CA2019461A1 - Method and device for purifying water - Google Patents

Abstract

Abstract of the Disclosure A method is provided herein for removing heavy metals and negatively-charged materials from water.
The method includes contacting the water with an adsorbent cloth or fabric at least part of which is cellulosic, which has been pretreated with an alka-li, which was then preferably heated mildly until it was dry, followed by washing, upon which high mole-cular weight polyethyleneimine has been adsorbed and fixed thereon with a cross-linking agent. Examples of suitable such cross-linking agents include bifunctional or multifunctional epoxy cross-linking agents, e.g., glutaraidehyde, epichlorohydrin, 1,4-butandioldiglycidyl ether, 1,2-ethanedioldiglycidyl ether, 1,3-diglycidylglycerol, triglycidylglycerol, pentaerythritol, tetraglycidyl ether, etc.

Description

~ ~3 s . ., This lnventlon relates to the purification of water which has been polluted by heavy metals. More particularly it relates to the production of a device for the purificatlon of such water, and io the device so produced.
Pollution of water by heavy metals has become a more serious concern because of the toxicity to aquatic lives and, most importantly, to humans who consume the water. Heavy me-tals are generally no-t metabolized and are not eliminated from the body, and hence they bioaccumulate and eventually inter-fere with normal physiological functions by combin-ing with reactive groups. Toxic metal ions (barium, cadmium, chromium, cobalt, copper, lead, mercury, nickel, tin and zinc) are commonly found in efflu-ents from chemical, metal and mining industries.
Iron, though nontoxic, supports growth of iron bac-teria, and iron and manganese impart foul taste and colour to water.
Increasing knowledge that even trace contamination of heavy metals seriously endanger public health has led to demands for more stringent legislation on the qualities of waste and potable waters, anci hence improved technologies are desired.
Precipita-tion treatment is a widely used method for removing heavy metals from water. Most metals are precipi-tated in water as hydroxides. However, since such precipi-tation depends on the solubili-ty of the metal hydroxide, the concentration of the metal remaining in the effluen-t is, in general, relatively high. The effectiveness of thls process is also affected by the na-ture and concentration of precipitation chemical and coagulant aids, and pH.
Furthermore, it is not particularly sufficient for the removal of mercury whose zero discharge is now demanded.

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Ion exchange processes are very effective in removing heavy metals so that metal concentrations in the effluent can be reduced -to 0.1-0.01 mg/l.
The processes are easily appllcable even to the cases where waste water volumes and/or metal ion concentrations frequently fluctuate. Ion excharlge resins are usually xegenerated for repeated use, and metals are removed in a small volume of elution which can be treated by precipitation or other metal recovery processes. However, ion exchange by -the resin is relatively unspecific. Thus if heavy m~als exist in a high concentration solutiGn along with other dissolved common ions (e.g., Na, Ca), the resin will not selectively remove the heavy metals desired and its exchange capacity will be rapidly reduced.
Heavy metal removal by chelating resins is far more effective as the process can achieve 0.01 -0.0005 mg/l of heavy metal concentrations in treated water. Selectivity of the resins for rernoval of specific ions is very high. However, some of metal ions specifically adsorbed on the resin are not readily eluted, which accorrlingly requlres a large volume of elution; otherwise they are not desorbed at all. Hence the chelating reslns are being used for water of low metal concentration, or at a final stage of water purification.
These resins, especially chelating resins are thus suitable for high purificatlon of water, but their costs are still hiyh. Development of inexpensive ion exchanger or chelating ma-terials are thus com-mercially desired. in particular, inexpenslve (and thus disposable) chelating support is desirable for a heavy metal removal device for domestic use, because regeneration procedure cannot be readily practised at home. Today, many municipal water 7_ plants do not perform special treatment for removing heavy metals excep-t the precipitation process, and many people still rely on untreated ground water and surface water which could be contaminated with heavy metals. Many commercialized water purification devices for domestic use are composed of activa-ted charcoal which is effective for the capture of toxic organic chemicals but lS not suitable for the remov-al of heavy metals.
Another serious concern with respect to potable water is pollution by pathogenic bacteria, viruses and parasites. Today, in many parts of the worid, water-borne diseases still remain a major menace to public health. According to some estimates, diar-rhea, which may be caused by bacterial, viral or parasitic infects, is responsible for six million deaths per year in the world. It is clear that the pollution of water with human wastes is a major potential source of serious diseases. This problem is not limited to the countries which have not yet established systems for the sanitary disposal of wastes. People in developed countries are also threatened to the hazards. Increasir-g demands on the water resources necessitate re-use of surface waters. Untreated or partially treated waste waters containing feces of an infected population are dis-charged into potential water supplies. Runoff from urban and agricultural areas into surface waters also introduce pathogens into water supplies. Com-monly, one municipality takes water for the water supply system from a water source immediate down stream from another municipality which drains its waste water into that water source.
Among the pathogenic organisms, the importance of viruses as agents of disease is well ~nown. Medical treatments, e.g., using antibiotics, have been developed for the cure of diseases caused by bac-teria, but no proper therapeutic treatment other than administration of vaccines is available against the diseases caused by viruses. Chlorine and other related chemicals are widely applied fo~ water dis-infection, but this process is not always adequate against viruses, Enteroviruses, reoviruses and ade-noviruses are very resistant to chlorine. Further-more, treatment of water with halogen has been known to form trihalomethanes and some carcinogens.
Consequently, the physical removal of bacteria and viruses by adsorption to solid surfaces is consid-ered to be a desirable alternative method. Inex-pensive and safely disposable adsorbents for path-ogenic agents in water should be useful in the places where adequate disinfection systems are not available, and should be desirable for domestic use.
Consequently, procedures and devices have been pro-posed in the patent and other literature to attempt to solve such problems.
Canadian Patent No. 1,085,388, issued September 9, 1980 to E. J. Haase, et al, related to a process for purifying industrial effluents, especially for decolorising effluents which are obtained in the text1le, paper and leather industries and from the manufacture of dyestuffs and brighteners, such as, for example, filtrates, residual liquors, rinsing water an washing water. The patentees taught that a rapid and adequate purification of industrial efflu-ents were achieved when these effluents were brought into contact with certain specifically-defined, cationically-modified cellulose materials.
~anadian Patent No. 1,169,735, issued June 26, 1984 to S. E. Jorgensen, provided a process for the production of an anion exchanger which was particu-larly suitable for the treatment of waste water.

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The patentee taught that the anion exchanger was a cellulose or a cellulose derivative which had been treated with polyethyleneimine in an aqueous reac-tion medium at a pH-value of 2-~, and the ion exchanger was recovered from the reaction mixture.
The patentee further taught that the starting mater-ial could advantageously be produced by first treat-ing comminuted bark with an alkali hydroxide solu-tion, e.g., sodium hydroxide solution, then washing with water, to a pH-value of 9 or below, thereafter treating the bark with sulphuric acid and finally washing with water to a pH-value above 4.
Canadian Patent No. 1,211,338, issued September 16, 1986 to I. W. Devoe, et al, provided a method of removing one or more metals excluding Fe3', Th4r and U22 from solution by contacting the solution with particularly defined insoluble composition.
U.S. Patent No. 3,979,285, patented September 7, 1976 to H. Wegmuller, et al, provided a process for purifying industrial effluents which comprised bringing the effluents into contact with a cellu-losic adsorbent which was pretreated with the poly-amidopolyamines condensation product of a polymeric fatty acid and a polyamine, to remove such sub-stances.
U.S. Patents No.s 4,025,428, patented May 24, 1977 to H. Wegmuller, et al; 4,097,376, patented June 27, 1978 by H. Wegmuller, et al; and 4,178,438, patented December 11, 1979 to J. Haase, et al, each provided a process for the purification of industrial efflu-ents, wherein the effluents were brought into con-tact with a specifically defined, cationically-modi-fied, cellulose-containing absorbent material.
U.S. Patent No. 4,525,456, patented June 25, 1989 by R. P. Rohrbach, provided a support matrix which immobilized enzymes by ion exchange forces, com-2 ~ r.

