Applicability of HDPC-supported Cu nanoparticles composite synthesized from anaerobically digested wheat straw for octocrylene degradation in aqueous solutions

The technical applicability of hydrochar-derived pyrolysis char-supported Cu nanoparticles composite (Cu NPs/HDPC) to the degradation of octocrylene (OC) was investigated in aqueous solutions in the presence of H 2 O 2 . The physico-chemical properties of the Cu NPs/HDPC composite before and after degradation reaction were described. The role of OH in this H 2 O 2 -led degradation was examined using electron spin resonance (EPR) technique. The possible degradation mechanisms of OC by the Cu NPs/HDPC-H 2 O 2 system and its degradation pathways were investigated. A relatively large surface area and pore volume of the HDPC (191.4 m 2  g −1 and 0.11 cm 3  g −1 , respectively) resulted in well-dispersed Cu NPs loading on the surface. The degradation efficiency of OC (50 μM) was 97.0% in the presence of Cu NPs/HDPC composite (0.5 g L −1 ) and H 2 O 2 (20 mM) at pH 5.6 in 4 h, which was significantly higher than in Cu NPs/biochar and the integrated HDPC-Cu NPs, i.e., 62.4% and 79.7%, respectively, under the same conditions (ANOVA test; p  ≤ 0.05). Several oxidation by-products of the OC included benzophenone, 3,3-diphenylacrylonitrile, and others. The OH, which resulted from the Fenton-like oxidation between the Cu species and H 2 O 2 on the HDPC surface, was the predominant factor responsible for the OC degradation in the solution. The OH formation was facilitated by a single-electron transfer process from the HDPC surface, in which the Cu NPs/HDPC composite with its C OH functional group promoted the decomposition of H 2 O 2 . These findings contribute to a novel approach of cost-effective wastewater treatment by adding value to unused waste materials from agricultural industries.