Band 22, Heft 12

The kinetics and thermodynamics of methylene blue adsorption from aqueous solution was studied using low-cost biomass graphite (CVDM) and graphene oxide (SGO) derived from black plum seed. The effects of pH in the range of 2.2–12.5, adsorbent dosage in the range of 25–100 mg and solution temperature in the range of 28.7–90 °C were studied. The optimum conditions were recorded at pH 4.8, dosage of 25 mg and solution temperature of 70 °C. The pseudo-second-order model demonstrated the best fit to experimental data ( R 2  → 1 and SSE = 3.69), rapid rate constant ( K s  = 0.0868 g/mg.min) and empirical adsorption capacity of 4.12 mg/g. The adsorption of methylene blue onto SGO increased with solution temperature to 70 °C before it decreased, suggesting a weakening of the attractive adsorbent-adsorbate forces due to collisions among methylene blue molecules.

This study focuses on enhancing the cementitious activity of coal gangue through a two-step process involving thermal activation followed by chemical alkali excitation. The coal gangue was first treated via a self-heating sintering decarbonization process, which effectively increased its reactivity without the need for additional solid fuel. Following thermal activation, chemical activation was performed using activators such as hydrated lime and lithium silicate to further improve the reactivity of the decarbonized coal gangue. The effectiveness of combining ground granulated blast furnace slag (GGBS) with the activated coal gangue was also evaluated. Results revealed that incorporating 35–45 % GGBS with activated coal gangue significantly enhanced both early and long-term strength, achieving an activity index exceeding 100 % under optimal conditions. The addition of 5 % hydrated lime significantly increased the 28-day activity index of the mineral powder to 82.7 %. Optimization experiments showed that reducing the content of decarbonized coal gangue and fine-tuning the proportions of activators further enhanced the overall activity index, reaching up to 103.7 %. This study provides a comprehensive approach to improving the resource utilization of coal gangue through integrated thermal and chemical activation, paving the way for its application in sustainable construction materials.

The quality of sintering ore and the efficiency of the blast furnace are both heavily dependent on the high-temperature performance and compatibility of iron ores. A novel characterization technique, the Assimilation Melt Breakover method, is proposed to test the electrical performance during assimilation in sintering. Utilizing the two-electrode method, the electrical resistance of mixtures of ferrite oxide and calcium oxide was measured during their assimilation. A rise in temperature is associated with a reduction in electrical resistance, adhering to the principles of Arrhenius Law. The changes in conductivity observed during the assimilation process accurately reflect the mineral phase transformations, encompassing alterations within the solid state and transitions from solid to melt. The transition is marked by a substantial reduction in electrical resistance, specifically from several thousand to a few dozen Ohms in melting assimilation, along with notable variations in the activation energy associated with conductance. This research has the potential to swiftly differentiate between the assimilation characteristics of different iron ores, as well as to assist in the utilization of an electric field in iron ore sintering.

