Treatment of highly-concentrated phenol wastewater with an extractive membrane reactor using silicone rubber

Application of membrane extraction process to the removal of phenol from its aqueous solution was investigated. The ability of poly (dimethylsiloxane), i.e. PDMS and poly (methyl vinyl) siloxane (PVMS) in the membrane extraction of water–phenol mixtures was compared. It was found that PDMS was more suitable for the operation under strong base condition. PDMS and sodium hydroxide solution were applied in the process. The effects of feed flow rate, phenol concentration, temperature and pH in the stripping solution and ionic strength on the process were studied. The effects of liquid flow status and system temperature on the membrane surface on the overall mass transfer coefficient (OMTC) and the permeability for phenol through the membrane were also discussed. The experimental results showed that the phenol removal efficiency was over 95% under the conditions of a flow rate 2.0 l·d–1, phenol >5000 mg·l–1, at 323.2 K and pH 13.0. OMTCs increased with increasing salt concentration. The order of OMTC was 10–7 m·s–1, and the experimental data was agreement with the Arrhenius relationship for the temperature dependence of the permeability of phenol through the polymer.

This ME process can be successfully applied for the extraction of highly-concentrated phenol from its aqueous solution. The removal efficiency of phenol in this process is over 95%. The following main conclusions can be drawn: • Though PVMS has higher diffusion characterization and removal efficiency than those of PDMS, the latter is suitable for long-term operation under strong base conditions. • Optimum conditions were obtained at a pH 13, 2.0 l·d–1 feed flow rate, 323.2 K and over 5000 mg·l–1 feed concentration. • The order of OMTC was 10–7 m·s–1, which was dominated by the membrane resistance in this process using silicone rubber. • Kov increased with the Reynolds number presenting logarithmic relation, and when Re was >51.8 in the feed solution on the tube side, the OMTCs were dominated by the membrane resistance. • Kov was in direct proportion to the temperature in this ME process, and our experimental data gave excellent agreement with the Arrhenius relationship for the temperature dependence of the permeability of phenol through the polymer. • OMTCs increased with increasing salt concentration.