Synthesis of Polyphosphate-Modified Mushroom Waste Adsorbent and Its Adsorptive Performance for Uranium

Abstract

To tackle the scarcity of uranium (U) and the interference of vanadium (V) in nuclear wastewater, we developed a mushroom waste-based adsorbent modified with different forms of phosphate anions (MS-P) for selective adsorption of U(VI). The mushroom biochar was optimized through activation at 700 °C with 2 g KOH, achieving a U(VI) adsorption efficiency of 97.68%. Screening of phosphate modifiers identified hydrogen phosphate as the optimal functionalization agent in terms of cost-performance balance, affording MS-P with a maximum adsorption capacity of 865.80 mg·g–1. The adsorbent exhibited rapid kinetics (equilibrium within 5 min) and maintained >70% efficiency after 4 regeneration cycles. Characterization via FTIR and XRD revealed that the adsorption mechanism involves the capture of uranium through two pathways: the phosphate anions on the adsorbent surface combine with uranyl ions to form Ca(UO2)2(PO4)2·2H2O and (UO2)3(PO4)2·4.8H2O, and the oxygen-containing groups on the material surface undergo coordination with uranium. This work demonstrates MS-P as a sustainable, high-capacity adsorbent derived from the valorization of agricultural waste, which provides a green and promising solution for nuclear wastewater remediation.