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.