Polymer-enhanced Ultrafiltration Research Articles

Removal of boron from water through soluble polymer based on N-methyl-D-glucamine and regenerated-cellulose membrane

This paper presents a systematic study of boron removal from simulated and real aqueous systems in northern Chile by means of polymer-enhanced ultrafiltration. Poly(glycidyl methacrylate-N-methyl-D-glucamine), P(GMA-NMG), was used to form complexes with boron, and a cellulose-regenerated membrane was used as a complex separator. The first tests were performed using two simulated water samples from northern Chile with the same pH and concentrations of boron, arsenic, and chloride. P(GMA-NMG) showed a maximum of 60% boron retention for these artificial waters. Studies of boron enrichment using P(GMA-NMG) with simulated water showed that the soluble polymer reached maximum retention capacity values between 2.0 and 4.0 mg of B retained per gram of polymer. SEM images and FTIR spectroscopy confirm the deposition of the polymer on the surface of the membrane after polymer-enhanced ultrafiltration, which explains the permeate flux decay observed in retention experiments. Finally, sorption–desorption tests of boron from real water samples show that it is possible to use the polymer P(GMA-NMG) to remove boron from waters of northern Chile. It is also possible to release the retentate and regenerate the water-soluble polymer.

Preparation and evaluation of heavy metal rejection properties of polysulfone/chitosan, polysulfone/N-succinyl chitosan and polysulfone/N-propylphosphonyl chitosan blend ultrafiltration membranes

Heavy metal rejection properties of chitosan based polysulfone/chitosan (PSf/CS), polysulfonef/N-succinyl chitosan (PSf/NSCS) and polysulfone/N-propylphosphonyl chitosan (PSf/NPPCS) ultrfiltration (UF) membranes were evaluated. The rejection of membranes towards the copper, cadmium and nickel ions was studied during ultrafiltration (UF) by polymer enhanced ultrafiltration (PEUF) processes. The flux change during the UF process and the effect of pH on the rejection were determined. The membrane recycling property was studied during PEUF process by filtering chelated CuSO4 solution. A maximum of 78% of Cu, 73% of Ni and 68% of Cd rejection for M-5 membrane, 75% of Cu, 71% of Ni and 66% of Cd rejection for M-8 membrane and 76% of Cu, 69% of Ni and 66% of Cd rejection for M-2 membrane with reasonably good flux was observed. Further improvement in heavy metal ion rejection was achieved by PEUF process. Membrane M-5 showed a maximum of 98%, 95% and 92% rejection for Cu, Ni and Cd respectively with steady state flux of 117L/m2h. An increase in membrane recycling property after the metal ion rejection was mainly attributed to the hydrophilicity of CS, NSCS and NPPCS.

Poly(N‐vinylpyrrolidone‐co‐2‐acrylamido‐2‐methylpropanesulfonate sodium): Synthesis, characterization, and its potential application for the removal of metal ions from aqueous solution

ABSTRACTIn the current study, poly(N‐vinylpyrrolidone‐co‐2‐acrylamido‐2‐methylpropanesulfonate sodium), poly(VP‐co‐AMPS), was prepared and used for the removal of Cu2+, Cd2+, and Ni2+ ions via a polymer‐enhanced ultrafiltration (PEUF) technique. The copolymer was synthesized by radical polymerization in an aqueous medium with a comonomer feed composition of 50:50 mol %. The molecular structure of the copolymer was elucidated by ATR‐FTIR and 1H NMR spectroscopy, and the average molecular weight was obtained by GPC. The copolymer composition was determined to be 0.42 for VP and 0.58 for AMPS by 1H NMR spectroscopy. The copolymer and homopolymers exhibited different retention properties for the metal ions. PAMPS exhibited a high retention capacity for all of the metal ions at both pH values studied. PVP exhibited selectivity for nickel ions. Poly(VP‐co‐AMPS) exhibited a lower retention capacity compared to PAMPS. However, for poly(VP‐co‐AMPS), selectivity for nickel ions was observed, and the retention of copper and cadmium ions increased compared to PVP. The homopolymer mixture containing PAMPS and PVP was inefficient for the retention of the studied metal ions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41272.

