Adsorption Of Organic Cations Research Articles

Real-Time Monitoring of Adsorption-Induced Scrolling of Colloidal Inorganic Nanosheets.

Inorganic nanotubes have attracted much attention due to their unique physicochemical properties. Nanotubes can be prepared by scrolling exfoliated nanosheets under ambient conditions. However, how the nanosheet scrolled in its colloidal state has not been experimentally visualized. In this paper, we directly observed the scrolling process of nanosheets upon adsorption of organic cations. Exfoliated flat nanosheets of niobate and clay in aqueous colloids were found to scroll by adding organic cations, such as exfoliation reagents, to the colloids. Employment of cationic stilbazolium dye enabled in situ observation of the dye adsorption and scrolling by optical microscopy based on changes in color and morphology of the nanosheets. The scrolling was promoted for nanosheets adsorbed with a stilbazolium dye with a longer alkyl chain, suggesting that the interaction between the hydrophobic parts of the dye cations is the driving force of the scrolling. This finding should encourage research on the formation of nanotubes from nanosheets and also provides important guidelines for the selection of appropriate exfoliation reagents when exfoliating nanosheets from layered crystals.

H ALIDE ION AND METHANOLIC EXTRACT OF IRVINGIA GABONESIS AS AN E NHANCED CORROSION INHIBITORY AGENT ON ALUMINIUM IN HCl

The in hibitory efficiencies of methanolic leaf extract of Irvingia gabonensis and the role of a halide ion as an enhancement on the inhibition of aluminium corrosion in HCl medium were studied at varying acid concentrations of 0.01M , 0.05M, 0.1M und er the influence of 3% NaCl. Result of the studies carried out by weight loss techni que showed that I. gabonensis is highly an efficient inhibitor for the corrosion of al umimium in HCl acid environment and its inhibitory efficiencies increases with respect to the time of exposure.. It was observed from the study that in the absence o f the plant extracts, the weight loss increases rapidly indicating an increase in corrosi on rate from 0.003g to 0.026g as acid concentration was increased from 0.01M to 0.1M . Conversely, when the plant extract was introduced, there were remarkable decrease in weight loss from 0.001g at 0.01M of HCl to 0.021g at 0.1M , showing a decrea se in corrosion of the metal. Experimental data proved that the highest corrosion rates w ere observed at the highest acid strength pointing that at a concentration of 0.1M H Cl, 19% efficiency was attained and a maximum efficiency of 67% was obtained at 0.01MHCl showing a correlation between concentration and inhibition of metal. It was also revealed that the inhibitory efficiency of I. gabonensis in HCl medium was magnif icently increased when a salt of halide ion was introduced showing a weight loss of 0.01g through 0.003g as acid strength increased from 0.01M to 0.1M. This could be attributed to that the fact that halide ion facilitates the adsorption of organic cat ions during metal corrosion by forming intermediate bridges between the metal surface and the positive end of the organic inhibitor and this forms a protective hydrophi lic film on the metal surface which provided a barrier to the dissolution of the metal into the acid medium.

MODIFICATION TECHNOLOGY OF MONTMORILLONITE BY POLYIONENES

Technology of obtaining montmorillonite modified by polyionenes is developed. Macromolecular polymer intercalation of a quaternary ammonium salt of montmorillonite intercrystalline space is shown to be accompanied with increased interlayer distances from 1.08 nm to 1.67 nm. The technique of synthesis of montmorillonite modified by polyionenes is suggested. Optimal conditions for sorption of polyionenes molecules with montmorillonite are found to be: the concentration of aqueous dispersion of montmorillonite is 1 %, the temperature of the reaction medium is 40 °C, the montmorillonite-polyionene ratio is 3 : 1, the processing time is 24 hours. The mechanism of montmorillonite modification is suggested to involve the next steps: connection of organic cations to montmorillonite surface determined by attachment of organic cations to exchange position during ion-exchange adsorption and adsorption of organic cations with acid sylanol groups, i.e. torn bonds on crystal faces. These processes are shown to result in more perfect structure by organic cations adsorption with acid sylanol groups (torn bonds on crystal faces).

Forming a filter media from zeolite modified with SDBAC for wastewater treatment process

This paper investigates the effects of several parameters (amounts of organic matter, grain size, content of solid phase, stirring rate, and temperature) on the adsorption of stearyl dimethyl benzyl ammonium chloride (SDBAC) in natural zeolite tuff in the process of formation of adsorbents based on organo-zeolite, a potential filter in waste water treatment process. Obtained results show that the most favorable ratio between the amount of SDBAC and zeolites is 50-75 mmol M+/kg. Larger grains have lower zeolite adsorption power of organic cations on the surface of zeolite, while favorable percentage of content of solids in the zeolite suspension is 10-20%. Interference between adsorption of mixture and temperature, especially in volumes of SDBAC lower than 75 mmol M+/kg of zeolite, have no significant impact on adsorption of organic cations on the surface of the zeolite. The obtained results present an initial step for defining the optimal operating parameters for forming adsorbents based on organo-zeolite as a filter potentially utilized in waste water treatment.

