Sheridan Institute of Technology

Oakville, Canada

Sheridan Institute of Technology

Oakville, Canada
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Huang Y.,University of Waterloo | Du J.,Tianjin Polytechnic University | Zhang Y.,Tianjin Polytechnic University | Lawless D.,Sheridan Institute of Technology | Feng X.,University of Waterloo
Journal of Membrane Science | Year: 2016

The removal of mercury (II) from water by polymer-enhanced ultrafiltration (PEUF) was carried out using polyethylenimine (PEI), polyvinylamine (PVAm) and poly(acrylic acid) (PAA) as the metal-binding polymers. All three water-soluble polymers had strong interactions with mercury (II) in aqueous solutions, and a high mercury rejection was achieved with PEUF. At a given polymer dosage, the permeate flux followed the order of PVAm > PEI > PAA, presumably due to different physiochemical properties (e.g., viscosity and interfacial property) of the solution systems. Membrane fouling by PVAm and PEI in cross-flow mode was insignificant, but the flux decline due to fouling by PAA was not negligible. The batch operation of PEUF was modeled based on mass balance, and the applicability of the model equations was validated with experimental data. For a given system, the mercury content in the concentrated retentate, the mercury retention rate, the batch time and membrane area needed to achieve a desired separation task could be predicted if prior knowledge of concentration dependences of permeate flux and solute rejection were known. The effects of the amount of feed solution to be treated per unit membrane area on the separation performance of batch PEUF was analyzed. © 2016 Elsevier B.V.


Wu D.,University of Waterloo | Huang Y.,University of Waterloo | Yu S.,Zhejiang Sci-Tech University | Lawless D.,Sheridan Institute of Technology | Feng X.,University of Waterloo
Journal of Membrane Science | Year: 2014

Thin film composite (TFC) nanofiltration membranes were formed by interfacial polymerization from polyethylenimine (PEI) and trimesoyl chloride (TMC) on a microporous polyethersulfone (PES) substrate. Membranes with a layer-by-layer structure were prepared by repeated cycles of sequential reactant depositions and reactions to improve the salt rejection. The resulting membranes were characterized for chemical composition, surface charge and morphology of the polyamide skin layer. The effects of the sequence of reactant depositions, the number of cycles of reactant deposition and reaction, the concentrations of the reactant solutions and temperature of heat treatment on the membrane performance were investigated. The resulting membrane formed by a single cycle of interfacial polymerization with 3.5wt% PEI and 0.7wt% TMC had a positively charged surface and showed a good nanofiltration performance; salt rejections of 95.1% for MgCl2, 94.4% for MgSO4, 80.5% for Na2SO4 and 85.1% for NaCl with a pure water permeation flux of 24.5L/(m2h) were obtained at a feed pressure of 0.8MPa gauge. The membranes formed with the PEI-TMC deposition sequence exhibited valley-ridge structures evenly distributed on the membrane surface, while the membranes made with a reversed deposition sequence (i.e., TMC-PEI) showed irregularly distributed nodular-like structures. In general, the PEI-TMC membranes were much more permeable than the TMC-PEI membranes. The salt rejections of the interfacially formed composite membranes were improved by proper heat treatment. © 2014 Elsevier B.V.


Chen Y.,University of Waterloo | Lawless D.,Sheridan Institute of Technology | Feng X.,University of Waterloo
Separation and Purification Technology | Year: 2014

A novel process mode for gas separation by means of membranes was presented. It involved cyclic pressure-vacuum swings for feed pressurization and permeate evacuation, thereby increasing the transmembrane pressure difference and the feed to permeate pressure ratio. The feed pressurization and permeate evacuation were preferably done using a single pump capable of pressurization and suction. Unsteady-state permeation associated with the pressure-vacuum swing permeation was analyzed to elucidate the working principle of the process, and a parametric study was carried out to evaluate the effects of design and operating parameters on the separation performance. To exemplify the feasibility and effectiveness of the process, air separation for oxygen enrichment was investigated as a model application. It was shown that the separation efficiency was enhanced by means of the pressure-vacuum swing, and both product purity and product throughput higher than those from conventional steady-state permeation could be obtained. © 2014 Elsevier B.V. All rights reserved.


Huang Y.,University of Waterloo | Du J.R.,Tianjin Polytechnic University | Zhang Y.,Tianjin Polytechnic University | Lawless D.,Sheridan Institute of Technology | Feng X.,University of Waterloo
Separation and Purification Technology | Year: 2015

This study deals with the concentration and removal of mercury (II) from wastewater by polymer-enhanced ultrafiltration (PEUF) using polyvinylamine as the mercury-binding polymer. A mercury removal as high as 99% was obtained, which was otherwise impossible to achieve with conventional ultrafiltration. Over the feed mercury concentration range tested (0-50 ppm), the PVAm dosage used did not affect the mercury rejection considerably, while water flux was reduced significantly at a higher dosage of PVAm. A flux vs pressure relationship typical of ultrafiltration of macromolecular solutes was observed because of the amine polymer used to bind mercury, and the limiting flux appeared to follow the gel layer formation model. The fouled membrane surface was cleaned periodically with dilute hydrochloric acid to recover the membrane permeability. Mercury removal with the PEUF was also tested with a simulated chlor-alkali wastewater that contained mercury and other chemicals (i.e., sodium chloride and sulfate), and the accompanying compounds in the feed solution were shown to influence the performance of PEUF for mercury removal. © 2015 Elsevier B.V. All rights reserved.