prising a core support on which was deposited a functionalized polyethyleneimine insoluble in water.
U.S. Patent No. 4,577,013, patented March 18, 1986 by J. Merz, et al, provided a specifically-defined ionically-modified cellulose materials which was suitable for being used as the stationary phase in processes for separating mixtures of ionically-charged components by chromatography.
B. Volesky, in U.S. Patent No. 4,320,093, provided biosorbents for the uptake of metals, in at least four applications: extraction and metal concentra-tion from ore-processing solutions; decontamination of mining wastewaters; extraction of valuable and/or strategic elements from sea water; and decontamina-tion of nuclear reactor waste solutions. These bio-sorbents include algal biosorbents for use in the concentration and recovery of gold and platinum.
Cellulose fiber and its derivatives are used as solid supports for purification and immobilization of biomaterials. However, fiber forms are readily compressible so that a column packed with these materials cannot be operated with a fast flow rate.
In contrast, cloth forms of the fiber are already compressed into such regular, compact and open structure that provide fast flow characters. Vari-ous types of ion exchangers and hydrophobic deri-vatives of cotton cloth have been proposed which can adsorb enzymes in active forms. Among them, poly-ethyleneimine-coated cloth has also been prepared through soaking cotton cloth in a diluted polyethy-leneimine solution. Although this cloth can be used for immobilization of enzymes, its capacities for heavy metal uptakes are too low to use it for water treatment.
Conventional polyethyleneimine is a highly bran-ched water-soluble cationic polymer, containing 2 ~ h ~

approximately 30% primary, 40% secondary and 30%
tertiary amine groups. The polyethyleneimine mole-cule, which takes a compact spherical form in water with a high density of primary amine on its surface, is strongly attracted to negatively charged colloids and solid surfaces, and hence one of the major tech-nical applications of polyethyleneimine is as a flocculant for waste water treatment. Since high molecular polyethyleneimine is safe and approved by the ~.S. Environmental Protection Agency, it is also used for clarification of municipal drinking water.
Furthermore, because amine groups numerousl-y con-tained in the polyethyleneimine act as electron donors to heavy metals, polyethyleneimine is an effective chelating polymer, as well as a weak anion exchanger. Thus, insolubilized polyethyleneimine in water should function as an adsorbent for materials containing negative charges (proteins, bacteria, viruses, humidic acids and colloids, e.g., clay), and heavy metals.
Water~insolubilization of polyethyleneimine to prepare anion exchange and/or chelating resins has been proposed heretofore using the method of cross-linking with various bifunctional reagents, e.g., epichlorohydrin, allyl chloride, ethylene dibromide, glutaraldehyde, toluene diisocyanate, etc. However, these gels are, in general, mechanically weak for a practical column process. On the other hand, mecha-nically strong anion exchange and/or chelating resins containing polyamine groups have been deve-loped and commercialized. One of them is, for example, a styrene-divinylbenzene copolymer modified with low molecular polyethylene-polyamine after chloromethylation. Their preparations are compli-cated and thus costly.

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An object of one aspect of the present invention is to provide an adsorbent which has high capability for chelating heavy metals and for adsorbing nega-tively-charged materials from water.
An object of another aspect of the present inven-tion is to provide a process for preparing an adsor-bent which has high capability for chelating heavy metals and for adsorbing negatively-charged mater-ials from water.
An object of yet another aspect of the present invention is to provide a method for removing heavy metals and negatively charged ions from water.
By one broad aspect of this invention, an adsor-bent cloth or fabric is provided for adsorbing heavy metals and negatively-charged materials, the cloth comprising a cloth or fabric substrate, at least part of which is cellulosic, which has been pre-treated with an alkali, followed by washing, upon which high molecular weight polyethyleneimine has been adsorbed and fixed thereon with a cross-linking agent.
The fabric upon which such high molecular weight polyethyleneimine has been adsorbed is preferahly heated mildly until it is dry prior to having the polyethyleneimine adsorbed and fi~ed thereon with the cross-linking agent.
The cloth or fabric preferably comprises a woven or a non-woven rayon fabric, or a woven or a non-woven rayonipolyester fabric or a woven or a non-woven woodpulp/polyester fabric, or a woven or non-woven cotton cloth or a woven or non-woven cotton/-polyester cloth or cellulosic paper; the fabric being either in its open apertured style or in ]ts highly absorbent, open-apertured style.
The cross-linking agent preferably comprises glutaraldehyde, epichlorohydrin, 1,4-butandioldi-2~1946~

glycidyl ether, 1,2-ethanedioldiglycidyl ether, 1,3-diglycidylglycerol, triglycidylglycerol, pentaery-thritol, tetraglycidyl ether, etc.
By another aspect of this invention, a process is provided for preparing an adsorbent cloth or fabric which comprises: pretreating a cloth or fabric sub-strate at least part of which is cellulosic with an alkali; washing the prëtreated substrate with water;
adsorbing high molecular weight polyethyleneimine therein; and cross-linking the adsorbed polyethyl-eneimine on said substrate with a cross-linking agent.
Such process preferably includes the step of heating the fabric which has been adsorbed mildly until it is dry prior to having the polyethylene-imine adsorbed and fixed thereon with the cross-linking agent.
The process of treating the substrate preferably comprises: pretreating a cloth or fabric substrate at least part of which is cellulosic with an alkali;
washing the pretreated substrate with water; adsorb-ing high molecular weight polyethyleneimine therein;
and cross-linking the polyethyleneimine on the sub-strate with a cross-linking agent.
The alkaline solutions that penetrate and swell the cellulose fiber include inorganic bases, e.g., LiOH, NaOH and KOH, and organic bases, e.g., alkyl-ammonium bases. However, 10-40% NaOH solutions known as "mercerization" solutions are generally used, for alkali-cellulose preparation. Accord-ingly, while the above-noted alkalis are applicable for the present invention, NaOH is preferable.
Wide range of NaOH concentration (e.g., 5 - 40%) can be applied according to circumstances. For certain preferred substrates soaking, in 6 - 12%
aqueous NaOH solution at room temperature for 10 ~ 3 - ln -minutes is recommendable. Thus, the alkaline solu-tion preferably comprises an aqueous solution of NaOH, e.g., having a concentration of 10% ~ 5~ by weight.
The water washing is preferably carried out untii the substrate has a pH of 7.
The amount of polyethyleneimine preferably adsorbed in the substrate is up to the maximum stoichiometric permeable amount, the process of absorbing the high molecular weight polyethylene-imine is carried out and until a maximum of the stoichiometric amount of said polyethyleneimine is adsorbed thereon. Preferably, the polyethyleneimine has a molecular weight of 60,000 + 20,000.
The temperature of the heating preferably ranges from 40 to 60C, and the preferable heating time is longer than 8 hours.
The cross-linking agent within the ambit of those previously described preferably comprises glutaral-dehyde, epichlorohydrin or 1,4-butanedioldiglycidyl ether.
By still another aspect of this invention, a method is provided for adsorbing heavy metals and negatively-charged materials which are present in water comprising contacting the water with a cloth or fabric suhstrate, at least part of which is cellulosic, which has been pretreated with an alkali, followed by washing, upon which high molecu-lar weight polyethyleneimine has been adsorbed and fixed therein with a cross-linking agent.
The contacting of the water with the cloth is pre-ferably achieved by passing the water through a column packed with the adsorbent cloth.
In other words, by the present invention simple and economic processes for the preparation of poly-etnyleneimine-coated cloths have been provided, the 2 ~

