A Novel Functionalized Hay-Derived Biochar for Recovery of Phosphorus Fertilizer from Dairy Wastewater

Runoff from nutrient-rich dairy wastewater has the potential to induce eutrophication in nearby bodies of water, resulting in fatal consequences for the fish and other animals within. The present study investigated a novel calcium hydroxide-coated hay-derived biochar (Ca-BC) for adsorption of phosphate from dairy wastewater. The Ca-BC was prepared via one-step thermal process for simultaneous pyrolysis and functionalization of a waste hay as a feedstock. The Ca-BC was comprised mainly of calcium hydroxide and various functional groups resulting in high reactivity between aqueous phosphate and the calcium hydroxide in the Ca-BC. Through the detailed adsorption isotherm, kinetic and thermodynamic studies, the Ca-BC showed much higher adsorption of phosphate than those of biochar made from various feedstocks. The Ca-BC also exhibited excellent recovery of phosphorus fertilizer from dairy effluent which could lead to practical application in the field. Overall, the hay-derived Ca-BC would be a low-cost and effective adsorbent for the recovery of phosphate from water and wastewater sources.