Wu D.,University of Waterloo | Yu S.,Zhejiang Sci-Tech University | Lawless D.,Sheridan Institute of Technology | Feng X.,University of Waterloo
Reactive and Functional Polymers | Year: 2015

Thin film composite (TFC) nanofiltration membranes were fabricated by interfacial polymerization using polymeric amine polyethylenimine (PEI) and monomeric amine piperazine (PIP) as the amine reactant. Membranes with a single-ply polyamide layer were produced by reacting trimesoyl chloride (TMC) with mixed amines of PEI and PIP, and incorporation of a small amount of PIP in PEI was found to increase the permeation flux effectively while still maintaining a good solute rejection. For instance, adding 10 wt% PIP in the amine reactant solution resulted in a 6-fold increase in permeation flux, while a 91.6% MgCl2 rejection was maintained. In addition, 2-ply polyamide membranes were also prepared by two cycles of PEI-TMC and PIP-TMC interfacial reactions separately, and they showed a higher rejection than the single-ply polyamide membrane. At a low PIP/PEI concentration ratio, the single-ply polyamide membranes formed with mixed amines of PIP and PEI tended to be more permeable than the 2-ply polyamide membranes. However, it was demonstrated that by properly controlling the PIP/PEI concentration ratio, the 2-ply polyamide membranes with both a higher permeation flux and salt rejection than conventional single-ply polyamide membranes could be produced. The resulting membranes were characterized for chemical composition, surface hydrophilicity, surface charge and morphology of the polyamide skin layer. © 2014 Elsevier B.V. All rights reserved.


Wu D.,University of Waterloo | Martin J.,University of Waterloo | Du J.R.,Tianjin Polytechnic University | Zhang Y.,Tianjin Polytechnic University | And 2 more authors.
Journal of Membrane Science | Year: 2015

Composite polyamide nanofiltration membranes comprising of an inner sublayer of polyethylenimine (PEI)/trimesoyl chloride (TMC) crosslinks and an outer sublayer of piperazine (PIP)/TMC crosslinks were fabricated via layer-by-layer sequential interfacial polymerization, and the chlorine resistance of the membranes was shown to be improved by the outer sublayer. The effects of chlorine exposure on the nanofiltration performance of the positively-charged polyamide membrane were investigated at different chlorination conditions (pH, chlorine concentration, exposure duration). In general, membrane chlorination resulted in an increase in membrane permeability, whereas the solute rejection could increase or decrease, depending on the charge properties of the solutes. Controlled chlorine exposure at low concentrations could enhance the water flux of the membrane without significant reductions in solute rejections for MgCl2 and MgSO4 (and, to a lesser extent, NaCl); the membrane retention of Na2SO4 was actually enhanced by the chlorine treatment. At a given chlorine concentration, the effect of membrane chlorination was intensified at both alkaline or acidic pHs as compared to membrane chlorination at pH 7. It was also shown that the customarily used chlorination intensity (ppmh), which is a composite parameter based on the product of chlorine concentration and chlorination time, was not adequate for use as a standalone parameter to characterize the chlorination conditions. © 2015 Elsevier B.V.


Huang Y.,University of Waterloo | Wu D.,University of Waterloo | Wang X.,Taiyuan University of Technology | Huang W.,Taiyuan University of Technology | And 2 more authors.
Separation and Purification Technology | Year: 2016

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. © 2015 Elsevier Ltd. All rights reserved.


Wu D.,University of Waterloo | Martin J.,University of Waterloo | Du J.,Tianjin Polytechnic University | Zhang Y.,Tianjin Polytechnic University | And 2 more authors.
Journal of Membrane Science | Year: 2015

Thin film composite membranes comprising of a polyamide (PA) and polydopamine (PD) were prepared and studied for dehydration of ethylene glycol. The chemical composition, surface hydrophilicity and sorption uptake of permeant in the active skin layer of the membranes were characterized, and the effects of the number and sequence of the PD and PA sublayers in the membrane skin on the pervaporation performance were studied. It was shown that using 1 or 2 PD sublayers as a surface layer (i.e., on top of PA) or a transition layer between PA and the substrate would increase both permeation flux and selectivity for dehydration of ethylene glycol. Since inorganic salts are often present in spent glycol solutions in practical applications, the influence of inorganic salt in the feed on ethylene glycol dehydration was also studied using NaCl as a representative salt. The presence of NaCl in the feed solution enhanced the separation factor, while the permeation flux was reduced. Unlike pervaporative separation of binary water/ethylene glycol solutions where the separation factor was reduced at a higher temperature, the separation factor increased with an increase in temperature when NaCl was present in the feed. © 2015 Elsevier B.V..

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