Genç-Fuhrman Hülya, Bregnhøj Henrik, McConchie David
Technical University of Denmark, Institute of Environment & Resources, Building 115, DK-2800 Kongens Lyngby, Denmark.
Water Res. 2005 Aug;39(13):2944-54. doi: 10.1016/j.watres.2005.04.050.
This study describes experiments in which sorption filters, filled with chemically modified red mud (Bauxsol) or activated Bauxsol (AB) coated sand, are used to remove As(V) (arsenate) from water. Bauxsol-coated sand (BCS) and AB-coated sand (ABCS) are prepared by mixing Bauxsol or AB with wet sand and drying. Samples of the BCS and ABCS are also used in batch experiments to obtain isotherm data. The observed adsorption data fit the Langmuir model well, with adsorption maxima of 3.32 and 1.64 mgg(-1) at pH values of 4.5 and 7.1, respectively for BCS; and of 2.14 mgg(-1) for ABCS at a pH of 7.1. Test results show that higher arsenate adsorption capacities can be achieved for both BCS and ABCS when using the columns compared to results for batch experiments; the difference is greater for BCS. Additional batch tests, carried out for 21 days using BCS to explain the observed discrepancy, show that the equilibrium time previously used in batch experiments was too short because adsorption continued for at least 21 days and reached 87% after 21 days compared to only 35% obtained after 4h. Fixed bed column tests, used to investigate the effects of flow rate and initial arsenate concentration indicate that the process is sensitive to both parameters, with lower flow rates (longer effective residence times in the columns) and initial arsenate concentrations providing better column performance. An examination of the combined effect of potential competing anions (i.e. silicate, phosphate, sulphate and bicarbonate) on the column performance showed that the presence of these anions in tap water slightly decreases arsenate removal. Each breakthrough curve is compared to the Thomas model, and it is found that the model may be applied to estimate the arsenate sorption capacity in columns filled with BCS and ABCS. The data obtained from both batch and column studies indicate that BCS and ABCS filtration could be effectively used to remove arsenate from water, with the latter being more efficient.
本研究描述了一些实验，其中使用填充有化学改性赤泥（Bauxsol）或活性Bauxsol（AB）包覆砂的吸附过滤器从水中去除As(V)（砷酸盐）。通过将Bauxsol或AB与湿砂混合并干燥来制备Bauxsol包覆砂（BCS）和AB包覆砂（ABCS）。BCS和ABCS的样品也用于批量实验以获得等温线数据。观察到的吸附数据与Langmuir模型拟合良好，BCS在pH值为4.5和7.1时的吸附最大值分别为3.32和1.64 mg g⁻¹；ABCS在pH值为7.1时的吸附最大值为2.14 mg g⁻¹。测试结果表明，与批量实验结果相比，使用柱体时BCS和ABCS都能实现更高的砷酸盐吸附容量；BCS的差异更大。使用BCS进行了21天的额外批量测试以解释观察到的差异，结果表明批量实验中先前使用的平衡时间太短，因为吸附持续了至少21天，21天后达到87%，而4小时后仅达到35%。用于研究流速和初始砷酸盐浓度影响的固定床柱测试表明，该过程对这两个参数都很敏感，较低的流速（柱体中更长的有效停留时间）和初始砷酸盐浓度可提供更好的柱性能。对潜在竞争阴离子（即硅酸盐、磷酸盐、硫酸盐和碳酸氢盐）对柱性能的综合影响进行检查表明，自来水中这些阴离子的存在会略微降低砷酸盐的去除率。将每条穿透曲线与Thomas模型进行比较，发现该模型可用于估计填充有BCS和ABCS的柱体中的砷酸盐吸附容量。从批量和柱体研究中获得的数据表明，BCS和ABCS过滤可有效地用于从水中去除砷酸盐，后者更高效。
