Pyrolysis of hyperaccumulator plants used for the phytoremediation of lead contaminated soil.

Abstract

This study focuses on the phytoremediation of lead (Pb) contaminated soil by hyperaccumulator plants. In this study, pyrolysis was utilized for the stabilization of Pb into a solid product. In the first stage of the study, three types of phytoremediation plants were used, rape (Brassica napus), sunflower (Helianthus annuus), and corn (Zea mays). Their seeds were sown in simulated soils prepared with the addition of Pb compounds in a laboratory. The effect of chelate on the remediation capacity of the plants was investigated by the addition of EDTA in different concentrations. In this way, the transportation of Pb from the contaminated soils to the plants was examined. In the second stage, the initial plant compositions were determined by elemental analysis (C, H, N, and S), as well as a moisture, ash, volatile matter, and fixed carbon analysis. The contaminated hyperaccumulator plants were pyrolyzed at 500°C, with a heating rate of 35° C/min, in a fixed bed stainless steel (380 S) 240 cm 3 reactor. After pyrolysis, the Pb contents of the solid and liquid products were determined. A Toxicity Characteristics Leaching Procedure (TCLP) analysis was also utilized for the solid product. In this study, high phytoremediation efficiencies were observed for the phytoremediation of Pb contaminated soil using sunflower, corn, and rape, especially in the case of the chelate addition. Of the three plants, the best Pb removal efficiency (92%) from the soil was obtained with the rape. According to the pyrolysis results, the highest yields of liquid and solid products were obtained from the sunflower with gas products being obtained from the corn pyrolysis.