A comparison of the characteristics and atrazine adsorption capacity of co-pyrolysed and mixed biochars generated from corn straw and sawdust.

The biochar used in this study was prepared from corn straw and sawdust mixed in a ratio of 1:1 (m/m) at temperatures of 300 °C and 800 °C, which adopted the methods of co-pyrolysis (BC300A and BC800A) and mixing of single biochar (BC300B and BC800B). The obtained biochar was characterized by SEM, BET and FTIR analysis. Adsorption properties, including the atrazine adsorption kinetics and isotherms of the four kinds of biochar to atrazine, were investigated. The results showed that a pseudo-second order kinetic model was suitable for describing the adsorption of atrazine by BC800B because its R2 value is greater than the pseudo-first order model. The adsorption capacity (qe) of BC800B, blended from the two single biochars produced at 800 °C, is 37.2 mg g-1, which is better than that of the other three species. This value is 4-6 times the qe values of BC300A, BC300B and BC800A, which are 6.74 mg g-1, 7.77 mg g-1 and 5.26 mg g-1, respectively. At higher pyrolysis temperature, the pore structure of biochar is more developed, the specific surface area is larger, and the species and number of surface functional groups are also significantly different. At the same time, the results also showed that the order of mixing and pyrolysis affected the characteristics and adsorption capacity of biochar. This study reveals the atrazine adsorption mechanism of four kinds of biochar and provides information about the potential of these types of materials for the removal of atrazine in the aquatic environment.