Chemical Cleaning of a Polyethersulfone Membrane Used for Concentrating the Effluent from Alkaline Peroxide Mechanical Pulping Plants

Fouling is one of the most common problems encountered when using membranes in treatment applications of papermaking wastewater. The alkaline peroxide mechanical pulping (APMP) process has been widely adopted all over the world. However, reports on the membrane treatment of APMP plant effluent are relatively rare. It is mainly attributed to the high operational cost of membrane recovery and replacement. So, we originally investigated the cleaning protocols for the polyethersulfone (PES) membranes fouled by APMP plant effluent. To maximize flux recovery, four chemical cleaning protocols were explored to clean the fouled membranes. Parameters evaluated included flux recovery percent, total solids, dichromate chemical oxygen demand (CODCr), five-day biochemical oxygen demand (BOD5), and color retentions of membranes. Scanning electron microscopy with an energy dispersive x-ray analyzer (SEM-EDX) and attenuated total reflection Fourier-transformed infrared spectroscopy (ATR-FTIR) were employed to give a more precise assessment of the cleaning processes. Results showed that the cleaning protocol of "0.2 wt% Triton X-100 + absorbent cotton'' presented the strongest cleaning effectiveness for the fouled PES membranes. Flux of the fouled membrane recovered to 98.5% that of the pristine membrane, and the retention of total solids, CODCr, BOD5, and color of the cleaned membrane were approximate to those of the pristine membrane. Examinations of SEM-EDX and ATR-FTIR revealed that the cleaned membranes had similar appearances with the pristine membrane, as well as elemental and chemical compositions.