High efficient coagulant simply by mechanochemically activating kaolinite with sulfuric acid to enhance removal efficiency of various pollutants for wastewater treatment

Abstract Coagulant has been widely used in the pretreatment of wastewater, and a simple and environment- friendly process to prepare high-efficiency coagulants is highly desired in response to the expected increase in amounts for water treatment. In this study, a novel process to prepare aluminum-based coagulant was developed by a mechanochemical activation of kaolinite, followed by co-grinding with concentrated sulfuric acid. The composition, structure and morphology of the coagulant were characterized using X-ray Powder Diffraction, Fourier Transform Infrared Spectrometer and Scanning Electron microscopy. Capacity of the product serving directly as coagulant, compared with pure aluminum sulfate, was evaluated by the removal efficiency of turbidity, phosphate, arsenate(V) and humic acid, reaching 99.9%, 91.2%, 89.6%, and 92.3%, respectively. Moreover, the formation of alum flowers was observed over a wide pH range of 4.3–9.0. The potential applications of the promising green coagulant in the pre-treatment process of sewage, through the simple preparation by non-thermal mechanochemical activation of kaolinite, provides a new route to utilize kaolinite-rich tailings of coal mining gangue etc.