Direct use of Fe-based photocatalyst in Humuturi’s soil incorporated with zinc oxide for enhanced photodegradation of methylene blue

Indonesia has abundant natural resources, including high-quality Fe-based minerals that can be used as adsorbents and photocatalysts. This study aims to use Fe-based photocatalyst in Hutumuri’s soil (IRSH) incorporated with zinc oxide (ZnO) to enhance the adsorption-photocatalytic ability towards methylene blue (MB) in solution. Simple impregnation of ZnO onto IRSH retains its structural and textural features, suggesting good stability. The band gap of ZnO/IRSH composites increases from 2.29 eV to 2.51 eV as ZnO loading increased, surpassing the band gap of IRSH. This band gap is within the visible-light range, indicating that ZnO/IRSH composites can absorb visible-light. These features enhance photocatalytic activity to 96%, which is higher than IRSH (75%) and ZnO (52%). Additionally, the addition of ZnO to IRSH decreases PL intensity, indicating decreased charge-carrier recombination rate. As a result, the photocatalytic activity of ZnO/IRSH is enhanced by efficient charge-carrier separation and transfer. Based on response surface methodology, the highest MB photodegradation by ZnO/IRSH is achieved at pH 9 and a dosage of 35 mg, consistent with the parameter effects. Finally, the photodegradation mechanism is proposed based on LC-MS analysis. This study provides a sustainable approach by utilizing natural-based photocatalyst for wastewater treatment.