Flocculation Performance of Hyperbranched Polyethylenimine-Grafted Cellulose in Wastewater Treatment

A green, high-efficiency flocculant based on hyperbranched polyethylenimine-grafted cellulose (hPEI-CE) was designed and successfully synthesized. The flocculation performance of the hPEI-CE with different amino group contents for treating simulated kaolin wastewater was evaluated in terms of turbidity, floc size, and zeta potential. Without the help of any coagulant aid, hPEI-CE with an amino group content of 3.97 mmol/g presented the best removal efficiency for kaolin particles. The residual turbidity of kaolin suspension decreased from original 490 NTU to 4 NTU under the optimized conditions, i.e., 2.4 mg/L of hPEI-CE flocculant at pH 7.0 for 30 min. Furthermore, two types of industrial wastewater were used to investigate the flocculation performance of hPEI-CE: silk printing and dyeing wastewater and machining wastewater. Total suspended solid (TSS), chemical oxygen demand (COD), and turbidity reduction reached up to 73.4%, 95.7%, and 87.4% for silk printing and dyeing wastewater, 96.2%, 79.9%, and 93.5% for machining wastewater, respectively, under each original pH condition. Moreover, highly effective removal of ammonia nitrogen, total iron, and total phosphorus was also obtained. The pH of the effluent was approximately neutral. All of the results show that the hPEI-CE flocculant has great application prospects in wastewater treatment.