cloths having higher capabilities for chelating heavy metal ions as well as for adsorbing negatively charged material, e.g., proteins and bacteria. It has thus been found that alkali pretreatment fol-lowed by washing with water allowed cloths, at least part of which were cellulosic, e.g., rayon cloth, to adsorb a large amount of high molecular weight poly-ethyleneimine from its concentrated solution. Fol-lowing this, the cloth was dried to strengthen the holding of the polyethyleneimine there-to.
Although such cloth exhibits the significant cap-abilities of binding proteins and chelatiny heavy metal ions, the polyethyleneimine which is fixed on the cloth is gradually released in water, especially in the aqueous solutions of chelatable metals. In order to fix the polyethyleneimine stably on the cloth, the process includes cross-linking adsorbed polyethyleneimine molecules with e.g., glutaralde-hyde, epichlorohydrin or 1,4-butandioldiglycidyl ether (BDGE). These regents are inexpensive and relatively safe and can be easily handled.
The substrate at least part of which is cellu-losic, may be a non-woven fabric, i.e., a non-woven rayon fabric, a non-woven rayon/polyester fabric, or a non-woven woodpulp, polyester blend. Such fabric may be either in its open apertured flat-type form or in its highly absorbent, open-apertured form.
It has been found that such fabrics produce suit-able substrates for the present adsorbent. Such fabrics are commercially available, under the Trade-mar~ SONTARA, e.g., rayon/polyester non-woven fabric blends may be used. SONTARA is the registered trade-mark of DuPont for its spin-laced fabrics.
SONTARA is a bul~y, soft, strong, conformable, lightweight sheet made of hydraulically interlaced fibers with no chemical or thermal bonding. These , @, i~; 3 substrates are free of chemical additives (e.g., resins), binder and finish (which would interfere with modiication); are soft, pliable and low lint-ing; and have nonravelling edges and good absor-bency.
Some typical properties of SONTARA are shown in the following table:
TYPICAL PHYSICAL PROPERTIES OF SONTARA
(English Units) UNIT THICKNESSSHEET GRAETRAPEZOID MULLENFRAZIER AIRROLL SIZE
WEIGHT TENSILE TEAR BURSTPERMEAEILITY(7~' ID CORE) (ozlyd ') (mils) (Ibs) (Ibs) (Psl) (CFM/II~ in. Iin.
MD XD MD XD ~? 0.5 ' H20) o.o, yds.
Style 100% Polyester 8000 1.2 14 23 14 6 5 40 500 44 4600 8001 1.0 11 17 8 7 3 Z3 600 44 5000 8010-- 1.3 18 25 14 7 5 33 750 44 4500 8100 4.0 40 70 45 35 40 120 215 44 1700 8103 2.0 22 40 22 14 8 50 290 44 3500 8122'' 2.4 27 45 25 15 7 57 320 44 2500 8125'- 1.8 17 31 16 11 5 44 420 44 4000 70130 Rayonl Polycsler F~lends 6407~ l 516 11 B 5 7 20 780 44 2600 8423 2.3 26 13 15 4 5 24 255 4~1 2600 55/45 Woodpulp/
Polyester Blend 81~01 2.014 35 17 8 6 35 85 44 4000 8B08 2.0 14 35 17 8 6 35 B5 44 4000 ASTM Dl117D1117 D1117 Dl117 D1117 D1117 Tes~ Melhod Sec. 17 Sec. 19 Sec. 7Sec. 14 Sec. 8 Sec. 6 In the accompanying drawings, Figure 1 is a graph showing the effect of NaOH
concentration used in the pretreatment of rayon cloth on the capacity of polyethyleneimine-treated cloth to adsorb BSA with BSA adsorption (in mg BSA/g cloth~ as ordinate and NaOH concentration (in ~ by weight) as abscissa;
Figure 2 is a graph showing the BSA adsorption to polyethyleneimine-treated with BSA adsorption (in mg 2 ~

BSA/g cloth) as ordinate and heatlng period (in hours) as abscissa;
Figure 3 is a graph showing the BSA adsorption to polyethyleneimine-coated SONTARA 8423 (uncross-linked), with BSA adsorption ~in mg BSA/g cloth) as ordinate and number of adsorption cycles as abscissa;
Figure 4 is a graph showing the effect of repeated use on Cu uptake by polyethyleneimine-coated SONTARA
8423 (uncrosslinked), with Cu uptake ~in mg/g cloth) as ordinate and number of adsorption cycles as abscissa;
Figure 5 is a graph showing repeated Cu adsorption by glutaraldehyde-crosslinked polyethyleneimine-SONTARA 8423 with Cu uptake ~in mg/g cloth) as ordi-nate and number of adsorption cycles as abscissa;
Figure 6 is a graph showing the effect of time of contact with Cu solution on Cu laptake by glutaral-dehyde-crosslinked polyethyleneimine-SONTARA 8423, with Cu uptake (in mg/g cloth) as ordinate and time (in hours) as abscissa;
Figure 7 is a graph of the BSA adsorption to poly-ethyleneimine-SONTARA 8423 crosslinked in various concentrations of glutaraldehyde, with BSA adsorp-tion (in mg BSA/g cloth) as ordina-te and concen-tration of glutaraldehyde (in % by weight) as abscissa;
Figure 8 is a graph of the Cu ion uptake by epi-chlorohydrin crosslinked polyethyleneimine-SONTARA
8423 with Cu uptake (in mg/g cloth) as ordinate and number of adsorption cycles as abscissa;
Figure 9 is a graph of the Cu ion uptake by poly-ethyleneimine-SONTARA 8~23 crosslinked with BDGE
with Cu uptake (in mg/g cloth) as ordinate and num-ber of adsorption cycles as abscissa;

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Figure 10 is a graph of the effect of higher BDGE
concentration and higher temperature on Cu ion uptake by polyethyleneimine-SONTARA 8423 with Cu uptake (in mg/g cloth~ as ordinate and number of adsorption cycles as abscissa;
Figure 11 is a graph of the kinetics of Cu uptakes by polyethyleneimine-SONTARA 8423 crosslinked with BDGE with Cu uptake (in mg/g cloth) as ordinate and time (in hours) as abscissa; and Figure 12 is a graph of the removal of E. coli from water by a fixed bed of polyethyleneimine-SONTARA 8423 crosslinked with 1% BDGE at room tem-perature, with optical density of effluent as ordi-nate and quantity of effluent (in ml) as abscissa.
Although polyethyleneimine has been shown to bind strongly to cellulose, the mechanism of such stable binding has not yet been elucidated. It has been speculated that the carboxyl group in cellulose may contribute to the ionic interaction between these macromolecules. However, it is believed that the introduction of carboxyl groups by carboxymethyla-tion of the cellulose hydroxyl groups does not greatly increase stable binding of polyethyleneimine to cellulose. It is not desired to be bound by any specific theoretical mechanism for such binding.
However, there may be other possible mechanisms, e.g., hydrogen bonding interaction, which may be effective for interaction between cellulose and polyethyleneimine. Since cellulose is rich in hydroxyl groups and polyethyleneimine is rich in amino groups, it is possible that hydrogen bonding may play a part in the interaction between them.
The crystalline structure of cellulose is stabilized by extensive interchain hydrogen bondings which can only partly be disrupted by strong alkali. In con-trast, rayon is regenerated cellulose whose hydrogen 2 ~

bondings could be more readily disrupted by the alkali than native cellulose (e.g., cotton). Alkali treatment should then increase the capacity of rayon to form hydrogen bonding with polyethylenelmine. It is also believed that the hydrogen bonding between cellulose and polyethyleneimine would increase as activity of water which hydrates the macromolecules is reduced by drying.
The following are examples of various aspects of this invention.
1. Preparation of PEI-Coated Rayon Cloth 1-1. Adsorption of Hiqh Molecular PEI ~nto Rayon/Polyester Cloth.
A 2 x 2 cm square of nonwoven rayon-polyester blended cloth ISONTARA 8407 rayon/polyester; 70/30, Du Pont, 50 g/m , apertured type or SONTARA 8423, 80 g/m2, flat type,) was soaked in 10 % by weight NaOH
at room temperature for 10 minutes, thoroughly washed with water, filtered on a glass-sintered fil-ter and blotted with paper. Polyethyleneimine (COR-CAT P-600T~, average molecular weight of approx.
60,000, Virginia Chemicals) was diluted to 11% by weight with water. 0.2 ml of this solution was added to the cloth segment placed in a glass vial which was then heated at 50C overnight on a block heater. The dried segment was washed with water extensively and filtered. If not further modified, it was rinsed with 0.5 N HCl and 0.5 N NaOH for 3n minutes each, and washed with water thoroughly on a glass filter.
1-2. Crosslinkinq of PEI on Cloth.
One segment (2x2 cm) of cloth treated with poly-ethyleneimine was soaked in 2 ml of aqueous 0.05-0.4% by weight glutaraldehyde solution at room tem-perature for 2 hours with occasional shaking, and then washed with water thoroughly.

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For crosslinking with epoxy reagents, a polyethy-leneimine-adsorbed cloth segment was placed in meth-5 anol for 10 minutes, filtered and soaked in 2 rnl of 0.5-3% by weight epichlorohydrin or BDGE in methanol at room temperature or 50C for 3 hours with occa-sional shaking. The segment was washed with meth-anol and water extensively.
All segments prepared above were soaked in 0.5 N
HCl and 0.5 N NaOH for at least 30 minutes each, and then washed with water.
2. Adsorption of BSA and Hemoglobin on PEI-Cloth One ml of 5% bovine serum albumin (BSA3 or bovine hemoglobin (Hb) was added to a 2 cm square segment of PEI-treated cloth of an aspect of this invention prepared as above described at room temperature for 1 hour, followed by washing with water on a filter.
To desorb ionically bound proteins, the cloth seg-ment was placed in 5 ml of l M NaCl solution at room temperature for l hour with occasional vortexing, and the extract was assayed for BSA or Hb. Since some Hb still remained bound to the cloth after extraction with l M NaCl, the segment was further washed with water and soaked in 1% sodium lauryl sulfate at 95C for l hour. The desorbed, non-ionically bound Hb was also measured by -the same method.
When the BSA binding trial was repeated, the seg-ment was regenerated with 0.5 N HCl and 0.5 N NaOH
and washed with water before re-adsorption of ~SA.

