Novel polyaluminum ferric chloride composite coagulant from Bayer red mud for wastewater treatment

A novel composite inorganic polyaluminum ferric chloride (PAFC) coagulant was prepared from Bayer red mud and was usable for wastewater treatment. The reaction parameters affecting the PAFC coagulant performance such as the type of alkali used as the polymerization adjuster, pH, reaction temperature, and reaction time were examined in this study. The structure and morphology of the product were characterized by infrared spectra (FTIR), X-ray diffraction, and scanning electron microscopy. The optimized conditions for preparation were decided as using Ca(AlO2)2 and NaOH together as the polymerization adjuster to reach a pH value of 2.47 with the mixture being kept at 80°C for 6 h. Furthermore, the coagulation performance of the PAFC coagulant was tested in real wastewater samples of pretreated oily sewage and printing and dyeing wastewater. The prepared PAFC coagulant outperformed commercially available PAC coagulant.