Chemical Engineering & Technology最新文献

Mercury catalysts used in industrial vinyl chloride monomer production are harmful to the environment and to health. In accordance with green chemistry, replacing mercury catalysts is a logical focus of academia and industry. Although precious metal catalysts offer excellent activity, they are expensive to implement widely. Copper catalysts are a cost-effective and eco-friendly alternative. Recent advances such as carrier doping, ligand modification, additive inclusion, and ionic liquid integration have increased their catalytic efficiency to often equal noble metal catalysts. This article evaluates these approaches and shows their potential for sustainable catalysis.

This study numerically investigates the flow characteristics of a viscoelastic fluid in a two-dimensional Hele–Shaw cell with hyperbolic expansions and contractions. The fluid's rheology is described using the Phan–Thien–Tanner constitutive model, with the governing equations solved using the finite-volume method in OpenFOAM. Within the explored range of Weissenberg numbers (0.5 ≤ Wi ≤ 4), increasing the Weissenberg number leads to higher velocity magnitude, reduced principal stress difference, and more pronounced elastic effects, resulting in a stable, symmetric flow. No vortex formation or instabilities are observed along the geometry. Furthermore, the analysis comprehensively examines velocity fields, principal stress differences, stress ratios, flow types, and apparent viscosities.

A multi-cyclone separator was provided with combination of venturis and cyclones. The gas–liquid co-current and countercurrent modes of the multi-cyclone separator were proposed. The two modes can be converted by adjusting the gas channels. The countercurrent mode was achieved when the liquid flow ranged from 7.5 to 17.5 L min⁻¹. For countercurrent mode, larger liquid flow is benefit for improving the gas circulation flow. There is a reasonable injected gas flow that makes the gas circulation flow reach peak value. There is a critical injection gas flow beyond which countercurrent cannot occur. In the limited range of gas–liquid countercurrent, the volumetric mass transfer coefficient and separation efficiency in countercurrent mode are better than that of co-current mode. When the injected gas flow is larger than the critical value, only the third stage mass transfer unit works as the performance of countercurrent mode will decrease sharply.

Olive mill wastewater (OMW) is rich in organic pollutants, particularly phenolic compounds (PC). Persulfate (PS)-based advanced oxidation processes have emerged as effective treatment methods. This study focused on optimizing PC removal using a catalytic Fenton-like process. A Plackett–Burman design was applied to screen key variables: PS and copper concentrations, reaction time, temperature, and initial pH. A central composite design with response surface methodology was then used to refine the process. The resulting second-order polynomial model showed excellent fit with experimental data. Under optimal conditions, a maximum PC removal efficiency of 62.09 % was achieved.

The adsorption of methylene blue (MB) onto silica synthesized from coal fly ash (CFA) was investigated to evaluate its efficiency, kinetics, and thermodynamics. Adsorption studies revealed nearly 100 % MB removal under optimized conditions (50 ppm MB, pH 7, 3.1 g adsorbent dosage, and 50 min contact time). Equilibrium data fitted best with the Langmuir isotherm model (R² = 0.9881, Q_max = 32.76 mg g⁻¹), confirming monolayer adsorption and strong adsorbate–adsorbent interactions. Kinetic modeling showed that the pseudo-second-order model (R² = 0.99) best described the process, indicating chemisorption as the dominant mechanism. Thermodynamic analysis confirmed that the adsorption was spontaneous and exothermic (ΔG < 0, ΔH = − 22.84 kJ mol⁻¹), with a decrease in system entropy, suggesting an energy-efficient process that favours lower temperatures. Reusability studies demonstrated that the silica adsorbent retained 97.5% ±  0.17 % MB removal efficiency over 12 cycles, highlighting its economic and industrial feasibility. Additionally, ethanol-based desorption proved to be effective, ensuring sustainable regeneration. These findings establish silica from CFA as a cost-effective, environment friendly, and highly efficient adsorbent for wastewater treatment applications, particularly in dye-contaminant removal.