3. Metal Ion Uptakes by PEI-Cloth One piece of 2x2 cm segment was shaken in 5 or lO
ml of 0.005-0.015 M CuS04 solutions at room tem-perature. The solutions were used without pH
adjustment unless otherwise stated. After a pre-determined length of time in hours the supernatant 20~4~

was analyzed for unabsorbed metal ion. Cu 2 adsorp-tion was calculated by subtracting the unabsorbed amount from the original amount.
When the cloth segment was repeatedly used to adsorb Cu 2 ions, it was regenerated with 0.5 N HCl and 0.5 N NaOH and washed with water before read-sorption of Cu 2 ions.
For uptakes of other metal ions, one segment of sample cloth was shaken in 10 ml of 0.01 M metal ion in 0.1 M acetate buffer ~pH 5.5) at room tempera-ture. The concentration of metal ion was determined by the method of chelatometric titration using 0.01 M ethylenediamine tetraacetic acid (EDTA) and pyridylazonaphthol as a metal indicator for Cu, Ni, Co. Pb, Zn, and Cd; 0.05 M Mg-EDTA and Erio Black T
for Hg, and Ca; 0.01 M EDTA and Erio Black T for Mn and Mg.

4. Adsorption of E. Coli Cells E. coli Crooks strain was grown in M63 medium con-taining 0.5% by weight glucose and 1 mM MgSO~, col-lected, washed twice with water or 0.9% NaCl and suspended in water or 0.9% NaCl. One 2x2 cm PEI-cloth segment was gently shaken in 3 ml of the sus-pension at room temperature. Optical density at 500 nm was measured to determine the amount of bacteria in the initial suspension and in the supernatant after 1 hour contact. The difference gave the amount of E. coli adsorbed onto the cloth.
For adsorption on a column, 10 or 30 pieces of polyethyleneimine-cloth segments cut into circles with 1.6 cm diameter were packed into a glass column to a height of 0.5 or 1.5 cm, respectively. E. coli suspensions of 0.6-1. 1X108 cells/ml were passed with a space velocity of 22-23 bed volumes per hour.
Optical density of every 5 ml of effluent was ~ J~, examined and cell adsorption capacity of cloth was calculated from hreakthrough bed volume.
The BSA adsorption capacity of polyethyleneimine-treated cloth of an aspect of this invention pre-pared as above described was used as a measure of amount of polyethyleneimi.ne binding to the rayon cloth.
Segments of nonwoven rayon cloth, SONTARA 8423, were soaked in water or 10% by weight NaOH for 10 minutes, washed with water and treaked with 1% by weight or 11% by weight polyethyleneimine solution, and their BSA adsorption were measured after washing with 0.5 N HCl, 0.5 N NaOH and. water.
The results are shown below in Table 1.
Table 1. Effects of Alkali and Polyethyleneimine Treatments on BSA Adsorption to SONTARA 8423 . _ .
pretreatment concentration PEI BSA adsorption (a)of PEI (%) treatment (b) _ (ma BSA/q cloth) water 1.0 short soaking 12 water ll.0 short soaking 23 10~ NaOH 1.0 short soaking 86 10,~NaOH 1.0 heating & drying 84 l~/o NaOH 11.0 heatig without dryness 261 l~o NaOH 11.0 heating & drying 538 .. ..
(a) For pretreatment of cloth, a 2x2 cm cloth seg-ment was soaked in water or 10% NaOH at room temper-ature for 10 min. and washed with water.
(b) After pretreatment, the segment was soaked in 3 ml of po~yethyleneimine solution at room tempera-ture for 1 hour (short soaking); or 0.2 ml of poly-e-thyleneimine solution was added and heated at 50C
for overnight until dryness (heating & drying); or 0.5 ml of polyethyleneimine solution was added and heated at 50~C overnight in a capped vial theating without dryness). All polyethyleneimine-treated segments were rinsed with 0.5 N HCl and 0.5 N NaOH
and washed with water before BSA adsorption pro-cedure.

Table 1 shows that, without alkali pretreatment, the cloth segments exhibited poor adsorption of BSA
whether they were applied with 1% by weight or 11%
by weight polyethyleneimine. However, when segments were soaked in 10% NaOH and then treated with 1% by weight polyethyleneimine, their BSA ddsorption greatly improved but, at this concentration of poly-ethyleneimine, seemed not to be affected by heating and drying during polyethyleneimine treatment. When alkali-retreated cloth was treated with 11% by weight polyethyleneimine solution and heated in a capped vial at 50C for overnight ~but not dried), further increase in BSA adsorption was observed.
When the cloth was heated in 11% by weight polyethy-leneimine at 50C until dryness, BSA adsorption was even greater.
These results indicate that alkali pretreatment, higher polyethyleneimine concentration, and heating and drying greatly increased polyethyleneimine bind-ing to the rayon cloth, which binding was stable against rinsing with diluted acid and alkali. There-fore, these factors were further investigated in detail as follows.
Since alkali pretreatment was found to be an important factor for polyethyleneimine binding to SONTARA 8423, the effect of NaOH concentration was examined to determine optimal NaOH concentration.
SONTARA 8407 was used to confirm the alkali effect in this rayon. The cloth segments ~2 cm square) were pretreated with various concentrations of NaOH

2~ 3 for 10 minutes at room temperature and washed with water. Removal of NaOH by washing was found to be necessary for polyethyleneimine binding. The seg-ments were then treated with 11% by weight po]ye-thy-leneimine (0.2 ml/segment) and dried at 50~C for overnight. After washing with 0.5 N HCl, 0.5 N NaOH
and water, the cloth was assayed for BSA adsorption as described hereinbefore.
Figure 1 shows that BSA adsorption to the poly-ethyleneimine-cloths greatly increased when the cloth was pretreated with higher than 6% by weight NaOH solution, and that the OptilllUIII COI-lCentratiOn was 10% for 10 minute soaking at room temperature.
Higher than 10% by weight NaOH and/or longer treat-ment time destabilized the cloth structure, and also reduced BSA adsorption capability.
To determine the optimum amount of polyethylene-imine added to cloth, the alkali-treated rayon cloths were treated with various concentrations of polyethyleneimine solutions and the BSA adsorption capacities of the resulting polyethyleneimine cloths were measured. 0.2 ml of polyethyleneimine solution added to a 2 cm square of cloth segment was just enough to saturate both types of rayon cloths, SON-TARA 8423 and SONTARA 8407.
The results are shown in Table 2.

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Table 2. BSA Adsorption Capacities of SONTARA 8407 and 8423 Treated with Various Amounts of Polyethy-5 leneimine ~a).
PEI solutions a~ded to 2 cm s~are cloth segment cloth volumeconcentration, %
ml~.~ 5.5 6.6 l~ 16.5 3 BSA adsorption,l~/g of cloth SOI~
8ac7 0.2 487512 - 82~ 776 712 8~23 0.1 - - 3~5 461 522 0.2 - _ 455 554 513 _ (a) The cloth segments were pretreated with 10%
NaOH, polyethyleneimine solution was added and heat-ed in an open vial at 50C to dryness overnight.
The resulting polyethyleneimine-cloth segment was rinsed with 0.5 N HCl and 0.5 N NaOH, washed with water and assayed for BSA adsorption.

Table 2 shows that SONTARA 8407 treated with 0.2 ml of 11% by weight polyethyleneimine exhibited the highest BSA adsorption capacity. Similar results were also observed for SONTARA 8423 as a 2 cm square segment which was added 0.2 ml of 11% by weight polyethyleneimine and then dried showed largest adsorption of BSA among the cloth segments examined. Administering higher than 11% by weight polyethyleneimine or more than 0.2 ml of polyethy-leneimine solution to the cloth did not improve BSA
adsorption capacity. It rather gave the cloth a 3i sticky surface and it was difficult to remove excess polyethyleneimine from cloth.
Thus, it has been found possible to apply l - 33 %
PEI solution just to saturate the cloth; 11_5 % is 2~9~

preferable for SONTARA 8407 and 8423, which corres-ponds 0.6l0.3 g of PEI per g of cloth, is preferably applied to these cloths.
We tried to apply the following PEI to the rayon cloth (known by the Trade-mark CORCAT):
CORCAT P-12 av.mol.wt. of PEI 1200 The cloth treated with Corcat P-12 and P-18 hardly adsorbed Cu ions. The cloth treated with P-150 adsorbed only 10 - 20 % of the Cu ions captured by the cloth treated with P-600. Hence the preferable molecular weight of PEI for this invention may be higher than 60,000 t 20,000.
To examine the effect of heating time and dryness, after NaOH pretreatment, to 2 cm square segments of SONTARA 8423 were added 0.2 ml of 11% by weight polyethyleneimine, heated at 50C for various per-iods and then their BSA adsorption capacities were determined.
Figure 2 shows that the protein adsorption increased linearly with the heating time until the cloth was completely dried after 8 hours.
To confirm this observation in SONTARA 8407, the alkali-treated segments of this cloth were similarly added polyethyleneimine solution and heated in vari-ous ways.
The results are shown in Table 3.

