Synthesis of visible light induced-flocculants via synergetic initiation of modified-titanium dioxide and potassium persulfate and their flocculation performances in the treatment of tetracycline

Abstract

Organic polymer flocculants as the typical chemicals are widely applied in wastewater treatment. The efficient initiation method will increase the synthesis efficiency of organic polymer flocculants and reduce their synthesis cost. Herein, a novel synergistic initiation system of modified-titanium dioxide (modified-TiO₂) and potassium persulfate (K₂S₂O₈) was applied to prepare a cationic organic polymer flocculants, VLIF, under visible light. The initiation mechanisms of VLIF were investigated via molecular dynamics simulation, experiments and characterization. The results indicated that there were synergies of modified-TiO₂ and K₂S₂O₈ during the initiation. Modified-TiO₂ was firstly excited and generated active radicals and electron-hole pairs. Photogenerated electrons reduced K₂S₂O₈. K₂S₂O₈ was subsequently excited and simultaneously facilitated the generation of free radicals of modified-TiO₂. The prepared VLIF possessed the excellent physical and chemical properties. It performed well in the treatment of wastewater containing tetracycline, colloidal particles and natural organic matters. The highest removal rate of tetracycline was 76.85% achieved by VLIF. The strong interaction between VLIF and tetracycline, micelles formed by sodium dodecyl sulfate (SDS) and tetracycline, bridging and adsorption all contributed to tetracycline removal from wastewater.