This study focused on developing slow-release fertilizers (SRFs) by coating pyrolysis oil on the fertilizer. The oils used included tire pyrolysis oil (TPO), wheat straw pyrolysis oil (WSPO), poplar wood pyrolysis oil (PWPO), and low-density polyethylene pyrolysis oil (LDPEPO). Coatings were created on fertilizer granules by co-pyrolysis at 200 °C in a fixed-bed pyrolysis reactor under nitrogen gas. The prepared SRFs included TPO-coated fertilizer (TPOCF), WSPO-coated fertilizer (WSPOCF), PWPO-coated fertilizer (PWPOCF), and LDPEPO-coated fertilizer (LDPEPOCF). Carboxylic, carbonyl, and hydroxyl compounds and functional groups in pyrolysis oils played an essential role by forming bonds and complexing with ions in NPK fertilizer. For uniform coverage of NPK fertilizer granules, maintaining a high nitrogen content in the fertilizer structure, and slower release of ions in a distilled water environment, WSPO and poplar wood were suitable.

The study of the adsorption behavior of silica in removing water vapor using computational chemistry methods provides better views on understanding the dehydration process. In pure adsorption and diffusion, the smaller kinetic diameter of water is the most important factor in decreasing the adsorption and increasing the diffusion of water vapor in silica pores. Moreover, in the mixed-use guest molecules, the hydrogen bond of the water vapor molecule and siloxane and the interaction between methane and water are effective factors in separating water vapor from methane in the process of dehydration of natural gas. Computational studies using Monte Carlo and molecular dynamics simulation showed that the highest amounts of adsorption calculated in pure and binary mixture adsorption are related to methane and water vapor, respectively. Furthermore, water vapor in a pure diffusion is more than methane, and in binary mixture diffusion, methane vapor shows a higher diffusion coefficient.

Selection of jaw crushers to be used in the first size reduction stages can be a challenge in the design of comminution circuits, given the impossibility of conducting tests at full scale and the limited representativity of small-scale tests. An alternative that has emerged is advanced simulation using the discrete element method (DEM). However, it requires detailed testing with very coarse particles, which can be challenging. The work presents detailed characterizations of particle shapes, breakage model, and contact parameters for simulations in Rocky DEM of an iron ore from Brazil. Validation consisted in comparing predictions to laboratory jaw crushing test results. Good agreement was found between measured and predicted throughputs, whereas simulations marginally underpredicted power and some overpredicted product fineness.

2,5-Dimercapto-1,3,4-thiadiazole modified wheat bran (DMTD-WB), a bio-sorbent synthesized by immobilizing DMTD onto WB, demonstrated outstanding selectivity for Ag(I) recovery from multi-metal wastewater. Under optimized conditions (30 °C, pH 3.0, dosage of 6.00 g L⁻¹), an Ag(I) adsorption efficiency of 98.15 % was achieved. Fixed-bed adsorption experiments further confirmed its selectivity, whereas regeneration tests indicated a recovery efficiency of 81.43 % for Ag(I) after five cycles. Thermodynamic analysis revealed a maximum adsorption capacity of 60.39 mg g⁻¹ at 40 °C. Kinetic and mass transfer studies identified chemisorption via coordination as the dominant adsorption mechanism, with the homogeneous solid diffusion (HSD) model providing a satisfactory fit for the adsorption kinetics. Overall, this study highlights DMTD-WB as a sustainable and efficient adsorbent for Ag(I) recovery, offering a value-added approach to agricultural waste utilization in wastewater treatment.

Pyrolysis is a thermal decomposition process occurring without oxygen, producing liquid oil, gases, and biochar from biomass. The key factor controlling pyrolysis is the thermal energy supplied intensity to the biomass. This study investigates the impact of heating boundary conditions on biomass pyrolysis through a mathematical model incorporating mass and energy conservation, solved numerically using the volume element method. The model is validated against experimental temperature data from a single spherical wood particle under convective heating. It is then applied to a sawdust layer under two conductive heating modes: constant temperature and insulated boundary. Results show that constant temperature heating accelerates pyrolysis threefold and increases tar and gas yields, whereas insulation slows heat transfer, delaying temperature stabilization but producing denser, higher yield char. These findings emphasize the importance of boundary conditions in optimizing biomass conversion.