Cadmium and zinc removal from water by polyelectrolyte enhanced ultrafiltration

The efficiency of two metal ions (cadmium, zinc) removal from aqueous solutions by ultrafiltration (UF) and Polymer Enhanced Ultrafiltration (PEUF) processes were investigated in this work. The UF and PEUF studies were carried out using an ultrafiltration tangential cell system equipped with 5.000 MWCO regenerated cellulose. A water-soluble polymer: the polyacrylic acid (PAA) was used as complexant for PEUF experiments. The effects of transmembrane pressure, pH, metal ions and loading ratio on permeate fluxes and metal ions removals were evaluated. In UF process, permeate fluxes increase linearly with increasing pH for different transmembrane pressure, which may be the consequence of the formation of soluble metal hydroxyl complexes in the aqueous phase. In PEUF process, above pH 5.0, the Cd(II) retention reaches a plateau at 90% and Zn(II) at 80% for L

Thermo-responsive properties of poly(N-isopropylacrylamide-co-acrylic acid) hydrogel and its effect on copper ion removal and fouling of polymer-enhanced ultrafiltration

Poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-co-AA) hydrogels with thermo-responsive properties were used as water-soluble polymer in a polymer-enhanced ultrafiltration (PEUF) process. The hydrogel–metal complexes were retained by cellulose acetate UF membrane (MWCO=20kDa) and their fouling behaviour were investigated at different pH and temperature. It was found that at lower temperature (<40°C), the retention of copper ion is superior compared to higher operating temperature. It provided more than 98% retention at pH 5 for 50ppm of Cu2+ using 0.5gL−1 PNIPAM-co-AA. Membrane at higher temperature showed the least fouling phenomenon as observed from the drastic increased of permeation flux. At higher temperature, the collapsed hydrogels became more hydrophobic therefore not favouring the interactions with the hydrophilic membrane surface.

Removal of heavy metal ions from mixed solutions via polymer-enhanced ultrafiltration using starch as a water-soluble biopolymer

In this study, aqueous solutions containing mixtures of heavy metals namely Zn (II), Pb (II), Cr (III), and Cr (VI) were treated by polymer-enhanced ultrafiltration (PEUF) using unmodified starch as binding biopolymer. The performance of starch in removing these heavy metals was compared with that of polyethylene glycol (PEG) a commonly used polymer in PEUF processes. Rejection coefficients and flux were studied under different values of pH solution and metal ion concentrations maintaining the transmembrane pressure constant at 1.5 bar. At pH 7, and starch concentration of 0.05%, the rejection was the highest at around 90%. As metal ion concentration increased from 10 to 50 mg/L, the rejection of metal ions decreased. It was found that starch gave higher rejection for Zn (II) and Cr (III) at 0.05 g/L of polymer concentration, whereas 1 g/L of PEG concentration gave higher rejection for Cr (VI) at 10 mg/L. The influence of metal ion concentration on Pb (II) rejection is not significant for the two selected polymers. The rejection of these metal ions by starch in this study is found to be influenced by granule structure that generally behaved in a non-ionic manner. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 359–367, 2015

Removal of zinc and lead ions by polymer-enhanced ultrafiltration using unmodified starch as novel binding polymer

The removal of zinc and lead from aqueous dilute solutions by polymer-enhanced ultrafiltration process using unmodified starch as a new binding polymer was studied. Experiments were performed to determine the effects of transmembrane pressure, pH, concentration of metal ions on the retention and permeate flux. The performance of the proposed new binding polymer was compared to that of polyethyleneimine a conventional polymer frequently used in polymer-enhanced ultrafiltration. The retention of zinc and lead ions reached 96 and 66 %, respectively, using 0.05 % unmodified starch at pH 7. Overall unmodified starch showed better retention for zinc ions then polyethyleneimine, whereas polyethyleneimine retention for lead ions was higher. Solution pH was found to have little effect on flux.

Experimental analysis, modeling and optimization of chromium (VI) removal from aqueous solutions by polymer-enhanced ultrafiltration

In the present study, an attempt was made to remove toxic heavy metal ion chromium (VI) using polymer-enhanced ultrafiltration (PEUF) process and polyethyleneimine (PEI) was selected as the chelating agent. The objective purpose of this work was to predict the performance index (PFI) of the membrane evaluated as the solute rejection times the permeate flux and then to optimize the process conditions, namely, cross-flow rate, transmembrane pressure, pH and polymer to metal ratio in order to maximize performance index for the removal of toxic chromium (VI) from aqueous solution. The maximum PFI values suggested by the Central Composite Design of response surface methodology (RSM) were quite high; the predicted PFI, especially for polymer to metal ratio >1 was 92.53Lm−2h−1, which hinted at the success of PEUF technique. Further, Artificial Neural Network (ANN) model was generated to validate the RSM predictions. The differences observed while comparing the optimization results along with the response surface (RS) plots derived by RSM with those provided by ANN models, reflected the advantages and disadvantages of both the methodologies, and essentially the non-linear character of the PEUF process. The accuracy of the predictive models was, nevertheless, affirmed by the comparison drawn between the predicted and experimental data.