- _3 -Table 3. Effect of Heating Condition for PEI Treat-ment on the BSA Adsorption Capacity of Resulting Polyethyleneimine-SONTARA 8407 (a).
heatlng heating state of cloth BSA
temperature tirne after heating adsorption ~C) _ (hr) (mq/q) '' 2 wet(b) 136 9 wet(b) 435 16 wet(c) 6a9 16 dry(b) 82a 1~ dry(b) 776 100 2 dry(b) 656 (a) The 2 cm square segments were soaked in 10%
NaOH for 10 minutes, washed with water, 0.2 ml of ~0 11% by weight polyethyleneimine was added and then heated under various conditions. The resulting polyethyleneimine-cloth segment was rinsed with 0.5 N HCl ancl 0.5 N NaOH, washed with water and assayed for BSA adsorption.
(b) The segment was heated in an open vial.
(c) The segment was heated in a capped vial.

Table 3 shows that polyethyleneimine-SONTARA 8407 also adsorbed more BSA with longer heating at 502C
for PEI treatment. However, the cloth heated over-night in a capped vial showed poorer BSA adsorption capability than the cloth heated in an open vial (thus dried), and hence complete drying was neces-sary to obtain greater BSA adsorption by the poly-ethyleneimine-cloth. However, if drying ternperature was too high, e.g., 80-100~C, so tha-t the polyethy-leneimine-cloth was dried up too fast, less BSA
adsorption was observed.

Accordingly, heating at mild temperatures, e.g., 50~C, until dryness for more than 8 hours, was appropriate for preparation of the polyethylene-imine-coated nonwoven rayon cloth exhibiting a suf-ficient protein adsorption. The long mild heating may be necessary for polyethyleneimine molecules to maximize interaction with the rayon cloth.
As described above, it has been found that the nonwoven rayon/polyester cloth, previously soaked in 10% by weight NaOH and then washed with water, was able to load a large amount of polyethyleneimine from 11% by weight polyethyleneimine solution, and that the following heating at 50~C until dryness confirmed the stable polyethyleneimine holding against washing with diluted acid and alkali.
The same treatments with polyethyleneimine were carried out to other cellulose materials, as well as an 100% polyester cloth as a control, and their BSA
adsorption capabilities were compared.
The results are shown in Table 4.
Table 4. BSA adsorption to fabrics and fiber treated with PEI(a) ._ _ fabrics and fiber BSA
_ adsor~t;on ~mq/q~

SONTAP~A 8407 rayon~polyester;70/30 842 SONTARA 8~23 rayon/poiyester;70/30 538 commercial rayon fiber 614 SONTARA 8801 wood pulp/polyesteri55/45 1~1 com~ercial cotton cloth (woven) 111 Whatman No.l filter paper 338 SONTARA 8122 10~/o polyester 10 .
(a~ All 2x2 cm cloth segments and 33 mg of rayon fiber were treated as described hereinabove.

201946~

Table 4 shows that rayon produced the polyethy-leneimine-~aterial possessing good BSA adsorption capacities which are equivalent to or greater than those of commercial DEAE-cellulose ion exchangers.
PEI-treated SONTARA 8423 and SONTARA 8407 adsorbed 538 and 842 mg BSA/g, respectively, while DEAE-Cel-lulose DE-23 and DE-52 (WHATMAN) were reported to adsorb 425 and 750 mg ~SA/g, respectively.
Compared with rayon, polyethyleneimine holding on wooden cellulose and cotton was less, reflecting the high density of alkali-resistant crystalline struc-ture in these native celluloses, but still consid-erable. PEI treatment described herein as an aspect of this invention can thus be widely applied to cel-lulose cloths in the same manner as to rayon cloths.
Little binding of polyethyleneimine to polyester was also observed, suggesting that polyethyleneimine holding on rayon/-polyester cloth was entirely due to polyethyleneimine binding to its rayon component.
Thus, it has been found that cellulosic materials (fabric, cloth, paper) can be used according to aspects of this invention. Rayon, (regenerated cellulose), is preferred to natural cellulose because of its increased adsorption of polyethy-leneimine. Non-woven cloth is preferable rather than woven cloth because of its superior character as a filter material.
Accordingly, the following substrates may pre-ferably be used according to aspects of this inven-tion: non-woven rayon cloth; non-woven rayon/-polyester cloth, e.g., SONTARA 8407, or SONTARA
8423; non-woven woodpulp/polyester cloth, e.g., SONTARA 8801; (cellulosic) paper, e.g., various filter papers; woven rayon cloth; woven rayon/poly-ester cloth; woven cotton cloth; and woven cotton/-polyester cloth.

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To examlne the stability of polyethyleneirnine fixed on the rayon cloth, ltS BSA and Cu ion adsorp-tion capabilities were repeatedly determined. Af-ter each adsorption assay, the polyethyleneimine-cloth was regenerated with 0.5 N HCl and 0.5 N NaOH.
Figure 3 shows the BSA adsorption to PEI-coated SONTARA 8423 (uncrosslinked). The cloth segment was repeatedly regenerated with 0.5 N HCl and 0.5 N NaOH
before each adsorption trial. Figure 3 shows that BSA adsorption to the polyethyleneimine-coated rayon cloth remained unchanged during at least 6 adsorp-tion cycles. This strongly suggests the possibility of the cloth may be used for enzyme immobilization.
Figure 4 shows the effect of repeated use on Cu uptake by polyethyleneimine-coated SONTARA ~423 (uncrosslinked). In every cycle, a 2 cm sguare segment of the polyethyleneimine-cloth was washed with 0.5 N HCl, 0.5 N NaOH and water, and contacted with 5 ml of 0.005 or 0.015 M CuS04 at room tempera-ture overnight to adsorb Cu ion. Figure 4 shows that Cu adsorption to the polyethyleneimine-cloth grad-ually decreased with repeated adsorption cycles.
Since Cu ions adsorbed on the cloth were thoroughly desorbed with 0.5 N HCl, which was judged from the disappearance of the blue colour from -the chelating complex, the possibility of Cu ion accumulation on the cloth must be excluded. Consequently, the observed decrease of Cu ion uptake indicated gradual release of polyethyleneimine from the cloth into water.
It has been found that polyethyleneimine was fixed on the alkali pretreated cloth with a certain stabi-lity but gradually released in aqueous Cu solution.
Cross-linking between amino groups of polyethylene-imine molecules would stabilize binding o~ polyethy-leneimine to the cloth.

Although various cross-linking reagents could be used, two types of the cross-lin~er were selected;
glutaraldehyde and epoxy reagents (epichlorohydrine and BDGE), because they are inexpensive, relatively low in toxicity and easy to handle to carry out cross-linking reactions. Furthermore, glutaralde-hyde is water-soluble so that the reaction can be carried out in water, and epoxy reagents form very stable bondings with amino groups.
Cross-linked polyethyleneimine-cloth~ were examined for their capacity to adsorb BSA and hemo-globin, m,etal ions and Escherichi cGli bacteria. TG
examine the stabili-ty of crosslinked polyethylene-imine, the cloth was repeatedly used for Cu adsorp-tion. The adsorption rate of Cu ion was also deter-mined, since this will determine the flow rate at which the cloth can be used in a column operation.
The polyethyleneimine-coated rayon cloths were treated with 0.05-0.4% by weight of glutaraldehyde at room temperature for 2 hours, and repeatedly used for adsorption of Cu ions. After each use, they were regenerated with 0.5 N HCl and 0.5 N NaOH, heated in water at 90C for 3 hours and then con-tacted with 5 ml of 0.005 M CuS04 overnight.
Figure 5 shows that the clo-ths treated with higher than 0.3% by weight glutaraldehyde exhibited stable Cu adsorption for 6 cycles of repeated use and regeneration.
Figure 6 shows the effect of time of contact with Cu solution on Cu uptake by glutaraldehyde-cross-linked polyethyleneimine-SONTARA 8423. One 2 cm square segment of polyethyleneimine-cloth cross-linked with 0.4% by weight glutaraldehyde was con-tacted with 10 ml of 0.002 or 0.01 M CuS04 for various periods of time a-t room temperature.