This research examines the performance variables, combustion, and the amounts of NOx, CO, HC, and K emissions in a diesel engine, using blends of hemp biodiesel and oleic acid biodiesel with conventional diesel. To obtain biodiesel from hemp oil and oleic acid, a heterogeneous sulfonated camphor catalyst (CASU-AL) was used for the transesterification of hemp oil and the esterification of oleic acid respectively. Several characterization tests were performed on the CASU-AL catalyst such as the acid-base titration method for the quantification of acid sites, XRD analysis to determine the areas of the carbonaceous material, images and composition of CASU-AL were obtained with SEM and EDX, the porosity characteristics and surface properties were assessed with BET analysis. Constant operating conditions were used in the autogenous reactor with a temperature of 200 °C, a reaction time of 23 min, and a quantity of sulfonated camphor catalyst of 0.033 % w. Several analyses were applied to the CASU-AL, several mixtures were made with conventional diesel, and different biodiesels were obtained in the laboratory. The mixtures were conventional diesel (DIE-100), hemp oil biodiesel (BAC-100), oleic acid biodiesel (BAO-100), Diesel-BAC mixture with 30 % hemp oil biodiesel (MDBAC-30), and Diesel-BAO mixture with 30 % oleic acid biodiesel (MDBAO-30). For the tests in a diesel engine, three speed zones were selected in the engine to identify the behavior at low speed at 1,200 rpm, medium speed at 1,400 rpm, and high speed at 1800 rpm. Combustion tests reveal that no significant variation is observed in the characteristics and performance of the diesel engine, however, in the gaseous products derived from combustion, significant reductions in carbon monoxide, unburned hydrocarbon, and an increase in nitrogen oxide emissions were achieved when using DIE-100 compared to BAC-100 and BAO-100. The tests showed a reduction in NOx, CO, HC, K, and smoke emissions when testing MDBAC-30 and MDBAO-30 in a laboratory diesel engine. A comparison of the properties of hemp oil-oleic acid biodiesels BAC-100 and BAO-100 with conventional diesel DIE-100 revealed that the different biodiesels used could be used alone or in a blend of 70 % diesel and 30 % biodiesel to fuel diesel engines by decreasing air pollutants and promoting lubricity in the engine. Our findings revealed that MDBAC-30 and MDBAO-30 showed the best engine performance and lowest emissions among all the tested fuels. In other words, MDBAC-30 and MDBAO-30 are the ideal fuel blends for diesel engines and do not require any modification to the engine.

When zinc hydrometallurgy is used to treat zinc oxide dust (ZOD), the fluorine (F) and chlorine (Cl) in the dust interfere with zinc electrowinning. To investigate the effectiveness of F and Cl removal from ZOD by different alkaline washing methods. Under the condition that 16 g/L Na 2 CO 3 was mixed with 6 g/L NaOH in equal volume 1:1 and reacted with the dust under the optimum condition of the liquid-solid ratio of 5 mL/g for 2 h at 70 °C, final pH of 10, and stirring intensity of 400 rpm, the dechlorination of cloth bag zinc oxide dust (CBZOD) and boiler zinc oxide dust (BZOD) were 94.81 % and 90.63 %, respectively, and the defluorination were 84.81 % and 24.50 %, respectively. To further reveal the reasons for the difficult removal of F from ZOD, a step extraction method and physical phase analysis of residue were used, which resulted in more than 98 % removable fluoride in CBZOD and up to 56 % insoluble residue in BZOD. Therefore, it is obvious that the removal effect is better due to the presence of large amounts of removable fluoride and chloride in CBZOD; the F states and percentage of insoluble fluoride are main reasons affecting the removal of F.

With the increasing demand for eco-friendly epoxides derived from vegetable oils, recent efforts have focused on developing methods for the epoxidation of sunflower oil. Sunflower oil, in particular, has emerged as a promising candidate for epoxidation due to its high content of unsaturated fatty acids, which provide abundant double bonds suitable for epoxide formation. In this study, epoxidized sunflower oil was produced using in situ formed peracid with a hybrid oxygen carrier combining formic acid and acetic acid. The optimal epoxidation reaction parameters were determined as follows: (1) a reaction temperature of 75 °C, (2) a catalyst loading of 0.9 g of hybrid oxygen carrier, (3) a stirring speed of 450 rpm, and (4) a hydrogen peroxide to sunflower oil molar ratio of 1.5. This research contributes to transforming sunflower oil into a value-added product, thereby reducing reliance on petroleum-based resources.

