The impact of particle size on the adsorption of citrate to hematite
The impact of particle size on the adsorption of citrate to hematite
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DOI：
10.1016/j.jcis.2015.08.028
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发表时间：
2015-12-15
影响因子：
9.9
通讯作者：
Lenhart, John J.
中科院分区：
文献类型：
--
作者：
Noerpel, Matthew R.;Lenhart, John J.
我们研究了柠檬酸在两种不同尺寸的赤铁矿纳米颗粒表面的吸附，采用批量吸附实验，傅里叶变换红外光谱，表面络合模型和计算分子模型。柠檬酸盐吸附在pH约2.5和5.5之间达到最大值，并随着pH从该范围增加或降低而下降。在高表面负载条件下，占主导地位的吸附柠檬酸盐结构是外层性质的质子化状态，随pH值而变化。在低pH值，也有证据表明，一个内层复杂的双核，双齿结构，其中羟基被去质子化，并发挥了积极的作用，在吸附。在低柠檬酸盐表面负载条件下也检测到内球复合物。表面积归一化的表面覆盖率是相似的两种尺寸的赤铁矿，但是，内球复杂的似乎是稍微更普遍的较小的赤铁矿。基于这些结构，三层表面络合模型包括两个外球络合物和一个内球络合物被用来描述的吸附数据的范围内的解决方案的条件与一组表面积依赖的平衡常数的两个赤铁矿大小。(C)2015 Elsevier Inc. All rights reserved.
We investigated the adsorption of citric acid on the surface of two different sized hematite nanoparticles using batch adsorption experiments, Fourier-transform infrared spectroscopy, surface complexation modeling and computational molecular modeling. Citrate adsorption reached a maximum between pH approximately 2.5 and 5.5 and declined as the pH was increased or decreased from that range. At high surface loading conditions, the dominant adsorbed citrate structure was outer-sphere in nature with a protonation state that varied with pH. At low pH, there was also evidence of an inner-sphere complex consistent with a binuclear, bidentate structure where the hydroxyl group was deprotonated and played an active role in the adsorption. An inner-sphere complex was also detected at low citrate surface loading conditions. Surface-area normalized surface coverages were similar for both sizes of hematite, however, the inner sphere complex appeared to be slightly more prevalent on the smaller hematite. Based on these structures, a triple layer surface complexation model comprised of two outer-sphere complexes and one inner-sphere complex was used to describe the adsorption data for both hematite sizes across a range of solution conditions with a single set of surface area dependent equilibrium constants. (C) 2015 Elsevier Inc. All rights reserved.