Removal of arsenate from ionic mixture by anion exchanger water-soluble polymers combined with ultrafiltration membranes

This study shows the influence of Cl^?, SO₄ ^2?, NO₃ ^?, SiO₃ ^2?, Na⁺, and Ca²⁺ on arsenate removal by anion exchanger polymers using the liquid-phase polymer-based retention (LPR) technique. The LPR was carried out in the presence of anion exchanger soluble polymers containing quaternary ammonium salts. These polymers were characterized by NMR. Compared with As(V) removal from deionized water, the results showed that in the presence of ionic mixture, the As(V) removal capacity decreased. However, P(ClVBTA) showed As(V) removal ability of 91?% when the ionic mixture was used. Polymers with chloride exchanger groups showed a higher ability to remove arsenate than the polymer that contains methyl sulfate as anion exchanger group. At higher arsenate concentration (47.6?mg L^?1), arsenate retention by the water-soluble polymers ranged between 58 and 91?%. This removal capacity increased gradually reaching 100?% retention when the arsenate concentration in the cell was minimum (5.5?mg?L^?1). The values of maximum retention capacity were 264?mg?g^?1 for P(ClMPTA), 260?mg?g^?1 for P(ClVBTA), and 200?mg?g^?1 for P(ClAPTA) at the total filtrate volume of 300?mL. The charge–discharge process found to be suitable for saturate the polymer with As(V) and then eluting As(V) for regenerating the extracting capacity of polymer.     

Photo-Fenton removal of water-soluble polymers

This paper presents the results of experiments carried out in a laboratory-scale photochemical reactor on the photodegradation of different polymers in aqueous solutions by the photo-Fenton process. Solutions of three polymers, polyethyleneglicol (PEG), polyacrylamide (PAM), and polyvinylpyrrolidone (PVP), were tested under different conditions. The reaction progress was evaluated by sampling and analyzing the total organic carbon concentration in solution (TOC) along the reaction time. The behavior of the different polymers is discussed, based on the evolution of the TOC–time curves. Under specific reaction conditions, the formation and coalescence of solid particles was visually observed. Solids formation occurred simultaneously to a sharp decrease in the TOC of the liquid phase. This may be favorable for the treatment of industrial wastewater containing polymers, since the photodegradation process can be coupled with solid separation systems, which may reduce the treatment cost.     

Synthesis of water-soluble polymers containing sulfonic acid and amine moieties for the recovery of metal ions using ultrafiltration

Copolymers from 2-acrylamido-2-methyl-propane sulfonic acid (APSA) and N-acryloyl-N-methyl piperazine (AP) were synthesized by radical polymerization with ammonium peroxydisulfate as the initiator. The copolymerization yield ranged between 93 and 95%. The copolymers were completely water soluble, and were characterized by FTIR and NMR spectroscopy. The copolymer composition was determined from elemental analysis through the S/C ratio. The binding capacity for metal ion was studied by the LPR technique at different pH and filtration factors. The retention depended strongly on the pH and on the copolymer composition. With increasing pH and increasing content of APSA units in the copolymer, the metal ion retention increased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 22–30, 2001     

Reverse osmosis with dynamically formed membranes from water-soluble polymers

Membranes were dynamically formed from poly(acrylic acid), poly(1-methyl-2-vinylpyridinium iodide), and methylcellulose on a Millipore filter. The effects of the conditions of membrane formation on reverse osmosis performances and the membrane structure were investigated. The primary factors that affect membrane performance were ascertained to be the kind and concentration of salts and the pH of the preparing solutions, the concentration and the polymerization degree of the membrane materials, the pore size of filters, and the pressure and circulation velocity during membrane formation. Two types of dynamically formed membranes, the membranes inside the filter and the membranes on the filter, were distinguished.     

The removal of toxic heavy metal cations by polysulfonebenzylthiourea reactive hollow fiber ultrafiltration membranes