A heterogeneous catalyst NaOH–NaAlO 2 /γ-Al 2 O 3 was prepared by supporting NaOH and NaAlO 2 on γ-Al 2 O 3 , and it was further employed for the oxidative degradation of lignin. The influence of the oxidant, the molar ratio of NaOH to NaAlO 2 , and calcination temperature of the supported catalyst on the catalytic activity were investigated. Air was found to be an effective oxidant for lignin conversion in the presence of heterogeneous catalyst. The total yield of monophenolic compounds (MPCs) from dealkaline lignin was 13.0 %, which was obtained by using NaOH–NaAlO 2 /γ-Al 2 O 3 calcinated at 550 °C as the catalyst with 2:3 M ratio of NaOH to NaAlO 2 at 170 °C for 2.5 h in air. Vanillin and syringaldehyde were found to be the main products, giving yields of 6.7 and 2.9 %, respectively. The conversion of lignin derived from wheat straw was also carried out under the identical conditions. Wheat straw lignin also displayed considerable conversion to MPCs in the presence of NaOH–NaAlO 2 /γ-Al 2 O 3 , and the total yield of MPCs at 12.3 % was obtained at 180 °C. NaOH–NaAlO 2 /γ-Al 2 O 3 was recovered by filtration after the reaction and reused without further treatment, and 11.0 % total yield of MPCs was obtained after four cycles.

In this research, a one-dimensional heterogeneous model is developed to simulate the partial oxidation of methanol to formaldehyde over a molybdenum-iron catalyst in an industrial isothermal reactor at dynamic condition. The considered isothermal reactor is modelled based on the mass and energy balance equations considering catalyst deactivation. Based on the simulation results, decline in the catalyst activity from 1.0 to 0.73 decreases the rate of formaldehyde production rate from 94.9 kmol h −1 to 89.63 kmol h −1 during process run time. Subsequently, a multi-objective optimization problem is programmed to enhance formaldehyde productivity and minimize the production decline during process run time. To select the effective decision variables, a sensitivity analysis is performed based on the developed dynamic model. Then, the programmed multi-objective optimization problem is replaced with a single objective by the weighted sum method, and the problem is handled by the genetic algorithm method to determine the optimal trajectory of coolant temperature. The simulation results showed that the average formaldehyde production rate increases from 92.11 kmol h −1 to 95.22 kmol h −1 when the optimal conditions are applied to the reactor.

This study investigated the effect of different treatment conditions on kaolinite-halloysite type as a support for TiO 2 and their potential application in photocatalysis. These nanocomposites are used to study the photodegradation of methylene blue, a dye widely used in the textile industry and released into the environment. Crystal structure, specific surface area, pore structure and the morphology of kaolinite were all studied using XRD, attenuated total reflectance (ATR), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and ultraviolet-visible light. The optical band gap increased with increasing kaolin loading from 2.93 to 3.14 eV. Compared with pure TiO 2 photocatalyst, the morphology and structure of kaolinite/TiO 2 composites can significantly improve their ability to adsorb organic pollutants and their photocatalytic activity: The photocatalytic efficiency of kaolinite/TiO 2 was evaluated by degrading the textile dye methylene blue (MB) under UV-light irradiation. The results showed an improvement from 71 % using TiO 2 to 98 % for nanocomposites kaolinite/TiO 2 using samples amount of 1 g/L and Co = 20 mg/L.

The inclined-axis stirring system is widely employed in industrial processes due to its exceptional mixing capabilities, ease of industrial retrofitting, and commendable safety and stability features. This study numerically investigates the multiphase flow characteristics within an industrial-scale inclined-axis stirring tank, utilizing the realizable k-ε model and the volume of fluid model. With the validated model, the impact of impeller rotational speed on the flow characteristics in the stirred tank is explored. The findings reveal several noteworthy observations: As the stirring speed increases, liquid level fluctuations intensify. At excessively high stirring speeds, a large number of bubbles are entrained and dispersed into the stirring tank. Multi-scale vortices are observed within the inclined-axis stirred tank. Notably, two relatively large-scale vortices manifest on either side of the rotating blade. Comparatively, the tilted arrangement of the stirring shaft disrupts the symmetry of the flow field. Regions beneath the blades and at the bottom of the stirred tank exhibit elevated liquid phase velocities, radial velocities, and axial velocities. The rising area of the fluid in the stirred tank is near the wall, forming a ring shape, while the center of the ring is characterized by descending fluid. These findings provide valuable theoretical insights for the structural configuration and considerations related to energy conservation in industrial agitation equipment.