The effect of carbonization temperature on the capacity and mechanisms of Cd(II)-Pb(II) mix-ions adsorption by wood ear mushroom sticks derived biochar

Abstract

Heavy metals often coexist in contaminated environmental media, and competition between heavy metals for adsorption sites influences the absorption capacity of biochar. In this study, the adsorption mechanism of pyrolytically modified wood ear mushroom sticks (250, 450, and 650 °C) as a new bio-adsorbent for single-ion and mixed-ion solutions Cd²⁺ and Pb²⁺ Biochar adsorption experiments showed that the adsorption abilities of Cd²⁺ and Pb²⁺ increased with increasing WMBC (wood ear mushroom sticks biochar) pyrolysis temperature. According to the Langmuir model, the maximum adsorption capacity of Cd²⁺ and Pb²⁺increased with higher pyrolysis temperature, being 29.84, 39.08, 46.16 mg·g^-1and 124.3, 186.8, 234.2 mg·g^-1, respectively for three different pyrolysis temperatures 250, 450, and 650 °C. WMBC exhibited a stronger adsorption ability for Pb²⁺ than for Cd²⁺. Competition between the two heavy metals severely inhibited the adsorption of Cd²⁺. Based on X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR) analyses, the dominant interaction mechanisms were determined to be complexation, ion exchange, precipitation, and C-π interaction. The results suggest WMBC shows promise as a novel, cheap, and effective adsorbent that can be used to remove both Cd²⁺ and Pb²⁺ pollutants from environmental media.