Environmental Progress & Sustainable Energy最新文献

The downstream processing of biocrudes obtained from direct biomass pyrolysis poses significant challenges due to stability issues, necessitating costly upgrading for further coprocessing with refinery feeds. This study examines the impact of torrefaction pretreatment on pyrolysis product distribution and biocrude composition using sawdust (SD) and groundnut shell (GS) feeds. Torrefaction was conducted at varying temperatures (200, 250 and 300°C) for 30 min under different reactor conditions. Increasing the severity of torrefaction resulted in decreased biocrude yields with reduced water content and gas formation, particularly evident with GS. A torrefaction temperature of 250°C and 30 min of pretreatment yielded higher phenolics and hydrocarbons. This increase in phenolics can be attributed to lignin enrichment during torrefaction, which, in the presence of a catalyst, undergoes deoxygenation leading to hydrocarbon formation. The influence of feed particle size, whether in powder or pellet form, on biocrude yield and composition was found to be minimal. Catalytic pyrolysis of SD using molecular sieve catalysts yielded the highest hydrocarbon (42%) and aromatic content (44%) at catalyst to biomass ratios of 1:1 and 2:3. The combination of torrefaction and pyrolysis was shown to enhance the quality of biocrude by increasing its hydrocarbon content, but at the expense of lower liquid yields. Experimental observations were supported by statistical analysis tools such as principal component analysis, which assessed pyrolysis product yields and composition.

In order to promote syngas yield and reduce carbon emission, Ni loaded ZrO₂ (Ni/ZrO₂) catalysts were prepared for the co-pyrolysis of cypress sawdust and green algae in a two stage fixed bed reactor. The syngas yield, syngas component, and carbon emission were investigated. The results showed that Ni/ZrO₂ catalyst could obviously increase the combustible gas component in syngas. H₂ content was increased from 7.5% (single component) and 8.12% (co-pyrolysis) to 16.56% (catalytic pyrolysis). CO content was also increased from 19.62% (single component) and 19.46% (co-pyrolysis) to 25.94% (catalytic pyrolysis). However the catalyst had a little effect on the syngas yield compared with single component pyrolysis and co-pyrolysis. The pyrolysis temperature could make great influence on the carbon emission. The carbon emission reduction was increased from 33.32 to 234.25 g CO₂ and from 105.94 to 369.23 g CO₂, respectively for green algae and cypress sawdust.

The outer prickly shells of the Ricinus communis (castor plant) have intrigued researchers interested in the synthesis of carbon black (CB) nanoparticles because of their excellent biocompatibility, low toxicity, and widespread availability. Both chemical and physical synthesis methods, such as pyrolysis and ball milling, are employed to obtain the fine-sized CB nanoparticles. The ball milling process is done for 5 h to reduce the size of the biochar from the pyrolysis process. The as-synthesized CB nanoparticles are characterized using Fourier transform infrared spectroscopy, x-ray diffraction, and field emission scanning electron microscopy analysis. The energy dispersive spectrum also confirmed that the nanoparticles are highly composed of carbon and oxygen. CB nanoparticles made from green materials are added to a low-concentrated biodiesel blend of waste fried edible oil at a rate of 100 ppm. The experiment was performed in a single-cylinder diesel engine under varying compression ratios (CRs) (16:1–18:1), loads (0–16 kg), and exhaust gas recirculation (EGR) rates (0%, 15%, and 25%). The results revealed that the existence of carbon in nanoparticles increased the mean gas temperature, and the mass fraction burned was also slightly higher than diesel. Raising both CR (16:1–17:1 and 16:1–18:1) and EGR (25%) boosted the cylinder pressure of CBB30 (1.844% and 10.391%, respectively). In contrast, it lowered the net heat release rate (7.88% and 14.56%, respectively). Similar to this, smoke emissions decreased by 6.38% and 15.02%, respectively, at the same CR and EGR parameters. On the other hand, brake thermal efficiency slumped by 7.22% and 10.13% concurrently.

This study aims to design a new multi-stage photoreactor with immobilized ZnO and assess its performance in reducing textile wastewater toxicity using solar energy. The electric conductivity measurement is retained as a detection method to obtain the residence time distribution (RTD) function. The RTD is then used to characterize the hydrodynamic behavior of the photoreactor and to evaluate its deviation from the distribution curves of ideal reactors. Solar experiments are conducted to demonstrate the performance of this multistage reactor towards the degradation of a textile azo dye namely Solophenyl Red 3BL (SR 3BL). The influence of the flow rate and the SR 3BL initial concentration (C_O) are considered. The variation of the flow rate slightly influences the SR 3BL photodegradation efficiency and it is inversely proportional to its concentration. The study of the reuse of the immobilized catalyst shows that the degradation efficiency of 98% is reached even after multiple photocatalytic cycles. The figure of merit collector area per order was in the range of 35 to 110 $��m^2�/�m^3�\text{order}�$. This result provides useful information for scaling up and estimating energy efficiency of the reactor.

