Process Engineering for Sustainable Systems

Leuven, Belgium

Process Engineering for Sustainable Systems

Leuven, Belgium
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Liu T.-Y.,Tsinghua University | Liu Z.-H.,Tsinghua University | Zhang R.-X.,Process Engineering for Sustainable Systems | Wang Y.,Tsinghua University | And 2 more authors.
Journal of Membrane Science | Year: 2015

A thin film nanocomposite (TFN) hollow fiber membrane containing nanoporous SAPO-34 nanoparticles was prepared on the dual-layer (PES/PVDF) hollow fiber substrate. The nanoparticle exposed TFN membrane (TFN(DOX)) was fabricated via the co-solvent (dioxane) assisted interfacial polymerization process. The TFN(DOX) had a larger nanoporosity and a higher crosslinking degree, which simultaneously led to an increased pure water permeability but a decreased salt permeability than the TFN membrane. The larger nanoporosity of TFN(DOX) membrane was ascribed to the effective exposure of nanoparticles, proved by the less PA coverage and the stable dispersion of nanoparticles in organic solution. Contributed by the exposed nanoparticles, the TFN(DOX) showed superior hydrophilicity and lower streaming potential than the TFN membrane. Compared to the NF-90, the TFN(DOX) membrane simultaneously improved the water flux and the rejections against tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate and tris(1,3-dichloro-2-propyl) phosphate molecules. In addition to the elevated pure water permeability of 20.1Lm-2h-1bar-1, the newly developed TFN(DOX) hollow fiber nanofiltration membranes have high rejections to both the multivalent electrolytes and micropollutant molecules, showing the potential applications in industrial wastewater treatment and drinking water purification. © 2015 Elsevier B.V.


Liu T.-Y.,Tsinghua University | Zhang R.-X.,Process Engineering for Sustainable Systems | Li Q.,Tsinghua University | Van der Bruggen B.,Process Engineering for Sustainable Systems | Wang X.-L.,Tsinghua University
Journal of Membrane Science | Year: 2014

In this study, a dual-layer hollow fiber ultrafiltration (UF) membrane was fabricated by the inner layer of poly(vinylidiene fluoride) (PVDF) via thermally induced phase separation (TIPS) method and the outer layer of poly(ether sulfone) (PES) via non-solvent induced phase separation (NIPS) method, respectively. The dope solution composition of the inner layer and outer layer and the intermediate-treatment agent between the two layers were studied. The mechanical strength of the dual-layer membrane was larger than that of the inner layer. The increased mechanical strength was attributed to two parts: the formation of the interfacial layer resulting from the penetration and dissolution effects of the outer layer dope solution into the inner layer, and the outer layer with high mechanical strength. The structure near the interface was controlled by the intermediate-treatment agents between the two layers. By decreasing the PVDF solubility of the intermediate-treatment agents, the porosity of the inner layer near the interface was increased, the pure water flux of the resultant membrane was improved and the dextran rejection was maintained. In addition to exhibiting a high rejection of bovine serum albumin protein molecules, the newly developed UF membranes have high tensile strengths of 10.1-11.1MPa with molecular weight cut-offs (MWCO) of 33-292kDa and pure water fluxes of 43-90Lm-2h-1bar-1. Such a novel UF dual-layer hollow fiber membrane is an attractive candidate for the effective treatment of municipal wastewater. © 2014 Elsevier B.V.


Liu T.-Y.,Tsinghua University | Li C.-K.,Tsinghua University | Pang B.,Tsinghua University | Van der Bruggen B.,Process Engineering for Sustainable Systems | Wang X.-L.,Tsinghua University
Desalination | Year: 2015

