Goh Kok-Hui, Lim Teik-Thye, Dong Zhili
School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Republic of Singapore.
Environ Sci Technol. 2009 Apr 1;43(7):2537-43. doi: 10.1021/es802811n.
A nanocrystalline Mg/Al layered double hydroxide (FCHT-LDH) adsorbent was developed and investigated through stoichiometric calculations, nitrate displacement investigation, comprehensive sorption/desorption experiments, and analyses with XPS, XRD, FTIR, CHNS/O, and EDX for better understanding of the predominant nature of arsenate (As(V)) interaction with FCHT-LDH. FCHT-LDH demonstrated a higher sorption capacity and a faster sorption rate compared to the layered double hydroxides (LDHs) prepared by conventional methods, due to its higher surface area, better porosity characteristics, and nanocrystalline property. These results also indicated the important role of hydrothermal treatment during the synthesis process for enhanced As(V) removal. The observed nitrate-arsenate molar displacement ratio, increased interlayer spacing, and decreased nitrogen content in the interlayer region revealed the predominance of anion exchange mechanism in As(V) sorption by FCHT-LDH. However, a slight pH increase during As(V) sorption equalization and the presence of ca. 25% irreversibly sorbed As(V) signified the occurrence of ligand exchange process as the secondary sorption mechanism. This specific sorption process that possibly involved formation of inner-sphere As(V) complexes with a monodentate mononuclear configuration at the aluminum center, rendered the FCHT-LDH a high affinity for As(V) over nitrate but induced hysteretic sorption/desorption characteristic that limited its regenerated sorption capacity.
通过化学计量计算、硝酸盐置换研究、综合吸附/解吸实验以及XPS、XRD、FTIR、CHNS/O和EDX分析，开发并研究了一种纳米晶Mg/Al层状双氢氧化物（FCHT-LDH）吸附剂，以更好地理解砷酸盐（As(V)）与FCHT-LDH相互作用的主要性质。与传统方法制备的层状双氢氧化物（LDHs）相比，FCHT-LDH具有更高的吸附容量和更快的吸附速率，这归因于其更高的比表面积、更好的孔隙特性和纳米晶性质。这些结果还表明了水热处理在合成过程中对提高As(V)去除率的重要作用。观察到的硝酸盐-砷酸盐摩尔置换比、层间距增加以及层间区域氮含量降低，揭示了FCHT-LDH对As(V)吸附中阴离子交换机制的主导地位。然而，As(V)吸附平衡过程中pH略有升高以及约25%不可逆吸附的As(V)的存在，表明配体交换过程作为次要吸附机制发生。这种特定的吸附过程可能涉及在铝中心形成具有单齿单核构型的内球As(V)配合物，使得FCHT-LDH对As(V)的亲和力高于硝酸盐，但导致了滞后的吸附/解吸特性，限制了其再生吸附容量。