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Figure 6 shows that the Cu uptakes reached a maxi-mum within 2 - 3 hours at 0.01M CuS04, and 3 - 5 hours at 0.002M CuS04. On the other hand, it is known that a resin of polyethyleneimine cross-linked with toluene diisocyanate requires more than 24 hours equilibration periods for metal ion adsorp-tion. It is also known that macroreticular chelat-ing resins containing amine groups also take more than 24 hours to reach to maximum Cu ion uptake in 0.01 M Cu solution. Thus, Cu adsorption to poly-ethyleneimine-cloth observed is a very rapid pro-cess. The polyethyleneimine fixed on the clGth r,ay be exposed to solution, and metal ions may be able easily to access to chelating groups despite of the net work formation of polyethyleneimine through cross-linking.
Cu adsorption capacity of polyethyleneimine-rayon cloth cross-linked with 0.4% glutaraldehyde was 61 mg per g of cloth (0O96 mmol/g) in 0.01 M CuS04 .
On the other hand, it is known that Cu uptakes by the resin of polyethyleneimine cross-linked with toluene diisocyanate is 90 mg Cu per g of polymer in 0.01 M cupric acetate. It is also known that thê
polystyrene resins containing polyamino groups adsorb 1.5 mmol of Cu per g of resin (95 mg/g) in 0.01 M Cu solution at pH 6.
The effect of glutaraldehyde cross-linking on pro-tein adsorption to polyethyleneimine-cloth was also examined.
Figure 7 shows the effect of ssA adsorption to PEI-SONTARA 3423 cross-linked in various concentra-tior,s of glutaraldehyde.
Figure 7 shows that BSA adsorption capability decreased with higher concentration of glutaralde-hyde, as cross-linking reduced the number of amino groups available for protein binding. However, the 2 ~

polyethyleneimine-cloths cross-linked with 0.3 or 0.4 % by weight glutaraldehyde still had consider-able adsorption capacities of 200-250 mg ssA/g.
Polyethyleneimine-rayon cloths were cross-linked with 0.5-3% epichlorohydrine or BDGE in methan~l at room temperature for 3 hours. To examine the stabi-lity of polyethyleneimine fixed on the cloths, 2 cm square segments of the resulting cloths were repeat-edly used for adsorption of Cu in 5 ml of 0.005 M or 0.01 M CuS04 at room temperature overnight. After each adsorption trial, segments of cloths were regenerated with 0.5 N HC1 and û.5 N NaOH, and heated in water at 9ûC for 3 - 4 hours.
Figure 8 shows the Cu ion uptake by epichloro-hydrin crosslinked polyethyleneimine-SONTARA 8423.
A 2 cm square segment of polyethyleneimine-cloth crosslinked with û.5, 1 and 3% by weight epichloro-2û hydrin at room temperature for 3 hours was repeat-edly regenerated with 0.5 N HCl and û.5 N NaOH, heated in water at 9ûC for 3-4 hr., and contacted with 5 ml of 0.005 M CuS04 at room temperature over-night.
Figure 8 shows that Cu uptakes by polyethylene-imine-cloths with 0.5 or 1% by weight epichloro-hydrine gradually decreased after 3 or 4 adsorption trials, respectively. Accordingly, the polyethy-leneimine-cloth was cross-linked with 3% by weight epichlorohydrine, and the resulting cloth conse-quently exhibited steady Cu uptakes for at least 9 adsorption cycles.
Figure 9 shows the Cu ion uptake by polyethylene-imine-SONTARA 8423 cross-linked with BDGE. A 2x2 cm polyethyleneimine-cloth segment cross-linked at room temperature in 0.5 or 1% sDGE was repeatedly regen-erated with 0.5 N HCl ar,d 0.5 N NaOH, and soaked in 2 ~

5 ml of 0.005 or 0.01 CuS04 at room temperature overnight for repeated Cu ion uptakes.
Figure 9 shows the Cu uptakes by BDGE-treated polyethyleneimine-cloths. Unlike epichlorohydrine-treated cloths, polyethyleneimine-cloth cross-linked with 0.5 and l. O~D BDGE at room temperature con-stantly adsorbed Cu ion in 0.005 M Cu solution at 0 least for 6 cycles. However, Cu uptake in 0.01 M Cu solution exhibited slight and gradual decrease dur-ing repeated uses. Therefore, the effect of cross-linking at higher concentrations of BDGE and higher temperatures was studied. The polyethyleneimine-rayon cloth segment was cross-linked with 3% BDGE at room temperature or with 1% by weight BDGE at 50C, and repeatedly measured Cu adsorption capacity in 10 ml of 0.01 M CUSO4.
Figure 10 shows the effect of higher BDGE concen-trations and higher temperatures on Cu ion uptake by polyethyleneimine-SONTARA ~423. A 2x2 cm segment of polyethyleneimine cloth, cross-linked in l % BDGE at room temperature or 50DC, or in 3% by weight BDGE at room temperature, was repeatedly regenerated with 0.5 N HCl and 0.5 N NaOH and contacted with 10 ml of 0.01M CuS04 for 3 hours for repeated Cu uptakes.
Figure ~0 shows that while the cloth cross-linked with 1% by weight BDGE at room temperature exhibited gradual decrease in its Cu adsorption, Cu ion uptakes by the polyethyleneimine-cloth cross-linked with 1% by weight BDGE at 50C or 3% BDGE at room temperature were unchanged during 6 adsorption cycles, indicating that polyethyleneimine was more extensively crosslinked under these conditions.
Cu adsorption capacities of these cloths were 80 mg Cu per g of cloth (1.3 mmol/g), which is com-parable to other chelating resins mentioned.

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The rates of Cu adsorption to the BDGE-cross-linked cloths were also examined.
Figure 11 shows the kinetics of Cu uptakes by polyethyleneimine-SONTARA 8423 crosslinked with BDGE. One 2 cm square segment of polyethyleneimine-cloth, cross-linked in 1% by weight BDGE at room temperature or 50C, or in 3% by weight BDGE at room temperature was soaked in 10 ml of 0.01M CuS04 for various period and Cu ion uptake was measured.
Figure 11 shows that Cu uptakes by these cloth reached maximum (80 mg Cu/g cloth) within 2 hours dnd hence their adsorption rates appeared to be much faster than those of chelating resins previously described. It is known that after 3 hour-contact with 0.01 M Cu solution at pH 6, macroreticular polystyrene resin containing polyamino groups adsorbed 58 mg Cu per g of resin. On the other hand, the BDGE-cross-linked polyethyleneimine-cloths of aspects of this invention adsorbed 68-76 mg Cu per g of cloth only in 1 hour contact time. This characteristic of polyethyleneimine-rayon cloths likely results from the open structure and hydro-philicity of the cloth on which polyethyleneimine was immobilized. As mentioned above, SONTARA 8423 and SO~TARA 8407 rayon cloths, exhibit affinity to water, unlike polystyrene resins. Such rapid adsorption of metal ions would be desirable for column operation, because water treatment need to be performed with a fast flow rate. The high adsorp-tion capacities and rapid adsorption rates would permit treatment of large volume of water per unit volume of column per unit time.
The advantage of this rapid adsorption of Cu ion was examined in column studies. When a Cu solution of 22 mg/1 was passed through l ml of the fixed bed which was formed of 10 circles (i.d. 1.6 cm) of 2 ~

polyethyleneimine-cloth cross-linked in 1% by weight BDGE at room temperature, no Cu ion was detected for 215 or 205 bed volumes of effluent at the space ~el-ocity of 66 or 105, respectively. It is known that a column of macroreticular chelating resin was able to treat 200-250 bed volumes of Cu solution of 21 mg/l at space velocities of 30-15. Thus, the polyethyleneimine-cloth provides faster flow rate in a column operation.
In addition to Cu, polyethyleneimine forms chelates with various heavy metals. Uptakes of various metal ions by the polyethyleneimine-cloth treated with BDGE were examined in 0.01 M metal solution at pH 5.5-6Ø
The results are shown in Table 5.
Table 5. Adsorption o~ metal ions on PEI-SONTARA 8423 crosslinked with BDGE(a).
pH adsorption capacity metal salt before after (mq/q) (m mol/q) Hg HgCl2 5.4 5.6 428 2.13 Cu Cu(CH3CO2)z 5.5 5.6 74.9 1.18 Ni NiC12 5.5 5.6 47.8 0.81 Co CoCl2 5.5 5.7 34.3 0.58 Cd Cd(CH3C02) 5.6 5.8 64.1 0.57 Zn ZnS04 5.5 5.637.5 0.57 Pb Pb(CH3CO2)~ 5.5 5.9 46.7 0.23 Mn MnSO4 5.6 6.1 1.8 0.03 (a) Polyethyleneimine-cloth was crosslinked in 3%
by weight BDGE at room temperature for 3 hours.

