Comparison of adsorption performance for Cd( II ) removal from aqueous solution using biochar derived from different types of carbon sources: aquatic plants, pine branches and peat

Abstract BACKGROUND Guizhou Province, China is rich in forest, peat and aquatic plants. The effect of biochar prepared by pyrolysis carbonization on the Cd(II) adsorption has not been effectively studied. In this work, the physicochemical structural characteristics of different biochars were investigated. On this basis, the influence of pH value, acid washing, adsorption time on Cd(II) removal efficiency and the characteristics of adsorption isotherms of four biochars were studied. The adsorption mechanism was discussed by adopting the Langmuir and Freundlich kinetic model. RESULTS The findings exhibited that PT contained a great amount of free humic acid, fulvic acid and montan wax, which had a considerable impact on the Cd(II) adsorption. The surface of biochar AP300 has a fine crack structure, and the specific surface area (SSA) is the largest, reaching 2.9006 m2/g. When the solution range in pH value above 6, the removal efficiency of PT and biochar AP300 for Cd(II) exceeds 80%. The acid‐washed biochar with increased SSA did not exhibit an increase in Cd(II) removal efficiency, or even decreased significantly. Under the same adsorption time, the Cd(II) removal efficiency was in the following order: PT>AP300>PT300>PB300. The fitting effect of the Freundlich model for the four biochars was more than a match for Langmuir model, and the former is more appropriate to expression of the adsorption mechanism of Cd(II). Among the four biochars, AP300 had the smallest ΔG°, and the Cd(II) adsorption was the most easily performed. CONCLUSION Both PT and AP carbon material adsorbents can both meet the removal of Cd (II) in water, and can be promoted to treat heavy metals in soil later. © 2023 Society of Chemical Industry (SCI).