Characterization of modified biochars prepared at low pyrolysis temperature as an efficient adsorbent for atrazine removal.

In this study, biochars (BC, ZnBC, and PBC) produced from wheat straw at relatively lower pyrolysis are successfully fabricated using different pretreatment techniques (without and with ZnCl2 or H3PO4). The specific surface area (SSA), elemental analysis, and Fourier transform infrared spectra (FTIR) are used to analyze physicochemical properties of unmodified and modified biochars. ZnBC and PBC show higher specific surface area and more micropore structure than pure BC. Kinetic models (pseudo-first order, pseudo-second order, and intra-particle diffusion) as well as isotherm models (Langmuir and Freundlich) are applied to analyze adsorption behavior. Adsorption on biochars can be better fitted by the pseudo-second-order and intra-particle diffusion models, indicating that micropores and mesopores play important roles on adsorption process and chemisorption is dominant. The adsorption process is also affected by physical and chemical adsorption. In conclusion, biochar is a low-cost, effective, and environment-friendly adsorbent implicating in the environment for pesticide removal. Graphical abstract.