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首页> 外文期刊>RSC Advances >Mechanisms that control the adsorption–desorption behavior of phosphate on magnetite nanoparticles: the role of particle size and surface chemistry characteristics
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Mechanisms that control the adsorption–desorption behavior of phosphate on magnetite nanoparticles: the role of particle size and surface chemistry characteristics

机译：控制磷酸盐纳米粒子上磷酸盐的吸附 - 解吸行为的机制：粒度和表面化学特征的作用

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Eutrophication caused by excessive phosphate discharge into surface water has raised wide concern, and the efficient removal of phosphates from wastewater using sorption methods is very important. In our study, magnetite particles with two different sizes and different surface characteristics were chosen as the sorbents to examine their adsorption and desorption behavior toward phosphate. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and N _(2) adsorption–desorption methods were used to characterize the morphological and surface chemical properties of the two differently sized magnetite particles. Adsorption kinetics and isotherm models (including the pseudo-first-order, Freundlich, Langmuir and Temkin models) were used to fit the experimental data, and to help with the mechanistic discussions. It was found that the nanometer-sized magnetite (nFe _(3) O _(4) ) has a much higher surface area, larger pore volume, higher amounts of surface functional groups, and a lower point of zero charge (pH _(PZC) ) value than the micrometer-sized magnetite (Fe _(3) O _(4) ). The adsorption kinetics show that reaching adsorption equilibrium in the case of nFe _(3) O _(4) is much slower, and the particle size or surface characteristics of the magnetite may become the main factor determining the adsorption rate of the phosphate to magnetite in the rapid or slow adsorption step, respectively. nFe _(3) O _(4) shows much stronger adsorption of phosphate compared to Fe _(3) O _(4) , which may be attributed to the larger surface area of the magnetite with a smaller particle size. In addition, the amount of functional groups and the surface electrical properties may also affect the adsorption of phosphate to magnetite by influencing the formation of the outer-sphere and/or inner-sphere complexes. The adsorption/desorption of phosphate to/from the magnetite decreases/increases with increasing pH, and the extent of change is more marked for nFe _(3) O _(4) . Increasing the ionic strength of the solution increases the adsorption of phosphate to the two differently sized magnetite particles, whereas the presence of humic acid only increases the adsorption of phosphate to Fe _(3) O _(4) . These trends may be caused by the different extents of change of the surface properties or the dispersion state of the two differently sized magnetite particles under different solution chemistry conditions. The results imply that when the synthesis of magnetite-based materials for phosphate sorption is performed, both the particle size and surface properties should be considered in order to realize the efficient and economical removal of phosphate from wastewater.
机译：通过过度磷酸盐排出地表水引起的富营养化提高了广泛的关注，并且使用吸附方法从废水中有效地除去磷酸盐非常重要。在我们的研究中，选择具有两种不同尺寸和不同表面特性的磁铁矿颗粒作为吸附剂，以检查它们对磷酸盐的吸附和解吸行为。扫描电子显微镜（SEM），X射线光电子能谱（XPS）和N _（2）吸附 - 解吸方法用于表征两种不同大小的磁铁矿颗粒的形态学和表面化学性质。使用吸附动力学和等温模型（包括伪一阶，Freundlich，Langmuir和Temkin模型）来适应实验数据，并帮助机械讨论。发现纳米尺寸磁铁矿（NFE _（3）O _（4））具有更高的表面积，孔体积较大，表面官能团的较高量，较低的零电荷（pH _（ PZC））值比千分尺大小的磁铁矿（Fe _（3）O _（4）））。吸附动力学表明，在NFE _（3）O _（4）的情况下达到吸附平衡速度较慢，磁铁矿的粒度或表面特性可能成为确定磷酸盐到磁铁矿的吸附速率的主要因素在快速或缓慢的吸附步骤中。 NFE _（3）O _（4）显示与Fe _（3）O _（4）相比的磷酸盐的更强烈吸附，其可以归因于具有较小粒径的磁铁矿的较大表面积。另外，通过影响外球和/或内球复合物的形成，官能团和表面电性能的量也可能影响磷酸盐到磁铁矿的吸附。磷酸盐与磁铁矿的吸附/解吸减少/随着pH的增加而增加，并且对于NFE _（3）O _（4）更加标记的变化程度。增加溶液的离子强度会增加磷酸盐对两个不同大小的磁铁矿颗粒的吸附，而腐殖酸的存在仅增加磷酸盐的吸附到Fe _（3）O _（4）。这些趋势可能是由不同溶液化学条件下的两个不同尺寸的磁铁矿颗粒的表面性质变化的不同范围或两种不同尺寸的磁铁矿颗粒的分散状态引起的。结果暗示，当进行磷酸盐吸附材料的合成时，应考虑粒径和表面性质，以实现废水中磷酸盐的有效和经济去除。

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