Microwave assisted synthesis and characterization of a ternary flocculant from chitosan, acrylamide and lignin

Flocculant based on natural polymers has been given extensive attention recently in view of its rich source, low cost and eco-friendliness. In this study, a ternary graft copolymer (chitosan-acrylamide-lignin, CAML) was synthesized using combined microwave irradiation and chemical free radical initiator (K2S2O8/Na2S2O3) techniques. The synthesis process of dosage of initiator and microwave irradiation time was optimized with the initiator dosage of 1% (w/w) and microwave irradiation time of 18 min at the power of 280 W. Further, the flocculation performance of CAML was evaluated by the removal capacity of a synthetic dye (Acid black-172). The color removal efficiency was 97.1% at the dosage of 200 mg L−1 for 100 mg L−1 synthetic dye wastewater. CAML also revealed broad flocculation window and effective pH range. The possible flocculation mechanism for dye removal from wastewater was charge neutralization, bridging, and sweeping effects in various wastewater environments. The ternary copolymer showed the potential as an efficient flocculant. •Chitosan-acrylamide-lignin ternary copolymer was prepared by microwave assisted method.•The color removal efficiency was 97.1% for acid black-172 simulated wastewater.•The amphoteric flocculant had a wide flocculation window and effective pH range.