Retention of copper by desert sands coated with ferric hydroxides

Due to the sandy character of the desert sandy soils, surface reactivity an d hence adsorption of micronutrients are very low. Therefore, different fra ctions from sand particles were coated with four partially hydroxylated fer ric sols of OH/Fe molar ratio of 1.00, 1.50, 2.00, and 2.84. The obtained r esults prove that the extractability of iron is reduced by increasing the O H/Fe molar ratio before its addition to the sand particles. Iron oxide coat ing of sand particles increased the amount of Cu adsorbed as compared with uncoated ones. With regard to the effect of polymerization degree of ferric sols, results show that decreasing OH/Fe molar ratio of iron sols enhanced the Cu adsorption maximum capacity, as calculated from the Langmuir equati on. The amount of adsorbed Cu increased by decreasing the size of sand part icles, Moreover, increasing the pH value of Cu equilibrium solution from 4. 5 to 7.5 resulted in more adsorption of Cu by ferric hydroxide-coated sand particles. (C) 1999 Elsevier Science B.V. All rights reserved.