Cleaner Chemical Engineering最新文献

Quality water is used for various daily chores like drainage, drinking, sanitation, agricultural, and other industrial applications, thus being the need of the hour. Water is a dominant raw material in manufacturing pharmaceuticals and chemicals; reliable and superior water sources are needed for many processes, including cooling, refining, and material extraction. The purpose of urban and industrial wastewater treatment is to eliminate contaminants, destroy toxicants, neutralise coarse particles, and destroy bacteria to increase the consistency of the discharged water to maintain the allowable amount of water to be discharged into or for agricultural property. So, the goal of water treatment is to lower BOD, COD, eutrophication, etc., in receiving water sources and stop radioactive compounds from spreading through the food chain. Pharmaceutical wastewater has a wide range of characteristics, including a high amount of organic matter, microbial contamination, a high salt content, and the inability to biodegrade. Following secondary application, residual quantities of suspended solids and dissolved organic matter exist. Therefore, advanced treatment is necessary to increase the efficiency of pharmaceutical wastewater effluent. In the methods described in this study, Advanced Oxidation and Bioremediation—the latter emerges as the most environmentally and commercially viable option. This paper discusses the many types of bioremediations, their applications, and their limits in the treatment of industrial wastewater with the goal of reducing the ecotoxicological impacts of pharmaceutical wastewater.

Better understanding of the dispersion and deposition of sub-micron particles in supercritical CO₂ (SCO₂) is crucial for the safe operation of supercritical thermal equipment. In present study, the numerical simulation was carried out to evaluate the deposition features of sub-micron particles in SCO₂. The anisotropic flow in the gas phase was predicted using the Re-Normalization Group (RNG) k-ε turbulent model and the particle trajectory was tracked using the discrete particle model (DPM). Moreover, the particle deposition under heating and cooling condition were presented. The effects of particle type, wall temperature, inlet flow velocity, temperature and pressure on particle deposition were investigated. The analysis found that the deposition velocity is more applicable to judging the particle deposition than the dimensionless deposition velocity. When SCO₂ is cooled, it promotes particle deposition, and when it is heated, it prevents deposition due to thermophoretic forces. Particles are easily deposited when SCO₂ exceeds the pseudo-critical point in the gaseous-like region. Moreover, stainless steel has greater deposition velocity than graphite due to the large density. The inlet flow velocity has different effects on particle deposition. It promotes the deposition of small particles, medium particles remain stable, and large particles first decrease and then increase. The particle diameter is closely related to the deposition distance. The deposition probability for 1 μm, 10 μm and 50 μm is 63%, 77% and 85% at 0–0.2 m, respectively.

The Nuclear Power Plant, which uses uranium as a fuel, is considered as a clean source of energy with low carbon footprint and less environmental damage. In processing the uranium ore, the filtration of alkaline leach slurry generated by oxidative pressure leaching is a challenge due to very fine grind size coupled with high total dissolved solutes (TDS). The present study aimed at improving and understanding the filtration of the leach slurry with the help of slurry rheology. The effect of solid concentration, temperature, particle size, and dosages of dewatering aids on the rheological behavior of the slurry and the filtration performance was investigated. The slurry rheology was delineated by the Herschel–Bulkley model, temperature effects were incorporated using the Arrhenius type model, and particle size distribution (PSD) was represented by the Rosin–Rammler PSD model. The dosages of dewatering aids were compared using rheological parameters. It was found that the filtration rate decreases as solid concentration increases (10 to 75%, w/w) due to an increase in the shear stress (9.93 to 757 Pa at 1400 s⁻¹). The leach slurry showed shear thickening at ≤ 60% solids (w/w) and shear thinning at ≥ 70% solids. The maximum solid packing volume fraction was found to be 0.59 and 0.54 at 1300 and 441 s⁻¹, respectively. Increase in filtration rate was observed at elevated temperatures as the apparent viscosity (at 1300 s⁻¹) decreased from 0.0195 Pa.s at 20 °C to 0.0135 Pa.s at 70 °C. The fluid flow activation energy was determined to be 5.5 and 7.1 kJ/mol at 1110 s⁻¹ for 50 and 73% solid concentration (w/w), respectively. When the particle size (d₉₀) was changed from 66 to 42 µm, a decrease in filtration rate was observed due to an increase in apparent viscosity from 0.0120 to 0.0163 Pa.s at 1400 s⁻¹. The high molecular weight polyacrylamide based non-ionic synthetic flocculant N 100 and non-ionic biodegradable polysaccharide surfactant guar gum formed flocs through the bridging mechanism and gave best flocculation results, and therefore selected. The present work helps the researchers in better understanding and improving the filtration process of ore slurries.

