A novel process for recovering Cd from the biomass of the hyperaccumulator Celosia argentea Linn

Abstract

Safe disposal of harvested metal-rich biomass is challenging for phytoextraction. This study designed and optimized a novel process for recovering cadmium (Cd) from the harvested biomass of the hyperaccumulator plant Celosia argentea Linn. The biomass was pyrolyzed at an optimum temperature of 350 ℃, where weight was lost by 59.7 %, and Cd (85.1 %) remained in the pyrolysis residue. X-ray diffraction analysis showed that the Cd in the residue mainly existed as Cd2(OH)3Cl and CdMn2O4. The pyrolysis residue was leached with H2SO4 at pH 0.5, and the highest Cd leaching ratio (91.1 %) was achieved. Manganese powder replaced over 91.3 % of the Cd in the leachate at room temperature for 2 h, yielding sponge Cd with a purity of 82.2 %. Approximately 190 mg of sponge Cd was recovered from 1 kg of biomass containing 269 mg·kg−1 Cd, with a total Cd recovery ratio of 70.7 %. These results indicate that the production of Cd sponges from Cd-rich biomass is feasible. This process, which mainly includes pyrolysis, leaching, and replacement, provides a potential method for safely disposing and utilizing Cd-rich biomass.