Papers by Keyword: Kinetics

Abstract: Herein, for the first time, we investigate the adsorption performance of nanoZn benzenedicarboxylate metal-organic framework (nanoMOF-5) as an efficient adsorbent material for Cr (VI) decontamination from polluted water. The synthesized Zn MOF-5 was fully characterized via FT-IR, XRD, HRTEM, BET, and TGA techniques. Moreover, the prepared Zn MOF-5 revealed a prominent surface area of 1169.32 m² g^-1, demonstrating its ability to be utilized as a capable adsorbent material. The adsorption profile of Cr (VI) onto the fabricated Zn MOF-5 was performed against the various parameters such as contact time, dosage, and initial Cr (VI) concentration. The optimum dosage from the Zn MOF-5 for 81.03% adsorption of 25 ppm Cr (VI) was 0.5 g L^-1 at pH=7 after 15 min. The Cr (VI) decontamination performance of the synthesized Zn MOF-5 recorded the maximum monolayer adsorption capacity of 91.22 mg/g. These data demonstrated that the synthesized nanoZn MOF-5 is a promising adsorbent material for the removal of Cr (VI) from wastewater. Keywords: Zinc Metal-Organic Framework (MOF-5), Cr (VI) Decontamination, Isotherm and Kinetics, Recyclability.

Abstract: The application of a photocatalyst with effective adsorption capacity and higher photocatalytic activity under direct sunlight for the treatment of industrial effluent contaminated with dyes has received increased attention. In this work, mesoporous TiO₂-NiO nanosheets were synthesized by a modified auto-combustion technique followed by thermal post-treatment at 400°C. The XRD pattern for modified auto-combusted resulting TiO₂ (sc) and TiO₂-NiO (sc) [5wt%NiO] nanosheets comprised of mixed-phase anatase and rutile for TiO₂ and cubic for NiO. The result of SEM demonstrated that the morphology of TiO₂ is a sheet and TiO₂-NiO is a rod-like structure. UV-vis spectroscopy results imply that the bandgap of TiO2 and TiO₂-NiO mixed phase is 3.1eV and 2.7eV. N₂ sorption (BET) showed a mesoporous structure and interpret specific surface areas of 19.528m²/g and 63.215 m²/g. Adsorption of the dye on the solid catalyst is inexpensive and efficient but disposing of the adsorbed dye is challenging. Among various dye removal techniques, photocatalytic degradation under direct sunlight is significant, cost-effective, and sustainable. Photocatalytic experiments using alizarin yellow as a model pollutant showed that the degradation percentage of AY was 93.54% in 120min for 100mg of TiO₂(sc) and 97% in 90min for 60mg of TiO₂-NiO(sc). Degradation of AY using TiO₂(sc) and TiO₂-NiO(sc) follows a pseudo-first-order reaction, whereas adsorption of AY on TiO₂-NiO(sc) follows the second-order kinetics, fits well in the Freundlich Isotherm model. Therefore, nanosized mesoporous TiO₂-NiO(sc) nanosheets with a p-n junction are considered efficient photocatalysts under direct sunlight due to narrowing down in bandgap, larger surface, and mixed-phase.

Abstract: The sorption method of purification of flushing water from non-ferrous metal ions in galvanizing-bath rooms of mechanical facilities was investigated, which is one of the most realistic ways to solve the problem of environmental protection from such pollution. The effect of preliminary thermal and chemical modification of the crystal structure in order to improve the sorption capacity of clinoptilolite was established. The kinetics of the copper ion exchange process on clinoptilolite in static conditions was determined.

Abstract: The volume of oil-contaminated wastewater generated from petrochemical industries and various oil fields is significant. The discharge of such oily wastewater endangers terrestrial and aquatic ecosystems due to the high organic load and toxicity of the oily components. Currently, there are several technologies available for the treatment of oily wastewater among which adsorption was observed to be a promising technique for the removal of oil emulsions from wastewater. In this study, acid modified and base modified pyrolyzed date seed was investigated for the removal of oil and oil emulsions from contaminated water. The effect of pH in the range of (2-12), temperature (30°C-70°C), date seed dose of (0.1-1 g) and contact time of (1-240 mins) was investigated for both the acid modified and base modified activated date seeds samples. Equilibrium sorption was attained after a contact time of 120 minutes. It was observed that base modified activated date seed resulted in 83% removal of oil. Both acid and base modified activated date seed showed a high percentage removal of 92.9 % and 94.3 % respectively at a lower acidic pH of 2. Concerning the equilibrium sorption kinetics, Pseudo-Second-order kinetic Model showed better fit as compared to pseudo first order kinetic model. Therefore, the adsorption of oily wastewater onto both acid and base modified activated date seeds are consistent with the second-order kinetic model. The Langmuir isotherm was found to be linear with high correlation coefficient values over the entire concentration range, which confirms that the Langmuir isotherm is more accurate to represent sorption by acid modified date seed unlike the case of base modified activated date seed where Freundlich isotherms were found to better fit the adsorption equilibrium data for base modified date seed. Keywords: Pyrolyzed date seeds; chemically modified activated date seeds; thermo-chemically modified lignocellulosic biomass; kinetics; equilibrium isotherms.

