Removal of Cadmium, Copper, Lead and Nickel from Aqueous Solution by White, Yellow and Red United Arab Emirates Sand

Problem statement: To remove toxic heavy metal ions from wastewater using local sand as a low cost adsorbent. Approach: Removal efficiency of Cd(II), Cu(II), Pb(II) and Ni(II) from aqueous solution by white, yellow and red UAE sand was investigated at 25.0°C using the methods of batch equilibrium adsorption and column filtration. In each case, a mixture containing 20 ppm of each ion was employed. In the equilibrium study, the effect of sand dosage was measured for mixtures containing 20 ppm of each ion. In the column filtration study, the mixture was added to a column packed with yellow sand and the composition of the effluent was measured for each 0.050 dm³ portion. Concentrations were measured on an inductively coupled plasma-atomic emission spectrometer “ICP-AES”. Results: Removal efficiency by sand type was found to follow the order yellow>white>red. At low sand dosages, removal efficiencies of Pb(II) and Cu(II) were much higher than those for Ni(II) and Cd(II). For example, at a sand dosage of 0.02 kg dm^-3, removal efficiencies of Pb(II), Cu(II), Cd(II) and Ni(II) were, respectively, 95, 86, 33 and 23% for yellow sand; 89, 86, 30 and 18% for white sand; and 75, 63, 12 and 13% for red sand. Column filtration using yellow sand confirmed that removal efficiency followed the order Pb(II)>Cu(II)>Cd(II)>Ni(II), with all four ions completely removed at mass ratios (metal/sand) lower than 3.0×10^-4. Conclusion: Equilibration on sand and sand filtration are most efficient for the removal Pb(II) and Cu(II). Sand filtration can be effectively utilized to separate Pb(II) and Cu(II) from a mixture containing all four ions.