Utilization of Rice Husk and Alum Sludge to Produce an Efficient Adsorbent Composite for Recovery of Nutrients from Wastewater

Abstract

This study focused on developing an adsorbent composite from rice husk and alum sludge to recover nutrients from wastewater, which could be used in the future for slow-release fertilizer production. A biochar-sludge composite (80B/20S) was created by modifying rice husk biochar with MgCl2 and using acid- and heat-treated alum sludge to extract ammonium and phosphate contents from wastewater. The physical and chemical properties of the materials were analyzed using various techniques, such as X-ray diffraction and scanning electron microscopy. In the nutrient recovery test, the contact time, adsorbent dosage, and initial concentration were evaluated. The adsorption equilibrium contact time for both ammonium and phosphate were found to be 8 h, and the maximum adsorption capacity by Langmuir isotherm for the 80B/20S composite was 185.53 mgNH4 +/g and 63.78 mgPO4 3-/g. The composite material had a higher surface area of 141.32 m2/g, which promoted its adsorption capacity. Additionally, this material demonstrated a removal efficiency above 85% when applied to actual wastewater. Since the composite is composed mainly of natural components, it has the potential to be used as a sustainable slow-release fertilizer for agricultural growth.