Catalytic ozonation with vanadium oxide-doped TiO2 nanoparticles for the removal of di-2-ethylhexyl phthalate.

Among various plastic additives, di-2-ethylhexyl phthalate (DEHP) has been a great concern due to its high leaching potential and harmful effects on both human and the ecosystem. For the effective oxidation and mineralization of DEHP by ozone in the existing TiO2 catalytic processes, the heterogeneous catalyst, vanadium oxide (V2O5)-incorporated TiO2 (V2O5/TiO2), was synthesized. The generation of hydroxyl radicals was promoted by cyclic redox reactions of vanadium atoms in V2O5/TiO2 via the increase of surface oxygen vacancies by the replacement of V5+ species in the lattice of TiO2. The catalytic ozonation in the presence of V2O5/TiO2 exhibited the significantly higher degradation of DEHP with the pseudo-second-order kinetic constant of 1.7 × 105 mM-1min-1 and the removal efficiency of 58.7% after 60 s in 2 mg/L of ozone. The degradation of DEHP was initiated by the shortening of the alkyl-side chain followed by the opening of esterified benzene moieties.

Novel method for the facile control of molecular weight cut-off (MWCO) of ceramic membranes.

This study demonstrates a simple and novel preparation method to prepare ceramic nanofiltration membranes with a precise and tunable molecular weight cut-off (MWCO) by packing variously sized nanoparticles into existing membrane pores. As a result, ceramic membranes with a MWCO from 1000 Da to 10,000 Da were successfully prepared with the narrow distribution of the pore size after the filtration-coating process. In addition, the effective porosity of the ceramic membranes was calculated from the results of the membrane properties by the Hagen-Poiseuille equation which fit within the range of the sphere packing theory from 17.3% to 41.8%. Furthermore, the results of nonlinear curve fitting between the MWCO and the nanoparticle size show a high accuracy, which implies that the MWCO of the ceramic membranes can be predicted using the curve fitting model with variously sized nanoparticles in the filtration-coating process. In conclusion, the novel filtration-coating method enables precise pore control and provides a tunable MWCO to ceramic membranes by preparing various sizes of nanoparticles.

The impact of gamma-irradiation from radioactive liquid wastewater on polymeric structures of nanofiltration (NF) membranes.

In this study, the impacts of gamma-irradiation from the low- and intermediate-level liquid radioactive wastewaters (LILW) to polyamide (PA) structures of nanofiltration (NF) membranes were investigated. As the gamma-irradiation increased to 300 kGy in the aqueous solution at 5 bar, both the salt rejection and the water permeability of NF membranes were decreased from 95.6 ±â€¯0.1%-74.6 ±â€¯0.5%, and from 33.7 ±â€¯0.3 LMH to 21.4 ±â€¯0.5 LMH, respectively. The surface free energy and Young's modulus of the membrane indicated the decrease in hydrophilicity and the increase in fragility of PA structure after gamma-irradiation. X-ray photoelectron spectroscopy and the streaming potential analysis exhibited that the gamma-irradiation resulted the increase in the cross-linked portion of the amide bonding from 28% to 45% due to the gamma-induced new bonding between unbound carboxylic groups and amine groups. Nuclear magnetic resonance analysis confirmed that the poly(p-phenylene) in polyamide structure were changed to poly(cyclohexane) and poly(cyclohexene) by hydrogen radical disproportionation generated from the gamma-irradiated water, and it is responsible to the increase of the cross-linked PA structures. The decrease in salt rejection and water permeability is attributed to the aging of PA structures by gamma-irradiation, thus, should be carefully monitored during the treatment of LILW using NF membrane processes.