Removal of arsenic from water by combination of electro‐oxidation and polymer enhanced ultrafiltration

Water‐soluble poly[glycidyl methacrylate N‐methyl d‐glucamine], P(GMA‐NMG), was synthesized and purified by ultrafiltration membranes. It was subsequently used for arsenic removal by coupling electro‐oxidation (EO) and polymer‐enhanced ultrafiltration (PEU) processes. In the EO‐PEU combined process, P(GMA‐NMG) was first used as supporting electrolyte during the exhaustive electro‐oxidation of As(III) to As(V) and then it was used to remove As(V) from aqueous solution through PEU. At first stage, the complete EO of As(III) to As(V) was performed with a platinum reticulated vitreous carbon (RVC)‐modified electrode and the advancement of the electrolysis was monitored by analytical electrodes. After the oxidation of As(III) to As(V), the PEU was carried out by washing method using regenerate cellulose membrane and 1 bar of pressure. The effects of supporting electrolytes and pH on EO‐PEU combined process were investigated. The best results showed that by using P(GMA‐NMG) as supporting electrolyte during the complete electro‐oxidation of As(III) to As(V) followed by PEU separation, almost 80% of As(V) was removed at pH 10. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 918–924, 2014

High performance ligands for the removal of aqueous boron species by continuous polymer enhanced ultrafiltration

Boron is an essential element for plant growth, but it may also result in toxicity when present in excessive amounts. In this study, continuous polymer enhanced ultrafiltration (PEUF) was developed to selectively recover aqueous boron species (collectively termed “boron” hereafter) from solution. The PEUF process consisted of complexing boron to a water-soluble polymer, removing all non-complexed solutes by UF, restoring the unloaded polymer, and isolating the newly freed boron by UF. Three different polymers were synthesized to complex boron. One was derived from N-meth-yl-D-glucamine (P1). Two others were derived from iminodipropyleneglycol (P2 and P2G). Operating parameters such as the boron/polymer ratio (0.01–1), pH value (7–10), and polymer type (P1, P2, and P2G) were assessed. An increase of the pH value led to increased boron retention. As well, a decreased loading value enhanced retention. A maximum retention of 90.1% exceeded the highest values reported in the literature under similar conditions. The permeate flux remained constant at≈20L/m2h, and operation was unaffected by classic problems such as fouling. The results showed that continuous PEUF utilizing the above polymers could serve as an alternative method for the removal of environmental boron.

Novel boron specific copolymers with quaternary amine segments for efficient boron removal via PEUF

In this study, a copolymer, poly (vinyl amino-N, N′-bis-propane diol-co-DADMAC) (GPVA-co-DADMAC) was synthesized in three comonomer ratios (2%, 5% and 10%) and efficiently exploited for boron removal via polymer enhanced ultrafiltration (PEUF). Boron concentration could be reduced from 10ppm down to 0.8ppm by the employment of novel copolymer in continuous PEUF at pH 9 and boron-to-polymer mass ratio (loading) of 0.001. Polymer precipitation was not observed even after complexation with boron. Boron retention was found to be highly pH dependent and boron concentration dependent at constant loading. Hence, efficient polymer regeneration can be expected due to high pH and concentration dependency of boron complexation. Moreover, permeate flux was not affected by the polymer concentration in the conditions studied (polymer concentration ≤10g/L; pressure drop: 2bar). Dynamic and static light scattering measurements showed that gyration radius of the polymers rises by dilution or by increasing pH of the solutions. Furthermore, a two-step equilibrium model was correlated with the experimental boron retention data. Having high boron binding affinity, hydrolytic stability and efficiency in boron removal, the synthesized copolymers possessing DADMAC segments seemed to be attractive and useful for large scale water treatment with PEUF systems.