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Table 5 shows that the cloth adsorbed various heavy metal ions in the order (on molar base):
Hg >Cu>Ni>Co>Cd~n>Pb>Mn. This order is almost similar to those known for the aminated chelating resins and resins of cross-linked polyethyleneimine.
Like Cu ions, these heavy metal ions, except Hg, were readily desorbed from cloth with 0.5-1 N HCl.
It is known that Hg adsorbed on aminated chelating resin may be eluted with 6 N HNO3 or 10 N HC1.
Potable water commonly contains Ca and Mg ions.
These ions are safe to health but lower the ion exchange capacities of cation-exchangers used in the treatment of water. In contrast, the polyethylene-imine-cloth adsorbed neither Ca nor Mg, and thus its heavy metal ions adsorption capacities are little affected by the presence of these ions in water.
Water may be contaminated with undesirable pro-teineous materials of different isoelectric points (pI). Polyethyleneimine-rayon cloths cross-linked with epichlorohydrin or BDGE were assayed for adsorption of BSA (pI ca. 5.0) and hemoglobin (pI6.8) in water. The cloth segment was soaked in ~5 5% protein solution for 1 hour, adsorbed protein was desorbed with 1 M NaCl and measured. Although all adsorbed BSA was extracted, the cloth segment to which Hb adsorbed still retained some hemoglobin colour after this NaCl extraction, indicating some Hb non-ionically bound to the cloth. Thus, the cloth was treated with 1% sodium lauryl sulfate at 95C and the eluted Hb was measured.

Table 6. Adsorption of BSA and Hb to Polyethylene-imine-SONTARA 8423 Cross-linked with Epichlorohydrin or BDGE (a).
crosslinking BSA adsorption(rng/g) Hb adsorption(r~/g) condition NaCl(b) total NaCl(b) sodiurn'auryl sulfate(c~
1 epichlorohydrin 0.5 %, r.t. 353 264 (211)(53) 1 %, r.t. 296 212 (161)(51) 3 %, r.t. 304 146 (104)(42) BD~E
l0 5 %, r.t. 383 221 (171)(50) 1 %, r.t. 342 188 (142)(46) 3 %, r.t. 224 89 ( 53)(36) 1 %, 50 C 67 - - -2WitilOUt crosslinking 538 277 (226) (51) .. . .. _ _ _ , ~a) Polyethyleneimine-cloth was cross-linked for 3 hours at room temperatures or 50C in 0.5-3% by weight crosslinking agents.
(b) BSA or Hb desorbed in 1 M NaCl at room tem-perature.
(c) Hb desorbed in 1% sodium lauryl sulfate at 95C after extraction with 1 M NaCl.

Table 6 shows that BSA adsorption capacities of PEI-rayon cloths decreased with higher concentra-tions of epichlorohydrin and BDGE used as cross-linking agents, as observed for glutaraldehyde cross-linking. However, cross-linked polyethylene-imine-cloths still exhibited the considerable cap-abilities of BSA adsorption, when cross-linking was performed at room temperature.

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Since Hb has a higher pI and thus less negative charges in water than BSA, adsorption of Hb to the polyethyleneimine-cloth was less than that of BSA, but was still considerable. Furthermore, some Hb exhibited non-ionic binding to the cloth, since they were not desorbed in 1 M NaCl but were desorbed in 1% sodium lauryl sulfate. Thus, the Hb adsorption may also involve hydrophobic interaction. The ethy-lene-containing backbone of polyethyleneimine is likely responsible for hydrophobic interaction.
The resul-ts indicate that the polyethyleneimine-cloth will adsorb negatively charged proteins through ionic interaction, as well as hydrophobic interaction. This ability of the polyethyleneimine-cloth to adsorb various proteins is useful in remov-ing undesirable proteineous impurities, e.g., pro-teins in the effluents from food industries, or various viruses which have protein coats.
Polyethyleneimine, as a cationic polymer, is believed to be able to adsorb bacteria, most of which are negatively charged in water. As a model, the adsorption of E. coli to polyethyleneimine-fixed rayon cloth was examined. A 2cm square polyethy-leneimine-cloth (uncross-linked or crosslinked with BDGE ) was soaked in 3 ml of E. coli suspension at room temperature for 1 hour.
The results are shown in Table 7.

~ ~3 ~

Table 7. Adsorption of E. coli to Polyethylene-imine-SONTARA 8423 from 1 Hour Contact (a).
~
initial concentration of cell PEI-SONTARA 8423 0.5xl08 1.0x108 2.2xl08 cells adsorbed per g of cloth 1 uncrosslinked 7.3x109 (67) crosslinked in 1% BDGE at r.t. 7.1x109 (61) in lYo BDGE at r.t. 5.1x109 (28)(b) in 1% BDGE at 50 C 3.3xlO9 (~9) 6.2xlO9 (45) 8.8xlO9 (23) in ~/oBDGE at 50 C 5.8xlC9 (40) -(a) One 2 cm square of cloth was contacted with 3 ml of cell suspension in water for 1 hour at room temperature. The number of bacteria in the original suspension and the supernatant was determined from optical density at 500 nm.
~b) The cloth segment was contacted with cell suspension in 0.9% NaCl.
The number in the parentheses shows the removal coefficient.

Table 7 shows that uncross-linked polyethylene-imine-cloth removed 84% of E. coli from 3 ml of sus-pension (1.0 x 108 cells/ml) in water in 1 hour and that BDGE-crosslinked polyethyleneimine-cloths also captured 82-67% of the bacteria. Cross-linking with BDGE appeared to cause only a small reduction of bacteria adsorption. The polyethyleneimine-cloth also efficiently adsorbed E. coli from the bacterial suspension in 0.9% by weight NaCl: the PEI cloth cross-linked with 1% by weight BDGE at room tempera-ture removed 60% of bacteria in 1 hour contact time.

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Table 7 also shows the removal coefficients which are related with the initial rate constant of bac-teria removal process as (removal coefficient~ = (V/Wt~.log(N~/Nt~
where V is volume of cell suspension, W is wei~ht of adsorbent, t is contact time, No is initial cell number and Nt is cell number at contact time t. The removal coefficients for BDGE-treated polyethylene-imine-cloth were 60-40 in water, and 28 in 0.9% by weight NaCl (the cloth treated with 1% by weight BDGE at room temperature). It is known that cross-linked poly(N-benzyl-4-vinylpyridinium bormide) effectively removes bacteria in physiological saline at 37C with a removal coefficient of 4.4. Although the conditions of bacteria adsorption are not iden-tical, the polyethyleneimine-cloths appear to remove E. coli more rapidly than poly(vinylpyridinium).
To examine the adsorption of E. coli to the poly-ethyleneimine-cloth in column operations, an E. coli suspension in water was passed through a column packed with BDGE-cross-linked polyethyleneimine-cloth segments and the optical density of effluent was plotted against effluent volumes. Figure 12 shows an example of the experiment. Figure 12 shows the removal of E. coli from water by a fi~ed bed of PEI-SONTARA 8423 cross-linked with 1% BDGE at room temperature. The volume of the bed formed of 30 circles (i.e., 1.6 cm) of cloth was 3 ml with 1.5 cm height. E. coli suspension of 1.1 x 10a cells per ml was passed through with space velocity of 22, and a breakthrough was observed at 13 bed volumes (40 ml) of effluent.
Further results are shown in Table 8.

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Table 8. Removal of E. Coli from Water by Columns Packed with BDGE-Crosslinked Polyethyleneimine-SONTARA 8423.

pieces cells in break- adsorbed condition of of space inf]uent ~hrouah cells Eer crosslinking clo~h velocity (cells/ml) (led vol.) g of cloth .., 0.5% BDGE,50C 10 ~3 l.lx108 20 1.2x101 1% BDGE, r.t. 10 23 l.lx108 35 2.1xlO
1% ~DGE, 50C 30 22 l.lx108 13 8.1x109 1 1% BDGE, 50C 30 22 5.9x107 20 6.~109 =

