Removal of cationic dye BR46 by biochar prepared from Chrysanthemum morifolium Ramat straw: A study on adsorption equilibrium, kinetics and isotherm

Chrysanthemum morifolium Ramat straw biochar (CMRSB) was prepared at three different temperatures, including 180 °C (CMRSB180), 200 °C (CMRSB200), and 220 °C (CMRSB220) by hydrothermal carbonization method and was used to remove Basic Red 46 (BR46) dye from water. The CMRSB samples were examined by ultraviolet spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and surface area and porosity analyzer. The adsorption mechanism was studie by adsorption isotherms and FTIR spectroscopy. The results illustrated that the three kinds of CMRSB had mesoporous and microporous structures, and the CMRSB prepared at 200 °C had an extensive specific surface area. The adsorption reaction of BR46 by CMRSB was explained by the pseudo-second-order model. Meanwhile, CMRSB200 and CMRSB220 also demonstrated a certain degree of conformity to the Elovich model. The kinetics experiment showed that the removal process conformed to Langmuir and Temkin adsorption isotherms. The maximum adsorption capacity of the three biochar was 32.26, 49.50, and 53.19 mg/g, respectively. Chemisorption was found as the primary step in the adsorption of BR46.