Physico-Chemical Characterizations of Tunisian Organophilic Bentonites

Organoclays were prepared from two tunisian purified Na-bentonites using benzyltetradecyldimethylammonium chloride (C14) and benzyldodecyldimethylammonium chloride (C12). The added quantities of organic salts, expressed as a function of the clay's cationic exchange capacity (CEC), have been varied from 0.3 to 4 CEC. Two different methods were investigated in order to determine the influence of the preparation method on the adsorption properties: on one hand, dry powder clay (method I) and, on the other hand, aqueous clay suspensions (method II) were mixed with the organic salt solutions. The adsorption of organic cations on clays was studied by adsorption isotherms, FTIR spectroscopy and X-ray diffraction. It appears that more salts are adsorbed in the clay interlayer space when using method II. The arrangement of salts within clay is rather complicated. It depends on clay composition, nature of tensioactive molecules, CEC of the clay, and preparation method. According to these parameters, the inserted surfactants can be arranged in monolayer, paraffin, or admicelles structures.

Interdisciplinarity of hydropedology

A new interdisciplinary subject hydropedology is developing owing to the necessity of sustaining optimal environments. Hydropedology provides the bridge between the disciplines of pedology, including soil macro- and micromorphology and vadose zone hydrology together with other disciplines dealing with land, air and water interfaces. Soil taxons and soil-forming processes are defined phenomenologically. Soil-forming processes which are usually linked have rates that differ by orders of magnitude. And, if soil polygenesis is considered, too, the equilibrium concept between the properties of soil taxons and soil forming factors is not applicable. The coupling of such processes on various tensorial orders leads to the conclusion that anisotropy is a general characteristic of soils. In order to ascertain the links between pedology and hydropedology, the formulation of physically meaningful transport parameters from a quantified knowledge of soil micromorphology is required. This linkage is achieved when the pore size distribution is reflected by the soil hydraulic functions, i.e. by the soil water retention equation and by the unsaturated hydraulic conductivity function. In future research, parameters of such functions must be related to quantified soil micromorphologic characteristics. The first attempt evaluating both functions is presented for soils manifesting a distinct bi-modal pore size distribution. A close cooperation of hydropedology with soil chemistry and microbiology will produce an insight into the role of organic substances upon the change of soil hydraulic parameters. The substances appear either as a consequence of soil pollution, or due to soil organic matter transformation. An example is presented on the change of saturated hydraulic conductivity caused by the adsorption of organic cations. Similar linkages are expected from the cooperation of hydropedology with plant physiology when the role of plant exudates upon the change of soil hydraulic functions is studied.

Influence of the Supporting Electrolyte Asymmetry on the Differential Capacitance Curves in a Model Description of Adsorption of Organic Cations at Electrode

Effect of supporting electrolyte asymmetry on the curves of differential capacitance of the electrical double layer during adsorption of organic cations at an electrode is considered within the Alekseev–Popov–Kolotyrkin model supplemented by a Frumkin isotherm. Taking into account the asymmetry substantially improves quantitative agreement between model calculations and experiment.

Montmorillonite treated with Rhodamine-6G mechanochemically and in aqueous suspensions

The mechanochemical solid-state adsorption of the cationic dye rhodamine-6G (R6G) by montmorillonite was investigated by XRD and simultaneous DTA-TG. Five different mixtures of R6G and montmorillonite were investigated. They contained 10, 20, 35, 50 and 100 mmol R6G per 100 g clay. The solid R6G was ground with the clay for five minutes. Mixtures were ground both in the absence of water (dry grinding) and with the adding of drops of water periodically, (wet grinding). There were no differences between samples obtained by wet or dry grinding. X-ray and DTA data were compared with those of R6G-montmorillonite obtained from aqueous suspensions. The mechanochemical products were different from those obtained from aqueous suspensions. The X-ray and DTA studies suggest that the mechanochemical adsorption of organic cations takes place on the external surfaces of the clay whereas in suspensions the adsorption takes place into the interlayer space. In the latter case the final stages of oxidation occur in temperatures higher than those of the neat dye whereas in the former they occur at lower temperatures.

Simultaneous DTA-TG study of montmorillonite mechanochemically treated with crystal-violet

The mechanochemical solid-state adsorption of the cationic dye crystal violet (CV) by montmorillonite was investigated by XRD and simultaneous DTA-TG. Solid CV was ground with the clay for 5 min and four different varieties of CV mechanochemically treated clay were investigated. X-ray and DTA data were compared with those of CV-montmorillonite obtained from an aqueous suspension. X-ray and DTA studies of a ground mixture and a ground mixture heated at 110°C suggest that the mechanochemical adsorption of organic cations takes place on the external surfaces of the clay. The study of a ground mixture washed with water, and washed with water and acetone reveal that water is essential for the penetration of CV into the interlayer space.

Organo-clay formulations of pesticides: reduced leaching and photodegradation

Adsorption of organic cations on several clay minerals is reviewed with an emphasis on the effect of ionic strength and modeling. The clay exchanged with suitable organic cations forms a basis for ecologically acceptable formulations of herbicides with reduced leaching, ground water contamination and enhanced weed control efficacy. Incomplete neutralization of the clay surface charge by an organic cation may be advantageous in achieving maximal adsorption of hydrophobic herbicides. One conclusion from these studies is that optimization of clay-based herbicide formulations requires a selection of structurally compatible organic cations preadsorbed on the clay at optimal coverage. New experimental results are presented for alachlor formulations, which significantly reduce herbicide leaching under conditions of heavy irrigation. We were able to demonstrate that organo-clay formulations of alachlor and metolachlor can increase crop yields in a 1-year field experiment. The photostabilization of pesticides is reviewed and improved organo-clay formulations of the herbicides trifluralin and norflurazon are described. A pillared clay, nanocomposite micro- and/or meso porous material, was effective in reducing leaching and in conferring photostabilization, without added organic cations.

Effect of temperature on the adsorption of organic cations on charged surfaces

Effect of temperature on the adsorption of organic cations on charged surfaces