Effective removal of algae and phosphate by CaO2-modified carbon nanotube-polyvinylidene fluoride pellets: Performance investigation and mechanistic insights

Simultaneous removal of toxic algae and phosphate nutrient is crucial to remediate algae-contaminated waters. Herein, we report the approach for synthesis of CaO2-modified carbon nanotube-polyvinylidene fluoride (CaO2-CNT-PVDF) pellets for the remediation. The pellets were prepared by an in-situ co-precipitation approach and optimized for the best performance through such key parameters as ratios of CNT, PVDF, CaCl2, H2O and hydroxides. The pellet prepared by 1 % of CNT, 0.25 M of H2O2 and CaCl2 with an incubation time of 8 h (termed as CHAT-1228) exhibited the best performance: inhibition of cyanobacteria growth at least for 40 d and uptake of phosphate of 3.6 mg/g CHAT-1228 (270.7 mg-phosphate per gram-CaO2). Our mechanistic studies showed that the cyanobacteria are inactivated by the slow and long-lasting H2O2 release and phosphate is removed via the chemical reactions between CaO2 and phosphate. Furthermore, CHAT-1228 can float on the water surface, making it possess easy recoverability and good reusability. It works well in uptake of phosphorous with pH ranging from 3.4 to 10.9 and in the presence of chloride, fluoride, nitrate, bicarbonate, and sulphate ions. This study demonstrates that the optimized CaO2-CNT-PVDF pellet has great potential for industrial applications in algae-laden water treatment.