The hollow fiber asymmetric matrix membranes were prepared with phase inversion by utilization of the chloromethyl polysulfone/polyethylene glycol/DMAC casting solution and chloromethyl polysulfone as membrane materials. The effects of composition of spinning casting solution and process parameters of dry–wet spinning on the structure of hollow fiber matrix membrane were investigated. Through the reaction between matrix membrane and thiourea, the highly qualified polysulfonebenzylthiourea reactive hollow fiber ultrafiltration membranes were able to afford. The adsorption isotherms of the polysulfonebenzylthiourea hollow fiber membrane for Cd²⁺ and Zn²⁺ were determined and the effects of mobile phase conditions and the operating parameters on removal performance of the polysulfonebenzylthiourea hollow fiber membrane for Cd²⁺ and Zn²⁺ were also investigated. The experimental results showed that adsorption isotherms of Cd²⁺ and Zn²⁺ could be described by the Langmuir isotherm, the polysulfonebenzylthiourea hollow fiber membrane could be operated at high feed flow rate, and a large‐scale removal of Cd²⁺ and Zn²⁺ could be realized. According to required recovery of Cd²⁺ and Zn²⁺ and the saturation degree of polysulfonebenzylthiourea hollow fiber membrane, the optimum loading amount of Cd²⁺ and Zn²⁺ should be selected in the actual removal of Cd²⁺ and Zn²⁺. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The performance of ultrafiltration membranes pretreated by polymers

The fouling of ultrafiltration(UF) membranes by protein has been reduced by surface pretreatment with various polymers. In most cases the treatment provided an increase in initial UF flux and a slower flux decline.

The ultrafiltration performance of the treated membranes appears to be influenced by the molecular configuration and size of the polymer as well as its interfacial structure.

Methylcellulose(MC) was found to be the most effective of polymers tested in enhancing UF flux, showing an average flux advantage of 30–40% for first usage. For multiple cycles of usage the benefits increased up to 100% after 5 cycles, due to the reduced amount and reversibility of the fouling protein deposit.     

Simultaneous removal of humic acid and heavy metal from aqueous solutions using charged ultrafiltration membranes

Lab-made negatively charged ultrafiltration (UF) membranes were used for simultaneous removal of humic acid (HA) and heavy metals from water. Effects of the HA/metal ratio, solution pH and ionic strength on rejection coefficients of HA and metals were investigated. The results showed that the rejection coefficients of both HA and metals increase with the increase of pH and the HA/metal ratio, and the decrease of ionic strength. This study indicated that charged UF could be an effective method for the simultaneous removal of HA and heavy metal harnessing the principle of complexation UF and electrostatic repulsion between the membrane and the HA–M complex of the same charges.     

Polyelectrolyte‐assisted removal of metal ions with ultrafiltration

The water‐soluble polymers poly(styrene sulfonic acid‐co‐maleic acid) and poly(acrylic acid‐co‐maleic acid) were investigated with respect to their metal‐ion‐binding ability with ultrafiltration. The studied metal ions included Ag(I), Cu(II), Ni(II), Co(II), Ca(II), Mg(II), Pb(II), Cd(II), Zn(II), Al(III), and Cr(III) ions. The retention properties of the polyelectrolytes for the metal ions depended strongly on the ligand type. As for the carboxylate ligands, with increasing concentration and pH, the metal‐binding affinity increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1091–1099, 2005     

Effect of solvents on performance of polyethersulfone ultrafiltration membranes: Investigation of metal ion separations

The new polyethersulfone (PES) based ultrafiltration membranes were formed using a two stage process of dry and wet phase inversion in non solvent coagulation bath. The effects of three different solvents such as, N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and Dimethyl sulphoxide (DMSO) of 82.5% and 85% concentrations on the performance of final membranes were extensively investigated. Scanning electron microscopy (SEM) image results proved that PES membranes with an asymmetric structure were successfully formed. The number of pores formed on the top layer of PES membranes using above-mentioned three solvents was the result of the combined effect of the thermodynamic properties of the system (composition, concentrations, and phase behaviour) and membrane formation kinetics, whereas, the formation of the macroporous sub layer of those membranes was controlled by the diffusion rate of solvent–nonsolvent. The flux of pure water, membrane resistance, mechanical stability, molecular weight cut-off (MWCO) and separation performance of the PES membranes were studied. Separation of metal ions from aqueous solutions was studied for Ni(II), Cu(II) and Cr(III) using two complexing polymer ligands: polyvinyl alcohol (PVA) and poly(diallyldimethylammonium chloride) (PDDA).The separation and permeate rate (flux) efficiencies of the new membranes are compared using different solvents and different PES/solvent compositions.     

