木薯渣基生物质炭对水中Cd2+ Cu2+的吸附行为研究

以木薯渣为原料,制备不同温度(350、450、550℃)的生物质炭(BC350、BC450、BC550),对其性质进行表征,探究吸附时间、溶液初始浓度、温度、p H对生物质炭吸附Cd~(2+)、Cu~(2+)作用的影响。结果表明:生物质炭对Cd~(2+)、Cu~(2+)的吸附平衡时间随着生物质炭热解温度的升高而缩短,伪二级动力学模型能较好地描述吸附动力学特性(R20.983)。吸附等温线符合Freundlich模型和Langmuir模型,但Freundlich模型拟合的线性更好,R2分别在0.951~0.998和0.992~0.998之间,说明生物质炭对Cd~(2+)、Cu~(2+)的吸附为多层吸附。lg KF值表示吸附能力,随生物质炭热解温度的升高而增大,说明BC550吸附效果最好,对Cd~(2+)、Cu~(2+)的最大吸附量分别为15.55和5.44 mg·g-1。生物质炭对Cd~(2+)、Cu~(2+)的吸附具有自发的特性,吸附量随p H的增加先增加后下降,最适p H分别为5.5和6.5。

Adsorption performance of Cd2+ and Cu2+ in aqueous solution by biochars prepared from manioc wastes

Three types of biochars(BC350, BC450 and BC550)were prepared by pyrolyzing manioc wastes at different temperatures(350, 450 and 550℃). 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-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.