Cadmium Adsorption and Photocatalytic Reusability of Modified Oil-Based Drilling Cuttings Ash

The alkali fusion-magnesium modified oil-based drilling cuttings ash (AM-Mg-OBDCA) was synthesized and characterized for its capacity to remove Cd(II) from aqueous solutions. Adsorption kinetics conformed to the pseudo-second-order model, underscoring a chemisorption-dominated mechanism, while Langmuir isotherm analysis determined a maximum adsorption capacity of 440.2 mg/g. Post-adsorption structural and chemical transformations, confirmed by SEM, FT-IR, XRD, and XPS analyses, revealed the contributions of electrostatic attraction, ligand exchange, surface precipitation, and cation exchange. Photocatalytic tests demonstrated that the CdS-A/M-g-C 3 N 4 (2:1) composite exhibited superior degradation of oxytetracycline hydrochloride (OTC) under visible light, suggesting potential applications in environmental remediation. However, reusability tests indicated a marked decline in adsorption capacity after initial use, pointing to the need for further material optimization. Overall, AM-Mg-OBDCA shows promise as an effective adsorbent for Cd(II) removal and a precursor for photocatalytic materials, offering a sustainable approach to wastewater treatment and resource recovery.