Removal of urea by adsorption using solid sorbent from photovoltaic industry waste

This study focuses on addressing environmental concerns arising from the growth of the agricultural sector especially in relation to the inadequate treatment of wastewater from agricultural effluent. Urea is a prevalent component in agricultural wastewater due to its widespread use as a fertilizer, and contributes significantly to nutrient runoff, which can lead to eutrophication, biodiversity loss, and disruption of aquatic ecosystems. This research aligns with the United Nations Sustainable Development Goals (SDG) 2030, particularly Goal 6 (Clean Water and Sanitation) and Goal 12 (Responsible Consumption and Production), by proposing innovative solutions for wastewater management and industrial waste reutilization. This work introduces the novel approach of using a solid adsorbent derived from photovoltaic waste for the effective removal of urea from aqueous solution. By utilizing waste material, this approach not only promotes sustainability, but highlights the dual benefits of mitigating industrial waste and addressing agricultural wastewater challenges. The alkaline sludge (AS) used in this study was obtained from the photovoltaic industry in Sarawak, Malaysia. The findings indicate that the most efficient adsorbent for urea removal was calcined alkaline sludge (CAS). Its effectiveness was attributed to the presence of SiO2 and CaSiO3, which likely provided active adsorption sites, despite a lower BET surface area primarily contributed by micropores and mesopores. Optimal urea adsorption conditions were achieved at an initial urea concentration of 30 mg/L, with an adsorbent loading of 0.2 g, a temperature of 40 °C, and an adsorption period of 6 hours. Under these conditions, the removal percentage of CAS was 82.50 %, with an adsorption capacity of 4.95 mg/g. A slightly elevated temperature of 40 °C enhanced adsorption by increasing the kinetic energy of the molecules within the system. The adsorbed urea was measured through a weight loss of 10.85 % in the temperature range of 450–720 °C. This study not only demonstrates a sustainable approach to managing agricultural wastewater, but also underscores the potential of repurposing photovoltaic industry waste into effective adsorbents. Future research could explore scaling up this approach and investigating its application to other contaminants in agricultural and industrial wastewater.

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