EFFECT OF MICRO-NANO SESAME STRAW BIOCHAR ON THE ADSORPTION OF Pb(II), Cd(II) AND Cu(II) IN AQUEOUS SOLUTION: A COMPARATIVE STUDY

In this paper, the adsorption characteristics and mechanisms of micro-nano sesame straw biochar on Cd(II), Cu(II), and Pb(II) in water have been systematically studied. The study of biochar adsorption characteristics was based on SEM, FTIR, XPS, adsorption kinetics and adsorption isotherm analysis. The results show that sesame straw biochar has a higher specific surface area and porosity, which is beneficial to the adsorption of heavy metals, and the functional groups play an important role in the adsorption process. The kinetics and isotherm analysis of biochar show that the pseudo-second-order kinetic model and Langmuir model are applicable. The maximum adsorption capacities of Cd(II), Cu(II) and Pb(II) are 10.66 mg/g, 26.36 mg/g and 334.82 mg/g, respectively, so biochar has the strongest affinity for Pb(II). In addition, because different heavy metals are adsorbed, the mechanisms involved in them also have slightly different contributions to biochar. In general, mineral interactions are the main contributing mechanism for adsorption. Moreover, the contribution of the pi-bond interaction in the adsorption process is relatively large, which is mainly the result of the combined effect of high pyrolysis temperature and micro-nano particle size.