Hindered diffusion of flexible polymers through polyimide ultrafiltration membranes

The hindered diffusion of polystyrene in dilute solutions of ethyl acetate through polyimide ultrafiltration membranes has been investigated. The present system did not show specific membrane‐solute interactions; furthermore, polystyrene can be considered as a flexible polymer coil. It is shown that the hindered diffusive permeability for monodisperse dilute solutions for a series of molecular weights can be compared well with the diffusive permeability curve of one polydisperse dilute polystyrene solution. In the case of very dilute solutions, the polymer coils have no interaction with each other, and the whole range of molecular‐weight‐dependent permeabilities can be determined from only one measurement. The diffusion behavior of polydisperse solutions through various polyimide membranes has been investigated as well. It was found that the diffusive permeability curve is strongly dependent on the type of membrane, that is, on the pore size distribution. It was not possible to calculate a pore size distribution from diffusion experiments due to mathematical limitations. Nevertheless, it was shown that hindered diffusion measurements are useful to estimate a maximum pore size for each membrane. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1180–1193, 2000     

New chelating polymers for heavy metal ion sorption

Twenty‐six new chelating polymers containing pyridyl (Py) or bipyridyl (Bipy) units as ligating centers were synthesized by free‐radical reactions of 2‐vinylpyridine, 4‐vinylpyridine, or 4‐methyl‐4′‐vinyl‐2,2′‐bipyridine with different dimethacrylate crosslinkers and evaluated for heavy metal ion sorption from aqueous solutions. Both the Py‐ and Bipy‐containing polymers are highly selective for Cu(II) over Co(II) and Ni(II) and for Hg(II) over Cd(II). The polymeric materials with Bipy binding sites generally exhibit more efficient metal ion sorption than do the corresponding Py‐containing copolymers. The metal ion sorption capacity of the copolymer also depends on the structure of the dimethacrylate crosslinker. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 849–856, 1999     

Electrospun fibrous membranes for efficient heavy metal removal

Heavy metal pollution is a growing environmental problem in recent decades, which requires immediate and urgent action. In this article, we provide an overview of the works published in the last decade concerning the development of electrospinning‐based micro‐ and nano‐porous membranes for efficient heavy metal removal. Apart from their super‐high surface‐to‐volume ratio, electrospun nanofibers possess a variety of surface groups which enable their further functionalization and functional nanoparticle incorporation. Compared to typical adsorbents, electrospun fibrous membranes are superior in many ways like higher permeation flux, lower pressure drop, flexible component adjustment, and even multi‐target adsorption. Therefore, electrospun‐based fibrous membranes hold great potential on the treatment of heavy metal contaminants. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40864.     

Boron removal by ion exchange membranes

Boron removal from aqueous solution was studied through Neosepta-AHA membrane by Donnan dialysis (DD) method as a function of concentration, pH, conduct time, membrane structure and effect of accompanying ions. The feasibility of the system was examined and the highest boron removal was obtained when the pH of the feed phase was 9.5. On the other hand, it was determined that reverse flow transition was accelerated by counter ions and HCO₃⁻ ion was found to be more effective than Cl⁻ and SO₄⁻² ions. It was determined that obtained results of AHA membrane was compared with Neosepta AFN and AMH membranes and the flow rate of boron through Neosepta AHA, AFN and AMH anion exchange membranes were found to be between 3.10⁻⁸−3232.10⁻⁸ mmol cm⁻² s⁻¹ depending on concentration of feed and receiver phases, pH as well as counter ion properties. The order for recovery of boron for membranes was found to be as AFN>AMH>AHA. It could be concluded that the DD method is an appropriate method for boron removal from aqueous solution when an appropriate counter anion was chosen at suitable pH value.     

Application of ultrafiltration membranes for removal of humic acid from drinking water

Humic acids are primarily a result of the microbiological degradation of surrounding vegetation and animal decay and enter surface waters through rain water run-off from the surrounding land. This often gives rise to large seasonal variations, high concentrations in the wet season and lower concentrations in the dry season. Alone humic acid is just a colour problem but when present in conventional treatment processes like chlorination, carcinogenic by-products like trihalomethane and haloacetic acid are formed. This, in addition to the demand for clean potable drinking water, has sparked extensive research into alternative processes for the production of drinking water from various natural/industrial sources. One of the major areas of focus in these studies is the use of membranes in microfiltration, ultrafiltration and nanofiltration. In this report the humic acid removal efficiency of ultrafiltration membranes with 3 kDa, 5 kDa and 10 kDa MWCO is examined. The membranes were made of regenerated cellulose and were in the form of cassette providing a 0.1 m² surface area. At first distilled and deionised water, known as milliQ water, was used as the background feed solution to which humic acid powder was added. It was found that all three membranes removed humic acid with an efficiency of approx. 90% and were capable of reducing initial concentrations of 15mg/L to below the New Zealand regulatory limit of 1.17 mg/L. The permeate flux at a transmembrane pressure of 2.1 bar was approx. 20 l/m²/h (LMH) and 40 LMH, respectively through the membranes with MWCO 3 kDa and 5 kDa. These membranes experienced significant surface fouling resulting in retentate flow rates as low as 11 litres per hour after just four runs compared to the recommended 60–90 l/h. Cleaning with 0.1 M NaOH slightly improved the retentate flow rate, but well below those obtained with fresh membranes. The 10 kDa membrane provided high retentate flow rates which evidently minimised fouling by providing a good sweeping action across the membrane surface while maintaining humic acid removal below the regulatory 1.17 mg/L level. The permeate flux through this membrane was initially high (140–180 LMH) and reduced to approx. 100 LMH after 10–12 min of operation. Increasing the initial humic acid feed concentration from 10 mg/L to 50 mg/L did not significantly decrease humic acid removal efficiency although the retentate flow rate was lower at higher concentrations. Finally the tap water was tested as the background solution and treated for the removal of humic acid. The presence of ions and other impurities in the tap water had little effect on humic acid removal. However, the permeate flux through 10 kDa membrane decreased from 100 LMH for milliQ water to 60 LMH for tap water after 20 min of operation.     

