Metal ions removal from wastewater or washing water from contaminated soil by ultrafiltration–complexation (original) (raw)
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Removal of heavy metal ions by polymer enhanced ultrafiltration
Desalination, 2012
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.
Desalination, 2004
Some results on metal ions removal from wastewaters using water-soluble polymers such as polyethylenimine (PEI), polyacrylic acid (PAA), polyacrylic acid sodium salt (PAASS) and poly(dimethylamine-co-epichlorohydrin-coethylene-diamine) (PDEHED) as chelating agents and the Cu 2+ ion as the model in combination with a polymer-assisted ultrafiltration process (PAUF) are reported. In particular, the performances of these polymers in Cu 2+ removal from wastewaters were compared. Tests of bonding capacity and best operating conditions of the process showed that complexation conditions depend on pH; indeed, copper ions are complexed by PEI, PAA, PAASS and PDEHED at pHs higher than 6, 4.6, 4.6 and 8, respectively. The decomplexation reactions took place at pH <3. Bonding capacity was 0.333 mg Cu 2+ /mg polymer, meaning a ratio of polymer/Cu 2+ = 3 (w/w) for PEI, PAA and PAASS. For the chelating agent PDEHED, a ratio of PDEHED/Cu 2+ = 0.5 (w/w) was determined. UF tests, realized at two transmembrane pressures (2 and 4 bar) by using five different flat-sheet membranes, showed that the PAA polymer and the PAN GKSS HV2/T membrane can be used when the objective of the purification process is to decrease metal concentration not lower than a certain value. The PDEHED polymer is useful if the objective of wastewater treatment is to obtain complete copper removal. Simple washings with tap water were enough for regeneration and reuse of the membranes.
Desalination, 2002
A process for recovery heavy metals-Cu(II), Ni(II), Pb(I1) and Cd(I1)-from industrial wastewaters has been studied. This process is called PSU (Polymer Supported Ultrafiltration), and includes complexation of metallic ions with polymers (polyethyleneimine-PEI, or poly(acrylic) acid-PAA), in order to make this solution flow through an ultrafiltration ceramic membrane and to obtain two different streams: permeate (nearly free of metal) and retentate (with high complex concentration). In a previous stage, complex stoichiometries and stabilities have been exhaustively studied by UV/visible absorbance spectrophotometry and potentiometric measures. Next, optimum operating conditions and best pH values affecting to permeate flux, complex formation, further polymer regeneration and polymer capacities have been achieved by means of ultrafiltration experiments. Flux and concentration values measured with these processes have been modeled with concentration polarization model, and mass transfer coefficients (k) and polarization concentrations (c,,,) have been obtained for different operation conditions. These data are not commonly reported in previous literature, although they are important for scale-up to an industrial process.
Journal of Applied Electrochemistry, 2005
The removal of heavy metals from aqueous systems such as wash-solutions of contaminated soil by using Polymer-Assisted Ultrafiltration (PAUF) has been studied. For the extraction of metal ions from contaminated soil citric acid is used as a chelating agent. Cu 2+ as metal ion and the polymer polyethylenimine (PEI) as ligand were used in the various experiments. Optimal chemical conditions for copper complexation by citric acid were determined by means of complexation tests. The results showed that citric acid is able to chelate copper ions at pH 5.5, while decomplexation occurs at pH £ 2. Maximum bonding capacity (saturation condition) was 0.625 mg Cu 2+ per mg citric acid, meaning 2 mol Cu 2+ per mol citric acid. Complexation tests in the system polyethylenimine-citric acid-copper showed that the polymer is able to complex the copper-citric acid chelate at pH = 6 while release occurs at pH < 3. The saturation condition was 0.333 mg Cu 2+ per mg PEI. The ultrafiltration tests, carried out at three trans-membrane pressures (2, 3 and 4 bar), showed the possibility of using the PAUF technique for copper ion removal from aqueous solutions.
Removal of heavy metals from water using polyvinylam 2016 Separation and Pur
This study deals with the removal of heavy metals (i.e., Co (II), Cu (II), Ni (II), Pb (II), Fe (III), Cd (II), Zn (II) and Mn (II)) from water with polymer-enhanced ultrafiltration using polyvinylamine (PVAm) as a complexing agent. At a PVAm dosage of 0.1 wt%, metal rejections as high as over 99% were achieved for Pb (II), Cu (II) and Fe (III). The coordination interactions between PVAm and the heavy metals were investigated using UV-vis spectral and conductometric analyses. It was shown that the performance of PEUF for metal rejection was related to the coordination interactions between PVAm and the heavy metals. It was also found that when divalent sulfate anions were present, the PVAm-metal complexes precipitated out of the solution at high metal concentrations. Thus PVAm could also be used as a flocculant for metal removal by flocculation.
