Banana stem and leaf biochar as an effective adsorbent for cadmium and lead in aqueous solution.

ABSTRACT: Lead (Pb) and cadmium (Cd) are toxic heavy metals commonly found in aqueous environments. Biochar as a green adsorbent generated from biomass feedstock may be used for effective removal of these heavy metals. This study investigated the adsorption kinetics and isotherms of Pb²⁺ and Cd²⁺ in aqueous solutions at different pH by biochar prepared from banana stem and leaf (BSL-BC) at 400 °C. Characterizations using scanning electron microscope, X-ray diffraction, and Fourier-transform infrared spectroscopy showed that the synthesized BSL-BC had rough surface, porous structure, and oxygen-containing functional groups. The adsorption of Pb²⁺ and Cd²⁺ onto BSL-BC reached equilibrium in 8 h and 200 min, respectively, with faster adsorption attained at higher pH and the optimum pH occurred at 5 (Pb²⁺) and 8 (Cd²⁺). All adsorption kinetic data followed the pseudo-second-order rate model. The adsorption isotherm data of Pb²⁺ and Cd²⁺ could be well-described by the Langmuir and Freundlich models, respectively, whereas neither the Temkin or Dubinin-Radushkevich models provided satisfactory fitting results. The maximum adsorption capacities for Pb²⁺ and Cd²⁺ were 302.20 and 32.03 mg/g, respectively. The calculated mechanism contributions showed that complexation with oxygen-containing functional groups, ion exchange, mineral precipitation, and Pb²⁺/Cd²⁺-π coordination accounted for 0.1%, 8.4%, 88.8%, and 2.6% to Pb²⁺ adsorption, and 0.4%, 6.3%, 83.0%, and 10.4% to Cd²⁺ adsorption, respectively. Therefore, mineral precipitation was likely the major mechanism responsible for adsorption of both Pb²⁺ and Cd²⁺ by BSL-BC. The results suggest that the synthesized BSL-BC has great potential for adsorption of Pb²⁺ and Cd²⁺ from aqueous solutions.

SUBMITTER: Liu X 

PROVIDER: S-EPMC8799728 | biostudies-literature |

REPOSITORIES: biostudies-literature