Removal of Pb(II), Cu(II), and Zn(II) from Aqueous Solutions by Amorphous Tin(IV) Hydrogen Phosphate Immobilized on Silica
2014
Zhu, Chun-Shui | Dong, Xian | Wang, Li-Ping
Amorphous tin(IV) hydrogen phosphate immobilized on silica (ATHPS) was investigated as an adsorbent for the removal of Pb(II), Cu(II), and Zn(II) from aqueous solutions to determine its applicability in remediation of heavy-metal contaminated saline water. The effect of pH, contact time, initial concentration of heavy metal ions, and salinity on adsorption was studied using a batch method. Equilibrium data were interpreted in terms of Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models. The Freundlich model provided the best fit to the equilibrium data. The selectivity sequence can be given as Pb(II) > Cu(II) > Zn(II). The kinetic data correspond well to the pseudo-second-order and Elovich models. The thermodynamic parameters (i.e., ΔG ⁰, ΔH ⁰, ΔS ⁰) were evaluated to predict the nature of adsorption process. The negative ΔG ⁰ values at various treatment temperatures for each ion indicate that the adsorption processes are spontaneous and endothermic in nature. The ATHPS material can be regenerated, and the adsorption capacity in model seawater is acceptable, although a higher ionic strength can inhibit adsorption. These results show the great potential of ATHPS in removing cationic heavy metal ions from saline water.
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