Functional water‐soluble polymers: polymer–metal ion removal and biocide properties

Water‐soluble polymers have attracted much interest due to their potential applications in environmental protection engineering to remove harmful pollutants and in biomedicine in the areas of tissue engineering, within‐body implants or other medical devices, artificial organ prostheses, ophthalmology, dentistry, bone repair, and so on. In this review, particular emphasis is given to the ability of water‐soluble polymers with amine, amide, carboxylic acid, hydroxyl and sulfonic acid functional groups to remove metal ions by means of the liquid‐phase polymer‐based retention (LPR) technique that combines the use of water‐soluble polymers and ultrafiltration membranes. The second part is dedicated to showing the potential application of functional water‐soluble polymers and their polymer–metal complexes as biocides for various bacteria. These polymers and polymer–metal complexes show an efficient bactericide activity, especially to Gram‐negative bacteria, Staphylococcus aureus reaching concentrations lower than 4 µg mL^?1. This activity depends on polymer size, type of metal ion, contact time and concentration of polymer and metal ion. The discussion reveals that in the case of the LPR process the efficiency of metal ion removal depends strongly on the type of polymer functional group and the feed pH value. In general, two mechanisms of ion entrapment are suggested: complex formation and electrostatic interaction. In the case of the medical use of water‐soluble polymers and their complexes with metal ions, the review documents the unique bactericide properties of the investigated species. The polymer‐metal ion complexes show a reduced genotoxic activity compared with free metal ions. Copyright © 2009 Society of Chemical Industry     

Metal cation removal by P(VC-r-AA) copolymer ultrafiltration membranes

A series of amphiphilic copolymers containing poly(vinyl chloride-r-acrylic acid) (P(VC-r-AA) ) was synthesized and used to prepare membranes via a nonsolvent induced phase separation method. The prepared membranes were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and water contact angle and zeta potential measurements. The copolymer P(VC-r-AA) chains did not dissolved in a coagulation bath, indicating that the AA segments were completely retained within the membrane. Enriching degree of AA segments in surface layer was 2 for copolymer membrane. In addition, the introduction of AA segments made the membrane electronegative and hydrophilic so that the membrane was sensitive to the solution pH. The fouling resistance, adsorption of Cu(II), Cr(III) and Ce(IV) ions and the desorption properties of the membranes were also determined. The copolymer membranes exhibited good antifouling performance with a fouling reversibility of 92%. The membranes also had good adsorption capacities for Cu(II), Cr(III) and Ce(IV) ions. The optimal pH for Cu(II) adsorption was 6 and the copolymer membrane has potential applications for low concentration Cu(II) removal.

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Heavy metal ion removal by amidoximated bagasse

Amidoximated bagasse (Am‐B) was prepared by treating sugarcane bagasse fibers with acrylonitrile in the presence of sodium hydroxide followed by aqueous hydroxyl amine. Adsorption of some heavy metal ions, namely, Cu(II), Hg(II), Ni(II), Cr(III), and Pb(II) on the prepared Am‐B at different metal ion concentration, intervals, and temperatures was studied. Also, the selectivity of the prepared Am‐B toward adsorption of the aforementioned metal ions in an equimolar mixture was studied. The effect of regeneration of Am‐B using ethylenediamine tetraacetic acid disodium salt (EDTA), up to five times, on its adsorption capacity of the aforementioned metal ions was investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 666–670, 2003