Camel dung (CM) and date stone (DS) are biomass resources that are abundant across the Gulf region and have the potential to produce sustainable renewable fuels and specialty products. Copyrolysis of CM with DS is an intriguing research approach to boosting both the production and quality of pyrolysis products, particularly biochar. The current study investigated the bio-energy potential of CM, DS, and CD-DS blend by assessing their physicochemical attributes, pyrolysis characteristics, and kinetic behaviour using thermodynamic analysis. To investigate the pyrolysis behaviour, the materials were thermally decomposed using a thermogravimetric analyser under non-isothermal conditions at different heating rates in a nitrogen environment. The findings of the physicochemical analysis established the bio-energy potential of the feedstocks for long-term energy generation. Thermal degradation profiles of the samples revealed multistage degradation due to the various components in their structure. While a positive synergistic effect between DS and CD was observed in the thermal profile of the blend. The average apparent activation energy of CD from the Friedman method, Flynn–Wall–Ozawa (FWO) model, Kissinger–Akahira–Sunose (KAS) method, and Starink model was 324, 167, 157, and 158 kJ/mol, respectively. Friedman, FWO, KAS, and Starink methods yielded average activation energies of 621, 315, 276, and 279 kJ/mol for DS, respectively. The mean activation energy of the blend estimated using the Friedman, FWO, KAS, and Starink methods was 210, 216, 206, and 207 kJ/mol, respectively. The thermodynamic outcomes reveal that slow pyrolysis of the specified feedstocks is a nonspontaneous process requiring external energy for their degradation. The findings of this study may aid in a better understanding of reaction processes and the expansion of pyrolysis applications of DS, CD, and their mix.

Management of Fly ash (FA), a thermal power plant waste, is a major global issue since a sizeable fraction of fly ash's annual generation is not effectively valorised. FA is a heterogeneous mix of crystalline and amorphous phases containing significant amounts of aluminium and silicon elements alongside high surface energy, making FA an economically suitable catalyst support framework. Accordingly, the development of a low-cost, recyclable fly ash-supported tin oxide solid acid catalyst has been investigated for esterification of stearic acid (SA) with methanol to produce methyl stearate (MS); which is regarded as biodiesel and is presently being blended with petro-diesel as a cleaner fuel substitute. The characterisations of the prepared SnO₂-FA catalyst (SFC) have been performed through TGA, XRD, BET-BJH and FESEM-EDS analyses. The optimal process conditions (assessed through response surface methodology (RSM)) viz. 475.06 °C calcination temperature, 3.39:1 weight ratio of SnCl₄.5H₂O: FA and 73.16 °C esterification temperature rendered a significant 85.734% SA conversion. The optimal mesoporous SFC comprising SnO₂ active phase possessed 11 m²/g specific surface area (much greater than that of the support material, FA: 0.60 m²/g); 0.0109 cc/g pore volume and 2.9 nm modal pore size. Important fuel properties of the optimally produced MS conformed to the ASTM biodiesel (B100) standards. The overall environmental sustainability of the process assessed through the openLCA platform (ecoinvent database 3.8) revealed lower environmental impacts of the developed process. The LCA study divulges the fossil depletion potential and the global warming potential of the overall process to be 4.34 kg oil Eq. and 4.03 kg CO₂-Eq. respectively. The present study could establish a green and effective FA valorisation avenue through a sustainable methyl stearate (biodiesel) production process.

