Research on the Effect of Coordinated Remediation of Heavy Metal Pollution in Roadbed Slope Soil by Combining Biochar with Reed

Abstract

This study investigated the effect of modified activated carbon combined with plants on the coordinated restoration of heavy metal pollution in roadbed slope soil. This study used wheat husks as raw materials, potassium hydroxide and permanganate as modifiers, and aquatic plant reeds to remediate heavy metals in roadbed slope soil. The adsorption amount and removal rate of heavy metals Cu, Pb, and Cr were investigated under adsorbent dosage, adsorbent physical structure parameters, different pH environments, and ternary composite heavy metal body experimental conditions. According to the experimental results, after activation, the total pore volume and total specific surface area of biochar increased significantly, 21.4 and 111.7 times those before activation, respectively. The order of removal rates of heavy metal ions by different adsorbents was Pb > Cr > Cu. When the adsorbent was biochar–reed joint remediation, the maximum adsorption capacity of Cu, Pb, and Cr was 31.25, 136, and 52.3 mg/g. The adsorption capacities of the two adsorbents (biochar and biochar–reed) for Pb were the highest, and the adsorption sensitivity of the adsorbents for Pb was higher than that for Cr and Cu. Under single-component conditions, the adsorption capacity of biochar to heavy metals Cu, Pb, and Cr was ranked as Pb > Cu > Cr. In a ternary solution system, the adsorption capacity of biochar to heavy metals Cu, Pb, and Cr was ranked as Cu > Cr > Pb. Considering the adsorption capacity and removal rate of nutrient-rich substances, as well as the cost and effect of the use of the adsorbent, the recommended amount of the adsorbent was 4–6 g.