Zn-modified biochar preparation from solvent free in-situ pyrolysis and its removal of methylene blue

In this study, Zn-modified biochar obtained through of Jerusalem artichokes straw with zinc carbonate was used to explore its effect on the adsorption of methylene blue. The physical and chemical properties of Zn-modified biochar were investigated using a variety of characterization, including SEM, BET, FT-IR, Raman, XRD, and XPS. Compared with the original biochar, the specific surface area (1037.17 m2·g−1) of Zn-modified biochar pyrolysis at 800 °C (Zn-BC 800) increased approximately 22 times. The adsorption of methylene blue with Zn-BC 800 could be more accurately illustrated by the pseudo-second-order kinetic model. The fitting results of adsorption isotherms showed that the Langmuir model could better suit the adsorption process at three different temperatures. At 318 K, Zn-BC 800 had a maximum adsorption capacity for methylene blue of 477.13 mg·g−1. According to the thermodynamic analysis, the process was a spontaneous endothermic reaction, and increasing the reaction temperature was beneficial to the reaction. Hydrogen bond and π-π interaction were the main mechanism of adsorption of MB by Zn-BC 800, which was determined by FTIR and XPS analysis. Zn-BC 800 still had a high adsorption effect on methylene blue after 5 cycles, indicating that the composite was a highly efficient cationic dye adsorbent, which could effectively remove dyes from wastewater.