Synthesis, characterization and application of polyacrylamide grafted bioflocculant

Abstract

Water pollution contributes to water scarcity by decreasing the amount of available freshwater. Grafted bioflocculants tend to have excellent wastewater remediation capabilities. The aim of this research was to synthesize, characterize and apply polyacrylamide grafted bioflocculant to wastewater treatment. Bioflocculant (TMT−1) produced by Bacillus pumilus JX860616 was grafted with acrylamide chains using a microwave initiated method. To optimize the synthesis, irradiation time and acrylamide concentration were varied. Optimum grade (TMT−1-g-PAM 2) was characterized by intrinsic viscosity, elemental analysis, SEM, FTIR spectroscopy, XRD and TGA. TMT−1-g-PAM 2's biosafety – on human embryonic kidney (HEK) 293 cells – was assessed by MTT assay. Its biodegradation was investigated by a composting method. The effects of dosage size, cations (BaCl2, KCl, NaCl, LiCl, CaCl2, MgCl2 and FeCl3), pH and temperature on the flocculating activities of the flocculant were evaluated, spectrophotometrically. The flocculation mechanism was determined by measuring zeta potentials using Zetasizer Nano. Optimum grade (TMT−1-g-PAM 2) was obtained when a concentration of 2.5 g of acrylamide was used for grafting on TMT−1 at irradiation time of 3 min. Changes observed in intrinsic viscosity, elemental analysis, SEM, FTIR, XRD, and TGA confirmed that grafting occurred. HEK 293 cells displayed high viability (75%) at 200 μg/ml of the flocculant. The removal of COD, BOD, N and P, in domestic wastewater, by the flocculant reached 98%, 54%, 53%, and 57%, respectively, when evaluated by spectrophotometric cell tests. The good flocculation efficiency by the flocculant means it has the potential to replace the traditional chemical flocculants.