Nutrient Capture and Circular Solutions: Zinc Chloride Activated Bamboo Biochar for Aquaculture Wastewater Nitrate Recovery

The growth of aquaculture farming has produced more nutrient-rich wastewater. This wastewater contributes to eutrophication in the water bodies. Meanwhile, the bamboo furniture industry generates large amounts of solid waste biomass wastes. Bamboo biomass waste could be used in many valuable ways because it is abundant, and has high strength and cellulose content, but it is still mostly underused and often ends up in landfills. To reduce water pollution and nutrient buildup caused by aquaculture wastewater (AW), capturing nutrients with bamboo-derived biomass offers a sustainable circular solution that turns waste into a valuable resource. This study explores the efficiency of zinc chloride (ZnCl2) activated bamboo biochar (ABB) to recover nitrate from AW. ABB was prepared using different impregnated ratios of ZnCl2 at 500 °C. The best prepared condition was further optimized for adsorption process by varying the dosage of ABB and contact time. Results shows that the most efficient nitrate adsorption was 68.8 % when ZnCl2 ABB was prepared at 500 °C using an impregnation ratio of 3. At optimum process parameter (2.5 g, 150 rpm and 90 min) the adsorption efficiency and capacity were further enhanced to 82.8% and 0.676 mg/g respectively. The adsorption process was well represented by Freundlich and pseudo second-order model. The adsorption efficiency decreased to 63.2 % when tested with actual AW due to other competing contaminants in the actual wastewater. This study demonstrates the potential of ABB as a sustainable nitrate recovery material from AW. Spent ABB could be further exploited as soil conditioner. This study contributes to circular economy practices by promoting nutrient recovery from wastewater and the reutilization of waste biomasses.