Polymer-enhanced Ultrafiltration Research Articles

Hexavalent chromium removal from aqueous solution by polymer-enhanced ultrafiltration

This study compares the effects of two different polymers using polymer-enhanced ultrafiltration (PEUF) to remove hexavalent chromium ions from an aqueous solution with a polyacrylonitrile (PAN) membrane. Two water-soluble polymers were examined: starch and polyethylene glycol (PEG). The analysis explored the impacts of solution pH, pressure, and polymer concentration on hexavalent chromium rejection and permeate flux. The results show that the hexavalent chromium rejection increased with increasing polymer concentration and solution pH. The rejection reached 90% and 96% with starch and PEG, respectively. At pH 10, it reached 100% with starch and 91% with PEG. Increasing the transmembrane pressure doesn’t affect the rejection of hexavalent chromium.

Removal of Cr(VI) from tanning wastewater using chitosan-SDS complexes in PEUF: Optimization and analysis via response surface methodology

In this study, we addressed the removal of hexavalent chromium (Cr(VI)), a highly toxic and soluble anionic heavy metal, using enhanced ultrafiltration (UF). The objective was to eliminate Cr(VI) species with molecular weights beyond the retention capability of standard UF membranes and achieve their retention through the incorporation of polymers and polymer-surfactant complexes within the UF membrane. Chitosan, a cationic polymer, and sodium lauryl sulfate (SDS), an anionic surfactant, were used in this context. The Cr(VI) solution was subjected to ultrafiltration in a laboratory-scale membrane cell, and its removal was assessed spectrophotometrically. Polymer and surfactant structures were characterized using turbidity, electrical conductivity, SEM-EDX, and FTIR analyses. Experimental studies were conducted using the face-centered central composite design (CCD) of the response surface methodology (RSM) to determine optimal removal and permeate flux values, as well as to unveil the relationships between the studied factors and the resulting responses.The results revealed that 100 % of the Cr(VI) species were removed from wastewater in the chitosan-based polymer-enhanced ultrafiltration (PEUF) study. With the chitosan-SDS complex, a removal efficiency of 98.33 % was achieved in synthetic wastewater. The PEUF study employing chitosan and the chitosan-SDS complex yielded permeate flux values of 30.73 L/h/m2 and 53.89 L/h/m2, respectively. The optimized conditions obtained from the models were then applied to real wastewater obtained from a leather industry tanning process. In the case of chitosan and the chitosan-SDS complex, the Cr(VI) removal efficiencies in the real wastewater were 4.40 % and 98.33 %, respectively.

Removal of Hexavalent Chromium from Water by Chitosan-Enhanced Ultrafiltration

Polymer-enhanced ultrafiltration has gained increasing attention as a selective separation process to remove small solutes, such as metal ions, from water or wastewater. Hexavalent chromium Cr(VI) is one of the metal ions in wastewater that has received considerable attention because of its toxicity. Chitosan was used in this study as the polymer to bind Cr(VI) to enhance its removal by ultrafiltration. The effects of chitosan-to-Cr(VI) ratio on Cr(VI) rejection and permeate flux were investigated. In addition, the fouling tendency was evaluated. Results showed that the addition of chitosan with a mass ratio of 12.5 increased the Cr (VI) rejection from 28% to 75% with a slight reduction in permeate flux from 12.5 L.m−2.h−1 to 9.3 L.m−2.h−1. Moreover, the reduced flux after 100 min of operation could be recovered using the backwash procedure by 89% compared to the initial flux.

