Synchronous Photooxidation–Coagulation for the Efficient Treatment of Algae-Laden Water by Utilizing Titanium Xerogel Coagulant

The combination of oxidation and coagulation is an effective strategy for algae-laden water treatment. Titanium xerogel coagulant (TXC) was reported to possess dual functionalities of coagulation and photooxidation, with the latter derived from acetylacetone (AA) present in its framework structure. In this study, synchronous photooxidation–coagulation of TXC was implemented to evaluate the efficiency of treatment of algae-laden water. The results showed that treatment with ultraviolet (UV) radiation and TXC (UV + TXC) significantly improved algal removal under neutral and alkaline conditions. At a dose of 5 mg of Ti/L, the efficiency of removal of algae increased from 12.2% to 66.9% compared to that of TXC coagulation alone (pH 7.0). The enhanced coagulation mechanism involved the effects of UV irradiation on the surface charge properties of algal cells and the inhibition of algal activity. The presence of AA partially alleviated cell rupture and reduced the rate of release of algal organic matter through its intrinsic photooxidation mechanism. N and P nutrients had negligible effects on the efficiency of the UV + TXC process, whereas Fe2+ and Cu2+ cations had complex effects. The synchronous photooxidation–coagulation process using TXC demonstrated highly efficient treatment of algae/As(III) co-contaminated water. Further research is warranted to explore the application of TXC in a practical polluted water body.