Lead Removal from Contaminated Shooting Range Soil using Acetic Acid Potassium Chloride Washing Solutions and Electrochemical Reduction

Abstract

Background.Cleanup of soils contaminated with toxic metals is a difficult task due to the method inefficiency and the destructive nature of clean-up techniques on soil ecosystems.Objectives.This study was performed to improve the removal efficiency of an acetic acid washing solution for the removal of lead (Pb) from soil. Acetic acid was used in combination with different concentrations of potassium chloride. In order to maximize the removal of Pb from the leachate, different electrode combinations were applied to the washing solutions.Methods.Acetic acid/potassium chloride washing solutions and electrochemical reduction were applied to lead-contaminated soil obtained from an impact berm of a major military shooting range in Ibadan, southwestern Nigeria. The soil was subjected to 5% acetic acid/5% potassium chloride (KCL) and 5% acetic acid/10% KCL solutions in an ex-situ batch experiment. The leachate was electrochemically reduced using 12 volt direct current with a current of 7 amps and 2.5 amps, with aluminum (Al)-Al, iron (Fe)-Fe, Al-Fe and Fe-Al electrodes.Results.The 5% acetic acid/5% KCL proved more efficient for Pb removal in soil with values ranging from 74.9% to 86.9% for 3% soil pulp densities with one washing time of 6 hours. Removal efficiency of Pb from the contaminated soil significantly decreased as the soil pulp density increased. The Al-Al and Al-Fe bipolar electrode combinations showed better removal efficiency of Pb from the leachates with values of 93.7% and 95.6% for 7 amps and 94.5% and 97.3% for 2.5 amps, respectively.Conclusions.The combined 5% acetic acid and 5% potassium chloride washing solution enhances the removal efficiency of Pb in soil and poses less risk to the soil ecosystem and the environment in general.

Batch washing of lead contaminated and spiked soils using extracts of dried Terminalia mantaly, Panicum maximum and Eleusine indica plants

“…Removal efficiency of Pb increased with increasing washing time except for Eleusine indica. This trend is similar to previously report soil decontamination experiment with SPD = 3% at increasing washing time showing promising removal efficiencies for Pb [17]. Test of significance was carryout using single factor analysis of variance at p = 0.05.…”

“…The most mobile of the bioavailable fractions, the exchangeable fraction was similarly lower in the contaminated soil (3.11%) than in spiked soil (81.2%). The contaminated soil showed similar characteristics to previous studies [17,41].…”

“…The variables considered are SPD and washing time. The soil washing experiment was adapted from our previously published article [17].…”

“…The percentage removal efficiency of Pb from soil samples (either contaminated or spiked soil) was calculated using the following equation [17,30,31]:…”

“…Soil washing offers the greatest advantage of highly effective removal efficiency of lead in contaminated soils and is among the best demonstrated available techniques listed for remediation [11,12]. A range of applications, for strong acids [13,14], weak organic acids [15][16][17], chelating agents [18], fluids or gases [19] and even water, have proven effective but with certain degree of limitations.…”