Enhanced adsorption of cadmium from aqueous solution by amino modification biochar and its adsorption mechanism insight

Cadmium (Cd) in industrial wastewater can accumulate in organisms in the aquatic environment, posing a severe threat to human health. Therefore, effective remediation of cadmium-contaminated water is necessary for public health and environmental sustainability. In this study, the amino groups were modified on the corn stalks biochar (CSBC) surface to prepare a highly selective Cd(Ⅱ) adsorbent (NH2-CSBC) by nitrification and reduction. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis demonstrated that amino groups were modified on the surface of CSBC. The adsorption capacity of NH2-CSBC for Cd(Ⅱ) was 4 times that of the original CSBC. The adsorption kinetics results showed that the Cd(Ⅱ) adsorption process by NH2-CSBC can be well described by the pseudo-second-order kinetic model. The maximum adsorption capacity obtained by the Sips model fitting reached 375.58 mg/g. The adsorption thermodynamic results indicated that Cd(Ⅱ) adsorption by NH2-CSBC was a spontaneous endothermic process. The analysis results based on FTIR and XPS before and after Cd(Ⅱ) adsorption showed that the amino functional groups on the surface of NH2-CSBC have strong complexation with Cd(Ⅱ). In summary, it is feasible to modify amino groups on the surface of biochar, and the obtained amino-modified biochar could adsorb Cd(Ⅱ) quickly and efficiently, showing great potential in the treatment of heavy metal wastewater.