Effect of Chain Length and Functional Group of Organic Anions on the Retention Ability of MgAl- Layered Double Hydroxides for Chlorinated Organic Solvents

Abstract

Nowadays, the contamination of groundwater and soils by chlorinated organic solvents is a severe and worldwide problem. Due to their swelling properties, Layered Double Hydroxides (LDHs) are potentially excellent compounds to retain chlorinated organic solvents from aquifers. By intercalating organic anions, the polarity of the interlayer space can be changed from hydrophilic to hydrophobic, enhancing the adsorption of chloro-organic molecules onto the alkyl chains of intercalated organic anions. In this study, organically modified LDHs were synthesized and their efficiency was tested in batch experiments with three different chlorinated organic solvents, namely trichloroethylene, 1,1,2-trichloroethane and trichloromethane (chloroform), to examine the influence of the chain length and the functional group of the intercalated organic anion upon the retention ability of a LDH due to different electronic interactions and different sizes of the interlayer space. All synthesized and used samples were characterized using powder X-ray diffraction, thermal analysis coupled with mass spectrometry and Fourier-transform infrared spectroscopy; freshly synthesized materials were additionally analyzed regarding their particle size distribution and specific surface area. Results of the batch experiments showed that only LDHs with intercalated long-chain organic anions could be efficient adsorbents for the removal of chlorinated organic solvents from contaminated water. A selective efficiency towards 1,1,2-trichloroethane and trichloromethane can be proposed for these reactants.

Layered Double Hydroxides with Intercalated Permanganate and Peroxydisulphate Anions for Oxidative Removal of Chlorinated Organic Solvents Contaminated Water

“…Lattice parameter a gives the average distance between two adjacent cations in the main layers. It can be calculated as twice the d-spacing of the reflexion of the (110) planes, which is responsible for the first peak of a doublet at approximately 60 • 2θ; a = 3.03 Å for MA-MnO4 and a = 3.02 Å for MA-S2O8, which were in relatively good agreement with the reported data for similar LDHs [18,20,29]. The typical doublet at approx.…”

“…Different aging times were selected from the information given in the literature and the previous experience of the authors regarding the synthesis of the selected materials. Data from the literature regarding MgAl-LDHs confirm that the well-formed hydrotalcite-like structure can already be formed with aging times of one day or less [18,25,26]. The synthesis of hydrocalumite-like materials using co-precipitation is usually carried out at higher temperatures [27,28].…”

Fluorescing Layered Double Hydroxides as Tracer Materials for Particle Injection during Subsurface Water Remediation

“…In recent years, the removal of chlorinated organic solvents, which can deeply penetrate aquifers, accumulating in the sub-surface as lenses of highly hazardous and toxic pollutants [1,2] from groundwater and soil, has become a major problem. Many laboratory-as well as field-scale studies exist considering different reaction pathways between reactants and the target contaminant, such as immobilization of contaminants [3][4][5][6][7][8][9] or in situ degradation of target contaminants into less hazardous or even non-hazardous substances [10][11][12][13][14][15][16][17][18]. Thereby, a major difficulty is the monitoring of reactants during the injection and after secondary mobilisation by groundwater flow.…”

“…The study presented here is focussed on the development of traceable particles by combining fluorescein, a commonly used, cheap, non-toxic, and non-harmful fluorescent dye, with hydrotalciteand hydrocalumite-like Layered Double Hydroxides. Please refer to previously published studies of the authors for a detailed description of the structure of the materials used here [8,14]. In recent years, Layered Double Hydroxides (LDHs) with intercalated fluorescent dyes have been widely studied and commonly synthesised via ion exchange [27][28][29] and reaction-diffusion [30] routes.…”

“…Further studies were carried out to compare the fluorescent LDHs presented here with previously studied reactive LDHs, which proved to be able to absorb and thus immobilize [8] or degrade [14] chlorinated organic solvents from aqueous solutions. To assess the potential traceability of the synthesised fluorescent LDHs in the subsurface, tests were carried out using an OIP-G system (Geoprobe Systems ® ), which is a novel tool developed for inducing fluorescence on contaminations caused by large polyaromatic hydrocarbon like creosote, coal tars, oils and fuels [26].…”