Preparation, characterization and coagulation performance of a composite coagulant formed by the combination of polyferric sulfate (PFS) and Ce³⁺

Abstract

A series of composite coagulants (Ce-PFS) with different Ce/Fe molar ratios or adding order of Ce³⁺ were prepared. FTIR, UV spectra, and XRD were employed to characterize the samples and Fe-Ferron time-by-time complexation colorimetry method was used to analyze their Fe species. The coagulation performance of the coagulants was evaluated through their decolorization rate for treating direct sky blue or direct fast claret dye wastewater. The results showed that the new bond of Ce–OH–Fe was formed between Ce³⁺ and polyferric sulfate (PFS), leading to the formation of a new compound. Ce³⁺ not only increased the molecular weight of the coagulant and the accumulation charge of the single particle, but also promoted the conversion of Fe(a) to Fe(b) and Fe(c). In addition, the performance of Ce-PFS was superior to PFS. The decolorization rate of Ce-PFS (Ce³⁺ was added after NaClO₃, Ce/Fe molar ratio was 0.6%) for treating direct sky blue could reach up to 98% at the dosage of 75 mg/L. Meanwhile, its decolorization rate for treating direct sky blue was higher than that of direct fast claret dye wastewater under the same condition.

Keywords:

• Composite coagulant
• Polyferric sulfate
• Ce³⁺
• Dye wastewater