An optimized CaO-functionalized alginate bead for simultaneous and efficient removal of phosphorous and harmful cyanobacteria.

Simultaneous removal of phosphorus (P) and algae is important to mitigate eutrophication, however, it is rather challenging in remediation of harmful algal blooms (HABs)-contaminated water. In this study, a wet alginate bead functionalized by CaO particle formed layer by layer was prepared with an in-situ method and optimized to remove phosphorous and inhibit algae growth. The stable HO release with a concentration level of 0.06 mM was observed for a period of 26 d. The content of peroxy groups (-O-O-) in the optimal bead was 0.44 mmol·g through permanganate-based titration study. For solution with an initial phosphorous concentration of 10 mg·L, the removal was around 97% in pH 3.0-10.0. XRD, SEM, and XPS studies and kinetic modelings showed that removal of phosphorus was mainly due to formation of insoluble Ca-P compounds in the bead. The CaO-functionalized bead inhibited algae growth with an effect lasting over 170 d, which was much better than liquid HO and Ca(OH) bead; the phosphorous removal with an efficiency of about 70% was simultaneously obtained. Furthermore, the bead demonstrated to be effective in removing algae in the realistic water from a reservoir. In summary, this study shows that the CaO-functionalized material is promising for simultaneous removal of phosphorous and management of HABs.