Ceramic membrane fouling and cleaning in ultrafiltration of desulfurization wastewater

• Foundation of ceramic UF membrane in the treatment of desulfurization wastewater.
• Fouling causes were sulfur and tar oil deposition on the membrane surface.
• Fouling mechanism was completion of pore blocking, and then cake layer formation.
• Propose an effective cleaning method with a flux recovery ratio higher than 98%.

Ceramic ultrafiltration membrane was applied to treat the desulfurization wastewater to avoid environmental pollution and further reclaim sulfur. However, membrane fouling is unavoidable. The key issue to solve the fouling problem is to understand the fouling mechanism, and find an effective way to regenerate the membrane. The results showed that the dominant resistance was caused by cake formation even at a low sulfur concentration. The filtration mechanism was tested to fit the complete pore blocking model. Sulfur and tar oil deposition on the membrane surface was significant, along with salts such as thiocyanate in the wastewater. Based on these, the effectiveness of various membrane cleaning methods was evaluated. The most effective one was adding 1% (w/w) NaOH solution mixed with 0.5% (w/w) NaClO, and then cleaning for 120 min at 50 °C, eventually the flux recovery ratio was always higher than 98%. Such effectiveness has verified the compositions of the foulants vice versa. Therefore, the ceramic UF membrane can be reused as a good alternative in the wastewater treatment.