Investigation of Adsorption Characteristics of an Engineered Adsorbent for Removal of Hexavalent Chromium from Aqueous Solutions

Application of iron oxide loaded sand (IOLRS) for the removal of hexavalent chromium has been investigated.The noral ilica sand was used in the experiments.IOLRS was characterized by XRD, and FTIR to investigate its specific characteristics.Particle size was found to be in the range 2.5 to 200 µm.Removal efficiency of adsorbent for Cr(VI) was determined for batch adsorption experiments.Effect of various important parameters such as concentration, pH, temperature and adsorbent dose on the removal of Cr(VI) was investigated.The removal of Cr (VI) was better in acidic pH range.The removal increased from 65 to 71.66 % by increasing temperature from 25 to 450C showing the process of removal to be endothermic.Kinetic studies revealed that removal process is governed by pseudo first order kinetic model.Intraparticle diffusion was not found to be rate limiting step in removal process.Langmuir and Freundlich adsorption capacity was found to be 0.36 and 0.18 mg/g respectively at 450C.Various thermodynamic parameters viz.ΔG 0 , ΔH 0 and ΔS 0 were determined.Value of ΔG 0 was found to be negative which confirms the feasibility of process while positive values of ΔH 0 further confirm endothermic nature of the process.Present study revealed that Iron oxide loaded riverbed sand (IOLRS) can be used as an alternative for the otherwise 'more expensive' adsorbents and resultant data may help in designing treatment plants for the Cr(VI) rich effluents.