Coagulation performance and floc characteristics of poly-ferric-titanium-silicate-chloride in coking wastewater treatment

A novel composite coagulant poly-ferric-titanium-silicate-chloride was synthesized and employed to treat one typical kind of industrial wastewater-coking wastewater. In this study, two composite coagulants, poly-ferric-titanium-silicate-chloride (PFTSC) and poly-titanium-silicate-chloride (PTSC), were prepared and employed to treat coking wastewater. The structure and morphology of the prepared PFTSC and PTSC were examined, and the compositions of the organic matter were characterized in the coking wastewater samples. Changes in the flocs were monitored during coagulation. The kinetic model of floc sedimentation was preliminarily investigated. We observed the formation of new Fe-O-Si and Ti-O-Si bonds: PFTSC showed a higher organic removal efficiency and turbidity than PTSC; PFTSC removed ≥ 93% of the turbidity in the coking wastewater. Based on the dissolved organic carbon, chemical oxygen demand, and ultraviolet absorbance at 254 nm characteristics, the corresponding organic matter removal rates were 24.1%, 10.7%, and 10.1%, respectively. PFTSC can target the removal of toxic organic compounds. Compared with PTSC, PFTSC flocs had a more compact structure and higher porosity, which indicated that PFTSC had a stronger removal capacity for suspended solids and organic matter. Floc sedimentation was suitable for fitting with the quasi-second-order kinetics model in the process of coking wastewater treatment. This study indicates that PFTSC is a prospective candidate for the pretreatment of industrial coking water, such as coking wastewater. • PFTSC and PTSC prepared and employed to treat coking wastewater. • Structure and morphology of PFTSC and PTSC examined. • Compositions of organic matter characterized in coking wastewater samples. • PFTSC showed higher organic removal efficiency and turbidity than PTSC. • PFTSC is prospective candidate for pretreatment of industrial coking water.