Increased chromium usage in industrial applications as chromium III and chromium VI, include metal plating, steel alloys, leather processing, medical applications, and chromium dyeing operations, has resulted in water pollution by Cr (VI) ions, which being toxic and carcinogenic has developed into significant environmental and health problems. The purpose of this research is to remove Cr (VI) ions from synthetic wastewater utilising modified sawdust as an inexpensive adsorbent. Two modified sawdust samples were produced, one using sodium hydroxide and one using sulfuric acid. The experimentation, based on several batch systems, has been undertaken at 25–65°C with 0.5–1.5 g/L sawdust dosage. These conditions were applied to remove Cr (VI) ions at concentrations of 1–6 ppm at pH values from 3 to 10. The results have shown that adsorption onto sawdust followed an intraparticle diffusion mechanism with various rate parameters from 0.65 to 5.24 mg g⁻¹ min, for treated and untreated sawdust. The distribution coefficient $��\left(k_c\right)�$, enthalpy $��\left(�\Delta �H�\right)�$, thermodynamic standard free energy $��\left(�\Delta �G�\right)�$, and entropy $��\left(�\Delta �S�\right)�$ were determined from a number of temperature studies. Kinetic studies showed that the pseudo-second order model gave the optimum correlation to the experimental results. The Freundlich and Langmuir isotherms were applied to analyse the experimental equilibrium results. The optimised conditions for the adsorption process were obtained using the D-optimal design method, and the maximum removal percentage of 100%, was determined at pH = 3, T = 25°C, adsorbent dosage = 1.5 g/L, and an initial Cr (VI) concentration = 5.72 ppm.

A halophytic microalga Tetraselmis sp. biomass diluted with deionized water and seawater was converted to biocrude with the hydrothermal liquefaction (HTL) process in a batch reactor at 310, 330, 350, and 370°C, 15 min with $��\approx �20�$ %w/w solids. The biocrude yield, carbon, and energy recovery in biocrude and hydrocarbon species distribution from deionized water base HTL (DW HTL) and seawater base HTL (SW HTL) were evaluated. The results revealed that irrespective of reaction medium, the yield in biocrude increased with an increase in temperature, reaching a maximum of 50–56 wt% at 350°C, characterized by a higher heating value of up to 35.6 MJ/kg. The carbon and energy recovery at 350°C were 85% and 89% respectively, for SW HTL, while the DW HTL stream was 10% and 12% lower. Also, the GC MS analysis of biocrude obtained from both streams contains a complex mixture of compounds such as hydrocarbons, phenolics, and large amounts of nitrogenated and oxygenated compounds. The metallic constituents in biocrudes derived from both steams showed no substantial variations. The study showed a marginal increase in biocrude yield and its HHV with a reduction in oxygen and nitrogen contents from the SW HTL stream, suggesting the potential of seawater as a reaction medium.

The drying procedure is an important consideration for the silicon powder processing. Herein, a comparative investigation of the drying efficiency, drying performance, and energy consumption of silicon powder after separation and purification of monocrystal silicon cutting slurry by using the hot air, far-infrared and microwave drying treatments. The results show that microwave drying of 30 g silicon powder takes only 12 min, which is much shorter than hot air drying of 200 min and far infrared drying of 40 min. The water evaporation energy consumption of microwave drying reached 73.5 g/kW·h, which was 3.3 times than that of far infrared drying and 16.5 times than that of hot air drying. For 1 kg of silicon powder, the power consumption of microwave drying was 8 kW·h, while the far-infrared drying was 26.7 kW·h, and the hot air drying was 133.4 kW·h, respectively. Therefore, effects of microwave power, drying temperature and drying time on the dehydration rate of silicon powder were investigated and optimized by response surface method, demonstrating that the microwave drying dehydration rate of 30 g silicon powder could reach 97.65%, and the power consumption could be reduced to 6.7 kW·h/kg under the conditions of microwave power of 1000 W, drying temperature of 89°C and drying time of 12 min. The present study shows that microwave drying of silicon powder is an energy-saving and efficient process with good industrial application prospects.

Solar distillation using solar stills is widely recognized as a clean and cost-effective method for producing freshwater. However, due to its straightforward design, solar still performance is greatly influenced by various physical characteristics. Many researches have evaluated solar still parameters, while only a few articles have concerned physical ones. Therefore, this article aims to investigate the effect of different physical parameters on solar still productivity through thermal modeling. The theoretical results were validated with those of a previous experimental model, showing a good agreement with each other. The results reveal that daily productivity experiences significant improvement with an increase in plate emissivity or insulation thickness. Conversely, an increase in water mass, glass absorptivity or insulation thermal conductivity leads to a substantial reduction in productivity. Notably, water transmissivity and plate absorptivity do not affect productivity. Modest enhancements in productivity can be achieved by reducing the effective emissivity between water and glass. While the initial temperature of water has a minor impact on productivity at low water mass, it exhibits a substantial improvement effect at high water mass. These results can be a good guidance for the designers and manufacturers to develop more efficient designs that maximize the production of clean water.

Naturally occurring xanthan gum (XG) has much commercial importance because of its excellent physicochemical, eco-friendly, and non-toxic properties. It is used in various applications like protein extraction, wastewater treatment, tissue engineering, drug delivery, food packaging, and so forth. XG is a natural material, and it has some limitations related to the mechanical stress, thermal stability, and hydration. To overcome the limitation, XG can be modified by adding third component or modification of operation for specific applications. XG can be modified by physical, genetically, enzymatically, or chemical processes. Revamped XG also enhances the efficiency toward adsorbing toxic metal ions and organics from synthetic or industrial effluents. The emphasis of present review article is to address the structural characteristics along with the focus on the developing chemically modified XG like grafted, cross-linked, nanocomposites, and functionally modified biopolymer. However, this review commences thorough discussion on numerous ways of modifications, which can be attempted in XG structure, expanding its applications for heavy metal ion along with dye removal.