Effect of Soil Washing with Ferric Chloride on Cadmium Removal and Soil Structure

Abstract

In China, arable soils contaminated with cadmium (Cd) threaten human health. Ferric chloride (FeCl3) is a highly efficient agent that can remove Cd from contaminated soils. However, it is unknown whether FeCl3 damages the soil structure and consequently affects crop growth. In this study, we investigated the impacts of Cd extraction by FeCl3 on the structure of a paddy soil on the basis of comparisons of control (without washing agents) and hydrochloric acid (HCl) treatments. According to our results, the removal efficiency increased with the decrease in soil initial pH, as adjusted by FeCl3. However, the low pH of 2.0 caused a partial loss of soil mineral components, with an Al release of 4.4% in the FeCl3-treated soil versus 1.3% in the HCl-treated soil. In contrast, the amount of released Al was less than 0.2% in the control and in the FeCl3 treatments with initial pH values of 3.0 and 4.0. The washing agents caused soil TOC loss of 27.1%, 17.5%, and 2.76% in the pH 2.0, 3.0, and 4.0 FeCl3 treatments, compared with 15.5% in the initial pH 2.0 HCl treatment. The use of FeCl3 represents an optimum tradeoff between removal efficiency and the loss of soil components to restore Cd-polluted soils by adjusting the initial pH to 3.0 with the addition of FeCl3. Under this condition, the amount of Al loss was less than 0.2%, and the extraction efficiency reached 40.3%, compared to an efficiency of 39.7% with HCl at an initial pH of 2.0. In conclusion, FeCl3 could effectively remove Cd from contaminated soil.

Cadmium Accumulation in Cereal Crops and Tobacco: A Review

“…For example, Ren et al [106] developed a novel magnetic EDTA-modified chitosan/SiO 2 /Fe 3 O 4 adsorbent (EDCMS) for the removal of Cd from an aqueous solution. FeCl 3 solution can also effectively remove soil Cd by regulating pH value [107]. The Cd accumulation in crops is not only affected by soil Cd level but also influenced by agronomic measures, such as water and fertilizer management [108].…”

Utilizing of sunflower seed husk through production of biochar and its application in systems for purification of water contaminated with cadmium

“…To protect the population from cadmium poisoning, several technological solutions are available to treat polluted water streams. The most common of them is the chemical method which is an extracting mechanism of Cd ions using a cleaning agent (most often ferric chloride (III)) [5]. Another decontamination technique is a novel developed in-situ ultra purification method incorporating both 'distillation' and 'zone refining' using simple see-through quartz wares [6].…”