The present work was successfully designed to prepare effective adsorbents from Moringa oleifera shells (PMOS) and chemically activated by zinc chloride (ZnCl₂) and calcined at different temperatures as 200, 300, 400 and 500 °C, for methyl red (MR) dye removal. Thereafter, the prepared materials were characterized using diverse analytical techniques as SEM, FTIR, XRD and BET. The results showed that the activated carbon prepared at 500 °C had a larger specific surface area (610.031 m²/g) compared to its original precursor (only 3.16 m²/g) or even the rest of prepared adsorbents. The maximum MR sorption capacity of the PMOS of 500 °C was the highest as much as 28.67 mg/g at ambient temperature.

The sorption capacity of raw M. oleifera shells and the tests of calcination effect of this material on the improvement of their capacity were studied in batch system by varying operating conditions such as: contact time, dye concentration, adsorbent dose, pH and temperature. The results confirmed that PMOS calcined at 500 °C with 1.0 g/L of dose and in acidic to neutral media at 25 °C, gives the most significant elimination rate (25.46 mg/g). Thermodynamic study shows that the retention of MR is an exothermic physisorption using PMOS calcined at 200 and 300 °C. Unlike materials calcined at 400 and 500 °C, the process was exothermic chemisorption.

In addition, adsorption isotherms and kinetics were studied using experimental data fitting to further understand and describe the dynamic equilibrium, dynamic kinetics, and mechanism of MR adsorption onto the calcined materials. As compared to Freundlich isotherm model, the Langmuir isotherm model provided a better fit with the experimental data for the different calcined PMOS (at 200 °C, 300 °C, 400 °C and 500 °C) exhibiting a maximum monolayer adsorption capacity of 25.45, 27.10, 28.13 and 28.91 mg/g, respectively. The linear pseudo-first-order kinetic model was found to be suitable for describing the adsorptive kinetics of all prepared activated carbons.

Lignocellulosic materials represent one of the clean alternative energy sources that have carbon in their building blocks, which can be processed into liquid biofuel and useful chemicals. Elemental compositions of biomass such as carbon (C), hydrogen (H) and oxygen (O) are key indicators for establishing calorific value, energy efficiency and carbon footprint during direct application as fuel and feedstock in thermochemical conversion. These characteristics usually require very expensive equipment, which may not always be readily available for examination of biomass feedstock. This study presents a new predictive non-linear model for ultanal characteristics of lignocellulosic biomass (C, H and O) derived from the proxanal attributes such as fixed carbon (FC), volatile matter (VM) following least square method. Four hundred and fifty (450) proximate analysis data from literature were used for model development and fifty (50) experimentally determined data points for model validation. The elemental composition {C=C[VMFC,(VM)²,(FC)], H=H[(VMFC),VM,FC] and O=O[(VM)^0.75,(1/FC)^0.33]} prediction models were developed and evaluated using indices such as average absolute percentage error (AAPE), average bias percentage error (ABPE) and coefficient of determination (R-squared). The results of analysis showed AAPE, ABEP and R-squared of 2.12%, 0.06% and 0.9993; 2.88%, 0.11% and 0.9989; 3.16%, -0.04% and 0.9982 for C, H and O model respectively. This suggests that the developed models could be used to predict the ultanal attributes of lignocellulosic biomass within 60<VM<90 and 10<FC<30 with high fidelity. The models would serve as a quick means of assessing lignocellulosic biomass prior to any bioenergy application.

