Performance study of ZrO2 ceramic micro-filtration membranes used in pretreatment of DMF wastewater

• 19-Channel ZrO2 microfiltration membrane was used in pretreatment of DMF wastewater.
• 0.2 μm ZrO2 membrane can effectively remove fine particles in DMF wastewater.
• Combined flushing, ultrasonic and chemical cleaning was effective for flux recovery.

Three kinds of 19-channel ZrO2 micro-filtration membranes with different pore size were used for pretreatment of dimethylformamide (DMF) wastewater from the polyurethane (PU) synthetic leather factories, which would enter the distillation column for further purification. The effects of membrane pore size, cross flow velocity (CFV) and transmembrane pressure (TMP) on ceramic membrane filtration performances were investigated. Experimental results indicated that the optimum membrane pore size, CFV and TMP were 0.2 μm, 3 m·s− 1 and 0.2 MPa, respectively, with the corresponding liquid turbidity removal rate of 99.62% and suspended solid content retention rate of 99.99%. The membrane fouling mechanism was analyzed by resistance in series model. The main resistance derived from the particle adsorption and sedimentation on the membrane surface. The ratio of particle adsorption and sedimentation resistance to total resistance was above 70% for the 0.2 μm membrane. The backflushing technology was applied and the effect of backflushing on the permeate flux was studied. The permeate flux eventually increased by 50% with the optimum backflushing pressure of 0.6 MPa, backflushing time of 5 s and backflushing interval of 20 min. A combination cleaning method was used to regenerate the ZrO2 micro-filtration membrane. The pure water flux recovered to 608.2 L·m− 2·h− 1 and flux recovery rate was 96.8% which indicated that the combination cleaning method was effective.