Adsorption characteristics, isotherm, kinetics, and diffusion of modified natural bentonite for removing the 2,4,5-trichlorophenol

Structural characterization of hexadecyltrimethylammonium-smectite composites and their potentiometric electrode applications

“…Moreover, the total amounts of waters removed from organosmectites below 200 • C are less than that of NaS and the elimination of the adsorbed waters from organosmectites occur at lower temperatures. This situation can be explained with the reduction of the surface energy and conversion of the silicate surface from hydrophilicity to hydrophobicity, which is in agreement with the results of the previously reported FTIR-ATR studies [24,26,36,41]. The thermal decomposition of organosmectites occurs in three stages: the dehydration of adsorbed water up to 140 • C, and then the decomposition of surfactant molecules which is followed by the dehydroxylation of smectite hydroxyl groups together with decomposition of organic carbonaceous residue of the surfactants, from 50 to 720 • C. The differentiation of the mass losses originating from dehydroxylation of smectite and decomposition of the organic cations by using the TG curves is highly difficult [80].…”

“…Intercalation of the HDTMA cations into Na-S layers caused a significant increase in the basal spacing values of organosmectites varying in the range of 15.61-35.50Å that point out that the penetration of the surfactant cations into the interlayer space of smectite occurs. These expansions of the smectite layers are related to the arrangements of HDTMA molecules depending on the ratio of HDTMA to CEC [10,18,22,26,36]. The arrangements of the surfactant molecules in the interlayer region of the smectite can be distinguished by comparing the interlayer expansions and molecular dimension of the surfactant.…”

“…The intensity of the bands at 3402 and 1635 cm −1 gradually decreased with the surfactant loading due to the fact that the water molecules coordinated to the exchangeable cations were removed by the replacement of the hydrated interlayer cations by HDTMA cations. This process causes the surface property of raw smectite to change from hydrophilic to hydrophobic character [13,26,36,37,40]. The ATR spectra of the 0. modes is independent from structural conformation and surfactant loadings into the organoclay [5,36].…”

“…This process causes the surface property of raw smectite to change from hydrophilic to hydrophobic character [13,26,36,37,40]. The ATR spectra of the 0. modes is independent from structural conformation and surfactant loadings into the organoclay [5,36]. Furthermore, the above result may provide further support for proposal of the previous studies pointing out that the antisymmetric CH 2 stretching mode is more sensitive to the conformational ordering than the symmetric CH 2 stretching mode [18,19,22,30].…”

Adsorptive Removal of a Reactive Azo Dye Using Polyaniline-Intercalated Bentonite

“…As natural clay, bentonite has been used widely as an adsorbent for much pollutant removal, including PPCPs, heavy metal, VOCs, etc. [20][21][22], due to its advantages such as large specific surface area, good cation exchange capacity, and excellent chemical and physical stability [23]. Unfortunately, raw bentonite is inefficient for reactive dye adsorption as a result of the repulsion between its negatively charged surface and the anionic dye molecules.…”