ABSTRACT

In the present work, the arsenate [As(V)] adsorption by loam and sandy loam soil was carried out as a function of initial As(V) concentration, pH, contact time, and adsorbent dose to ensure As adsorption and its mobilization in the soil of arsenic-affected areas. The As(V) adsorption with varying time and initial As(V) concentrations were analyzed using the linear and nonlinear forms of the adsorption isotherms and kinetic models. Based on the comparison of R² values and calculated q_e values, the linear pseudo-second order and non-linear pseudo-first order and second-order kinetics showed better applicability of S1 (loam) than S2 (sandy loam) soil samples for arsenate adsorption. The loam soil (S1) also exhibited maximum adsorption capacity and low As(V) mobility due to the presence of soil organic matter and low phosphorus content. The FTIR results showed that soil surface functional groups (─COOH, O─H and Fe─O group) were predominantly involved in As(V) binding via surface complexation or coordination. Results derived from equilibrium adsorption isotherms showed that the data fitted well to both the linear and non-linear Langmuir adsorption isotherms. The monolayer surface adsorption (q_max) in S1 sample (29.41 µg/g) was better than that in the S2 soil (27.39 µg/g), indicating strong surface affinity of S1 toward As(V) than S2 soil sample. This observation was also supported by the separation factor (R_L values). Results on thermodynamic parameters (ΔH°, ΔS° and ΔG°) showed spontaneous and endothermic nature of adsorption. The activation energy (Ea) calculated for the surface binding of As(V) onto S1 (4.56 kJ mol^–1) and S2 soil (7.15 kJ mol^–1) indicated that the surface binding of As(V) by both the soils was an energetically favorable physico-chemisorption. The results on adsorption characteristics of both soil samples indicated that adsorption efficiency and retention ability of loam soil (S1) was better than sandy loam (S2) soil.

摘要

在目前的工作中，壤土和砂壤土对砷酸盐 [As(V)] 的吸附是作为初始 As(V) 浓度、pH、接触时间和吸附剂剂量的函数进行的，以确保 As 吸附及其在土壤中的迁移。受砷影响地区的土壤。使用吸附等温线和动力学模型的线性和非线性形式分析了随时间变化和初始 As(V) 浓度变化的 As(V) 吸附。基于R ²值的比较和计算出的q _e值，线性准二级和非线性准一级和二级动力学表明S1（壤土）比S2（砂壤土）土壤样品对砷酸盐吸附的适用性更好。由于土壤有机质和低磷含量的存在，壤土 (S1) 也表现出最大的吸附能力和低的 As(V) 迁移率。FTIR结果表明，土壤表面官能团（─COOH、O─H和Fe─O基团）主要通过表面络合或配位参与As(V)的结合。来自平衡吸附等温线的结果表明，数据很好地拟合了线性和非线性 Langmuir 吸附等温线。单层表面吸附 (q _max) 在 S1 样品 (29.41 µg/g) 中优于 S2 土壤 (27.39 µg/g)，表明 S1 对 As(V) 的表面亲和力比 S2 土壤样品强。这一观察结果也得到了分离因子（RL_值）的支持。热力学参数（ΔH°、ΔS°和ΔG°）的结果显示吸附的自发和吸热性质。^{计算 As(V) 与 S1 (4.56 kJ mol –1} ) 和 S2 土壤 (7.15 kJ mol ^–1 )表面结合的活化能 ( Ea )) 表明两种土壤对 As(V) 的表面结合是一种能量上有利的物理化学吸附。两种土壤样品的吸附特性结果表明，壤土（S1）的吸附效率和滞留能力优于砂壤土（S2）。