Recovery of Ammonium and Phosphate from Wastewater by Wheat Straw-based Amphoteric Adsorbent and Reusing as a Multifunctional Slow-Release Compound Fertilizer

To minimize the negative impact of nitrogen and phosphorus pollution from wastewater and improve fertilizer use efficiency, a novel multifunctional slow-release compound fertilizer was prepared by recovery of NH₄⁺ and H₂PO₄^– from aqueous solutions onto amphoteric straw cellulose (ASC) adsorbent. The effects of adsorbent dosage, solution pH, contact time and ionic strength on adsorption were investigated. The adsorption quickly reached equilibrium. The maximum NH₄⁺ adsorption capacity of ASC was 68.4 mg g^–1 at around pH 7.0, whereas it was 38.6 mg g^–1 for H₂PO₄^– adsorption at pH 5.0. Moreover, the feasibility of reusing the nutrients-laden carrier material as a multifunctional slow-release compound fertilizer was determined. The study demonstrated the product with excellent slow-release and water-retention properties. Thus, it could improve soil moisture content and reduce soil moisture evaporation rate and was economical and environmentally friendly for application in horticulture and agriculture.