Nano aluminum-based hybrid flocculant: Synthesis, characterization, application in mine drainage, flocculation mechanism

Given the characteristics of high turbidity and trace emulsified oil in mine drainage, which leads to the problems of low settling efficiency and poor treatment efficiency in the coagulation/flocculation treatment process, there is an urgent need to develop efficient, economical, and stable flocculants. In this study, a new hybrid flocculant Al-P(AM-DMDAAC-BA) was synthesized by the solution copolymerization method, and its viscosity, molecular weight, and cationic degree were 1492.93 mL/g, 7.44 × 106 Da and 16.97%, respectively. The physical and chemical properties of Al-P(AM-DMDAAC-BA) were characterized by Fourier transform infrared spectroscopy (FTIR), Nuclear magnetic resonance (1H and 13C NMR), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Thermogravimetric (TG), and Zeta potential. SEM, Zeta potential, and laser particle size measurement characterized the properties of flocs. Batch wastewater treatment experiments analyzed the flocculation treatment efficacy. The results of the analysis are as follows. Aluminum hydroxyl complexes were attached to organic polymers via -Al-O-C- bonds. Acrylamide (AM), dimethyl diallyl ammonium chloride (DMDAAC) and butyl acrylate (BA) were linked to each other by Carbon-carbon double bond (-CC-). The aluminum-based complex is dispersed as nano-microspheres in the hybrid flocculant and cross-linked to the organic branched chains. Al-P(AM-DMDAAC-BA) is thermally stable and less susceptible to thermal decomposition. It possesses strong electrical neutralization ability and rapid floc growth ability. It has excellent turbidity removal (reduced to 7.96 ± 1.15 NTU) and emulsified oil removal (reduced to 0.23 ± 0.01 mg/L) performance. The flocculation mechanism is mainly attributed to the electro-neutralization of the hybrid flocculants and the adsorption bridging effect of organic branched chains.