Sorption characteristics and mechanisms of oxyanions and oxyhalides having different molecular properties on Mg/Al layered double hydroxide nanoparticles

• Published in: Journal of hazardous materials Vol. 179; no. 1; pp. 818 - 827
• Main Authors: Goh, Kok-Hui, Lim, Teik-Thye, Banas, Agnieszka, Dong, Zhiling
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.07.2010; Elsevier
• Subjects: Adsorption; Algorithms; Aluminum; Aluminum Hydroxide - chemistry; Anion exchange; Anion exchanging; Applied sciences; Atmospheric pollution; Chemical engineering; Chromates - analysis; Electrophoresis; Exact sciences and technology; Halogens - analysis; Hydrogen-Ion Concentration; Hydroxides; Ion exchange; Kinetics; Layered double hydroxide; Ligands; Magnesium; Magnesium Hydroxide - chemistry; Metals - analysis; Nanoparticles; Oxyanion; Oxyhalide; Oxyhalides; Pollution; Sorption; Spectroscopy, Fourier Transform Infrared; Surface Properties; Thermodynamics; Vanadates - analysis; X-Ray Diffraction; X-ray photoelectron spectroscopy; Sorption; Anion exchange; Oxyhalide; Layered double hydroxide; Oxyanion; Surface complex; Molecular structure; Ligand; Nanoparticle; Desorption; Ultrafine particle; Exchange reaction; EXAFS spectrometry; Batchwise; Electrophoretic mobility; Aerosols; Air pollution; Ion exchange
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2010.03.077

The sorption ability of fast-coprecipitated and hydrothermally-treated Mg/Al layered double hydroxide nanoparticles (FCHT-LDH) for various oxyhalides and oxyanions was evaluated. Interactions of oxyhalide such as monovalent bromate or oxyanions such as divalent chromate and divalent vanadate with FCHT-LDH were investigated using a combination of macroscopic (batch sorption/desorption studies and electrophoretic mobility (EM) measurements) and microscopic techniques (CHNS/O, XRD, FTIR, XPS, and EXAFS analyses). The sorption studies on various oxyanions and oxyhalides suggested that their sorption characteristics on FCHT-LDH were largely governed by their ionic potentials and molecular structures. Oxyanions which have ionic potentials higher than 7 nm −1 were found to be more readily sorbed by FCHT-LDH than oxyhalides with ionic potentials lower than 5 nm −1. The results obtained also demonstrated that trigonal pyramid oxyhalides showed a lower degree of specificity for FCHT-LDH than the tetrahedral coordinated oxyanions. From the macroscopic and microscopic studies, monovalent oxyhalide sorption on FCHT-LDH was postulated to occur mainly via anion exchange mechanism with subsequent formation of outer-sphere surface complexes. For polyvalent oxyanion sorption on FCHT-LDH, the mechanisms were possibly associated with both anion exchange and ligand exchange reactions, resulting in the coexistence of outer-sphere and inner-sphere surface complexes.