Progress of Ultrafiltration-Based Technology in Ion Removal and Recovery: Enhanced Membranes and Integrated Processes

Toxic ions from industrial wastewater entail important challenges to the environment. Ultrafiltration (UF) with low operation pressure and high permeability has been widely used for macromolecules and suspended solids separation. However, UF cannot be directly used to separate ions from wastewater due to the large pore size of UF membranes. Recently, the design of enhanced UF membrane structures and UF-based integrated processes expands the application of UF for ion removal. This review aims to summarize the latest developments of UF membranes preparation as well as integrated UF processes in ion removal. First, the advanced materials for UF membranes preparation are discussed, with specific attention on active nanomaterials including inorganic materials, organic materials, and biomaterial-based materials. The design principles such as pore size control and composite thin layer fabrication of enhanced UF-based membranes for ion removal are illustrated. Next, integrated processes such as micellar-enhanced UF, polymer-enhanced UF, electro-driven UF, and other UF-based combined processes are reviewed. Finally, current application limitations and future perspectives in the enhanced UF membrane for ion removal are discussed. This review presents potential approaches for the preparation and application of enhanced UF membranes in sustainable ion removal from wastewaters.

Removal of Cr(VI) by ultrafiltration enhanced by a cellulose-based soluble polymer

In this study, polymer-enhanced ultrafiltration (PEUF) was used to remove chromium ions (Cr(VI)) from water using quaternized hydroxyethyl cellulose ethoxylate (QHECE) as the extracting agent. The polymer was structurally and thermally characterized before and after loading, where Fourier transform spectra were used to corroborate the Cr(VI) binding sites. Thermogravimetric analysis showed an increase in the residual mass due to the formation of macromolecular aggregates from the water-soluble polymer (WSP) and Cr(VI). SEM/EDX was used to corroborate the presence of Cr(VI) on the WSP surface. The washing method was used to study Cr(VI) retention as a function of the solution pH, WSP quantity, pressure, Cr(VI) concentration, membrane type and presence of interfering ions (NaCl, Na2SO4 and NaHPO4) at three Cr(VI):interferent molar ratios (1:1, 1:2 and 1:4). In addition, the polymer reusability was studied over six sorption-desorption cycles. Next, the enrichment method was used to determine the maximum retention capacity of the polymer. Finally, PEUF was used to test Cr(VI) removal in simulated industrial electroplating wastewater.By varying different parameters, 92 % retention efficiency was achieved at pH 9.0 using a polymer mass of 50 mg, a pressure of 2.0 bar, an initial Cr(VI) concentration of 30 mg L−1 and a 10-kDa regenerated cellulose membrane. Increasing the Cr(VI):interferent molar ratio was found to decrease the retention efficiency, and significant decrease was obtained for the highest ratio of sulfonate ions to Cr(VI) used. Finally, the maximum retention capacity was determined to be 299.46 mg g−1 using the enrichment method, and it was demonstrated that the polymer could be reused for up to four consecutive sorption-desorption cycles.

Polymer-enhanced ultrafiltration–electrodeionization hybrid system for the removal of boron

The consumption of ultrapure water (UPW) is continuously increasing owing to its numerous applications.

Removal of Antimony(III) and Antimony(V) from water samples through water-soluble polymer-enhanced ultrafiltration

Addressing antimony (Sb) contamination, which is caused by the use of Sb compounds in various industries, is crucial. This study aims to compare two different Sb removal mechanisms: ion exchange and chelation. Therefore, two different water-soluble polymers—glycidyl methacrylate-N-methyl-D-glucamine and poly 2-(acryloyloxy)ethyl trimethylammonium chloride—were synthesized and used to remove Sb(III) and Sb(V) using the polymer-enhanced ultrafiltration (PEUF) method.The removal of Sb(III) was pH-dependent and extremely difficult at a pH of 1.2. However, when the pH of the solution was increased to 11, the Sb(III) removal rate increased to 77%. The Sb(III) removal rate was 28% at an Sb(III):polymer mole ratio of 1:5, which increased to 77% at a mole ratio of 1:20. Sb(III) removal was discovered to be unaffected by the low concentrations of Na+, K+, Ca2+, and Mg2+ ions in the solution, maintaining a Sb(III) removal rate of 77%.The test parameters showed different characteristics for Sb(V) removal. Increasing the pH of the solution from 1 to 9 correspondingly increased the removal rate from 0% to 45%, but increasing it further to 11 decreased the removal rate to 14%. The removal rate of Sb(V) was 67% at a Sb(V):polymer mole ratio of 1:60. Sb(V) removal was discovered to be unaffected by low concentrations of SO42−, NO3−, and PO43− anions in the solution. However, notably, the Sb(V) removal rate decreased from 67% to 58% in the presence of Cl− ions.The results demonstrate that Sb removal via chelation was more effective than by ion exchange, and it remained unaffected by the presence of interfering ions.

