Law Yong Ng

Utilization of self-synthesized ZnO nanoparticles in MPR for industrial dye wastewater treatment using NF and UF membrane

AbstractThis study attempted to use zinc oxide (ZnO) nanoparticles in membrane photocatalytic reactor (MPR) for industrial dye wastewater treatment. Performance comparison of nanofiltration (NF) and ultrafiltration (UF) in the MPR system were investigated to produce cleaner discharge and to retain the ZnO for reuse. From the results, the optimum operational condition of MPR occurred under pH 11 and 0.1u2009gu2009L−1 of ZnO loading. NF membrane performance improved after the addition of ZnO nanoparticles in the wastewater; in terms of normalized flux reduction (65%), colour removal (100%), chemical oxygen demand (92%), turbidity reduction (100%) and total suspended solid rejection (100%). In contrast, UF membrane showed worse performance, due to the permeation of dye molecules and nanosized ZnO across the UF membrane pores. Membrane characterizations of field emission scanning electron microscopy and energy dispersive X-ray results confirmed that the ZnO nanoparticles and NF membrane application has a great potent...

Enhancement of polysulfone membrane with integrated ZnO nanoparticles for the clarification of sweetwater

Clarification is one of the main steps in producing glycerin from glycerin–rich solution (namely sweetwater) in oleo-chemical industry. In this study, ZnO nanoparticles (9–12xa0nm in diameter) were incorporated into polysulfone (PSf) membranes to improve the membrane antifouling properties toward the fatty acids in sweetwater. The hybrid membranes were fabricated through wet phase inversion method. The modified membranes exhibited better water permeability, membrane surface hydrophilicity (improvement from 82° to 62.1°) and resistance toward fouling by fatty acids. In this study, the best membrane was obtained in the presence of 3% of ZnO nanoparticles, which showed good fouling resistance, high solution flux and a very high rejection of fatty acids (≥80%) in comparison with the pure PSf membranes, at the same experimental conditions. The enhanced membrane performances during the clarification of sweetwater were attributed to the unique properties of ZnO nanoparticles that were uniformly dispersed in the PSf structures.

Integrated adsorption-solar photocatalytic membrane reactor for degradation of hazardous Congo red using Fe-doped ZnO and Fe-doped ZnO/rGO nanocomposites

In this work, synergistic effect of solar photocatalysis integrated with adsorption process towards the degradation of Congo red (CR) was investigated via two different approaches using a photocatalytic membrane reactor. In the first approach, sequential treatments were conducted through the adsorption by graphene oxide (GO) and then followed by photocatalytic oxidation using Fe-doped ZnO nanocomposites (NCs). In the second approach, however, CR solution was treated by photocatalytic oxidation using Fe-doped ZnO/rGO NCs. These nanocomposites were synthesized by a sol-gel method. The NCs were characterized by X-ray diffraction (XRD), photoluminescence (PL), Fourier transmission infrared (FTIR), ultraviolet–visible (UV-vis) spectroscopy, and field emission scanning electron microscopy (FESEM). It was observed that Fe-doped ZnO could enhance the photoactivity of ZnO under solar light. When Fe-doped ZnO were decorated on GO sheets, however, this provided a surface enhancement for adsorption of organic pollutants. The photocatalytic performances using both approaches were evaluated based on the degradation of CR molecules in aqueous solution under solar irradiation. Nanofiltration (NF) performance in terms of CR residual removal from water and their fouling behavior during post-separation of photocatalysts was studied. Serious flux declined and thicker fouling layer on membrane were found in photocatalytic membrane reactor using Fe-doped ZnO/rGO NCs which could be attributed to the stronger π–π interaction between rGO and CR solution.

Development of a nanofiltration membrane for humic acid removal through the formation of polyelectrolyte multilayers that contain nanoparticles

AbstractPoly(sodium-4-styrenesulphonate) (PSS) and poly(diallyldimethylammonium chloride) have been employed to construct polyelectrolyte multilayers on a polyethersulphone substrate for use in the nanofiltration of humic acid. Self-synthesised Ag2O and commercial ZnO nanoparticles were incorporated into the multilayers separately, showing increases in the permeability from 7.53xa0±xa01.83 to 8.39xa0±xa01.37 and 8.62xa0±xa01.03xa0Lxa0m−2xa0h−1xa0bar−1, respectively, with no significant leaching observed in the permeates. All polyelectrolyte-modified membranes exhibited good film-formation stabilities and high humic acid retention capabilities, which ranged from 93.14xa0±xa02.43 to 95.57xa0±xa03.87%. Less humic acid solutes were deposited onto the surface of the polyelectrolyte-modified membrane, which was confirmed through field emission scanning electron microscopy images. The contact angle was reduced from 44.00xa0±xa03.46° to 39.10xa0±xa03.47° when the membrane surface was hydrophilised with PSS as the terminating layer.