Papers by Author: Qi Zhang

Abstract: The microfiltration (MF) and nanofiltration (NF) integrated membrane technologies were used in the advanced treatment of dyeing wastewater. The ZrO₂ MF membrane was used to remove colloidal species from the wastewater before NF. The effects of permeate flux, COD_Cr rejection, the removal effects of ammonia nitrogen and total phosphorus by polyamide NF membrane were investigated. The results indicated that the turbidity removal efficiency was 76.7%~95.0%. COD_Cr rejection was range from 33.3% to 54.9% by MF. After the process of NF, COD_Cr rejection was between 66.65% and 91.18%. The removal effects of both color and turbidity were 100%. The value of pH was 6~7. The COD_Cr was smaller than 60mg•L^-1. The value of ammonia nitrogen was smaller than 7mg•L^-1. The value of total phosphorus was smaller than 0.5mg•L^-1. It came up to the quality standard of recycling raw water for industrial uses. It can be used as the water for industrial.

Abstract: The NaA/PTFE composite membranes were synthesized on polytetrafluoroethylene (PTFE) film by hydrothermal secondary growth (HSG) method and scratching (ST) method. The structure and morphology were characterized by XRD and SEM. The pervaporation(PV) performance of NaA/PTFE composite membranes were evaluated with dimethylformamide (DMF)/water mixtures. The XRD results showed that NaA/PTFE composite membranes kept the zeolite crystal feature of A type. The substrate, PTFE and zeolite were firmly combined together by the SEM photos. The results of PV showed that the flux and the separation factor of NaA/PTFE composite membrane prepared by HSG method with 4 crystallization times were 0.54 kg/m² h and 23, respectively. The flux of NaA/PTFE composite membrane prepared by ST method was much larger than that of NaA/PTFE composite membrane prepared by HSG method, but separation factor was lower.

Abstract: Three kinds of commercial PVA composite membranes with different crosslinking degrees (PVA-1, PVA-2 and PVA-3) were used to separate DMF/H₂O mixtures. Their pervaporation performance was investigated at different operation temperatures. The results showed that PVA-1 was the most suitable one for separating DMF/H₂O mixtures. When operation temperature was 60°C and downstream pressure was lower than 6kPa, flux reached to 0.59 kg·m^-2·h^-1 and separation factor was 33 for PVA-1 membranes. Aspen Plus^® was applied to simulate the normal distillation for retentate from pervaporation unit. Comparing with the two-effect distillation, the cost of concentrating DMF could be reduced 16.2% to 19.2% for DMF aqueous solution with different composition by hybrid processes. The cost would be the lowest for a hybrid process that concentrated the feed into 50wt% by pervaporation firstly, then concentrated retentate to 99.6wt% by two-effect distillation