Removal of Cerium from Wastewater Based on Polymer-Enhanced Ultrafiltration Technology through Polyethersulfone-g-Poly(N-vinyl-2-pyrrolidone) Modified Membrane

Removal of Cerium from Wastewater Based on Polymer-Enhanced Ultrafiltration Technology through Polyethersulfone-g-Poly(N-vinyl-2-pyrrolidone) Modified Membrane

Removal of Dyes by Polymer-Enhanced Ultrafiltration: An Overview.

The current problem of contamination caused by colored industrial effluents has led to the development of different techniques to remove these species from water. One of them, polymer-enhanced ultrafiltration (PEUF), has been systematically studied in this mini review, in which research works from 1971 to date were found and analyzed. Dye retention rates of up to 99% were obtained in several cases. In addition, a brief discussion of different parameters, such as pH, interfering salts, type of polymer, dye concentration, and membrane type, and their influence in dye removal is presented. It was concluded from the above that these factors can be adapted depending on the pollutant to be remediated, in order to optimize the process. Finally, theoretical approaches have been used to understand the intermolecular interactions, and development of the studied technique. In this revision, it is possible to observe that molecular docking, molecular dynamics simulations, density functional theory calculations, and hybrid neural-genetic algorithms based on an evolutionary approach are the most usual approximations used for this purpose. Herein, there is a detailed discussion about what was carried out in order to contribute to the research development of this important science field.

An integrated membrane distillation, photocatalysis and polyelectrolyte-enhanced ultrafiltration process for arsenic remediation at point-of-use

Arsenic contamination of drinking water is a result of natural and/or anthropogenic activities, causing undesirable detrimental effects on the environment and the human health. Herein, an integrated process based on Membrane Distillation (MD), photocatalysis and Polymer-enhanced Ultrafiltration (PEUF) was developed for an effective remediation of arsenic (As). This approach, whose effectiveness was demonstrated by experimental tests on artificial solution mimicking As-contaminated water in the area of Sila Massif (Italy), ensured a near total water recovery and a rational management of residual contaminants.MD allowed to produce high-quality freshwater from contaminated feedwater containing As in the range of 0.059-5 mg·L-1, without deterioration of the transmembrane flux up to a recovery factor of 98.8%. Furthermore, a photocatalytic step was applied on MD retentate to convert arsenite As (III) into arsenate As(V), the latter subsequently removed by PEUF with efficiency of 98.2%. Speciation analysis demonstrated the necessity to reduce the feed pH to 5.6 in order to avoid the risk of scaling in MD stage, whereas Na2CO3 softening at pH 9 before the photocatalytic stage ensured both the reactive precipitation of Ca and Mg ions and the depletion of bicarbonate ions.

Polyelectrolytes applied to remove methylene blue and methyl orange dyes from water via polymer-enhanced ultrafiltration

In the present work, polymer-enhanced ultrafiltration (PEUF) was used to study the purification of coloured wastewater. Methylene blue (MB) and methyl orange (MO) dyes were removed from aqueous solutions using water-soluble polymers: poly(2-acrylamide-2-methyl-1-propanesulfonic acid) (PAMPS) and poly(diallyldimethylammonium) chloride (PDDA), respectively. The PEUF technique has the advantage that it can be performed in homogeneous media to clean wastewater, where the novelty focuses on the water-soluble polymers used. Both polymers were first fractionated using an ultrafiltration membrane composed of regenerated cellulose with a molecular weight cut off (MWCO) of 10 kDa followed by subsequent freeze-drying. The removal of both dyes by ultrafiltration in the absence and presence of polymer was systematically studied. The performance of the polymers was studied under different parameters, such as the effect of the MWCO for the ultrafiltration membrane, the pH of the solution, the polymer:dye molar ratio, the initial dye concentration, the interference effect of NaCl and Na2SO4, and consecutive cycles of sorption-desorption. Under optimal conditions, a maximum removal efficiency of approximately 98% and 90% was achieved for MB and MO at pH 6.0 using initial MB and MO concentrations of 3.5 mg L-1 and 80 mg L-1, respectively, together with an ultrafiltration membrane with a MWCO of 10 kDa. The presence of interferents in the PEUF process was found to be not significant for dye elimination. Finally, the reusability of both polymers was demonstrated to be effective after four sorption-desorption cycles.

