Natural Mineral Sorbents Research Articles

Effect of the acidic treatment on the adsorption and structural properties of the natural mineral sorbent M45C20

Adsorption and structural properties of the initial natural mineral sorbent M45C20 and the sorbent treated with 2.33 M H2SO4 were studied. The sorbent mainly consists of montmorillonite and clinoptilolite. Aluminum, calcium, magnesium, sodium, and potassium ions are removed from the structure under the action of the acid. The specific surface, porosity of the sorbent, and pore size increase during this process. The sorption of ammonium ions in the natural samples predominantly follows the ion-exchange mechanism (exchange to calcium, magnesium, sodium, and potassium ions). The acid treatment changes the composition of the cation-exchange complex and results in an increase in the sorption capacity to ammonium ions by a factor of ∼1.3.

The role of external and internal mass transfer in the process of Cu2+ removal by natural mineral sorbents

The kinetics of Cu2+ sorption on to zeolite, clay and diatomite was investigated as a function of initial metal concentrations. For consideration of the mass transfer phenomena, single resistance models based on both film and intraparticle diffusion were tested and compared. The obtained results suggested that the rate‐limiting step in Cu2+ sorption strongly depended on the sorbent type, as well as on initial cation concentration. The decrease in external mass transfer coefficients with the increase in initial metal concentrations was in excellent agreement with expressions based on Sherwood and Schmidt dimensionless numbers. The internal diffusivities through zeolite particles were in the range 1.0 × 10−11 to 1.0 × 10−13 m2/min, depending on the Cu2+ concentration and the applied theoretical model.

Study of structure and properties of native and activated natural mineral sorbents

Compositions, structures, textural characteristics, and other properties of natural types of mineral, including aluminosilicate, siliceous, carboniferous types, and mixed zeolite-containing siliceous units, are investigated. It is established that zeolitic and shungitiferous types possess porous structure, gaizas, and mixed zeolitic siliceous units, which are basically medium-porous sorbents. Changes in the character of compositions, structure, and properties at sorbents chemical activation are analyzed. It is established that the acid activation of almost all sorbents is accompanied by silicon dioxide; additionally, textural characteristics increase and decrease in true specific gravity. There is a reduction in the specific surface area at the alkaline and acid activation of gaizas; however, at the same time, the total volume and pore diameter increases. Studies have shown the possibility of using activated sorbents for clearing potable water of iron ions.

Specific 137Cs-sorption capacity parameters of soils and mineral sorbents

The selective sorption of cesium by some soils, minerals, and natural mineral sorbents was studied using new methodological and experimental approaches. It was found that the total capacity of two types of highly selective sorption sites significantly differing (by several orders of magnitude) in the selectivity coefficients of Cs-K ion exchange makes up 0.5–6% of the total capacity of the ion exchanger. The values of the radiocesium interception potential were determined for the studied soils and minerals.

Study on Alkali-Metal Vapor Removal for High-Temperature Cleaning of Coal Gas

Six natural mineral sorbents and a series of self-made sorbents were used to remove alkali-metal vapor from high-temperature coal gas. Results indicate that the self-made sorbent GM6 is the best sorbent with the highest sodium compound content, under the conditions of 1173 K, a gas velocity of 16 L/min, a reaction time of 3 h, and a NaCl concentration of 0.13 mg/L. It is shown that the sodium compound content is dependent on the chemical constituents and the microporous structure of sorbent, based on the surface area data. Results of X-ray diffraction (XRD) analysis and the kinetics indicate that the adsorption process of GM6 is physical adsorption in an N2 atmosphere and it is controlled by the diffusion of a sodium resultant layer. The adsorption process in a N2/H2O(2%) atmosphere is mainly a chemical adsorption that is controlled by both the chemical control and the product-layer diffusion control.