Experimental Study On Preparation And Heavy Mental Adsorption Capability Of Metallic Salt Modified Quartz Sands

Heavy metal ion is a severe pollutant. In order to improve the heavy metal ion adsorption capability of quartz sands, the quartz sands are modified by applying relevant modifier. In this experiment, two kinds of modified filter material were prepared, in which quartz sand was chosen as a carrier to be coated with aluminium chloride and magnesium chloride by the deposition process at alkaline condition, respectively. By comparing the pre-modified and post-modified physical characteristics of quartz sands surface, through specific surface area test, SEM (Scanning Electron Microscope) inspection, XRD (X-Ray Diffractometer) and etc, the results reveals that the specific surface areas of aluminium chloride and magnesium chloride modified sands were increased to 9.38 and 6.12 times compared to the original quartz sands. What's more, the surface roughness of modified sands was also improved obviously and the surface porosity was greatly denser than that of original one. The major components of the two modified sands surface were Al(OH)₃ and Mg(OH)₂.Additionally, by analyzing the possible influences of modifying condition to wasted water containing Zn²⁺,Cd²⁺, the research shows that the pH value was an important factor on the heavy metal removal by the modified sands. The removal rates of Zn²⁺ by aluminium chloride,magnesium chloride modified sands and original quartz sands were 68%,54% and 41% under the condition of pH value with 7.00. It was also found the removal efficiency was enhanced with the increase of pH value, and the removal rates of Zn²⁺ by the two modified sands were both above 95% under the condition of 9.0. In the same way, when pH value equal 7.00, the removal rates of Cd²⁺ by aluminum chloride,magnesium chloride modified sands and original quartz sands were 59%,47% and 39%. The removal efficiency was also enhanced with the increase of pH value. When pH value was near 9.0, the removal rates of Cd²⁺ by aluminum chloride,magnesium chloride modified sand were 71% and 67%.The continuous experimental study on the treatment of galvanized wastewater using the two modified quartz sands was also conducted. It was shown that the removals of Zn²⁺ improved a lot. In the first 5 hours of the filtration,the removal rate of Zn²⁺ of aluminum chloride modified sands was kept of 70%, nevertheless, after 5 hours, it reduced quickly. In contrast, the removal rate of Zn²⁺ by magnesium chloride modified sands was about 60% in the first 3 hours.Ultimately the experimental data and research on theory and kinetics of heavy metal adsorption capability demonstrate that the adsorption of the two modified sands was dominated by chemical reaction. The adsorption isotherms of Zn²⁺ and Cd²⁺ both have the high consistency with Langmuir adsorption mode. Furthermore, the analysis of the two modified sands adsorption kinetics of Zn²⁺ and Cd²⁺ discovers that two modified sands adsorption reaction is more likely to satisfy Lagergren kinetic rate equationâ… .