Genetic algorithm (GA) assisted optimization was used in the adsorptive removal of bromocresol green (BCG) from solution. The adsorbent was acid-functionalized corn cob (AFCC). The properties of the adsorbent were investigated via instrumental analysis involving Fourier Transform Infra-Red (FTIR) and Scanning electron microscopy (SEM). Non-linear modeling involving various degrees of isotherm models were used in the isotherm study. Adaptive neuro-fuzzy inference systems (ANFIS), response surface methodology (RSM), and artificial neural network (ANN) were used to model the BCG removal. The result of the instrumental analysis showed that the properties of the AFCC were enhanced after the acid carbonization process with a surface area of 903.7 m²/g. The modeling and predictive adeptness of the ANFIS, RSM, and ANN was very significant with correlation coefficient (R²) of 0.9984, 0.9865, and 0.9979 with root mean square error (RMSE) of 0.00308, 0.00898, and 0.00351, respectively. Validation of the models’ optimization indicated maximum adsorption capacities of 38.04, 34.41, and 41.94 mg/g for RSM-GA, ANN-GA, and ANFIS-GA, respectively. Freundlich, Khan, and Marczewski-Jaroniec isotherms best described the adsorption isotherm for two-term, three-term, and four-term isotherm modeling respectively. Calculated values of Gibbs free energy change (∆G_max = -7.55 KJ/mol), enthalpy change (∆H = 35.84 KJ/mol), and entropy change (∆S = 130.20 Jmol⁻¹K⁻¹) indicated the adsorption process was spontaneous, endothermic and with increased randomness respectively. The study showed that the low-cost AFCC obtained from agro-waste has desirable adsorbent properties for the treatment of BCG polluted wastewater.

Traditional methods of disposing and storing plastic waste in Ghana, such as at damping sites and landfills, have put the environment and human life at risk for years. A sustainable and efficient solution is to shift to a circular economy by recycling plastic waste into alternative fuels. Therefore, this study focussed on the segregation of plastic waste and its conversion into fuel products via pyrolysis in the temperature range of 350 – 420 °C. In a kilogram-scale pyrolysis fixed-bed batch reactor, a large quantity of condensate oil was produced with minimal amounts of non-condensable gases, chars, and waxes. Gas chromatography, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermal gravimetric analysis were used to characterise the condensate oils. The measured fuel properties of the various condensate oil types were remarkedly similar to those of commercial fuels (gasoline, diesel, and kerosene). This makes them suitable alternatives to conventional energy sources, with the potential to significantly improve living conditions, reduce environmental pollution, and cut down on the need to import refined fossil fuel. Finally, the condensate oil from the individual plastic waste types outperformed the mixed-plastic waste in terms of fuel properties and yield.

Algal biofuel is a promising green energy for the future, but harvesting algae remains a major challenge. To overcome this obstacle, magnetic separation using magnetic nanoparticles is proposed as a simple, highly efficient yet cost-effective method to collect microalgae. Magnetite (Fe₃O₄) nanoparticles are the typical materials of choice, but their performance varies depending on the pH of the water, furthermore, they can be toxic to algal cells. Hence, a more stable and non-toxic alternative replacement for Fe₃O₄ is needed. In this work, we explore the use of biocompatible manganese-containing magnetic ferrite nanoparticles (NPs) to harvest Chlorella sorokiniana and Scenedesmus obliquus microalgae. Using this novel NP, we achieved a harvesting efficiency of roughly 90% for Chlorella sorokiniana and 80% for Scenedesmus obliquus up to three cycles consistently throughout a wide pH range of 2–12. This was due to the high stability and reversible attachment of the NPs to the algal cells. Surface analysis of the NPs-Algae by Fourier transformed infrared (FTIR), the microbial adhesion to hydrocarbons (MATH), zeta potential, and the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory indicated acid-base interactions and hydrophobicity effects are the driven forces for NPs-algae interaction instead of simple electrostatic attraction. Overall, our study provided a more efficient magnetic harvesting approach for algae and a more in-depth understanding of the separation mechanisms to improve and advance the algae biofuel industry.