Waste to worth: Facile preparation of CaO2 derived from oyster shells for highly efficient degradation of organic contaminants based on Fenton-like system

In recent years, CaO2 has been frequently used as a substitute for H2O2 to address the limitations of H2O2. However, commercially available CaO2 are facing the shortcomings of low purity and limited preparation conditions. Oyster shells can provide superior and abundant biomass calcium element with low cost for developing CaO2. In this work, highly purified CaO2 functional biomaterials were prepared via a facile approach derived from waste oyster shells, which were applied in a Fenton-like system to remove organic pollutants. Experimental results indicated that the oyster shells-derived CaO2 with 100 % purity exhibited a greatly enhanced catalytic performance compared with other CaO2 materials in Fenton-like catalytic degradation of organic pollutants, which can be completely removed within 60 s. The high purity of CaO2 would facilitate the release of H2O2 during the Fenton-like catalytic reaction and promote the generation of more active species to oxidize pollutants. Besides, the abundant trace metal elements originated from oyster shells can further motivate the Fenton-like reaction and accelerate the degradation of pollutants, endowing oyster shells-derived CaO2 an excellent catalytic activity. Furthermore, the Fenton-like catalytic mechanism was proposed on basis of tests of radicals trapping and electron spin resonance, validating the vital roles of ⋅OH, ⋅O2– and 1O2 generated throughout the reaction process. This work not only provides a novel and low-cost approach to exploit CaO2 with highly efficient catalytic ability, but also realizes the effective resource utilization of waste shells.