Imino-bis-propane diol functional polymer for efficient boron removal from aqueous solutions via continuous PEUF process

Boron contamination is an environmentally serious problem especially due to its hazards on plants. In this work, newly synthesized poly (vinyl amino-N, N′-bis-propane diol) (GPVA) is presented as an excellent chelating polymer for boron removal. Boron concentration could be reduced from 10ppm down to 0.4ppm via total recycle Polymer Enhanced Ultrafiltration (PEUF). Experiments revealed that the polymer shows the highest PEUF boron rejections (96% at pH 9.0) reported so far, without precipitation in a wide concentration range. Detailed investigations such as effect of pH, loading (boron-to-polymer mass ratio) and polymer concentration showed that, the boron binding is highly pH dependent and increases with boron concentration at constant loading. Furthermore, permeate flux was found as nearly independent from polymer concentration up to 10g/L at 200kPa pressure drop. In addition, gyration radius of the polymer in solution increases while increasing pH and polymer concentration in the presence of boron as inferred from Dynamic and Static Light Scattering measurements. Regarding with high efficiency and hydrolytic stability of GPVA, its use in combination with PEUF would be of interest for large scale and long term use in boron removal.

Effect of membrane surface charge on filtration of heavy metal ions in the presence and absence of polyethylenimine

Abstract Polymer enhanced ultrafiltration (PEUF) was used to study the retention and flux of aqueous solutions of heavy metals. The metal ions investigated were: Cu2+, Zn2+, Ni2+, Cr6+, Co2+ and Cd2+. For each metal solution, stirred dead-end ultrafiltration experiments were performed in the presence and absence of polyethylenimine (PEI) at different pHs. Addition of PEI significantly affected both the retention of the metal ions and the flux of the filtration process. In the absence of PEI, significant rejection of metals only occurred at higher pH values. This can be attributed to the formation of insoluble metal compounds (hydroxides) at pH 6 or greater. In the presence of PEI the retention was greater than the retention without PEI due to the formation of metal/ polymer complexes. This retention was also sensitive to pH with higher values of retention at near neutral or slightly acidic conditions. Although a reduction of flux due to the addition of PEI was anticipated (the flux was reduced by about 50...

Polymer enhanced ultrafiltration of mercury using chitosan impregnated ceramic membrane

Abstract This work reports the removal of mercury from synthetic wastewater by polymer enhanced ultrafiltration (PEUF). A ceramic membrane was prepared from locally available clay and the membrane surface was impregnated using chitosan to reduce the pore size to ultrafiltration range. The average pore size of the membrane was determined from air permeability data and found to be 12 nm. Polyvinyl alcohol (PVA) was used as the chelating agent. The effects of PVA dose, mercury concentration, pH and transmembrane pressure on mercury rejection were investigated. Rejection increased with the increase of PVA dose and decreased with the increase of initial mercury concentration and transmembrane pressure. The maximum rejection of mercury and PVA was found to be 85% and 99.7% respectively. The optimum pH for the operation was also determined. The flux declination rate was observed to be more at higher PVA dose and less at higher pressure. A preliminary membrane cost estimation approach was adopted based on the man...

Polymer enhanced ultrafiltration of mercury using chitosan impregnated ceramic membrane

Abstract This work reports the removal of mercury from synthetic wastewater by polymer enhanced ultrafiltration (PEUF). A ceramic membrane was prepared from locally available clay and the membrane surface was impregnated using chitosan to reduce the pore size to ultrafiltration range. The average pore size of the membrane was determined from air permeability data and found to be 12 nm. Polyvinyl alcohol (PVA) was used as the chelating agent. The effects of PVA dose, mercury concentration, pH and transmembrane pressure on mercury rejection were investigated. Rejection increased with the increase of PVA dose and decreased with the increase of initial mercury concentration and transmembrane pressure. The maximum rejection of mercury and PVA was found to be 85% and 99.7% respectively. The optimum pH for the operation was also determined. The flux declination rate was observed to be more at higher PVA dose and less at higher pressure. A preliminary membrane cost estimation approach was adopted based on the manufacturing cost of raw materials and reported.

Removal of heavy metal ions by polymer enhanced ultrafiltration: Batch process modeling and thermodynamics of complexation reactions

A batch process of polymer enhanced ultrafiltration (PEUF) for the removal of Cu(II) ions from aqueous effluents has been developed in an installation equipped with mineral membranes at laboratory scale. It has been proposed a model based on mass conservation equations and kinetics of complex formation reactions of macromolecular species comprising a metallic ion and a water-soluble polymer. The model predicts the temporal evolutions of metal concentration in permeate and rejected streams. Moreover, it enables to establish the operating pH values to tackle the stages of metal retention and polymer regeneration, and also to calculate conditional formation constants of the macromolecular complex as a function of pH and temperature.

