Cr(Ⅵ)在碱性土壤中的吸附解吸规律的研究

Study on the Adsorption and Desorption of Hexavalent Chromium in Alkaline Soils

为进一步研究Cr(Ⅵ)在碱性土壤中的吸附解吸规律,选用武汉东西湖区蔬菜基地的土壤进行土柱的吸附解吸动态试验。通过试验发现,通入溶液的流速越快,穿透时间以及达到吸附饱和的时间就越早,而初始溶液浓度的增加也会适当缩短整个吸附饱和的过程。吸附率随流速的下降而增加,在相同初始浓度的条件下,较低的流速具备更高的吸附效率。而初始浓度及流速对解吸过程的影响并不明显,Cr(Ⅵ)在碱性土壤解吸过程中伴有明显的拖尾现象。吸附穿透曲线均可以利用Thomas模型和Yoon-Nelson模型来进行计算分析,利用Thomas模型求得饱和吸附量q0以及吸附速率常数kth;利用Yoon-Nelson模型得到流出液浓度达到初始浓度50%的时间τ,从而对Cr(Ⅵ)在该碱性土壤中的吸附过程进行预测分析,为减少土壤重金属污染提供理论参考。

In order to explore the adsorption and desorption of hexavalent chromium in alkaline soils ,soils from the vegetable bases of Dongxihu district in Wuhan city were chosen to make dynamic test .It is found from the experiment results that the faster the flow rate ,the earlier the breakthrough time and the earlier the adsorption saturated time .While the more the initial concentration of Cr （Ⅵ） solute ,the shorter of the adsorption saturated process .And the adsorption rate will increase with the slow rate decrease .Mo‐reover ,soil with slower flow rate is of more adsorption efficiency .However ,initial concentration and slow rate do not impact the de‐sorption of Cr（Ⅵ） .While the tailing can be seen in the desorption of Cr （Ⅵ） in alkaline soils .The Thomas model and Yoon-Nelson model are used to analyze the adsorption breakthrough curve of Cr （Ⅵ） .Furthermore ,the adsorption saturation mass q0 and adsorp‐tion rate coefficient kth were estimated with the Thomas model ,while the time point when the outlet concentration of Cr （Ⅵ） equals to the initial concentration of Cr （Ⅵ） was estimated with the Yoon-Nelson model .Adsorption of Cr（Ⅵ） in alkaline soils can be pre‐dicted in this study ,which will provide theoretical references to reduce heavy metal pollution in soil .