Xu Dani, Peak Derek
University of Saskatchewan, 51 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5A8.
Environ Sci Technol. 2007 Feb 1;41(3):903-8. doi: 10.1021/es0620383.
The fate and mobility of boric acid in the environment is largely controlled by adsorption reactions with soil organic matter and soil minerals to form surface complexes (Soil Sci Soc. Am. J. 1991, 55, 1582; Geochim. Cosmochim. Acta 2002, 67, 2551; Soil Sci. Soc. Am. J. 1995, 59, 405; Environ. Sci. Technol. 1995, 29, 302). In this study, boric acid adsorption on pure am-Al(OH)3 and 5% (w/w) humic acid (HA) coated am-Al(OH)3 were investigated both as a function of pH (4.5-11) and initial boric acid concentration (0-4.5 mmol L(-1)). Batch adsorption isotherm experiments were also conducted with samples exposed to atmospheric CO2 and anaerobic (N2) conditions to examine the effects of dissolved CO2 on boric acid adsorption. Boron (B) K-edge X-ray absorption near-edge structure (XANES) spectroscopy was used to investigate the coordination of boric acid adsorbed at mineral/water interfaces. The XANES spectra of boric acid adsorption samples showed that both trigonally and tetrahedrally coordinated B complexes were present on the mineral surface. Both macroscopic and spectroscopic experiments revealed that the combination of HA coating on am-Al(OH)3 and dissolved CO2 decreased boric acid adsorption compared to adsorption on pure am-Al(OH)3.
硼酸在环境中的归宿和迁移性在很大程度上受其与土壤有机质和土壤矿物质发生吸附反应形成表面络合物的控制（《土壤科学美国协会杂志》，1991年，第55卷，第1582页；《地球化学与宇宙化学学报》，2002年，第67卷，第2551页；《土壤科学美国协会杂志》，1995年，第59卷，第405页；《环境科学与技术》，1995年，第29卷，第302页）。在本研究中，研究了硼酸在纯am-Al(OH)₃以及5%（w/w）腐殖酸（HA）包覆的am-Al(OH)₃上的吸附情况，考察了其作为pH值（4.5 - 11）和初始硼酸浓度（0 - 4.5 mmol L⁻¹）的函数关系。还对暴露于大气CO₂和厌氧（N₂）条件下的样品进行了批量吸附等温线实验，以研究溶解CO₂对硼酸吸附的影响。利用硼（B）K边X射线吸收近边结构（XANES）光谱研究了吸附在矿物/水界面的硼酸的配位情况。硼酸吸附样品的XANES光谱表明，矿物表面同时存在三角配位和四面体配位的B络合物。宏观实验和光谱实验均表明，与在纯am-Al(OH)₃上的吸附相比，am-Al(OH)₃上HA包覆和溶解CO₂的共同作用降低了硼酸的吸附。
