Li Hongying, Guo Xisheng, Ye Xinxin
Institute of Soil and Fertilizer, Anhui Academy of Agricultural Sciences, Hefei 230031, China.
Institute of Soil and Fertilizer, Anhui Academy of Agricultural Sciences, Hefei 230031, China; Key Laboratory of Materials Physics, Centre for Environmental and Energy Nanomaterials, Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China.
J Environ Sci (China). 2017 Feb;52:141-150. doi: 10.1016/j.jes.2016.04.005. Epub 2016 May 2.
Hydroxyapatite (HAP) has been widely used to immobilize many cationic metals in water and soils. The specific reason why an increase in the surface area of HAP enhances cadmium (Cd) uptake, but has no effect on lead (Pb) uptake, is not clear. The aim of this study was to determine the factors causing the differences in sorption behavior between Cd and Pb by evaluating HAPs with different surface areas. We synthesized HAPs with two different surface areas, which were characterized by X-ray diffraction, N adsorption, and scanning electron microscopy, and then evaluated them as sorbents for Cd and Pb removal by testing in single and binary systems. The sorption capacity of large surface area HAP (1.85mmol/g) for Cd in the single-metal system was higher than that of small surface area HAP (0.64mmol/g), but there were no differences between single- and binary-metal solutions containing Pb. After the Cd experiments, the HAP retained a stable structure and intact morphology, which promotes the accessibility of reactive sites for Cd. However, a newly formed precipitate covered the surface and blocked the channels in the presence of Pb, which reduced the number of potential adsorption sites on HAP for Cd and Pb. Remediation experiments using Cd- and Pb-contaminated soil produced similar results to the solution tests. These results indicate that alterations of the structure and morphology during the reaction is an important factor influencing metal sorption to HAP.
羟基磷灰石（HAP）已被广泛用于固定水和土壤中的许多阳离子金属。HAP表面积增加会提高镉（Cd）的吸附量，但对铅（Pb）的吸附量没有影响，其具体原因尚不清楚。本研究的目的是通过评估不同表面积的HAP来确定导致Cd和Pb吸附行为差异的因素。我们合成了两种具有不同表面积的HAP，通过X射线衍射、N吸附和扫描电子显微镜对其进行了表征，然后在单金属和双金属体系中测试，将它们作为去除Cd和Pb的吸附剂进行评估。在单金属体系中，大表面积HAP对Cd的吸附容量（1.85mmol/g）高于小表面积HAP（0.64mmol/g），但含Pb的单金属和双金属溶液之间没有差异。Cd实验后，HAP保持了稳定的结构和完整的形态，这促进了Cd反应位点的可及性。然而，在有Pb存在的情况下，新形成的沉淀覆盖了表面并堵塞了通道，这减少了HAP上Cd和Pb潜在吸附位点的数量。使用Cd和Pb污染土壤进行的修复实验产生了与溶液测试相似的结果。这些结果表明，反应过程中结构和形态的改变是影响金属对HAP吸附的一个重要因素。