Removal of Zirconium (Zr) from Aqueous Solution by Polymer Enhanced Ultrafiltration

Although the world output of zirconium has been declining, increasing zirconium consumption cannot compete with this situation. For this reason, removal and recovery of zirconium become important. This work is focused on the removal of Zirconium (as ZrO22+) ions from an aqueous solution using polymer-enhanced ultrafiltration (PEUF) techniques with water-soluble Poly (sodium-p-styrene sulfonate, SSS) sorbent. The negatively charged sulfonic acid groups in the polymer interact with positively charged ZrO22+ cation thereby enabling the efficient removal of ZrO22+through ultrafiltration. The effect of polymer: zirconium mole ratio, initial solution pH, and the presence of interfering ions on the removal of zirconium was investigated. The obtained results demonstrated that ZrO22+ can be removed from the aqueous solution by the PEUF technique with more than 99% efficiency at pH ≥ 2 using polymer: Zr molar ratio of 5:1. The presence of interfering ions did not affect the percent removal of ZrO22+.

Removal of Nitrate from Wastewater with Polymer-Enhanced Ultrafiltration (PEUF)

Polymer-enhanced ultrafiltration (PEUF) is an advanced technology for the efficient separation of heavy metal ions and organic matter from outlet water. The removal of nitrate ions from wastewater via PEUF was investigated using polyethyleneimine(PEI) and cationic polyacrylamide(CPAM). When the concentration of NO3 - was 20 mg/L, the dosage of PEI/CPAM was 0.1 wt%, the best rejection were obtained, rejection of NO3 - were 92.8% and 80.2%, respectively, and rejection of PEI and CPAM were 92.3% and 83.3%, respectively. Effect of pH value on NO3 - rejection was obvious, rejection of NO3 - decreased sharply with the increase of pH value. However, there was no obvious changes on the PEI rejection. The PEUF process was considered to be more suitable for nitrate rejection using PEI as a polymer reagent.

Use of sodium alginate biopolymer as an extracting agent of methylene blue in the polymer‐enhanced ultrafiltration technique

AbstractIn this study, the removal of methylene blue (MB) cationic dye from an aqueous solution was investigated using the polymer‐enhanced ultrafiltration (PEUF) technique with sodium alginate (SA) as an extracting soluble polymer, in combination with an ultrafiltration membrane of regenerated cellulose with a 10 kDa molar mass cut‐off. SA was characterized via Fourier‐transform infrared spectroscopy and thermogravimetric analysis. For ultrafiltration studies, the washing method was used to evaluate various experimental variables, such as the pH, SA dose and initial MB concentration, and adsorption isotherms to identify the optimal adsorption conditions. Finally, the regeneration of the SA polymer was evaluated in five consecutive cycles of adsorption–desorption of MB. In the obtained characterization results, the structural composition of SA and the characteristic thermal stability of the polymer were verified. The PEUF results demonstrated that a retention capacity of 98% of the MB was realized at pH 8.0 using 0.025 g of SA at an initial optimal MB concentration of 50 mg L−1. It is possible to observe that the Freundlich model better explain the interaction between the dye and the polymer surface. According to the results is demonstrated the regeneration capacity of the polymer and its subsequent reuse.

Study on the treatment of sudden cadmium pollution in surface water by a polymer enhanced ultrafiltration process.