Polymer binding/ultrafiltration as a method for concentration and separation of metals
Journal of Membrane Science, 1993
A hybrid method for the separation and concentration of metals was investigated. The method includes binding of target metal ions by a polyelectrolyte into water soluble macromolecular compounds and subsequent membrane separation of the bound metals from unbound components. The influence of the composition and pH of the solution on the effectiveness of the separation process was studied. A mathematical model of this process was developed. The competitive character of interaction of metals with a polymer, metal ion hydrolysis and other phenomena were taken into account in the model. Optimum process conditions were determined and applied to the solution of particular problems such as the recovery of valuable metals from sea water and treatment of industrial wastes.
Journal of Membrane and Separation Technology, 2014
Water pollution by metal ions contaminants is a worldwide alarming problem. Clean and safe water is becoming in the same time an increasing scare resource. Thus, to keep this fundamental resource available and suitable for use, water treatment methods are investigated by means of numerous research studies since the purification of water and its re-use and, in a larger scale, the environmental protection will be essential henceforth in any strategy of development. Membrane processes, in general, and ultrafiltration, in particular, develop, without stopping, since the beginning of the sixties to meet the vital need for environmental safety which justifies the policies of durable development adopted today all over the world. Thanks to its growing, ultrafiltration becomes an irreplaceable weapon in the control of pollution. It is classified as a soft and clean technology since it needs low energy consumption and ensures a notable reduction in pollution production during the treatment step. Ultrafiltration is a pressure driven membrane process with the ability to separate molecules in solution on the basis of size. A microporous ultfafiltration membrane retains species with molecular weight higher than its cut off, while small molecules as solvents and microsolutes can pass freely through it. Thus, metal ions aren't rejected by ultrafiters. However, ultrafiltration can be used to remove metal ions from aqueous solutions by coupling the process with complexation. Indeed, the complexation of metal ions using water soluble polymers as substrates is able to expand artificially the size of the metallic species so as to make possible their rejection by the microporous ultrafilters. The complexation-ultrafiltration hybrid process was first suggested at the end of the sixties by A. S. Michaels. Since then, many studies have shown its effectiveness in the treatment of aqueous solutions containing metal ions. This paper gives an overview of academic studies that illustrate and demonstrate the efficiency and the promising of the hybrid process in the purification of water from metal ions contaminants beforehand sequestered by adequate watersoluble macromolecular substrates.
Complexing agents for metal removal using ultrafiltration membranes: a review
Environmental Chemistry Letters, 2019
Water pollution by human activities is major issue. In particular, toxic metals are of particular concern, thus calling for advanced methods to remove metals from contaminated waters. Here we review the use of polymeric complexing agents such as pectin, alginate, chitosan, polyethyleneimine, polyacetic acid, polystyrene sulfonate sodium polyacrylate, polyvinyl alcohol and diethylaminoethyl cellulose, to increase the efficiency of metal removal up to 100% by ultrafiltration.
DESALINATION AND WATER TREATMENT, 2021
Polymer-enhanced ultrafiltration was used to separate heavy metal ions from their multicomponent mixtures. Model solutions containing an equimolar mixture of Cu(II), Zn(II), Cd(II), Ni(II), Cr(III) were supplemented with poly(sodium acrylate) PSA (a metal-binding polymer) and the ultrafiltration process was carried out. The separation effectiveness of individual metal ions was studied under various process conditions (amount of PSA, pH, total metal concentration, presence of coexisting ions), and the possibility of simultaneous or selective (competitive) separation of individual ions from a multicomponent mixture was evaluated. Effective simultaneous separation of metal ions occurred in solutions containing a sufficient polymer dosage (polymer/metal molar ratio C PSA /C M ≥ 7) and at a sufficiently high pH (pH ≥ 6). Since the polymer showed differential affinity for the metals tested (Cr(III) ≈ Cu(II) > Cd(II) >> Zn(II) > Ni(II)), partially selective separation of ions from the mixture at a decreased pH or lowered C PSA /C M was possible. In addition, certain co-occurring ions (especially versenate, EDTA) decreased the separation effectiveness of Cu(II), Zn(II), Cd(II) and Ni(II). These preliminary observations were confirmed by the ultrafiltration concentration of the metal mixture, carried out at different values of the process parameters, and the subsequent decomplexation-ultrafiltration process (pH = 2), enabling the recovery of concentrated metal solutions of varying composition, depending on the process conditions.
Environmental Progress & Sustainable Energy, 2014
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 nonionic manner.