滇池底泥制备的生物炭对重金属的吸附研究

Heavy Metal Sorption Characteristics of Biochars Derived from Dianchi Lake Sediment

重金属污染无法被生物降解而易通过食物链富集,对环境生态影响极大.而生物炭对重金属有很强的吸附能力,其在农业和环境中的巨大应用前景使之近期成为土壤学和环境科学的研究热点.本实验将滇池底泥制成生物炭吸附Cu(Ⅱ)、Cd(Ⅱ)和Pb(Ⅱ),然后采用Langmuir等温曲线对实验数据进行了拟合.实验结果显示400℃以下烧制的生物炭对Cu(Ⅱ)、Cd(Ⅱ)和Pb(Ⅱ)的吸附随烧制温度的升高而降低,并且Pb(Ⅱ)>Cu(Ⅱ)>Cd(Ⅱ),表面络合可能是金属在生物炭上吸附的主要机理.500℃烧制生物炭(C500)对Cu(Ⅱ)的吸附高于400°C烧制的生物炭(C400),C400和C500对Pb(Ⅱ)的吸附突然增加,可能是随烧制温度的升高,生物炭形成芳香环结构,与金属离子之间发生阳离子-π键作用,从而增强生物炭对Cu(Ⅱ)和Pb(Ⅱ)的吸附.

Heavy metal pollution is extremely toxic to the environment and organism, which has attracted a great deal of research attention. Biochars have high sorption capacity to heavy metals. The research on biochar produc- tion and application has become one of research hotspots of soil science and environmental science recently be- cause of its huge application prospect in agriculture and environment. In this paper, surface sediment in Dianchi Lake is collected and thermally- treated. The obtained biochars are used to adsorb Cu （II）, Cd （II） and Pb （II）. The sorption isotherms are fitted by Langmuir model. The results show that the sorption of Cu （II）, Cd （II） and Pb （II） on biochars which are treated below 400 ~C decrease with pyrolysis temperature. The sorption coefficients follow the order of Pb （II） 〉 Cu （II） 〉 Cd （II）. Surface complexation could be one of the major mechanisms controlling the sorption of metal ions on biochars. The sorption of Cu （II） on biochars treated at 500 ~C （C500） is higher than that at 400 ~C （C400）, and the sorption of Pb （II） on C400 and C500 are suddenly increased. Biochars are abundant of aromatic ring structure after thermal treatment, and the cation - ~r interac- tion between biochars and cations enhance the sorption of Cu （II） and Pb （II）.