Band 23, Heft 5

Cashew nutshell liquid (CNSL), a highly versatile byproduct of the cashew processing industry, offers remarkable potential across a broad spectrum of industrial and chemical applications. Extracted from the soft, spongy honeycomb structure inside the hard outer shell of the cashew nut, this dark reddish-brown, viscous liquid is a rich, renewable source of unsaturated phenolic compounds. Among bio-based raw materials, CNSL stands out for its cost-effectiveness, high chemical reactivity, and wide applicability in the production of polymers, coatings, resins, and biofuels. This review presents a comprehensive analysis of various extraction techniques used to isolate CNSL, with a particular focus on chemical extraction methods. Three primary extraction approaches – thermal, mechanical, and chemical – are discussed, each uniquely influencing the yield and composition of the extracted CNSL. Special attention is given to chemical extraction methods such as solvent extraction, Soxhlet extraction, and supercritical carbon dioxide (SC–CO 2 ) extraction, evaluating their efficiency, selectivity, and scalability. He extracted CNSL typically contains four major constituents: anacardic acid, cardanol, cardol, and 2-methyl cardol, with their relative proportions depending heavily on the extraction technique and operational conditions. Beyond traditional methods, this review also highlights recent advancements in green chemical processes aimed at reducing environmental impacts while enhancing material performance. These innovations pave the way for sustainable production of industrial chemicals and biomaterials from cashew waste, supporting global initiatives toward a circular economy and the principles of green chemistry.

This review offers an in-depth analysis of pyrolysis as a sustainable route for converting corn-based biomass including corn stover, corn cob and corn stalk into valuable bio-oil and biochar. Amidst the growing demand for renewable and environmentally friendly energy alternatives, corn-derived agricultural residues have gained attention as attractive feedstocks due to their widespread availability, cost-effectiveness and ecological advantages. Although various conversion pathways such as chemical, biochemical and thermochemical have been explored, pyrolysis stands out as the most extensively investigated and efficient thermochemical method. Drawing from existing literature, this study systematically evaluates a range of pyrolysis techniques including slow, fast, catalytic, hydro-pyrolysis and microwave-assisted processes. The analysis underscores the significant impact of operational parameters and reactor design on product yield and composition. Nevertheless, key challenges such as catalyst deactivation, process optimization and scalability continue to hinder the commercial adoption of some pyrolysis approaches. By highlighting these issues, the review pinpoints current research gaps and proposes future directions aimed at improving process efficiency and product selectivity. In addition, the review incorporates a sustainability perspective through the lens of life cycle assessment (LCA) offering insights into the environmental impacts, carbon footprint and resource efficiency of bio-oil and biochar production from corn-based biomass. Ultimately, this comprehensive overview serves as a roadmap for advancing pyrolysis technologies toward large-scale and sustainable biofuel production from corn-based biomass.

Access to clean and safe drinking water remains a global challenge, particularly in remote and coastal regions where freshwater sources are scarce or contaminated by seawater. Solar stills have emerged as an eco-friendly and sustainable solution to address these challenges by harnessing plentiful solar energy for water distillation. Despite its potential, the widespread adoption of solar still has been hindered by low productivity and intermittent sunlight throughout the day. To overcome these barriers, researchers worldwide have explored a wide array of performance enhancements in active and passive solar still modifications, as well as design modifications to the integration of fins, nanocoatings, and phase-change materials (PCM). This review explores the application of nanomaterials in both active and passive solar stills. It highlights recent advancements, outlines current challenges, and identifies key areas for future research. The integration of nanotechnology into solar stills holds significant promise for enhancing the efficiency of water purification systems, thereby contributing to sustainable solutions for global water scarcity issues.

This study is the first to compare batch and semi-batch gasifier systems for turning sunflower stalks into useful products, filling an important gap in our understanding of gasification technologies that use biomass fuel. This study investigated the production and characterization of biochar and ash derived from sunflower stalks using batch and semi-batch gasifiers. The conversion process, lasting 90 min, employed the top-lit updraft mechanism to generate sunflower stalk ash and biochar under both systems. The yields of batch-based samples were 34.60 % for biochar (BSB) and 19.40 % for ash (BSA), while semi-batch samples yielded 20.80 % (SSA) and 18.55 % (SSB). Elemental analysis revealed significant carbon enrichment from 44.2 % in raw feedstock to 85.4 % in semi-batch biochar, representing a 93 % increase in carbon concentration. The biochar produced in the batch gasifier exhibited a surface area of 364.127 m 2 /g, compared to 392.508 m 2 /g for the semi-batch gasifier biochar, as determined by BET analysis. Scanning Electron Microscopy (SEM) revealed a more porous structure in the semi-batch biochar. Fourier Transform Infrared Spectroscopy (FTIR) analysis identified both similarities and differences in the functional groups between the biochar and ash samples from both systems. Thermogravimetric analysis (TGA/DTA) showed a higher mass loss in the semi-batch ash (SSA) compared to the batch sample (BSA), indicating greater thermal stability in the batch biochar. These findings showed the potential of sunflower stalk biochar and ash for diverse applications such as soil improvement, pollutant removal, and energy conversion, while also providing insights into optimizing carbonization processes for enhanced material properties.

