Controlled synthesis of innovative carbon-based CaO2 materials with boosted oxygen release performance in the aqueous environment

CaO2 has been widely used as an oxygen-releasing material in bioremediation to improve the aerobe activity, but conventional encapsulation methods are difficult to control the oxygen-releasing rate and realize the full conversion of CaO2. In this work, innovative biochar-loaded CaO2 was prepared by an in-situ precipitation method. The biochars were modified using base-/acid-treatment to establish the relationship between the biochar properties and the oxygen releasing performance. Results indicated that increasing the oxygen content of biochars from 11% to 12% to -20% caused a significant rise in CaO2 loading amount from -6 wt% to 13-14 wt%. The biochar with an average pore size equivalent to CaO2 nanoparticle sizes (-12 nm) exhibited the longest oxygen-releasing time of 7.5 d, while the others presented shorter releasing periods of < 2.4 d. Meanwhile, a higher oxygen content of biochar triggered a decrease in the oxygen-releasing amount. Results from bioremediation experiments indicated that when comparing with the pure CaO2 material, the optimized loading material (CaO2 @BC800) nearly doubled the amount of bacteria while negligibly changed the pH of solution, giving a significant increase in the removal of diesel oil pollutant. Correspondingly, the in-situ loading on biochar can facilely regulate the oxygen-releasing performance and enhance the removal efficiency of bioremediation.