Aqueous phosphorous adsorption onto SnO2 and WO3 nanoparticles in batch mode: kinetic, isotherm and thermodynamic study.

This study investigated the removal of phosphorus (PO₄⁻³-P) from water samples by SnO₂ and WO₃ nanoparticles (NPs). The effects of adsorbent dosage, pH, contact time and temperature with an initial concentration of 50 mg L⁻¹ of P were investigated. SEM-EDX, FTIR, XRD, and BET analyses were performed to characterize these nanoparticles. The results indicated that the maximum adsorption capacity of SnO₂ and WO₃ NPs was 21.5 and 19.0 mg g⁻¹, respectively and occurred at pH = 3. Within 40 min of operation, about 47.2% and 45.2% of P ion were removed from the solutions by SnO₂ and WO₃ NPs, respectively. The kinetics of P adsorption from solutions was analyzed by fitting the experimental data to the pseudo-first and second-order kinetic models. The result showed that the pseudo-second-order kinetics model provided much better R² values. In the multi-component solutions, in the presence of Cl⁻, NO₃⁻ and Cr₂O₇²⁻ ions, the adsorption rates decreased to (26.2% and 28.5%), (27.2% and 30.0%), and (48.0% and 33.0%) by SnO₂ and WO₃ NPs, respectively. Thermodynamic data (ΔG°< 0) fitting showed that the reactions of adsorption of P were spontaneous. In general, the nanoparticles of SnO₂ had better efficiency in the removal of phosphorous from water. [ABSTRACT FROM AUTHOR]