Greenhouse gas emissions have become a pressing concern in recent times, with CO 2 emerging as the primary culprit behind global warming, rising sea levels, and disruptions to ecosystems. Of all the greenhouse gases, CO 2 ’s impact on global warming stands out as the most significant. To address this issue, activated carbon (AC) has gained prominence as an effective CO 2 adsorption agent, owing to its porous structure, expansive surface area, cost-effectiveness, and environmentally friendly properties. In this current research, activated carbon was produced from castor stalk biomass through a single-stage chemical activation process known as pyrolysis. This method is lauded for its cost-efficiency, simplicity, and minimal environmental impact. Potassium hydroxide (KOH) and aluminum sulfate (ALUM) were employed as the activating agents. Subsequently, the synthesized activated carbon was subjected to Methylene Blue adsorption testing to evaluate its CO 2 adsorption capacity, among other potential applications. The characterization of the activated carbon derived from castor stalk involved a series of techniques, including CHNS analysis, proximate analysis, SEM, FTIR, XRD, and BET surface area analysis. These analyses unveiled the impressive attributes of the castor stalk-derived activated carbon, featuring an exceptionally high surface area of 1,687 m 2 /g, a substantial pore volume of 1.015 cm 3 /g, and a pore diameter of 2.71 nm. Furthermore, the Methylene Blue adsorption test yielded a remarkable value of 447.72 mg/g with 89.5 % adsorption efficiency. High CO 2 adsorption capacity (2.46 mmol/g) was observed over castor stalk-derived activated carbon. The comparative study shows higher CO 2 adsorption capacity in comparison to activated carbon derived from various biomasses using KOH as the activating agent. So, the present study shows activated carbon derived from Castor stalk using KOH and Alum as activating agent can be a promising method for CO 2 adsorption.

Recently, cyclones have been widely recognized as efficient tools for separating particles from solid-gas mixtures in various sectors. The current research examines how the width and quantity of circular holes in the vortex finder of the Stairmand gas cyclone affect the flow field and overall performance. Sixteen cyclone geometries were numerically investigated at inlet velocities of 8.8 m/s and 17.6 m/s. At 8.8 m/s gas velocity, the 4-hole geometry has a lower cut-off diameter than the other configurations. The no-hole geometry displays a lower cut-off diameter (d 50 ) at a gas velocity of 17.6 m/s. The 12-hole geometry achieves the lowest pressure drop at 17.6 m/s. The pressure drop initially increases with an increase in the number of holes up to 5–6 holes and then decreases. At 8.8 m/s, the no-hole geometry demonstrates lower pressure drops. It is found that although the cut-off diameter has an inverse relationship with the number of holes, the pressure drop is related to the number of holes and size. This study offers important new information for improving the construction and functionality of these separation devices in various industrial contexts.

The high cost of utilizing phosphogypsum resources and the low added value of the resulting product represent significant challenges that have limited the large-scale use of phosphogypsum. This work proposes an approach for the valorization of phosphogypsum by converting it into high-value calcium acetate. To enhance the reaction rate and control the overall cost, the carbonation reaction – an essential step influencing product quality in the production of calcium acetate from phosphogypsum – was systematically investigated from a kinetic perspective. The results show that the carbonation reaction follows the shrinking-core model. A kinetic equation was developed within the temperature range of 25–40 °C and sodium carbonate concentration range of 200–350 mol m −3 , and the temperature dependence of the reaction rate constant was established. The experimental results indicate that the carbonation process exhibits a low activation energy. A calcium carbonate purity exceeding 90 % was achieved by reacting phosphogypsum in 0.25 M sodium carbonate solution at room temperature for 10 min. In addition, the removal of impurities originating from phosphogypsum during the reaction process was also discussed, and the final calcium acetate product was characterized to confirm its high purity and structural integrity. The proposed method holds significant potential for reducing production costs and promoting the large-scale, value-added utilization of phosphogypsum.

Bubble growth and formation process directly determines the bubble size, which is crucial for gas-liquid flow systems. Understanding the behaviors of bubble growth and formation in detail is crucial for predicting bubble diameter. This study investigated the effects of orifice parameters ( e.g. , orifice size, contact angle), fluid properties ( e.g. , liquid viscosity, density, surface tension coefficient), and operating conditions ( e.g. , gas inlet velocity, gravitational acceleration) on bubble growth and detachment characteristics ( e.g. , bubble shape, detached diameter, time) under quasi-static conditions using Coupled Level-Set/Volume-of-Fluid method. Empirical correlations of bubble detachment diameter, shape, bubble rising velocity, and bubble-induced liquid velocity at relatively low gas flow rates were proposed to understand the bubble growth mechanism. The mechanism of bubble formation under different orifice wettability conditions was revealed by establishing the relationship between critical and static contact angles. Finally, a new bubble diameter model was developed by considering the effects of a broad range of fluid properties, orifice size, contact angle, and inlet gas velocity. The new model significantly extends the applicability of the traditional bubble formation theoretical model derived from the simple buoyancy force and surface tension force balance, individually decreasing the deviations of predicted bubble diameter at the contact angles of 52 and 105° from 47.3  and 10.47 %–5.41  and 8.14 % and providing some theoretical basis for bubble formation and the reasonable closure of interphase force models based on bubble morphology.

This work was aimed to establish the adsorptive properties of crayfish shell biochars for methylene blue dye removal. The adsorbents were prepared via pyrolysis at 650 and 800 °C and yield the surface area of 665 and 635 m 2 /g, respectively. The latter biochar, designated as CFB800, exhibits a dye adsorption capacity of 50.5 mg/g, which is nearly double that of the former (CFB650), with a capacity of 23.0 mg/g. The equilibrium capacity decreased with increasing adsorbent mass, but increased with increasing initial concentration and temperature. The equilibrium data fitted well with Langmuir model. The methylene blue adsorption onto crayfish shell biochars is favourable and spontaneous. Hence, crayfish shell is a promising resource of biochar to treat dye-containing wastewater.