Sorption properties of atrazine by biochars prepared from manioc wastes in soil

Three types of biochars (BC350, BC550 and BC750) we re prepared by pyrolyzing manioc wastes at different temperatures (350, 550 and 750益) under an oxygen-limited condition, the structures and compositions of BC were characterized. According to the guideline106 batch experiment, adsorption kinetics and isotherms of atrazine in biocharadded soil were studied. The results showed that BC c燥uld shorten balance time of atrazine, and it had positive correlation with the content of BC. For the same intake, time of reaching balance of BC750 was the shortest, as 5% BC750 only needed about 30 min. The data were fitted greatly to the pseudo -second -order model with R2 in 0.864 ~1.000. The isotherms of atrazine were nonlinear; the joint of partition and pore-filling was a major mechanism. Temkin equation was the best model for 3% BC750 and 5% BC750, and using Langmuir and Freundlich model to describe the other 13 treatments was perfect. logKF was an important parameter to represent adsorption capacity, which increased with the increasing content of BC increasing. As to different types of BC, logKF was shown in order of BC750>BC550>BC350, which indicated that the affinity of atrazine was relative with charring temperature of BC. In addition, adsorption - desorption process of atrazine showed obvious hysteresis, all the HI values were greater than 1 with following BC750 > BC550 > BC350, which belonged to the negative lag effect and suggested that the desorption rate was greater than the adsorption rate.