beads are diluted with water, neutralized with 0.5 g. of and filtered to. yield 111 g. of wet beads (60% solids) containing 16.81% chlorine after drying.

These wet chloromethylated beads are diluted with water and heated to azeotrope off EDC. The beads aire filtered and diluted with 60 cc of water in a 500 ml 3-necked round bottom flask equipped with a stirrer, thermometer and dry ice condenser. To this stirred mixture is added 60 g. of 50% NaOH and 169 g. of 40% aqueous dimethylamine. The mixture is heated to reflux ( 56°G. ) over 1/2 hour and held at reflux for four hours.

The dry ice condenser is replaced with a distillation condenser and the excess dimethyl amine is stripped off until the temperature of the reaction mixture reaches 104°C. The subsequent mixture is refluxed for two hours and cooled. to room temperature. The resin is then washed with water until the pH of the effluent is less than 8.

The wet yield of beads is 131.6 g. (52-61% solids). A sample of the dried resin contains 1.7% CI and 4.6% Na and. an AEC. of 2.58 meq/g. and a CEC of 2.37 meq. /g.

■ ' Process TI.

This process is identical to process I above except that the organic phase is diluted with DIBK (di-isobutyl ketone) extender before adding the organic phase, the Amber-lite XE-305 and water slurry. The DIBK constitutes about 10% of the organic phase by weight. Only about .90% of the total monomer charge methyl acrylate (MA)-DVB - diethylene glycol divinyl ether (DEGDVE) is incorporated into the final dry product giving a net hybrid yield of about 92-95%.· The.

DIBK is . steam stripped from the batch prior to cooling and washing the product.

• The 92-95% yield is typical of lauryl peroxide catalyzed, polymerization. 98-100% yields are subsequently obtained with henzoyl peroxide as catalyst.

Process III .

In this process a 28% Triton X-100 in water solution is first prepared. Triton X-100 is a Rohm and Haas non-ionic surfactant. To this stirred solution is then added the. organic phase containing methyl acrylate, catalyst and crosslinking agents. After vigorous stirring to form a relatively stable- emulsion, dry Amberlite XE-305 is added and. stirred in the emulsion for about 30-60 minutes. At the end of this time, the agitation is stopped and the. excess emulsion filtered or siphoned from the beads. The beads are then suspended in salt solution and heated with stirring to 55-70° C. for 6-24 hours to polymerize the monomer mix incorporated into the beads. The batch is then heated to 95°C. for about two hours to ensure complete polymerization. The beads are subsequently cooled, filtered, washed, and dried to afford the final hybrid copolymer. The amount of emulsion incorporation into the beads is not reproducible from batch to batch, prior to removal of the excess emulsion Hence, the amount of monomer mix incorporated into the final copolymer bead varies widely batch to batch.

Process IV This process differs from Process III in that the excess emulsion is not filtered from the batch. Instead, saturated sodium chloride solution is added to the batch to break the original emulsion. The de-emulsified monomer outside the beads is then rapidly absorbed into the Amber-lite XE-305 beads. The resultant batch is either heated directly to polymerize the monomer or is just filtered to remove the salt solution and re-diluted with fresh salt solu tion prior to heating. Processing' is then continued as described for Process III. This process has the advantage over Process III in that all of the organic phase (monomer mix) intitially charged to the reactor to form the emulsion subsequently ends up incorporated into the Amberlite XE-305 beads and final hybrid copolymer.

Procedure V Synthesis of Resin based on . vinylbenzyl chloride (VBC) A VBC-60% DVB-40% copolymer is prepared using a. suspension polymerization technique and methyl isobutyl carbinol as phase extender. The copolymer is then filled with monomer mix using a process as follows.

