Methyl orange removal by combined visible-light photocatalysis and membrane distillation

A photocatalytic membrane reactor combining a visible-light BiOBr photocatalyst and direct contact membrane distillation was studied for the removal of methyl orange from an aqueous solution. The hierarchical flower-like BiOBr microspheres, assemblies of BiOBr nanosheets, exhibited high efficiency for methyl orange photo-degradation under visible-light irradiation and due to their large specific surface area, their visible-light absorbance and the lower recombination of photo-generated electrons and holes. The main active species during the photo-degradation process was determined to be O-2 radicals. The organic pollutant and catalyst were retained on the feed side, as themembrane distillation only allowedwater vapor to permeate through the hydrophobic membrane, leading to a high quality water stream on the permeate side. The micrometer size of the BiOBr photocatalyst may prevent fouling of the polytetrafluoroethylene membrane, making the photocatalytic membrane reactor applicable for industrial wastewater treatment

Determination of 214 pesticide residues in green vegetables using QuEChERS-ultra high performance liquid chromatography coupled with quadrupole time of flight mass spectrometry

Objective A method for the determination of 214 pesticide residues in green vegetables by QuEChERS using ultra high performance liquid chromatography coupled with quadrupole time of flight mass spectrometry was established. Methods After extracted by acetonitrile, the green vegetables were cleaned-up by a mixed sorbent with primary secondary amine (PSA), C18, Na2SO4 and graphitized carbon black (GCB). The target compounds were separated by Waters ACQUITY UPLC BEH C18 column (2.1 mm×100 mm, 1.7 μm) using 5 mmol/L ammonium formate solution (0.1% formic acid) and acetonitrile as mobile phase by gradient elution, and analyzed in positive electrospray ionization mode by time of flight mass spectrometry scan-information dependent acquisition (IDA) -product ion scan. Results All the 214 pesticides showed good linear relationships in the range of 4-1 000 ng/L, and the correlation coefficients (r2) were higher than 0.99. The recoveries at three different spiked levels for all target compounds in blank matrices were 41.9%-128.5%, and the relative standard deviations (RSD) were 0.4%-14.3% (n=6). The limits of detection and quantitation of the method were 0.004-5.443 and 0.206-18.125 μg/kg, respectively. Eight pesticide residues were detected in the real samples. Conclusion The method was suitable for rapid screening and analysis of pesticide residues in green vegetables with the advantages of accuracy, rapidity, simplicity, high sensitivity and high throughput

Designing triple-layer superhydrophobic/hydrophobic/hydrophilic nanofibrous membrane via electrohydrodynamic technique for enhanced anti-fouling and anti-wetting in wastewater treatment by membrane distillation

Developing high-performance membranes for membrane distillation (MD) to treat highly saline industrial wastewater is of great significance. In this work, a superhydrophobic/hydrophobic/hydrophilic triple-layer membrane combining an electrosprayed superhydrophobic top layer, an electrospun hydrophobic nanofibrous intermediate layer and a hydrophilic microporous membrane substrate was fabricated by using electrohydrodynamic techniques. The top superhydrophobic surface possesses a unique surface morphology composing of hydrophobic SiO2-polymer microbeads with nanoscaled protrusions and interconnected thin nanofibers, which contributed to the enhanced water flux for desalination in direct contact MD. By tuning the concentrations of hydrophobic SiO2 nanoparticles and polyvinylidene fluoride-co-hexafluoropropylene for electrospraying the top layer, the triple-layer membrane showed both enhanced anti-fouling and anti-wetting properties due to the reduced liquid-solid contact area and stable Cassie-Baxter state. The triple-layer membrane exhibited stable MD performances when using real seawater and industrial flue gas desulfurization wastewater as the feed solutions, while no obvious fouling and wetting being observed even at 60% water recovery. This study provides an effective approach for fabricating a high-performance triple-layer superhydrophobic/hydrophobic/hydrophilic membrane for potential practical MD applications for industrial wastewater treatment