Manganese-modified natural sand in the remediation of aquatic environment contaminated with heavy metal toxic ions

摘要

The present communication aims towards the possible exploitation of modified natural sand materials in the remediation of the heavy metal toxic ions contaminated aquatic environment. The surface of the sand was modified as depositing the nano-particles of manganese (i.e., manganese-modified natural sand: MMNS) and the mineral phase of manganese was perhaps depicted to be pyrolusite as indicated by the XRD analytical data. The d-spacings of quartz was significantly enhanced with the manganese modification indicated the manganese caused an apparent increase in basal spacing of sand structure. SEM images and the EDX analysis showed that manganese nano-particles are evenly distributed onto the surface of sand. The BET surface area of the MMNS was increased significantly. The amount of manganese aggregated was found to be 1002.6 mg/Kg of sand and the stability tests suggested that the nano-particles aggregated onto the sand surface are fairly stable within the pH region 3-10. Further, the removal behavior of this MMNS was employed for the attenuation of two important heavy metal toxic ions i.e., Pb(II) and Cu(II) in aqueous medium. The uptake of these two metal ions followed the Freundlich adsorption isotherm. The removal capacity of MMNS estimated with the Freundlich approximation was found to be 0.4596 mg/g for Cu(II) and 2.996 mg/g for Pb(II). Further, the 1000 times increase in ionic strength caused for relatively insignificant change in uptake of these two ions onto the solid surface points it a predominant strong chemical binding involved at the solid/solution interface. The column experiments and the breakthrough curves suggested that material possessed significantly high removal capacity i.e., 0.190 and 0.895 mg/g, respectively, for Cu(II) and Pb(II) even under the dynamic conditions.