Investigation of the Mechanism of Sulfur Dioxide Adsorption from Gas Emissions of Sodium Bisulfite Production

It is proposed to purify industrial gas emissions from sulfur dioxide by the adsorption method. Waste from the power industry - sludge from the chemical water treatment of Kazan CHPP-1 - was used as an adsorption material. Its chemical composition is presented. Experimental studies of a new sorption material based on energy waste for gas purification from sulfur dioxide have been carried out. The kinetic dependence and isotherm of the adsorption process are obtained. The mechanism of the process of adsorption of sulfur dioxide by sorption material at different temperatures has been studied. The Gibbs free energy, differential heat, and activation energy of adsorption are determined. The economic and environmental impact of modernization of procedure for cleaning gas emissions from sulfur dioxide in sodium bisulfite production at JSC “Chemical factory named after L.Ya. Karpov” was measured.

Adsorption, Antibacterial and Antioxidant Properties of Tannic Acid on Silk Fiber

Natural bioactive compounds have received increasing attention in the functional modification of textiles. In this work, tannic acid was used to impart antibacterial and antioxidant functions to silk using an adsorption technique, and the adsorption properties of tannic acid on silk were studied. The adsorption quantity of tannic acid on silk increased with decreasing pH in the range of 3–7. The rates of the uptake of tannic acid by silk were well correlated to the pseudo-second-order kinetic model, and the calculated activation energy of adsorption was 93.49 kJ/mol. The equilibrium adsorption isotherms followed the Langmuir model. The adsorption rate and isotherm studies demonstrated that the chemical adsorption of tannic acid on silk occurred through the ion-ion interaction between tannic acid and silk. Tannic acid displayed good building-up properties on silk. The silk fabric treated with 0.5% tannic acid (relative to fabric weight) exhibited excellent and durable antibacterial properties. Moreover, the silk fabrics treated with 2% and 5% tannic acid had good and durable antioxidant properties. The treatment by tannic acid had less impact on the whiteness of the silk fabric. In summary, tannic acid can be used as a functional agent for preparing healthy and hygienic silk materials.

Equilibrium, Thermodynamic and Mechanism Studies of Malachite Green Adsorption on Used Black Tea Leaves from Acidic Solution

This study reports the equilibrium adsorption mechanism and thermodynamics for the removal of Malachite Green (MG) from acidic solution using Used Black Tea Leaves (UBTL) as a low cost adsorbent. The effect of initial dye concentration, processing temperature and the presence of electrolytes on the adsorption from acidic solutions were investigated in batch process. Adsorption process was attained to the equilibrium at about 24 hours. Adsorption isotherms of MG on UBTL for different temperatures were constructed at pH 2.0 and the equilibrium adsorption data were analyzed using different model equations such as Langmuir, Freundlich, Temkin, Dubinin-Radushkevich (D-R), Harkin-Jura, Halsey, Elovich-Larionov and Flory-Huggens isotherms. The experimental results were reasonably correlated by Langmuir, Flory-Huggins and D-R models than other isotherm models. The maximum adsorption capacity (qm), intensity of adsorption (b) and separation factor (Rb) were calculated from Langmuir plot and activation energy of adsorption (Ead) was determined from D-R isotherm. At pH 2.0, the equilibrium adsorption capacity of UBTL to MG is 110 mg∙g-1 at 30°C, which was increased with increasing temperature suggested endothermic nature of adsorption. Thermodynamics parameters: ΔGads, ΔHads and ΔSads were calculated from Langmuir constant (b). The positive values of enthalpy and free energy, and negative value of entropy suggested that the adsorption is less spontaneous and surface migration or fragmentation of MG molecules on UBTL surface might be occur. Again, the low value of activation energy of adsorption (Ead = 0.3 kJ∙mol-1 <8 kJ∙mol-1) suggested that the adsorption is controlled by physical in nature. A possible mechanism involvement of protonation is proposed from the effect of electrolytes during the adsorption of MG on UBTL at pH 2.0.