Sustainable innovation: Removal of chromium (VI) from wastewater from plastic chromium plating industries using rice husk as photocatalyst

• Rice husk ash is an active photocatalyst for removing Chromium. • A remotion of up to seventy percent of Cr(VI) was observed. • The catalyst dosage and irradiation time significantly influence in the Cr(VI) remotion. Plastic Chromium Plating Industries, tanneries, and other sectors discharge their wastewater into water sources without proper treatment, releasing large quantities of toxic substances such as hexavalent chromium Cr(VI). This heavy metal is highly harmful to the environment and human health. Additionally, rice husk ash is an agro-waste with low TiO 2 content that consumes land resources and creates environmental problems. This study proposes using rice husk ash as a photocatalyst to remove Cr(VI) from industrial wastewater. The rice husk was treated by acid leaching and calcined for 2 h at 800 °C. Experiments were carried out with wastewater samples from plastic chromium plating industries in Bogotá using several catalyst doses (1, 2, and 3 g/L) and UV irradiation times (15, 30, and 45 min) following a 2 × 3*3 factorial design. Experimental results demonstrated that using 3 g/L of rice husk ash and 45 min of UV irradiation achieved up to 70 % Cr(VI) removal. This approach mitigates water pollution and enhances sustainability by reducing reliance on non-renewable resources and fostering circular economy strategies through the valorization of organic waste. The results support the feasibility of using rice husk ash as an efficient and eco-friendly catalyst to mitigate pollution and protect public health and the environment. An optimal removal threshold of 70 % was adopted as a reference for assessing the performance of the photocatalytic process, which is in line with recent studies highlighting this level as suitable for scalable applications.