In this study, a dual-layer hollow fiber nanofiltration (NF) membrane was fabricated with an inner layer of poly(vinylidene fluoride) (PVDF) via thermally induced phase separation (TIPS), and an outer layer of cellulose diacetate (CA) via non-solvent induced phase separation (NIPS). The intermediate-treatment using dimethyl formamide (DMSO) between the two layers increased the porosity of inside surface of outer layer. The nanopore of the outside surface of outer layer was molecularly designed by controlling the dope solution composition, i.e., the polymer concentration, the co-solvent additive (acetone) ratio and TiO2 nanoparticle loading. By increasing the acetone ratio and TiO2 nanoparticle loading, the pore size became narrower and the pore size exhibited dominate effects on both filtration and separation performances. Moreover, biofouling and bacterial growth on the membrane were reduced by increasing the TiO2 nanoparticle loading. The dual-layer (CA/PVDF) hollow fiber membranes had high strengths larger than 8MPa, Na2SO4 rejections of 90-95% and pure water permeabilities of 1-4Lm-2h-1bar-1. The feasibility of treating RO concentrates by the resultant membrane was proven by the effective removal of total organic compounds (>90%) and low rejection of total dissolved salts (<60%). © 2015 Elsevier B.V.


Liu T.-Y.,Tsinghua University | Bian L.-X.,Tsinghua University | Yuan H.-G.,Tsinghua University | Pang B.,Tsinghua University | And 4 more authors.
Journal of Membrane Science | Year: 2015

A high-flux thin film composite (TFC) hollow fiber nanofiltration (NF) membrane was fabricated using a barrier layer of polypiperazine amide synthesized via interfacial polymerization (IP) on a previously prepared dual-layer (PES/PVDF) hollow fiber substrate, which was synthesized via the two-step TIPS/NIPS method. The permeability of the TFC membrane was smaller by an order of magnitude than that of the substrate, which was due to the formation of a thick barrier layer. The structure of the barrier layer was controlled via the addition of cyclic ethers (dioxane, oxolane and trioxane). By increasing the polarity of cyclic ethers, the thickness of the barrier layer and the dense layer was reduced due to the piperazine concentration in the organic phase. Comparing with oxolane and trioxane, the addition of dioxane resulted in a narrower pore size as that of the conventional IP process, which was ascribed to the narrow IP reaction zone via the immiscibility of interface. With the addition of dioxane up to 2wt%, the barrier layer became thinner, the pure water flux of the resultant membrane was improved and the dextran rejection was maintained. The novel hollow fiber NF membrane has a permeability of 16.6Lm-2h-1bar-1, a MWCO of 330Da and a tensile strength of 10.3MPa. This membrane had a higher rejection of total organic carbon and a lower rejection of total dissolved solids of the secondary effluent from a petrochemical industry plant, which proves the potential of this membrane in municipal, agricultural and industrial wastewater treatment. © 2014 Elsevier B.V.


Liu T.-Y.,Tsinghua University | Tong Y.,Petrochina | Liu Z.-H.,Tsinghua University | Lin H.-H.,Tsinghua University | And 3 more authors.
Separation and Purification Technology | Year: 2015

Abstract The reverse osmosis (RO) pretreatment of the petrochemical refinery wastewater has been investigated using the dual-layer (PES/PVDF) hollow fiber nanocomposite membranes, which were fabricated comprising MWCNTs in both layers via the two-step TIPS/NIPS process. The dual-layer hollow fiber nanocomposite membrane had the reduced fouling propensity, the improved compaction resistance and the higher filtration performance than the dual-layer hollow fiber (PES/PVDF) membrane. The low concentration of bacteria in the permeate caused RO membrane biofouling due to the rapid growth in the environment of extracellular polymeric substances (EPS). In order to inhibit the RO membrane biofouling, EPSs were removed by using the hollow fiber nanocomposite UF membrane, including polysaccharides, biopolymers and proteins. The rejection of biopolymers (MWCO = 33 kDa) was higher than that of polysaccharides (MWCO = 40 kDa). With respect to protein removal, it was found that the bovine serum albumin and rejection of 90% could be achieved, which was strongly dependent on pH. The EPS removal achieved up to 98.2% with the optimized carboxylated MWCNTs loading in the (NcPES-0.2%)/(NcPVDF-0.5%) hollow fiber nanocomposite membrane. The permeate treated by the hollow fiber nanocomposite membrane had effectively inhibited the RO membrane biofouling by Escherichia coli, as a result of the lower concentration of turbidity and EPS. The resultant hollow fiber nanocomposite ultrafiltration membrane shows the feasibility of removing EPS coupled with a low rejection of total dissolved salts, which yields a superior pretreatment method to reduce biofouling of the subsequent purification by reverse osmosis. © 2015 Elsevier B.V.

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