Adsorption performance of Cd 2 + and Cu 2 + in aqueous solution by biochars prepared from manioc wastes

Adsorption performance of Cd2+ and Cu2+ in aqueous solution by biochars prepared from manioc wastes XIAO Yao1, GE Cheng-jun1,2, ZHANG Li1, LI Fang-ze1, YUE Lin1, YU Hua-mei1,2* (1.College of Environment and Plant Protection, Hainan University, Haikou 570228, China; 2.Key Laboratory of Environmental Toxicology in Haikou, Haikou 570228, China) Abstract:Three types of biochars(BC350, BC450 and BC550)were prepared by pyrolyzing manioc wastes at different temperatures(350, 450 and 550 益). The characteristics of biochars and the influential factors of Cd2+ and Cu2+ to biochars in aqueous(such as contact time, initial concentration, temperature and pH value)were investigated. The results showed that the adsorption balance time of Cd2+ and Cu2+ re原 duced with the increase of pyrolysis temperature. The adsorption kinetics’data were fitted greatly to the pseudo-second-order model (R2= 0.983). Adsorption isothermal of Cd2+ and Cu2+ onto biochars fitted well with both Freundlich and Langmuir model. The Freundlich model was better in the two models with R2 in 0.951~0.998 and 0.992~0.998 for Cd2+ and Cu2+, respectively, which also indicated that Cd2+ and Cu2 + were adsorbed onto the biochar by interaction via multilayer. The lgKF was an important parameter to represent adsorption capacity, which increased with the increasing pyrolysis temperature. This indicated that the adsorption capacity of BC550 was the best in the three types of biochars. The maximum adsorption amounts of Cd2+ and Cu2+ were 15.55 and 5.44 mg·g-1 respectively. The adsorption of two heavy metals on biochars was a spontaneous process. The adsorption capacity of Cd2+ and Cu2+ to biochars increased initially and then decreased with the increase of pH value. The optimum pH values of Cd2+ and Cu2+ to biochars in aqueous were 5.5 and 6.5, respectively.