Synergistic coagulation of bauxite residue-based polyaluminum ferric chloride for dyeing wastewater treatment

Considering that Fe, Al elements in bauxite residue are active components for water purification, an effective polyaluminum ferric chloride (PAFC) coagulant derived from bauxite residue, with Fe2O3 content > 5.1%, Al 2 O 3 % > 6.5%, basicity > 65%, was successfully prepared. The effect of as-prepared PAFC on the zeta potential for printing and dyeing wastewater was investigated. Comparing with polyferric chloride (PFC) and polyferric sulfate (PFS) for printing and dyeing wastewater treatment, prepared bauxite residue-based PAFC exhibited the optimal performance in the aspects of chromaticity and chemical oxygen demand (COD) removal rate. Furthermore, the combination of bauxite residue-based PAFC and PFS for synergy coagulation of such wastewater demonstrated an obvious positive effect. With the proportion between as-prepared PAFC and PFS to be 2.5:1, the COD of treated wastewater could be further reduced to meet the national level A standard of China, providing a promising route to solve the problem of substandard printing and dyeing sewage outfall by a simple coagulation strategy.