Recovered poly manganese chloride (PMnCl2) from industrial waste sludge to decolorize and detoxify textile dyes and comparison with alum

The coagulation process for treating wastewater pollutants, due to its simplicity and safety, has received growing attention for a while. In this research, manganese chloride in industrial wastewater sludge can be recovered to produce poly manganese chloride as an effective and low-cost coagulant for the treatment of industrial pollutants. However, in recovering manganese chloride, there are some factors that affect efficiency, such as hydrochloric acid concentration, agitation force during acidification, contact time, and temperature. To describe the coagulant’s morphological and elemental structure, scanning electron microscopy (coupled with energy dispersive spectroscopy) and Fourier transform infrared spectroscopy were used. The purpose of this research is to determine the ideal recovery coagulant conditions and assess this coagulant’s efficacy in comparison to a conventional coagulant, alum, to treat textile dyes reactive yellow (RY17) and direct blue (DB53). In this paper, the results show that the optimum acidification concentration was 30% with a stirring speed of 300 rpm for 100 min at 80°C. Using a jar test, the optimum dose for the recovered coagulant was 30 mg⸱l−1. The decolorization of RY17 and DB53 was found to be 90.33% and 86.11%, respectively. The chemical oxygen demand and total organic carbon were reduced by 80.96% and 83.82%, respectively, for RY17, while for DB53 they were reduced by 76.53% and 80.28%, respectively. At the same dose of alum, the decolorization of RY17 and DB53 was 85.42% and 80.34%, respectively. The decolorization performance illustrated that at the same dosage, the recovered coagulant has slightly higher quality than the alum coagulant.