Comparing the performance of various nanofiltration membranes in advanced oxidation-nanofiltration treatment of reverse osmosis concentrates.

Reverse osmosis (RO) technique plays an important role in the treatment of secondary biochemical effluent. However, the reverse osmosis concentrate (ROC) with high salinity and organic pollutants generated from this process remains a challenge to be tackled. The O3-assisted UV-Fenton advanced oxidation process (AOP) as a pretreatment for the nanofiltration (NF) was used to treat the ROC of industrial wastewater. The optimal removal rates of COD and UV254 were 80.4 and 77.4%, respectively. In the NF process, four types of commercial NF membranes (NF90 (Dow, USA), DK (GE, USA), NT101, and NT103 (NADIR, Germany)) were used to treat the AOP effluent. The effects of operating pressure and feed temperature on ion rejection were investigated. The results show that NF90 and NT103 membranes had better rejections to monovalent ions, while DK and NT101 membranes could effectively separate monovalent and divalent ions and their ion rejections decreased with the increase of feed temperature. With the NF90 membrane, the highest TDS removal rate of 89.65% was obtained at the operating pressure of 1.2 MPa.

Microwave assisted esterification of acidified oil from waste cooking oil by CERP/PES catalytic membrane for biodiesel production.

The traditional heating and microwave assisted method for biodiesel production using cation ion-exchange resin particles (CERP)/PES catalytic membrane were comparatively studied to achieve economic and effective method for utilization of free fatty acids (FFAs) from waste cooking oil (WCO). The optimal esterification conditions of the two methods were investigated and the experimental results showed that microwave irradiation exhibited a remarkable enhanced effect for esterification compared with that of traditional heating method. The FFAs conversion of microwave assisted esterification reached 97.4% under the optimal conditions of reaction temperature 60°C, methanol/acidified oil mass ratio 2.0:1, catalytic membrane (annealed at 120°C) loading 3g, microwave power 360W and reaction time 90min. The study results showed that it is a fast, easy and green way to produce biodiesel applying microwave irradiation.

Kinetics of esterification of acidified oil with different alcohols by a cation ion-exchange resin/polyethersulfone hybrid catalytic membrane.

Hybrid catalytic membranes consisting of cation ion-exchange resin particles (CERP) and polyethersulfone (PES) were prepared by immersion phase inversion and used as heterogeneous catalysts for the esterification of acidified oil with methanol, ethanol, propanol and butanol. The membranes were characterized by ion exchange capacity and swelling degree tests. The membranes were annealed at different temperatures to improve catalytic activity and membranes annealed at 393 K had the highest catalytic activity. Butanol allowed the highest free fatty acids (FFAs) conversion of 95.28% since it has better miscibility than the other alcohols which strengthened mass and heat transfer. Furthermore, pseudo-homogeneous kinetic models of the esterification of acidified oil with the four alcohols were established according to the experimental data. The kinetic models can well predict the FFA conversion.

Preparation and characterization of the organic-inorganic hybrid membrane for biodiesel production.

A novel organic-inorganic hybrid membrane as heterogeneous acid catalyst for biodiesel production was prepared from zirconium sulfate (Zr(SO4)2) and sulfonated poly(vinyl alcohol) (SPVA). The structure and properties of the hybrid catalytic membrane were investigated by means of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), thermogravimetry (TG), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The catalytic performance of the hybrid membranes was tested by the esterification of the acidified oil with methanol. It was found that the Zr(SO4)2 particles were better dispersed in SPVA matrix as a result of the stronger interaction between Zr(SO4)2 and SPVA compared with Zr(SO4)2/poly(vinyl alcohol) (PVA) hybrid membrane. Esterification results showed that the conversions of free fatty acid (FFA) in acidified oil were 94.5% and 81.2% for Zr(SO4)2/SPVA and Zr(SO4)2/PVA catalytic membranes, respectively. The stability of Zr(SO4)2/SPVA catalytic membrane is superior to Zr(SO4)2/PVA catalytic membrane.