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.
Highlights
Environmental pollution in Asia has increased along with economic development
During periods of high economic growth, farmland in Japan was contaminated by cadmium (Cd), which is a toxic heavy metal that has diffused in the soil
Charcoal was examined for practical usage in the field as a remediation material for Cd contamination by conducting three evaluation experiments
Summary
Environmental pollution in Asia has increased along with economic development. During periods of high economic growth, farmland in Japan was contaminated by cadmium (Cd), which is a toxic heavy metal that has diffused in the soil. The soil in several regions in Japan still contains unhealthy levels of this metal. Farmlands are located near industrial land that houses refineries; Cd concentrations in the agricultural areas in Japan are higher than those in other countries. Toxic heavy metals are included in products themselves and in byproducts. If improper disposal methods, such as illegal waste-dumping or mixing into domestic garbage, are followed, heavy metals could leach into the environment. Toxic heavy metals are dissolved into ions by precipitation and can be discharged into underground water, rivers, or oceans. Because Cd is absorbed by crops, this toxin can enter the human body and bioaccumulate via oral intake of contaminated plants
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