Search Results (1,771)

Photocatalytic CO₂ reduction to high-value-added C₂+ products is a practical route from an economic viewpoint for advancing the industrialization of CO₂ conversion. Despite significant progress in catalyst modification in recent years (such as defect engineering, heterostructure construction, and single-atom modification), the generation of C₂+ products still faces challenges due to the slow kinetics of multi-electron reactions and the high thermodynamic barrier for C-C coupling. Moreover, the severely imbalanced molar ratio of CO₂ to H₂O in the traditional liquid-phase reaction systems exacerbated the challenge to the unfavorable situation. This article summarizes various strategies to improve the yield of C₂+ products through the regulation of reaction environments, including: (1) increasing the partial pressure of CO₂ to enhance its solubility; (2) using alternative solvents like ionic liquids to reduce water content; (3) transitioning the reaction system from liquid phase to gas phase; (4) designing a three-phase (gas–liquid–solid) interface or floating photocatalysts to optimize reactant transfer and local concentration; (5) utilizing photothermal synergistic effects to enhance the reaction temperature and efficiency under concentrated light. It also discusses the role of different reactor designs in improving the reaction environment. Finally, it emphasizes that future research should pay more attention to the optimization of the reaction environment engineering in addition to catalyst design, providing new perspectives for achieving efficient and highly selective C₂+ products in CO₂ photoreduction. Full article

Given the rising demand for phosphate, a critical mineral for many countries due to its essential role in fertilizer production and global food security, reprocessing waste generated during phosphate mining has become increasingly important to mitigate demand pressures and reduce the environmental impact of the mining industry. This study aims to develop a sustainable hydrometallurgical process to recover residual phosphate from a lithology present in mining waste rock. To this end, a thermodynamic analysis was first performed to assess reaction feasibility during leaching and precipitation. A two-step process was then proposed: the first step involves leaching carbonates (mainly calcite) using acetic acid, optimized through response surface methodology based on a Box–Behnken design; the second step consists of precipitating calcium with phosphoric acid to produce a value-added by-product (brushite) while simultaneously regenerating the acetic acid. A preliminary economic assessment was conducted to evaluate process feasibility. The results show that acetic acid is highly selective for carbonates, yielding a phosphate concentrate containing 30% P₂O₅ with complete phosphate recovery under the following conditions: 3.4 molL⁻¹ acid concentration, 28 °C reaction temperature, a liquid-to-solid ratio of 6 mLg⁻¹ (14.2% solids), and a reaction time of 49 min. In the precipitation step, a calcium recovery of 97% was achieved under optimal conditions (20 °C, 15 min, 500 rpm stirring, and a P:Ca ratio of 1). Furthermore, the preliminary economic assessment indicates that the developed process, based on the use of an organic acid and its recycling, generates a net profit, confirming its economic viability and its contribution to environmentally sustainable phosphate processing. Full article

Low-concentration methane emissions from landfills, manure management, wastewater treatment, and ventilation streams are difficult to mitigate using conventional capture and oxidation because of high air-to-fuel ratios, variable flows, and unfavorable economics. Methanotrophic bioreactors provide an aerobic biological route to oxidize methane at ambient conditions and, in selected cases, enable valorization into biomass and bioproducts. This review synthesizes methanotrophic reactor technologies for dilute methane, emphasizing the design and operational constraints that control performance. We classify systems into (i) fixed-film gas–solid configurations (biofilters, biocovers, biotrickling filters, and bioscrubbers), (ii) suspended-growth gas–liquid reactors (stirred tanks, bubble columns, and loop/airlift designs), (iii) membrane-based and intensified contactors that decouple methane and oxygen delivery and enhance mass transfer, and (iv) hybrid and in situ approaches for diffuse sources. This review presents key metrics and discusses how mass transfer, moisture and temperature control, nutrient supply, and microbial ecology interact to define achievable removal. We further summarize recent techno-economic and life-cycle studies to identify dominant cost drivers, particularly air handling and gas–liquid transfer, and the concentration regimes where biological oxidation is competitive with catalytic or thermal alternatives. Full article