Abstract: The diagrams of isothermal transformation based on kinetic curves R = (τ) for retained austenite in high-strength alloy low-carbon at overcooling have been built. It is shown that the temperature of quenching influences the stability at overcooling and resistance to isothermal transformation of austenite at sub-zero temperatures.

Abstract: An eco-friendly and low cost modified mixture of both Wild Carob and Cupressus sempervirens with H₃PO₄ (Cupcar-H₃PO₄) was prepared to extract a cationic dye (Crystal Violet) from an aqueous solution in a batch reactor at the laboratory of chemical engineering, Department of Process Engineering, Faculty of Technology, Farhat Abbas Setif University-1. The pH effect, contact time, initial concentration of dye, ionic strength and temperature were investigated in this study. The Maximum adsorption capacity was found to be 117.26 mg/g at 25°C for a natural pH (ph =6.22). The active functional groups of Cupcar-H₃PO₄. These peak shifts indicated that especially the bonded –OH groups, C–O stretching of ether groups, and C=C group played a major role in CV adsorption onto Cupcar-H₃PO₄. The new bands of low intensity which appeared at 890 cm⁻¹ and 813 cm^-1 after CV adsorption and which could be attributed to a υ (CV-biosorbent) constituted the most striking result. Kinetics of biosorption of crystal violet (CV) was analyzed and the results showed that both pseudo order (PSO) and the pseud nth-order model (PNO) models gave most accurate fit than the pseudo-first-order model (PFO). Isotherm data were analyzed by four classical models, Langmuir and Freundlich with two parameters, Sips and Redlich-Peterson with three parameters. And for more information on the mechanism of CV uptake on the Cupcar-H₃PO₄ material, three advanced models are applied to isothermal data, Monolayer with one energy (M1), Monolayer with two energies (M2), and Double layer with one energy (M3). For the classical models and in the case of the two parameters models the Langmuir one gives a better fit for the data isotherm according to the R². In the case of three parameters models, both Sips and Redlich-Peterson accurately described experimental data. Monolayer with two energy sites model (M2) was shown to be the most appropriate advanced statistical physics model for fitting CV biosorption onto the Cupcar-H₃PO₄ biosorbent, this model suggested that the CV pollutant was adsorbed at two different Cupcar-H₃PO₄ biosorbent sites, and that a variable number of CV molecules could be adsorbed at each site; from this, the CV dye was adsorbed with 2 different adsorption energies. The changes in the enthalpy, the standard free energy and the entropy were also evaluated and the reaction was found to be spontaneous, endothermic and physical in nature.

Abstract: It has been established that external uniaxial tensile stresses influence the character and kinetics of the g®a-transformation in cold-rolled martensite steel at sub-zero temperatures (down to -60 °C).

Abstract: The boride coatings are characterized by attractive set of properties: high wear resistance and good high-temperature corrosion. In present research the diffusion boride coatings were obtained on X39CrMo17-1 stainless steel. The pack-boriding process was conducted using commercial Ekabor 2 powder. The influence of time of process on thickness and chemical composition was analysed. The boriding process was conducted in 2, 4, 6 hours at 1000 °C using retort furnace. The obtained coating was characterized by double layer structure and contained the FeB in outer layer and Fe₂B in inner layer. The thickness of boride coatings increased with process time. The analysis of obtained results showed that the optimal thickness of coating was obtained during 4-h pack boriding.

Abstract: The paper deals with the investigation of the parameters for the structural and kinetic rate equation of the carbonates dissociation reaction, in accordance with the obtained results of the nonisothermic experiment, in the conditions of gradient temperature presence in the investigated samples. The most significant is the study of physicochemical transformations kinetic laws, which degree of completeness effects the quality of intermediate products directly, that is decarbonization and sintering. The main part of the process, when phosphorites are heated, takes place in a solid phase. The feature of topochemical reactions is their localization in the aria between a solid phase surface of the initial substance and the reaction products. This surface is formed and changed, as a result of chemical and power technological process for roasting, determining the dependence of the reaction rate on time. The method of thermal analytical experiments is used. The reverse kinetic problem is solved in the temperatures range of the chemical–technological process for roasting phosphate raw materials on conveyor indurating machines. The authors propose a method of approximate calculation for the parameters of kinetic equations which allows to reduce errors, caused by the heat exchange processes in a measuring cell, significantly. The obtained results and their accuracy are suitable for the practical application.

Abstract: Wet etching of Si₃N₄ was conducted in superheated water at 160 °C with different additives type and concentration. In general, etching rate of Si₃N₄ increased with the pH of solution. However, it is difficult to fully explain the Si₃N₄ etching behavior just with the pH of solution. The OH^- concentration (or pH) in superheated water at 160 °C are different from the pH of solution at room temperature. Therefore, the OH^- concentrations in superheated water at 160 °C were calculated using van't Hoff equation, equilibrium constant equations, mass and charge balance equations. The calculated OH^- concentration at 160 °C showed better correlation with Si₃N₄ etching rate than that of initial pH of solution.