Nineteen g. of Triton X-200 and 120 ml H20 is charged to a 2-liter reaction flask equipped with a mechanical stirrer, thermometer, reflux condenser, and a heating mantle, and is stirred vigorously for 15 minutes. Monomer mix consisting of 190.0 g. ethyl acrylate, 8.2 g. DVB (55.9%), 1.6 g. diethylene glycol vinyl ether (DEGDVE) and 4.0 g. AIBN, is then added and the mixture is stirred for 15 minutes. An additional 333.3 ml. of 1^0 is added and the mixture is stirred for .15 minutes.. The VBC copolymer is then added and the slurry stirred, for 1 hour. One hundred ml of saturated NaCl solution is then added over a 5 minute period, the mixture is stirred for 15 minutes and is then heated to 75° over 1 hour and is held at 75° for 20 hours. The reaction mixture is then heated to 95°, held at 95° for two hours, cooled and washed. The yield, based on dry resin, is 282 g.^ indicating 85% incorporation of monomer. The resin is then treated with -300 ml H20, 400 ml NaOH. (50%) -and 635 ml di-methylamine (DMA) (40%) and refluxed at 45° for. four hours. The excess DMA is then distilled off, the flask, is heated to 105° and held at 105° for two hours. The reaction mix-., ture is then cooled, and the resin washed until effluent i$ neutral. The resin is evaluated and has a thermal salt capacity of 56.7 mg/15 ml of resin at pH=5.0.

Procedure VI 1. . Preparation of Styrene/Divinyl Benzene (DVB) Hybrid Copolymer Containing Dimethyl Itaconate (DMI) The hybrid copolymer is prepared by the following procedure. Styrene/DVB ( 100 g . ) and 400 g. tap water were introduced into a 1 liter, 3-necked flask fitted with mechanical stirrer,, reflux condenser, inlet tube, thermometer, heating mantle, and thermowatch assembly.. To the flask was added a p emixed solution of 173.96 g. dimethyl itaconate (DMI), 7.62 g. DVB (53.9% assay), 1.31 g. diethylene glycol divinyl ether (DEGDVE), 20.27 g. diisobutyl ketone (DIBK), and 3.6 g. lauroyl peroxide over a period of 1/2 hour with stirring. The stirring was continued for an additional tl/2 hour followed by heating the mixture to 60°C for 20 hours. After azeotropic distillation of the DIBK, the copolymer was isolated, washed with water, and oven dried, yield was 243.6 g (86.2%). 2. Chloromethylation Procedure The hybrid copolymer was chloromethylated in a 2 liter, 3.necked flask equipped with mechanical stirrer, reflux condenser, thermometer, and external cooling bath.

The hybrid copolymer (143.6 g.), 999 ml ethylene dichloride (EDO, and 746 g. of chloromethyl ether ,(CME.) were stirred in the flask for 2 hours, cooled to 0-5°C, and 332 g. of AlCl^ added incrementally over a two hour period while maintaining the temperature at 0-10°C. Upon completion of the AiCl^ addition, the temperature was raised to 25°C and held for 3 hours. The reaction was quenched by pouring into 1 liter of. chilled methanol while maintaining the temperature below 35 °C. The mixture was stirred .15 minutes, stick filtered, and the resin washed with 1 liter of methanol. Removal of the methanol from the resin was followed by the addition of 1 liter of DI water and addition of 50% NaOH to make the solution basic. After heating to 100°C for 15-20 minutes, the solution was cooled and stick filtered. An analytical sample of the resin contained. 14.78% CI. 3. Aminolysis-Hydrolysis of the Chloromethylated Hybrid Copolymer , . ■ The entire chloromethylated hybrid copolymer sample was placed in a 2 liter, 3-necked flask fitted with mechanical stirrer, thermometer, dry ice condenser, and heating mantel. To the flask was added 120 g. cracked ice, 120 g. of 50% NaOH, and 338 g. of 40% dimethylamine (DMA). The mixture was stirred at ambient temperature for 1 hour, then heated to reflux for hours and finally to ~100°C for 2 hours to remove the excess DMA (dry ice condenser replaced with water cooled condenser for this last step). The product was isolated, washed with water, and stored. wet. Analysis gave 9.9 CI and 4.5% N. General properties of the resin were measured as 49.41% solids, 3.10 meq/g. total anion exchange capacity (TAEC), and 1.52 meq/g. cation exchange capacity (CEC). Thermal salt capacities (mg NaCl/15 cc. ) were measured at pH 6-8 using a 540 ppm NaCl solution. Measured values were 46.61 (pH 6), 77.81 (pH 7), and 43.95 (pH 8).

