Purification, characterization and application of dual coagulants containing chitosan and different Al species in coagulation and ultrafiltration process

Wenyu Wang , Shuang Zhao , Qinyan Yue , Baoyu Gao , Wen Song , Lijuan Feng


Received April 22, 2016,Revised June 16, 2016, Accepted June 24, 2016, Available online July 14, 2016

Volume 29,2017,Pages 214-221

The objective of this study was to investigate the effect of different Al species and chitosan (CS) dosages on coagulation performance, floc characteristics (floc sizes, strength and regrowth ability and fractal dimension) and membrane resistance in a coagulation–ultrafiltration hybrid process. Results showed that different Al species combined with humic acid in diverse ways. Ala had better removal efficiency, as determined by UV254 and dissolved organic carbon, which could be further improved by the addition of CS. In addition, the optimal dosage of different Al species was determined to be 4.0 mg/L with the CS concentration of 1.0 mg/L, by orthogonal coagulation experiments. Combining Ala/Alb/Alc with CS resulted in larger flocs, higher recovery, and higher fractal dimension values corresponding to denser flocs; in particular, the floc size at the steady state stage was four times larger than that obtained with Al species coagulants alone. The results of ultrafiltration experiments indicated that the external fouling percentage was significantly higher than that of internal fouling, at around 85% and 15%, respectively. In addition, the total membrane resistance was significantly decreased due to CS addition.

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