Effect of phosphate rock on the solubility of heavy metals in soils saturated with industrial wastewater

Abstract

Irshad, M., Khan, R. U., Jadoon, S., Hassan, A. and Egrinya Eneji, A. 2014. Effect of phosphate rock on the solubility of heavy metals in soils saturated with industrial wastewater. Can. J. Soil Sci. 94: 543–549. An in situ technology for immobilizing metals in polluted soils could be a more effective approach to managing their toxicity to the environment, especially plants. The aim of this study was to investigate the effect of milled phosphate rock (PR) on the sorption of Ni, Cd and Cu ions in differently textured soils polluted with industrial wastewater. For this purpose, soils were mixed with two particle size fractions (0.2 mm and 1 mm) of PR material. Each material was applied at the rate of 0, 2.5 and 5%. Results showed that PR amendment reduced the solubilization of heavy metals in the order sandy clay loam>sandy loam>loamy sand. Metal concentrations in soils saturated with industrial wastewater were in the order Ni>Cd>Cu. Solubilization of metal ions in soils also reduced with the increase in the amount of rock phosphate added. This occurred more with the finer PR fraction. The concentrations of heavy metals in soils varied directly with their respective concentrations in the wastewater. Saturating soil with wastewater for a longer time increased the solubility of heavy metals. The adsorptive capacity of heavy metals from the respective aqueous solution also increased with increasing shaking time. The finer PR particles better enhanced the sorption capacity of heavy metals. This study indicated that the retention of heavy metals by PR mineral in contaminated soils may reduce the contamination risk in surface and subsurface waters.