Treatment of paper mill wastewater using a composite inorganic coagulant prepared from steel mill waste pickling liquor.

Graphical abstract Highlights • A composite inorganic coagulant PFASC was prepared using steel mill waste pickling liquor to treat the paper mill wastewater. • PFASC is effective in decreasing the COD and Chroma of paper mill wastewater. • The cost-effective technology has been implemented in a recycled fiber paper mill. Abstract In this study, a waste pickling liquor from a steel mill, which is rich in iron and acid, was used as the main raw material to prepare a composite coagulant: polymeric ferric aluminum sulfate chloride (PFASC). The as-prepared PFASC was used, together with PAM, for the tertiary treatment of papermaking wastewater to decrease its COD and Chroma. The Results from FT-IR and XRD of PFASC, supported the conclusion that polymeric ferric aluminum hydroxide hydrates compounds/ complexes are formed in the synthesized PFASC. When applied to a waste water sample from a paper mill, PFASC, together PAM, leads to decreases in COD and Chroma by 65.3% and 71.2%, respectively (initial pH 7.5, 1 ml/L PFASC, 1.0 ppm PAM). The technology has been implemented at a paper mill, and the obtained results are consistent with those from the laboratory. [ABSTRACT FROM AUTHOR]