The recent increase in nanomaterial usage has led to concerns surrounding its health risks and environmental impact. The food chain is an important pathway for high-trophic-level organisms absorbing and enriching nanomaterials. Our study therefore simulated nanometer titanium dioxide (nano-TiO2) transfer along a 2-step food chain, from the unicellular alga Scenedesmus obliquus to the water flea Daphnia magna. We also explored the effect of sodium dodecyl benzene sulfonate (SDBS) on nano-TiO2 bioavailability. A suspension of 10 mg/L nano-TiO2 was optimally dispersed in aqueous solutions by 5 mg/L SDBS. After 72 h, S. obliquus growth was not significantly affected by 10 mg/L nano-TiO2, 5 mg/L SDBS and their mixed suspension. SDBS not only improved nano-TiO2 stability in water, but also increased its uptake in S. obliquus and enhanced its accumulation in D. magna. Our study suggests that nano-TiO2 is mildly toxic to S. obliquus, and can be transferred along the aquatic food chain with a biomagnification effect.

A positively charged, composite, hollow-fiber nanofiltration (NF) membrane was fabricated by interfacial polymerization using polyethylenimine and trimesoyl chloride as reactive monomers. Rejection rates of different salts and dyes were measured by the NF membranes at various pH values. The effects of dye and salt concentrations on the membrane performance for dye purification were investigated. The dye and salt rejection rates would gradually decrease with an increase in the dye and salt concentrations. Then the influence of the volume concentration factor on dye purification during constant volume batch diafiltration process was studied. The results indicated that the higher of the concentration factor was, the better the concentration effect would be, and the less time would be needed.

Comb-like amphiphilic copolymer was synthesized by esterification reaction of styrene maleic anhydride and methoxy polyethylene glycol. The synthesized copolymer was characterized by H-Nuclear magnetic resonance and Fourier transform infrared (FTIR) spectroscopy. Finally, the copolymer was used to improve the hydrophilicity and biocompatibility of ultrafiltration polyethersulfone membranes. The properties of modified membranes were characterized by attenuated total reflection Fourier transform infrared spectrometer, scanning electron microscope and water contact angle. The ultrafiltration performance of the membranes was investigated by dynamic filtration bovine serum albumin and extracellular polymeric secretions solution. The membrane modified with 2 wt% copolymer displayed the best permeation and antifouling properties. The biocompatibility of the membranes was also evaluated by protein adsorption, platelet adhesion and hemolysis test. The results revealed that the modified membranes had good biocompatibility featured by the lower platelet adhesion, protein adsorption and a little hemolysis.

In this study, thin-film composite nanofiltration (NF) hollow-fiber membranes were used to remove heavy metals from actual electroplating wastewater. The effects of the operating pressure, feed temperature, and feed pH on the membrane performance for the treatment of electroplating wastewater were investigated. The rejection rates for chromium, copper, and nickel ions reached 95.76%, 95.33%, and 94.99%, respectively, at 0.4 MPa. With a rise in the feed temperature, the permeate flux increased while the rejection rates of heavy metals did not significantly change. It was evident that the feed pH greatly affected the permeate flux and heavy-metal rejection as well. In addition, all of the rejection rates of heavy metals by the membrane were over 94.8% throughout the electroplating wastewater concentration process. Also, the NF hollow-fiber membrane showed good stability in electroplating wastewater with a pH value of 2.31.

Novel nanofiltration (NF) membrane was developed from hydroxyl-ended hyperbranched polyester (HPE) and trimesoyl chloride (TMC) by in situ interfacial polymerization process using ultrafiltration polysulfone membrane as porous support. Fourier transform infrared spectroscopy (FTIR-ATR), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and water contact angle (CA) measurements were employed to characterize the resulting membranes. The results indicated that the crosslinked hyperbranched polyester produced a uniform, ultra-thin active layer atop polysulfone (PSf) membrane support. FTIR-ATR spectra indicated that TMC reacted sufficiently with HPE. Water permeability and salts rejection of the prepared NF membrane were measured under low trans-membrane pressures. The resulting NF membranes exhibited significantly enhanced water permeability while maintaining high rejection of salts. The salts rejection increase was accompanied with the flux decrease when TMC dosage was increased. The flux and rejection of NF 1 for Na2SO4 (1 g/L) reached to 79.1 l/m2 h and 85.4% under 0.3 MPa. The results encourage further exploration of NF membrane preparation using hyperbranched polymers (HBPs) as the selective ultra-thin layer.

•Positively charged composite NF hollow fiber membranes were fabricated.•Preparation conditions of the NF hollow fiber membrane were optimized.•Preparation process of the NF hollow fiber membrane was simplified.•Different salts and dyes were used to evaluate properties of NF membranes.A positively charged composite nanofiltration (NF) hollow fiber membrane was prepared by interfacial polymerization with polyethyleneimine (PEI) and trimesoyl chloride (TMC) as the reactive monomers. The preparation conditions were optimized, and a relatively simple preparation process was developed. In the optimized preparation process, Na3PO4 is not needed and the heat-treatment process can be omitted, which saves operation time and reduces cost. The surface morphology and chemical structure of the resulting composite NF membrane were characterized by scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). Pure water flux, contact angle, molecular weight cut-off (MWCO) and surface zeta potential of the composite NF membrane were also evaluated. The rejection of the NF membrane for MgCl2 (1 g/L aqueous solution at 0.4 MPa) was above 97.0%, and the permeate flux was approximately 35.3 L/m2 h. Furthermore, the NF membrane also showed excellent rejection performance for different dye molecules. The rejections of the NF membrane to brilliant blue KN-R, cationic red X-GTL, acid red B, rhodamine B and cationic gold yellow X-GL were 99.9%, 99.8%, 98.8%, 97.5% and 96.7%, respectively.