Effect Of Humic Acid And Calcium Chloride On Dyeing Wastewater Treatment In Hybrid Photocatalysis-Membrane System

A novel photocatalysis-hollow fiber membrane hybrid system has been used in this study, to investigate the influence of humic acid (HA) and calcium chloride (CaCl2) on the dyeing wastewater treatment. Special attentions were paid on the decolorization rate of dye Reactive Brilliant Red X-3B (X-3B) and permeability of membrane, the relative mechanisms were also discussed.The experimental results obtained in hybrid system show that the influence of HA and CaCl2 on the efficiency of decolorization of azo dye X-3B were similar to the performances in single photocatalysis process. The X-3B decolorization rate decreased with the increase of the concentration of HA, and increased with the increase of the concentraion of CaCl2. The coupling of photocatalysis and membrane sepration could not change the effect mechanism of HA and CaCl2 on the photocatalytic process, but the decolorization effciency of dye in hybrid system was slightly lower than that in single photocatalytic process because of the circulation of feed solution and the deposition of TiO2 on membrane surface. The influence of HA and CaCl2 on membrane permeability flux in hybrid system showed great difference from that in single membrane sepration process. In single membrane sepration process, because the presence of complexation between HA and CaCl2, the membrane fouling increased with the increase of HA, while with the increase of CaCl2 concentration, the membrane fouling increased (<5 mmol L-1) at first and then decreased (>5 mmol L-1). In hybrid system, the interactions among HA-CaCl2-TiO2, which originated from charge interaction and complexation, dominated the fouling behavior of membrane. As a result, low concentration of HA (<3 mg L-1) could reduce the membrane flux attenuation, and membrane fouling presented continuous decrease as the increase of Ca2+ concentration. Further more, compared with the single membrane sepration process, membrane fouling had been greatly reduce because of the photocatalytic degradation of HA and dye, and the pre-filtering effect of deposited TiO2 cake layer on target polutants.