文章摘要
张亚莉,杨杰文.零价铁粉对水稻土中六价铬的还原作用 及其影响因素研究[J].广东农业科学,2019,46(4):51-57
零价铁粉对水稻土中六价铬的还原作用 及其影响因素研究
Study on the Reduction Effect of Zero-valent Iron on Cr( Ⅵ ) in Paddy Soil and Its Influencing Factors
  
DOI:10.16768/j.issn.1004-874X.2019.04.008
中文关键词: 水稻土  零价铁粉  六价铬污染  还原作用  溶液因素
英文关键词: Paddy soil  zero-valent iron  Cr( Ⅵ ) pollution  reduction  solution factors
基金项目:国家自然科学基金面上项目(41671235)
作者单位
张亚莉,杨杰文 广东海洋大学农学院广东 湛江 524088 
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中文摘要:
      【目的】研究雷州半岛水稻土吸附 Cr(Ⅵ)反应特征以及零价铁粉对水稻土中 Cr(VI) 的还原作用, 分析相关因素对上述过程的影响。【方法】通过批处理等温吸附和动力学实验,考察反应物浓度、时间、pH、 离子强度和陪伴离子等因素对 Cr(Ⅵ)吸附量和还原比例的影响,并用相关反应模型对数据进行拟合分析。【结果】 在所研究的 0.1~2.0 mmol/L 初始浓度范围内,水稻土对 Cr(Ⅵ)吸附未达到饱和,吸附等温线可用 Langmuir 方 程拟合(R2=0.9963)。提高 pH 和离子强度将抑制 C(Ⅵ)吸附,且吸附动力学曲线可用假一级反应动力学方程 拟合(R2=0.9935)。在所研究的反应条件下(初始溶液 pH4.0、0.20 mmol/L Cr(Ⅵ)、0.01 mmol/L NaCl、5.0 g 土 +0.25 g 零价铁粉、体系总体积 250 mL),Cr(Ⅵ)还原比例可达 100%。溶液中 Cr 质量衡算表明,所生成的 Cr(Ⅲ)可部分被吸附到固体表面。磷酸根和邻菲罗啉的存在均可降低 Cr(Ⅵ)还原比例,提高反应体系 pH 不利于 Cr(VI)还原,其比例可从 pH4.34 时的 100% 下降至 pH6.87 时的 56.3%。【结论】水稻土吸附 Cr(Ⅵ) 反应机理包含静电吸附,高 pH 条件所导致的土壤表面对 Cr(VI) 的静电斥力增加以及背景电解质中阴离子的竞争 吸附均可减少水稻土对 Cr(Ⅵ)的吸附量;零价铁粉对水稻土中 Cr(Ⅵ)的还原比例随 pH 升高逐渐减少,且 磷酸根的存在有抑制作用。
英文摘要:
      【Objective】The present study aimed to reveal the reaction characteristics of Cr( Ⅵ ) adsorbed by paddy soil and examine the reduction effect of Cr( Ⅵ ) by zero-valent iron ( ZVI,) in the soil, and analyze the effect of relative factors on the above-mentioned process. 【Method】The batch isotherm adsorption and kinetics experiments were performed to investigate the effects of reactant concentration, reacting time, pH, ionic strength and accompanying anions on the adsorption and reduction of Cr( Ⅵ ) in the mixed system of paddy soil and ZVI. The experimental data was also analyzed with adsorption and kinetic model.【Result】The adsorption saturation was not obtained with the initial concentrations ranging from 0.1 to 2.0 mmol/L and the adsorption isotherm could be well fitted by Langmuir equation (R2=0.9963). The increase in pH and ionic strength was unfavourable for Cr( Ⅵ ) adsorption and the kinetic curve could be properly fitted by pseudo-first-order kinetic equation (R2=0.9935). With the introduction of ZVI, the added Cr( Ⅵ ) (0.20 mmol/L ) was totally transformed to Cr( Ⅲ ) under the present reaction condition, and the calculation of aqueous Cr mass balance indicated that a certain amount of the generated Cr( Ⅲ ) were adsorbed by the solid surface. The presence of phosphate and 1,10-phenanthroline could inhibit the Cr( Ⅵ ) reduction. Moreover, Cr(VI) reduction would be suppressed as the solution pH increased, evidenced by the reduction percentage decreased from 100% at pH 4.34 to 56.3% at pH 6.87. 【Conclusion】The electrostatic adsorption was involved in Cr( Ⅵ ) adsorption by the paddy soil. The enhancement of electrostatic repulsion between the soil surface and Cr( Ⅵ ) and the competitive adsorption between Cr( Ⅵ ) and chloride ions contained in the supporting electrolyte could jointly decrease the Cr( Ⅵ ) adsorption in the soil. Low pH was favourable for the occurrence of Cr( Ⅵ ) reduction by ZVI in the soil, and the reduction would be inhibited in the presence of phosphate and 1,10-phenanthroline.
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