Fungal spores are the main active ingredients in fungal preparations. In this study, we evaluated vegetative spore (oidia) production of the Latvian isolate of Phlebiopsis gigantea PG 182 using liquid-surface (LSF) and solid-state (SSF) fermentation processes in the 450 mL and 700 mL jars, respectively. The effects of medium depth (0.5 or 0.7 cm), malt extract (ME) syrup concentration (25, 50, and 75 g/L) and duration time of cultivation (7, 14, 21 and 28 days) on oidia production and partly on mycelium biomass yield were evaluated in the LSF experiments. The highest spore yields (0.88 ± 0.22) × 10⁷ and (1.10 ± 0.31) × 10⁷ (95% CI) (oidia/g liquid medium) were achieved on day 28 in the LSF process using a medium depth of 0.5 cm and ME concentrations of 25 and 50 g/L, respectively. While in the SSF process, pine sawdust enrichment with wheat bran (0, 5, 10, 15, and 25%) and cultivation time (14, 21 and 28 days) were evaluated under conditions of 8 cm substrate depth. The most promising result was obtained on day 28 with 10% bran supplementation, reaching (24.73 ± 5.09) × 10⁷ (95% CI) (oidia/g solid medium), which is 1.45 and 3.17 times more than after 21 and 14 days of cultivation, respectively. Our findings indicate that SSF with a 10% wheat bran additive produces superior spore yields for P. gigantea isolate PG 182, exceeding benchmarks set by comparable research. Potential for further improvement remains by optimizing the wheat bran (WB)-to-substrate ratio and refining the thermal processing of the solid substrate. Full article

Post-recycling plastic waste contamination in freshwater ecosystems represents an escalating environmental threat, while algal blooms continue to generate vast quantities of underutilized biomass. Addressing both challenges, this study investigated the co-hydrothermal liquefaction of Chlorella pyrenoidosa with representative post-recycling plastic wastes polypropylene, polyethylene terephthalate, and Nylon-6 as a dual-resource valorization strategy. Experiments were conducted in a 1000 mL high-pressure batch reactor at 350 °C for 30 min, with varying biomass-to-plastic feed ratios. Systematic product characterization, including functional group, elemental analysis, Van Krevelen diagrams, and heating value assessment, was employed to elucidate synergistic effects and evaluate product quality. Results revealed that co-processing with polyethylene terephthalate achieved the highest biocrude yield of 71.5%, with an enhanced higher heating value of 35.7 MJ kg⁻¹, surpassing the 62.4% yield from microalgae alone. Nylon-6 blends also improved oil yield to 69.6% while producing aqueous fractions enriched with ε-caprolactam, indicating the recovery of valuable nitrogenous monomers. In contrast, PP exhibited limited reactivity toward oil generation but produced carbon-rich biochar with a higher heating value up to 41.4 MJ kg⁻¹, comparable to high-grade solid fuels. Mechanistic analyses confirmed that plastics acted as hydrogen donors, promoting deoxygenation, radical stabilization, and selective depolymerization, thereby improving both liquid and solid fuel fractions. By employing ecologically relevant freshwater feedstocks from Thailand, this work advances beyond prior studies dominated by marine biomass or synthetic surrogates, providing realistic insights into resource integration within polluted inland waters. The co-hydrothermal liquefaction process simultaneously mitigates eutrophication-driven algal blooms and persistent plastic pollution while generating fuels and functional carbon materials, directly contributing to a circular bioeconomy. The demonstrated synergy between biological and synthetic wastes highlights a scalable, catalyst-free route to energy-dense biofuels and multifunctional biochar. These outcomes align strongly with SDG which offer a pragmatic framework for waste-to-energy transition in freshwater-dependent regions. Full article

The valorization of agro-industrial by-products is a sustainable approach to recovering high-value bioactive compounds. In this study, Opuntia ficus-indica (L.) Mill. seed press residues were investigated as a source of phenolic and flavonoid compounds using microwave-assisted extraction (MAE). A multi-step optimization strategy was implemented, combining preliminary single-factor experiments (OVAT), response surface methodology based on a Box–Behnken design (BBD), and machine learning modeling using K-nearest neighbors coupled with the dragonfly algorithm (KNN_DA), followed by desirability-based validation. The effects of ethanol concentration (50–100%), microwave power (400–800 W), extraction time (2–4 min), and liquid-to-solid ratio (30–50 mL/g) were evaluated on Folin–Ciocalteu reducing capacity (FCRC), AlCl₃ complexation response, and antioxidant activity assessed by DPPH radical scavenging and reducing power assays. Optimal conditions were identified at 50% ethanol, 800 W microwave power, 4 min extraction time, and a liquid-to-solid ratio of 47.28 mL/g. Under these conditions, FCRC reached 376.85 ± 0.23 mg GAE/100 g DW and 49.16 ± 0.33 mg QE/100 g DW for AlCl₃ complexation response, with prediction errors of 2.80% and 0.82%, respectively. The optimized extracts exhibited enhanced antioxidant activity. These findings confirm MAE as a rapid and environmentally friendly technique and highlight the predictive performance of the KNN_DA model for process optimization. Full article

