Practical Use of Charcoal as a Remediation Material for Cadmium-polluted Soil

Abstract

The purpose of this study is to examine the practical usage of charcoal as a biomass remediation material for cadmium (Cd) polluted soil in the environment. In the field application of this material, it is necessary to consider handling methods and the environmental impact of the used materials. The following types of experiments were conducted in this study: (1) heavy metals competitive removal in solution, (2) condition of Cd re-elution from Cd-adsorbed charcoal in solution, and (3) Cd re-elution from Cd-adsorbed charcoal left in columns of soil and charcoal for long periods. The competitive removals depended on the concentrations of heavy metals. All heavy metals included in the low-level concentration were removed by charcoal efficiently. Although 65-100% of the Cd adsorbed by the charcoal was desorbed by strongly acidic water (pH 1.5), 0.8-1.6% was desorbed by water with a pH of 4.5, equivalent to the pH of acidic rain. The Cd re-elution rates from columns by both acidic and distilled water were low immediately after beginning the experiments and were not detected after two and three months. Therefore, these three experiments demonstrated the possibility of simultaneously removing two or more heavy metals by using the charcoal, processing the contaminated charcoal by using strong acids, and allowing the contaminated charcoal to stay in the environment safely for long periods.