The Effect of pH on Citric Acid Leaching of Soil Contaminated with Heavy Metals

Abstract

The effect of pH on the citrate leaching behavior of heavy metal ion was investigated to develop an eco-friendly process for removing heavy metals from soil contaminated with copper, zinc, and lead. The leaching tests were performed using citrate solution with pH adjusted by mixing citric acid and sodium citrate under the following leaching conditions: particle size, under 75 µm; temperature, 50 o C; citrate concentration, 1 kmol/m 3 ; pulp density, 5%; shaking speed, 100 rpm; leaching time, 1 hour. The difference of pH before and after the leaching test was not observed, and this result indicates the direct effect of hydrogen ion concentration on the leaching of metals was insignificant. The removal ratios of copper, zinc, and lead from the contaminated soil decreased with increasing pH. The thermodynamic calculation suggests that the leaching behaviors of metal ions were determined by two reactions; one is the reaction to form complex ions between heavy metal ions and citrate ion species, and the other is the reaction to form metal hydroxide between heavy metal ions and hydroxide ion.

WITHDRAWN: Integrated analysis of distribution characteristics, controlling factors, source apportionment, and potential remediation requirements of Pb in a typical karst region

“…The pH is a crucial factor that controls the geochemical behavior of Pb and Hg. Excessively low or high pH values can increase the content of soluble and exchangeable ions, thereby affecting the accumulation of total ions (Jung et al, 2013;Zeng et al, 2011). pH analysis of the surface soil in the study area revealed a pH range of 3.22-8.42.…”