Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece.
J Colloid Interface Sci. 2010 Feb 15;342(2):427-36. doi: 10.1016/j.jcis.2009.10.063. Epub 2009 Oct 29.
Highly efficient sorbents for phosphate removal from aqueous solutions based on the calcined forms of Fe(III)-substituted Layered Double Hydroxides (LDH) materials have been developed in this study. Hydrotalcite-like materials with Mg/M(3+) approximately 3 (where M=Al(3+), Fe(3+) or combined) have been synthesized following simple co-precipitation method and were subsequently calcined in air at 450 degrees C. Both as-synthesized and calcined materials were characterized by means of X-ray Diffraction (XRD), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), elemental (C) analysis, N(2) porosimetry, Scanning Electron Microscopy (SEM). All the materials were evaluated for the sorption of phosphates by batch equilibrium sorption experiments and kinetic measurements (effect of contact time). It was shown that chlorides or nitrates, being the charge-balancing anions in the LDH structure, are more easily exchanged by phosphates compared to carbonates. In the Fe(III)-modified LDHs, an increase of the Fe loading led to the decrease of the sorption efficiency. The maximum uptake of phosphates for both the Mg-Al LDH and Mg-Fe LDH samples containing mainly carbonates as charge-balancing anions was relatively low (ca.<or= 25mgP/g sorbent) while it was higher for the LDH samples containing mainly chlorides (approximately 80mgP/g). On the other hand, the maximum sorption capacity for the calcined Mg-Al LDHs and the calcined Fe(III)-substituted sorbents were very high, ca. approximately 250 and approximately 350mgP/g, respectively. The sorption data of both the as-synthesized and calcined LDHs was best fitted by the Freundlich model. Both the Mg-Al and Fe-substituted LDH sorbents were regenerated with mixed aqueous solution of NaCl and NaOH and were reused with a small loss of removal efficiency.
本研究开发了基于煅烧的三价铁取代层状双氢氧化物（LDH）材料的高效除磷吸附剂。采用简单共沉淀法合成了具有 Mg/M(3+) 约为 3（其中 M=Al(3+)、Fe(3+) 或两者组合）的水滑石类似物，并在空气中于 450°C 下煅烧。通过 X 射线衍射（XRD）、电感耦合等离子体原子发射光谱（ICP-AES）、元素（C）分析、N2 孔隙率、扫描电子显微镜（SEM）对合成的和煅烧的材料进行了表征。通过批量平衡吸附实验和动力学测量（接触时间的影响）评估了所有材料对磷酸盐的吸附性能。结果表明，在 LDH 结构中作为电荷平衡阴离子的氯化物或硝酸盐比碳酸盐更容易被磷酸盐取代。在 Fe(III) 修饰的 LDH 中，随着铁负载量的增加，吸附效率降低。对于主要含有碳酸盐作为电荷平衡阴离子的 Mg-Al LDH 和 Mg-Fe LDH 样品，磷酸盐的最大吸附量相对较低（约<或=25mgP/g 吸附剂），而主要含有氯化物的 LDH 样品的吸附量较高（约 80mgP/g）。另一方面，煅烧的 Mg-Al LDH 和煅烧的 Fe(III) 取代吸附剂的最大吸附容量非常高，分别约为 250 和 350mgP/g。合成的和煅烧的 LDH 的吸附数据均通过 Freundlich 模型拟合得最好。Mg-Al 和 Fe 取代的 LDH 吸附剂均用 NaCl 和 NaOH 的混合水溶液再生，并在去除效率略有降低的情况下重复使用。
