Efficiency and Mechanisms of Sunlight-Driven Photocatalytic Degradation of Total Petroleum Hydrocarbons Using Pyrolyzed Drilling Waste Residue

This study addresses the challenges associated with deep-well drilling mud cuttings, including large waste volumes, high transportation costs, and complex organic pollutants. A low-cost synergistic technology was developed for the resource utilization of pyrolyzed drilling waste residue (PDWR) and the in situ remediation of oil-contaminated drill cuttings. A ternary photocatalytic system consisting of PDWR, H 2 O 2 , and oxalic acid was proposed and demonstrated to effectively degrade total petroleum hydrocarbons (TPH) in drill cuttings under solar irradiation. Systematic optimization identified optimal dosages of PDWR, H 2 O 2 , and oxalic acid as 250 mg, 280 mg, and 90 mg, respectively. The addition of oxalic acid significantly enhanced photocatalytic oxidation performance, increasing H 2 O 2 utilization by 63.8% and improving the TPH degradation rate by a factor of 3.03. Under optimal conditions and 7 days of solar irradiation, TPH degradation efficiencies of 65.19–88.66% were achieved for initial TPH concentrations ranging from 5000 to 12,000 mg kg −1 . Mechanistic analysis revealed that a Fenton-like reaction between transition metals in PDWR and H 2 O 2 dominated the photocatalytic process, while oxalic acid facilitated metal redox cycling through coordination and electron transfer, promoting sustained generation of reactive oxygen species (·OH). This study demonstrates a feasible and sustainable approach for high-value utilization of drilling waste residue and solar-driven in situ remediation of oil-contaminated drill cuttings, highlighting its strong potential for practical application.