Removal and recovery of Cr(VI) from synthetic and industrial wastewater using bark of Pinus roxburghii as an adsorbent

In the present study, the potential of Pinus roxburghii bark as an adsorbent for the removal of heavy metals such as Cr(VI), Ni(II), Cu(II), Cd(II) and Zn(II) from aqueous solution at ambient temperature was investigated. Adsorption capacity of the material was found to be 4.15, 3.89, 3.81, 3.53 and 3.01 mg g(-1) for Cr(VI), Zn(II), Cu(II), Ni(II) and Cd(II), respectively, at an initial metal ion concentration of 50 mg L-1 at pH 6.5. The effect of concentration, contact time, adsorbent dose, solution pH, adsorbent particle size, salinity and hardness on the adsorption of Cr(VI) were studied in detail in batch experiments. The equilibrium contact time for Cr(VI) adsorption was found to be 1 h. Adsorption equilibrium data fit well to the Freundlich isotherm in the concentration range studied. The maximum adsorption (96.2%) was recorded at pH 3 for the initial Cr(VI) concentration of 50 mg L-1. The adsorbed metal ions from industrial wastewater were recovered using 0.1 M HCl solution. The column operation was found to be more effective compared to batch process. The percent recovery of Cr(VI) from industrial wastewater by column operation and batch process was found to be 85.8 and 65%, respectively. The results show that Pinus roxburghii bark can be used as a cost-effective adsorbent for the removal and recovery of Cr(VI) from wastewater.