■ In the Examples, MIBC is methylisobutylcarbinol and ABN is azobisisobutyronitrile.

Some embodiments of the process of the invention will now be described, for the purposes of illustration only, in the following Examples: EXAMPLES .All' waters used in these Examples were prepared by dissolving the appropriate salts in high quality 1 meg ohm or better, deionized water. The. soft waters studied' are pure solutions of NaCl at various concentrations. The hard waters contained calcium, magnesium, sodium, chloride and sulfate. The. terms low and high TDS, soft and hard water refer to the United States classification of hard waters; C.N. Dafor and E.J. Becker, U.S. Geological Survey Water Supply Paper 1812.(1964).

The TDS measurements were made by conductiv ty: C.J. Lin.d, U.S. Geological Survey Professional Paper 7000 (1970) pp. 27-2-280. The calcium- was> measured using a Corning Calcium Analyzer Model 7f940. All concentrations are '.expressed as ppm as CaCO^. The data plotted in. the Drawings show egeneration ciuality, product quality, average product quality, and, in the case of bare waters, calcium.

The values for the regeneration are read off the left side of the graphs. The values are instantaneous readings' .as measured by conductivity. The values' for product quality are read on the right side of the graphs^ The product plots are instantaneous readings as measured by conductivity.

The average product quality plot is the numerical average of the instantaneous leakage to specific points in the run. The calcium data presented represent instantaneous leakage as determined by the Corning .Calcium Analyzer.

The regeneration shown is the regeneration immediately preceding the load cycle plotted. The data presented, was obtained, after bed equilibrium , had been established under the conditions of the run.

These 15 Examples provide a cross section of the waters and operating parameters that have been studied in the laboratory.

The resin used was a thermally regenerable hybrid resin (as hereinbefore defined).

In the accompanying drawings: Figure 1 relates to the desalination of high TDS soft water using countercurrent column operation. Line A relates to regenerant, line. B. to product and line C to average product quality. .

Figure 2 relates to the desalination of high TDS soft water using co-current column operation. Line A relates' to regenerant, line.B to product and line C to average product quality.

Figure 3 relates to the desalination of high TDS soft water using a moderate TDS regenerant stream. Line A relates to regenerant, line B to product and line C to average product quality.

Figure 4 relates to desalination of brackish water. Line A relates to. regenerant, line B to product and line C to average product quality.

Figure 5 relates to desalination of high hardness high TDS water. .Line A relates to product and :,line B.to average product quality.

Figure 6 relates. to desalination of very hard water with ■4 moderately high TDS. Line A relates to regenerant. TDS and line B to regenerant calcium. Line C relates to product TDS, line D to average product quality and line E to produc calcium.

Figure 7 relates to desalination of very. hard water with high TDS. Lines A and B relate to regenerant TDS and calcium respectively and lines C, D and E to product TDS , product calcium and average product quality respectively.

Figure 8 relates to desalination of very hard water with moderate TDS. Lines A and B relate to the regeneration, Line A giving total ppm hardness as CaCO^ and line B to Ca++.

Lines'C, D and E relate to leakage, line C to total, line D + + to average quality, and line E to Ca respectively.

Figure 9 relates to desalination of brackish water. containing •1198 ppm NaCl as CaCO^. Line A relates to regenerant, line B to product and line C to average product quality.

Figure 10 relates to desalination of low TDS water (8.6 ppm as CaCO^). Line A relates to regenerant, line B to product and line C to average product quality.