The removal of cadmium(ii) pollution in surface water by a polymer enhanced ultrafiltration (PEUF) process was investigated. Three water soluble polymers, chitosan (CTS), polyvinyl alcohol (PVA) and polyacrylate sodium (PAAS), were selected for this study. Of the three polymers, PAAS had strong interactions with Cd2+, and the PEUF achieved a high removal of Cd2+; therefore, PAAS was used as a complexing agent for the simulated cadmium pollution experiment. Experiments were performed as a function of the aqueous pH, polymer/Cd2+ ratio (P/M), ionic strength and humic acid. Under optimum experimental conditions, the Cd2+ removal rate reached 100%. pH was the main factor affecting removal of Cd2+, which decreased to 60% at a pH of 4. The Cd2+ removal was found to decrease as NaCl and HA were added. The analysis showed that the mechanism of NaCl could be a compressed electric double layer, while the mechanism of HA and H+ was competitive complexation. Finally, UF membrane fouling, the dissociation of PAAS–Cd and the regeneration of PAAS were investigated. The results showed that the higher P/M was, the lower the pH, the higher the HA concentration, and the more serious the UF membrane fouling were. The dissociation rate of PAAS–Cd reached 99.8% at a pH of 2.5. When the P/M was 5, the removal rate of Cd reached 99.6% with the addition of 20% new PAAS in the regenerate. This result showed that the PEUF process could be a promising method for removing Cd pollution in surface water.

Sulfate removal using colloid-enhanced ultrafiltration: performance evaluation and adsorption studies.

Colloid-enhanced ultrafiltration (CEUF), i.e., micellar-enhanced ultrafiltration (MEUF) and polymer-enhanced ultrafiltration (PEUF), was investigated to remove sulfate ions from aqueous solution in batch experiments, using cetyltrimethylammonium (CTAB) and poly(diallydimethylammonium chloride) (PDADMAC) as colloids, respectively. Ultrafiltration performance was evaluated under different initial concentrations of sulfate (0-20 mM) and CTAB/PDADMAC (0-100 mM). The highest retention rate (> 99%) was found in dilute sulfate solutions. At high sulfate concentrations (e.g., 10 mM), a dosage of 50 mM CTAB or PDADMAC can retain approximately 90% of sulfate ions. Though concentration polarization behavior was observed, membrane characterization indicated that the fouling was reversible and membranes can be reused. Furthermore, adsorption equilibrium and kinetics studies show that Freundlich isotherm and pseudo-second-order kinetics can describe the sulfate-colloid interaction, indicating that the surface of absorbents are heterogeneous and the rate-controlling step is chemisorption. Both MEUF and PEUF show potential as effective separation techniques in removing sulfate from aqueous solutions. Under the same conditions examined, PEUF shows advantages over MEUF in its higher retention at lower polymer-to-sulfate ratios, cleaner effluent, and higher adsorption capacity, but compromises on severer flux decline and a tendency of membrane fouling. To overcome this disadvantage, membranes with higher molecular weight cut-off can be used.

Complexation properties of water-soluble poly(vinyl alcohol) (PVA)-based acidic chelating polymers

Water-soluble polymers are attractive materials for pollutants removal thanks to their ability to easily interact with soluble metal cations. In the present contribution, the chemical modification of biocompatible and non-toxic poly(vinyl alcohol) (PVA) was achieved with ethylene diamine tetraacetic acid (EDTA) groups, thus leading to new water-soluble polymers, named PVA(EDTA). Modification was carried out using Mitsunobu's reaction as an original pathway to obtain statistical copolymers with different EDTA functionalization rates in the PVA chains. Preliminary study about the variation of EDTA rate and chain length permitted determining the optimal polymeric structures. Then, sorption properties of heavy metal (i.e. Co(II), Ni(II), Zn(II), Pb(II), Cd(II), Cu(II)) on structures containing 15% of chelating agent were determined by performing thorough adsorption isotherms or determining removal percentage, at a high or low concentration, respectively. Additionally, the performances of the polymers were tested in a more complex effluent constituted by previous pollutants in the presence of Ca(II) and Mn(II) cations. We demonstrated that water-soluble PVA(EDTA) led to a great improvement of sorption properties in comparison with PVA. Indeed, results obtained showed high sorption capacities for Pb(II), Ni(II), Zn(II), and good selectivity towards some cations, in consistency with EDTA-metal complex formation constants. Isotherm Titration Calorimetry measurements allowed evidencing the complexation stoichiometry, and determining the interaction constant and the enthalpy. This study highlighted the interest of modifying basic commercial polymers with chelating agents for further applications based on Polymer Enhanced Ultrafiltration (PEUF) process.

