Thermally activated recycled pottery waste as a porous aluminosilicate sorbent for efficient Uranium(VI) removal from...

The sustainable management of radioactive wastewater requires low-cost and eco-friendly materials capable of efficiently removing U(VI) from aqueous systems. In this work, recycled pottery waste, a ubiquitous aluminosilicate by-product, was thermally activated at 550, 650, and 750 °C to produce novel sorbents (RP1-RP3) for U(VI) adsorption. The materials were comprehensively characterized by XRD, SEM-EDS, BET, DLS, zeta potential, and FTIR to elucidate structural and surface modifications induced by calcination. The results revealed a progressive improvement in crystallinity, porosity, and surface charge with temperature, culminating in RP3 (750 °C) exhibiting the highest surface area (34.35 m² g^-1) and most negative zeta potential (-38.46 mV). Batch adsorption studies demonstrated that U(VI) removal strongly depended on pH, sorbent dose, and contact time, with optimal uptake achieved at pH ≈ 4. The adsorption followed pseudo-second-order kinetics and was best fitted by the Langmuir and Sips isotherm models, confirming monolayer chemisorption on homogeneous active sites. The maximum adsorption capacities reached 49.5 mg g^-1 for RP3, while thermodynamic parameters indicated a spontaneous, endothermic, and entropy-driven process. Mechanistic interpretation supported a multi-step pathway involving electrostatic attraction, surface complexation, and intraparticle diffusion. RP3 exhibited excellent reusability, maintaining >87% adsorption efficiency after five cycles using H₂SO₄ as an effective desorbing agent. When tested with real radioactive wastewater, RP3 achieved a 74.2% U(VI) removal efficiency despite competing ions, confirming its high selectivity and structural stability. This study establishes thermally activated recycled pottery as a cost-effective, reusable, and environmentally sustainable sorbent for uranium (VI) remediation, integrating waste valorization with Radioprotection.