Study of Cr(III) desorption process from a water-soluble polymer by ultrafiltration

Polymer Enhanced Ultrafiltration (PEUF) has been reported as a suitable process to separate heavy metals from pollutant wastewaters. Desorption of metal ion is a required step in order to recycle the polymer. At acidic pH values, nearly quantitative desorption has been achieved for divalent ions but a limited efficiency has been reached for trivalent ions. This paper studies the Cr(III) desorption yield from ethoxylated polyethylenimine (EPEI) by means of an ultrafiltration ceramic membrane. Experimental results show that about only 20% of the chromium (III) remains adsorbed at pH 1. The feasibility of several sorption isotherms (Langmuir, Freundlich, Redlich–Peterson and Temkin) was tested to describe the binding of chromium (III) and EPEI and the Freundlich one showed the best fits with experimental data at all pH values. Further, it was observed that normalized permeate fluxes decreased as initial Cr(III) concentration and pH were higher. Membrane fouling was analyzed by long–term experiments at different pHs which indicate that the intermediate pore blocking was the main mechanism of fouling.

Rare Earth Ion from Aqueous Solution Removed by Polymer Enhanced Ultrafiltration Process

An efficiency of rare earth (europium, Eu) removal from aqueous solutions by polymer enhanced ultrafiltration (PEUF) process was investigated using two water-soluble polymers polyacrylic acid (PAA) and polyethylenimine (PEI). The effects of loading ratios of Eu to PAA or PEI, pH of solution and the added salt on Eu removal were evaluated. It was shown that the binding capacities for PAA and PEI to Eu ions were 0.8g Eu/g PAA and 0.5g Eu/g PEI, respectively. Eu ion rejection R decreased significantly at a low pH compared to the results at high pH, regardless of using PAA or PEI. Compared to the PAA case, PEI enhanced UF was more sensitive with changing pH. The effect of the added salt was slightly weak at pH 4-5.At the decomplexation stage, when permeate volume was equal to three times than that of the retentate, Eu removal efficiency (X) of Eu-PAA enhanced UF was 79.5% while that of Eu-PEI enhanced UF was 76.1%, and the polymer PAA and PEI could be recovered more than 97% and 93%, respectively. Eu in the retentate could be extracted effectively and the purified PAA and PEI solution were obtained. The recovered PAA and PEI solution was same as the fresh PAA and PEI solution in PEUF processes carried out by using the recovery recovered PAA and PEI as complex agents.

Polymer enhanced membrane filtration of metals: retention of single and mixed species of metal ions based on adsorption isotherms

The binding and retention of single metal ions and mixtures of metal ions with polyethylenimine (PEI) was studied using polymer enhanced ultrafiltration (PEUF). Using a highly branched chain form of PEI (Sigma Aldrich 181979) with an average molecular weight 750,000 and approximately 60,000, ultrafiltration experiments were carried out in the stirred dead-end ultrafiltration mode. The results of the binding studies show that the Langmuir isotherm offers a good description of the binding process. At pH 5.5, the maximum polymer binding (Q max) and binding affinity constant (K L) were determined according to Langmuir isotherms. It was observed that the maximum amount of metal ions bound to the polymer for Cu2+, Zn2+, Ni2+ and Cd2+ decreased substantially in solutions containing mixtures of metal ions when compared to the values obtained for single metal ion solutions. For Cr6+ and Co2+ no significant decrease was seen. These data indicate that the binding capacity of Cr6+ and Co2+ remain constant in competit...

Chitosan based ceramic ultrafiltration membrane: Preparation, characterization and application to remove Hg(II) and As(III) using polymer enhanced ultrafiltration

This work presents the fabrication of chitosan based ceramic membranes using dip coating technique. Low-cost ceramic supports were prepared from local clay of IIT Guwahati and kaolin with an average pore size of 1093 nm and porosity of 0.37. Different ceramic membranes were prepared by varying chitosan concentration and dipping time and were characterized using scanning electron microscope (SEM), air and hydraulic permeability tests. The average pore sizes were in the range of 760–13 nm which confirmed that the chitosan impregnated ceramic membranes were applicable for both microfiltration (MF) and ultrafiltration (UF) applications. An increase in both chitosan concentration and dipping time was found to reduce the pore size. The lowest pore size ultrafiltration membrane (pore size: 13 nm) was used for the removal of mercury and arsenic from wastewater by polymer enhanced ultrafiltration (PEUF) technique using polyvinyl alcohol (PVA) as the chelating agent. The effects of initial concentrations of mercury, arsenic and PVA on the extent of removal of both the heavy metals were investigated in detail. The efficiency of PEUF was explored in terms of rejection of metals and permeates flux. Almost 100% removals were observed for both 500 μg L −1 mercury and 1000 μg L −1 arsenic.