Improved Photodegradation of Methylene Blue Using Cost-Effective and Renewable Fe-Supported Fibrous Nano-silica from Palm Oil Fuel Ash

This study explores the use of fibrous nano-silica (KCC-1) derived from sustainable and renewable waste palm oil fuel ash (POFA) for the photocatalytic degradation of methylene blue (MB), a prevalent environmental pollutant. The synthesis of this eco-friendly material utilises agricultural waste and enhances its catalytic properties by incorporating iron (Fe) particles. Commercial Fe₂O₃ impregnated the synthesised KCC-1, creating the Fe/KCC-1 photocatalyst. Extensive characterisation techniques confirmed the catalyst’s excellent properties, including FESEM, XRD, XRF, BET, FTIR, and UV–Vis DRS. The fibrous morphology, amorphous silica structure with Fe, and silica-rich composition of POFA were verified. The photocatalytic degradation of MB was studied, achieving 87.6% degradation under the best conditions: 240 min of UV irradiation, 3 g/L catalyst dosage, pH 6, and 10 mg/L initial MB concentration. This improvement is attributed to enhanced charge separation and increased active sites facilitated by the iron decoration. The experimental data fit well with the pseudo-first-order kinetic and Langmuir isotherm models, indicating monolayer adsorption on a homogeneous surface. The study found that pH solution is the most crucial factor, with degradation efficiency directly proportional to pH. A degradation mechanism involving MB adsorption on the catalyst surface, followed by the generation of reactive oxygen species like hydroxyl radicals and superoxide anions upon light irradiation, leading to MB degradation, was proposed. This research demonstrates the effectiveness of Fe/KCC-1 derived from waste POFA as a photocatalyst for efficient MB degradation, with potential applications in wastewater treatment.