Tea-Waste-Mediated Magnetic Oxide Nanoparticles as a Potential Low-Cost Adsorbent for Phosphate (PO 4 3−) Anion Remediation.

In the current study, magnetic oxide nanoparticle-impregnated tea waste (TW-Fe₃O₄) is employed as an adsorbent to remove phosphate ions (PO₄³⁻) from an aqueous solution. By utilizing a variety of analytical methods, the TW-Fe₃O₄ nano-adsorbent was characterized by FE-SEM, TEM, EDX, BET, FTIR and XRD. The FE-SEM of TW-Fe₃O₄ demonstrated the adsorbent's granular morphology with a variety of magnetic nanoparticle sizes and shapes. The XRD of TW-Fe₃O₄ showed two diffraction peaks at 2θ values 30.9° and 35.4°, which are in correspondence with the diffraction pattern of magnetite. The synthesis of a TW-Fe₃O₄ adsorbent with a greater surface area and porosity was demonstrated by BET analysis. Numerous adsorption factors like initial concentration of PO₄³⁻ ion, pH of the medium, contact time, temperature and adsorbent dose were optimized for phosphate removal. The maximum removal of 92% was achieved by using the adsorbent dose of 1.2 g at 323 K (pH 5). Pseudo-second-order and intra-particle diffusion models were fitted to the sorption kinetic, whereas adsorption isotherm data were found well fitted to Freundlich and Dubinin–Radushkevich (D-R) models. The highest adsorption capacity of TW-Fe₃O₄ towards phosphate ions was 226.8 mg/g, which is significantly higher than other reported bio-adsorbents. According to thermodynamic data, phosphate adsorption at the solid–liquid interface was of an endothermic and spontaneous nature and characterized by enhanced inevitability. [ABSTRACT FROM AUTHOR]