Adsorption, separation and recovery performance of spherical PR/CMC/AC composites for cadmium-contaminated soil remediation

Abstract

Activated carbon (AC) is considered to be an excellent adsorbent due to its high specific surface area and various functional groups. AC powders are available in sizes ranging from 44 to 150 μm. Its particle size prevent its separation from the soil. Therefore, when AC powder is applied to Cd-contaminated soil, it only reduces the bioavailability of Cd and Cd is not necessarily removed but semi-immobilized. Recovery of adsorbent materials from the soil is therefore a preferred soil remediation method. In order to achieve the separation of Cd from soil and the recovery and reuse of AC, a batch of phenolic resin (PR) -carboxymethyl cellulose (CMC)-activated carbon (AC) composite (PCC-800) with uniform particle diameter (diameter 0.8 mm) and high compressive strength was prepared. PCC-800 composites were made of PR/CMC/AC calcined at 800 °C in a certain ratio. The Barrett−Joyner−Halender results showed that the PCC-800 spheres own a mesoporous structure. The compressive strength of PCC-800 pellets was 20.6 N. After first adsorption cycle, total Cd in the soil decreased by 52.18% while bioavailable Cd decreased to 25.68% of the original soil. After three cycles, the recovery rates of PCC-800 were 90.37% and the adsorption regeneration was 72.73%. The PCC-800 immobilized Cd by adsorption, precipitation and complexation reaction. This study demonstrates the potential for developing adsorbents that are both easily separable from soil and highly effective in adsorption.