Electrochemical reduction of Cr(VI) in the presence of sodium alginate and its application in water purification

Chromium (Cr) is used in many manufacturing processes, and its release into natural waters is a major environmental problem today. Low concentrations of Cr(VI) are toxic to human health and living organisms due to the carcinogenic and mutagenic nature of this mineral. This work examined the conversion of Cr(VI) to Cr(III) via electrochemical reduction using gold electrode in an acidic sodium alginate (SA) solution and subsequent removal of the produced Cr(III)-SA by the polymer-enhanced ultrafiltration (PEUF) technique. A solution of SA in nitric acid was used both as an electrolytic medium during the voltammetric measurements and bulk electrolysis and as an extracting agent during the PEUF technique. The electroanalysis of Cr(VI) was performed by linear sweep voltammetry in the presence of acidic SA solution to study its voltammetric behavior as a function of the Cr(VI) concentration, pH, presence of Cr(III), SA concentration and scan rate. In addition, the quantitative reduction of Cr(VI) to Cr(III) was studied through the bulk electrolysis technique.The results showed efficient reduction with well-defined peaks at approximately 0.3 V vs. Ag/AgCl, using a gold working electrode. As the pH increased, the reduction signal strongly decreased until its disappearance. The optimum SA concentration was 10 mmol/L, and it was observed that the presence of Cr(III) did not interfere in the Cr(VI) electroanalysis. Through the quantitative reduction by bulk electrolysis in the presence of acidic SA solution, it was possible to reduce all Cr(VI) to Cr(III) followed by its removal via PEUF.

Removal of azoic dyes from aqueous solutions by chitosan enhanced ultrafiltration

A cationic chelating polymer, namely biopolymer chitosan CHI with a molecular weight of 117 kDa is employed in the present study to bring about the retention of azoic dyes from its aqueous solutions by way of polymer enhanced ultrafiltration (PEUF). The effects of process parameters, namely, operating time, CHI and sodium chloride concentrations, transmembrane pressure, and pH of solution on the retention rate and permeate flux were examined. CHI enhanced ultrafiltration achieved in the presence of CHI shows an increasing in the retention rate up to 86% for methyl orange (MO) and 89% for Direct Blue 71 (DB71). The retention rate of the studied azoic dyes decreases with sodium chloride concentration increasing. High retention percentage was also obtained at pH range from 2 to 6. In addition, the permeate flux decreases when both, feed chitosan concentration and pH of solution increase.

Hydroxyl-terminated poly(ethyleneimine) polymer enhanced ultrafiltration for boron removal

Boron removal is an important separation process which requires an excessive operational cost owing to the complex nature of boron in aqueous solutions. Polymer-enhanced ultrafiltration (PEUF) has been widely adopted for boron separation due to the low operational cost and high separation productivity. In this study, novel hydroxyl-terminated poly(ethyleneimine) (HPEI) polymers; namely, HPEI-Diol and HPEI-Gluconamide, were designed and synthesized as the boron chelating polymers. A polyphenylenesulfone (PPSU) UF membrane was fabricated to have a pure water permeance of around 82.8 L.m−2.h−1.bar−1 with a molecular weight cut off (MWCO) of around 128 kDa. The boron rejection coefficient of the pristine PPSU UF membrane was as low as 6.38% which was attributed to the negatively charged surface of the PPSU membrane. Introducing either HPEI or HPEI-Diol polymer into the boron feed solution increased the boron rejection of the UF process to around 45%. Meanwhile, the HPEI-Gluconamide polymer was found to possess the highest boron retention efficiency with a boron rejection of around 94% at pH 4, which may be ascribed to the higher number of grafted hydroxyl groups.