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

Problem statement: To remove Pb(II) from wastewater using local UAE sand and then to recover the removed Pb(II). Approach: Removal efficiency of Pb(II) from wastewater was investigated using white, yellow and red United Arab Emirates sand with pore sizes < 300 μm. Two methods were employed: batch equilibrium and column filtration. In the batch equilibrium study, the effect of sand type and dosage on Pb(II) removal efficiency was investigated. In the column filtration study, removal efficiencies were measured using yellow sand at 0.100 dm 3 intervals while continuously injecting 300 ppm Pb(II) solution into the column. Pb(II) concentrations were determined using inductively coupled plasma-atomic emission spectrometer (ICP-AES). Measurements were carried out until saturation of the column by Pb(II) was attained. Recovery efficiency of Pb(II) was initially investigated using distilled water, 0.100 mol dm −3 HNO 3 and pH 8.0 aqueous solutions.Recovery via chelation with Ethylenediaminetetraacetic Acid (EDTA) was then attempted. Results: Batch experiments showed that yellow sand was more efficient than either white or red sand in removing Pb(II), with a maximum removal capacity of 0.030 kg Pb(II) per kg yellow sand. Accordingly, yellow sand was selected for column filtration experiments. In column filtration, the removal capacity rose to a maximum of 0.086 kg Pb(II) per kg sand. When sand containing removed Pb(II) in batch experiments was equilibrated overnight with EDTA solutions in stoichiometric excess, 86.6% recovery was observed. By comparison, recovery using EDTA in column filtration was 94.7%. Recovery by injection of either water or 0.100 mol dm −3 HNO 3 solution was either negligible or much lower than that obtained with EDTA. Conclusion: Column filtration using UAE yellow sand is an efficient and inexpensive method to remove Pb(II) from wastewaters. Pb(II) can be efficiently recovered from yellow sand columns by chelation with EDTA.