Cd2+ ions removal by silica, iron hydroxide and their equimolar mixed oxide from aqueous solution

The current study focuses on the characterization and comparative sorption of Cd2+ ions on silica, iron hydroxide and their equimolar mixed oxide (0.5 M SiO2:0.5 M Fe(OH)3) from aqueous solutions. These adsorbents are characterized for surface area, EDX, FTIR, TG/DTA, XRD and pHPZC. Cd2+ sorption studies are performed at pH 5 in the temperature range 288–318 K. Sorption data are found well fitted to the Langmuir model with R2 > 0.98. The mixed oxide has been found to have the highest selectivity towards the Cd2+ ions. Thermodynamic parameters show the process to be endothermic and spontaneous and also reveal that the electrostatic interactions play the dominant role in the overall mechanism of the uptake of Cd2+ ions. The ΔH0, ΔS0, and ΔG0 values found for equimolar mixed oxide are the arithmetic mean of silica and iron hydroxide.