Figure 11 relates to desalination of brackish water (854 ppm, NaCl as CaCO^).. Line A relates to the regeneration and lines B and C to product and average product-quality respectively.

Further details regarding these examples are given in the summary of operational conditions given in the follov-dn Table IV.

TABLE IV Floy/ Rate 2 gals./cu. ft./min., Resin and Influent Solut Total Dissolved Regenerant • Influent Solids ppm ppm as Mode of Tem Fiqure pom as CaCO. as CaCO- CaC0„ Operation 415 ppm NaCl 415 ppm D.I. Water Counter- current 2 448 ppm NaCl 448 ppm D.I. Water Cocurrent 3 428 ppm NaCl 428 ppm 170 ppm- Counter- NaCl current 996 ppm NaCl 99.6 ppm D.I. Water Counter- current 342 ppm Na+ 486 ppm D.I. Water Counter- 94 ppm Ca++ ' current 50 ppm Mg+÷ 394 ppm CI 92 ppm S .O 4. 29 ppm a+ 253 ppm D.I.. Water Counter- 143 ppm Ca++ current 81 ppm Mg++ 215 ppm CI . 38 ppm so4" Figure 1198 pom NaCl 1198 ppm 616 ppm Counter- NaCl cu rent 10 8.6 ppm NaCl 8.6 ppm D.I. Water Cocurrent 11 854 pp:m MaCl 854 ppm 427 ppm NaCl Cocurrent * The data was. obtained after equilibrium was established with a 12/4 volume load cycle and a 4 bed volume regeneration cycle. In a numbe beyond the tv/elth bed volume in order . to better the shape and direct

Claims (14)

■ ;. · .. -32- i ' WHA ' WE CLAIM IS:

1.. A process for removing, ions from liquid containing at least one metal salt which comprises: a) contacting the liquid with thermally regenerable hybrid resin (as hereinbefore defined) to absorb metal salt, and b) regenerating the hybrid resin by contact elution with an aqueous fluid at a temperature greater than that of the treated liquid at the time of its contact with the resin.

2. A process as claimed in Claim 1 wherein the hybrid resin comprises host polymer having weak base functionality and guest polymer having weak acid functionality. '

3. A process as claimed in Claim 1 or 2 wherein the. guest polymer. is a gel polymer.

4. A process as claimed in any preceding Claim wherein the amount of guest polymer is from 50 to 300 parts, by weight per 100 parts by weight of host polymer.

5. A process as claimed in any preceding Claim wherein the host polymer matrix comprises units from vinyl benzyl chloride monomer.

6. A process as claimed in any preceding Claim wherein the guest polymer matrix comprises units of aliphatic monomer.

7. A process as claimed in any preceding Claim wherein the guest polymer matrix comprises units from dimethyl ita-conate. .

8.. A process as claimed in any one of Claims 1 to wherein the hybrid resin is derived from a styrene/divinyl-benzene macroreticular host copolymer containing separately polymerized methacrylate/divinylbenzene guest polymer.

9.. A process as claimed, in any one ,of Claims 1 to wherein the hybrid resin is derived from a styrene/divinyl-benzene macroreticular host copolymer containing separately polymerized dimethyl itaconate/divinylbenzene guest polymer.

10. A process as claimed in Claim 9 wherein the dimethyl itaconate/divinylbenzene guest polymer additionally contains units from diethylerie glycol divinyl ether.

11. A process as claimed in any preceding Claim wherein the liquid to be treated contains at least one' salt of a monovalent metal.

12. A process as claimed in any preceding Claim wherein the liquid to be treated contains sodium chloride.

13. A process as claimed in any preceding Claim wherein the aqueous regenerating fluid is deionized water or saline solution.

14. .A process as claimed. in any preceding .Claim wherein' the liquid to be treated is industrial feed water, domestic water or brackish water. For Jhe //Applicants DR. RElrfi LD/COHN AMD PARTNERS