摘要
利用系列摇瓶振荡实验，研究了在砂质土壤介质中腐殖酸（HA）对Cr（Ⅵ）还原作用及增强土壤表面对其吸附的影响。通过改变反应接触时间、pH值、HA投加量等条件，确定了最佳吸附反应条件。结果表明：砂质土壤中存在HA时，可使Cr（Ⅵ）还原为毒性较小的Cr（Ⅵ），明显增强土壤对可溶态Cr离子的吸附能力，比同等条件下无HA的土壤吸附量增大1倍以上。一般整个反应过程约8h即可达到稳定。pH值对Cr的还原和吸附有很大的影响，酸性条件下的吸附量比碱性条件可增大1倍，最佳pH值为2—4；当pH〉5时吸附能力急剧下降，pH=10时吸附去除量降为20％。有HA存在时砂质土壤土对Cr（Ⅵ）的吸附反应为一级动力学反应，K298=0．0335min^-1，砂土对CrO4^2-的等温吸附曲线较好地满足Langmuir公式。
The present paper aims to introduce the authors＇ investigation on the effect of humic acid （HA） on the reduction and adsorption of hexavalent chromium in the sandy soil matrix by using a series of shaking experiments under the laboratory conditions. The optimum conditions for the absorption reaction of Cr（Ⅵ） were defined through altering the effects of reaction times, pH values, concentrations of HA and adding amounts, etc. The experimental results we have gained prove that the present of HA helps to reduce toxic Cr（Ⅵ） to less toxical Cr （Ⅲ）, and twice enhances the adsorption of Cr（Ⅵ） in a soluble form in comparison with the natural sandy soil without HA. The whole reaction may last 8 hours in a stable and steady manner. The reaction and adsorption of Cr（Ⅵ） turned to be greatly affected by the pH values in the soil matrix. The optimum reaction would occur at pH 2 - 4, but the soil＇ s adsorption would sharply decrease if pH 〉 5 while the adsorption amount drop to 20% if pH 〉 10. In general, the removal rate by adsorption could be twice higher at the acid conditions than at the alkaline conditions. The adsorption of Cr（Ⅵ） by sandy soil at presence of HA may follow the first-order dynamic reaction when the rate constant K = 0.033 5 min^- 1 at the temperature of 25 ℃ . Thus, the isothermal adsorption curve of chromate in the sandy soil proves to be well matched with the Langmuir equation.
出处
《安全与环境学报》
CAS
CSCD
2006年第4期1-4,共4页
Journal of Safety and Environment
关键词
环境工程
Cr(Ⅵ)
腐殖酸
砂质土壤
吸附
还原作用
络合作用
environmental engineering
hexavalent chromium
hu mic acid
sandy soil
adsorption
reduction
complex ion