E. coli adsorption capacities of BDGE-treated polyethyleneimine-cloth in the column, judged from brea~through capacities, were 10' cells/g at a space velocity of 22-23. In contrast, poly(vinyl-pyridinium) also exhibited similar capacities but the space velocity of effluent was 10 times less than the procedure of the present invention. These results suggest that PEI-cloth column could effec-tively remove bacterial from water with a rapid flow rate.
The process according to the invention can be carried out discontinuously, semi-continuously or continuously. In principle, the following embodi-ments are suitable.
a) the so-called stirring process in which the water to be purified is stirred with the PEI-cloth in a vessel or a series of vessels and then sepa-rated off;
b) the so-called fixed bed process in which the liquor to be purified is fed through cellulose material arranged in a filter-like mannerr The present invention provides a non-obvious improvement over previously referred-to Canadian Patent No. 1,169,735. Canadian Patent No. 1,169,735 is based on ionic adsorption of polyethyleneimine, unlike hydrogen bonding which is the theoretical basis of the present invention.
Canadian Patent No. 1,169,735 necessitates the ad~ustment of pH of the PEI to 4 to 5 so that PEI (-NH-,-NH2) becomes, PEI (-N~2;-,-NH3;) which can ionically adsorb to the S03- group in NaOH-washed, H2SO~-washed, sulfonate lignocellulose (sulfonated lignin rather than cellulose) or unidentified acid groups in washed pine bark.
The present invention necessitates the disruption of H bondings in rayon, so that hydroxyl groups in rayon can form H-bondings with the N atoms of PEI.
Thus, there is no need to adjust the pH of polyethy-leneimine in the process of an aspect of this inven-tion.
Canadian Patent No. 1,169,735 provides adsorbents in a particule form, requiring a separation mecha-nism, e.g., clecantation, filtration or centrifuga-tion, whereas the use of a cloth form as in aspects of the present invention provides easy separation.
Since in the process of Canadian Patent No.
1,169,735 the polyethyleneimine is ionically adsorbed, NaCl seems to strip polyethyleneimine, necessitating polyethyleneimine reloading, in one aspect of -this invention, polyethyleneimine is chemically cross-linked, and thus is stable during regeneration.
It is believed that the product produced by the process of Canadian Patent No. 1,169,735 may be satisfactory for the treatment of industrial efflu-ents, but it is believed that it could not be used for treatment of drinking water.

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Comparative experiments were carried out in the process and utility of the adsorbent cloth of the present invention and the product of Canadian Patent 1,169,735 since the alkali and acid washings taught in Canadian Patent No. 1,169,735 are too strong for the rayon cloths which are preferred embodiments of this invention, much milder washings were employed.
The ~ollowing experiments were carried to examine the effect of acid treatment on the adsorp-tion of PEI to the substrate.
The test procedure was as follows:
A 2 cm square of SONTARA 8423 was soaked in 10% by weight NaOH at room temperature for 10 min, washed with water, soaked in 0-60% by weight H2SO4 at room temperature for 2 or 4 hours, and then washed with water. After 0.2 ml 11% PEI (without pH adjustment) or 7% by weight PEI (pH 4.5 with HCl) was added, it was then heated at 50C overnight, and washed with water, 0.5N NaOH and water.
The BSA adsorption capacity as a measure of PEI
holding on cloth was then determined, with the fol-lowing result.
2~`acid treatment PEI BSA adsorption (m~ per 2 cm square of cloth~_ ~,bX2S04, 2 h ll % 14.6 2~o H2SO4, 2 h 11 % 14.4 304~/oH2SO4~ 2 h 11 ~O 14.6 50/o H2SO9, 2 h 11,' 13.0 O'~o H2SO4, 4 h 7o,6, pH 4.S 14.0 20/~oH2S04, 4 h 7,', pH 4.5 12.5 3540% H2S04~ 4 h 7 %, pH 4.5 12.5 60% H2S04, 4 h 7 %, pH 4.5 8.4 2 ~

As a result of these tests it can be seen that treatment with 60% by weight H2SO4 for 4 hours harmed the cloth. Acld treatment applied to rayon cloth did not improve the polyethyleneimine retain-ing on the cloth. Application of polyethyleneimine solution whose pH was adjusted to acidic (e.g., 4.5) also did not improve the polyethyleneimine retaining on the cloth.
There appears to be no advantage of acid treat-ment. The purpose of NaO~ and acid treatments in Canadian Patent No. 1,169,735 were not described.
However, it appears that they merely remove alkali and acid-soluble impurities from the bark.
The present invention provides a new method for fixing a large amount of high molecular weight poly-ethylenimine on nonwoven cloth. The polyethylene-imine-fixed cloth was, as a result, stable for repeated regeneration and storage in water, and exhibited high adsorption capacities of heavy metal ions, proteins and bacterial and viruses.
The polyethyleneimine-cloth adsorbed these sub-stances at much faster rate than the previously developed chelating resins. A column packed with the polyethyleneimine-cloth could be operated for the removal of heavy metal ions and bacteria at rapid flow ratês.-The flow rate depends upon the volume and size of column and the metal ion concentration in water.
The ability of the column can be estimated from the capacity of treated water under the required flow rate.
The polyethyleneimine-cloth of an aspect of this invention, adsorbs meta:i ions under static condition faster than a chelatir-g resin of the prior art. A
column study carried out with the polyethyleneimine-cloth of this invention, also exhibited the compar-2 ~

able results. These suggest that the faster flow rate (linear flow rate: Ml/cm2/hr) may be available to the polyethyleneimine-cloth column so that the column with smaller diameter can be used for purify-ing a certain volume of water.
All materials used to prepare the polyethylene-imine-cloths are relatively safe and inexpensive, and the preparation is simple. Accordingly, these economical and highly effective polyethyleneimine-cloths should be useful for recovering metal ions from water, final treatment of industrial waste water and purification of drinking water, especially for domestic use since the cloths are disposable.

Claims (18)

1. An adsorbent cloth or fabric for adsorbing heavy metals and negatively charged materials com-prising a cloth or fabric substrate, at least part of which is cellulosic, which has been pretreated with an alkali, followed by water washing, upon which high molecular weight polyethyleneimine has been adsorbed and fixed thereon with a cross-linking agent.

2. The adsorbent cloth of claim 1 wherein said fabric upon which said high molecular weight poly-ethyleneimine has been adsorbed is heated mildly until it is dry prior to having said polyethylene-imine adsorbed and fixed thereon with said cross-linking agent.

3. The adsorbent cloth or fabric of claim 1 wherein said cloth or fabric comprises a woven or a non-woven rayon fabric, or a woven or a non-woven rayon/polyester fabric or a woven or a non-woven woodpulp/polyester fabric, or a woven or non-woven cotton cloth or a woven or non-woven cotton/poly-ester cloth or cellulosic paper; the fabric being either in its open apertured style or in its highly absorbent, open-apertured style.

4. The adsorbent cloth or fabric of claim 1 wherein said cross-linking agent comprises glutaral-dehyde, epichlorohydrin, 1,4-butandioldiglycidyl ether, 1,2-ethanedioldiglycidyl ether, 1,3-digly-cidylglycerol, triglycidylglycerol, pentaerythritol, or tetraglycidyl ether.

5. A process for preparing an adsorbent cloth or fabric which comprises:
pretreating a cloth or fabric substrate at least part of which is cellulosic with an alkali;
washing said pretreated substrate with water;
adsorbing high molecular weight polyethyleneimine therein; and cross-linking said polyethyleneimine on said sub-strate with a cross-linking agent.

6. The process of claim 5 including the step of heating said fabric heated mildly until it is dry prior to having said polyethyleneimine adsorbed and fixed thereon with said cross-linking agent.

7. The process of claim 4 wherein said process of treating said substrate comprises:
pretreating a cloth or fabric substrate at least part of which is cellulosic with an alkali;
washing said pretreated substrate with water;
adsorbing high molecular weight polyethyleneimine therein; and cross-linking said polyethyleneimine on said sub-strate with a cross-linking agent.

8. The process of claim 5 wherein said alkali is an inorganic base or an organic base.

9. The process of claim 5 wherein said inorganic base is selected from the group consisting of LiOH, NaOH and KOH.

10. The process of claim 8 wherein said organic base is an alkyl ammonium base.

11. The process of claim 9 wherein said inorganic base is a 10-40% by weight solution of the NaOH.

12. The process of claim 9 wherein the aqueous solution of NaOH has a concentration of 10% 1 5% by weight.

13. The process of claim 5 wherein said cross-linking agent comprises glutaraldehyde, epichlo-rohydrin 1,4-butandioldiglycidyl ether, 1,2-ethane-dioldglycidyl ether, 1,3-diglycidylglycerol, trigly-cidylglycerol, pentaerythritol, or tetraglycidyl ether.

14. The process of claim 5 wherein said water washing is carried out until the substrate has a pH
of 7.

15. The process of claim 5 wherein said adsorbing of said high molecular weight polyethyleneimine is carried out and until a maximum of the stoichiome-tric amount of said polyethyleneimine is adsorbed thereon.

16. The process of claim 15 wherein said poly-ethyleneimine has a molecular weight of 60,000 +
20,000.

17. A method for removing heavy metals and nega-tively charged material from water which comprises contacting said water with an adsorbent cloth or fabric at least part of which is cellulosic, which has been pretreated with an alkali, followed by water washing, upon which high molecular weight polyethyleneimine has been adsorbed and fixed there-on with a cross-linking agent.

18. The method of claim 12 wherein said contact-ing is achieved by passing said water through a col-umn packed with said adsorbent.