The aim of this study was to investigate the potential for co-bioleaching of ground printed circuit boards (PCBs) and flotation tailings using a single-stage biohydrometallurgical process. The ground PCB sample was a finely divided waste product from industrial shredding, which was collected using an air filtration system. The flotation tailings sample was mainly composed of pyrite (49%), quartz (29%), gypsum (8%), feldspar (8%), and chlorite (6%). The experiment was carried out in laboratory-scale reactors at 35 °C with constant aeration and a flotation tailings pulp density of 5% (solid-to-liquid ratio). In a control reactor, only flotation tailings were leached. In an experimental reactor, both flotation tailings and ground PCBs were leached simultaneously. The experiment was conducted in two stages. In the first stage, the experiment was carried out in a batch mode. The second stage involved two reactors operating continuously in cascade. During the experiment, we monitored the dynamics of several key parameters as a function of PCB concentration, including pH, redox potential, the concentrations of Fe³⁺ and Fe²⁺ ions, and the number of microbial cells. The 16S rRNA gene analysis revealed that the presence of PCBs had a significant effect on the composition of the microbial community. The concentration of PCB was gradually increased in order to examine the limits of the process and optimize potential economic benefits. The increase was done in 3 stages: 5 g/L in the first stage, from 5 to 12 g/L in the second stage, and up to 35.5 g/L in the third stage. However, this increase had a negative effect on the pyrite oxidation rate and the effectiveness of PCB bioleaching in continuous mode. The bioleaching efficiency of copper from printed circuit boards (PCBs) was above 70% in batch mode and above 80% in continuous mode at PCB concentrations up to 12 g per liter. Copper recovery decreased to around 53.1–61.6% as the PCB concentration continued to increase. The nickel leaching efficiency in batch mode was 46.3 ± 4.8%. In continuous mode, the nickel recovery decreased as the PCB concentration increased, reaching 48.53% in the first stage, then declining to 37.62% in the second stage and finally dropping to 27.06% in the third stage, depending on the higher concentration of PCB. Full article

Amid growing environmental pressure and increasing demand for resource sustainability, the efficient recovery of valuable metals from spent lithium-ion batteries (LIBs) has become a critical challenge in the field of resource recycling. Therefore, a novel approach is presented for selective lithium (Li) and manganese (Mn) separation from LiNi_xCo_yMn_1−x−yO₂ by combining carbothermic reduction roasting and selective leaching. Low-cost glucose (C₆H₁₂O₆) was selected as the reduction roasting reductant, which converts the cathode materials into water-soluble lithium carbonate (Li₂CO₃), water-insoluble cobalt (Co), nickel (Ni), and manganese oxide (MnO). Wet magnetic separation was employed to preferentially extract Li while simultaneously removing excess carbon from Ni, Co, and MnO. Under optimal roasting conditions at 600 °C for 90 min followed by wet magnetic separation with a liquid–solid ratio of 30 mL/g for 30 min, 95.42% of Li was preferentially extracted. Subsequently, at a formic acid (HCOOH) concentration of 1.6 mol/L, liquid–solid ratio of 6 mL/g, and leaching time of 30 min, 94.29% of Mn was selectively extracted from the wet magnetic separation products, whereas Ni and Co were leached at 6.13% and 7.22%, respectively. The acid-leaching residue can be recycled as a Ni-Co alloy. Full article

Recovery of scandium from chloride-bearing process liquors formed during titanium–magnesium production remains constrained by trace-level metal content and chemically aggressive solution matrices. Within the present study, the retention behaviour of Sc³⁺ species in strongly acidic chloride media was examined through batch-mode interaction with gel-type sulfonated cation exchangers, namely KU-2-8, Lewatit SP112H, Purosorb SAC140H, and Purolite C-150H. Quantitative evaluation of sorption efficiency was performed by calculating equilibrium uptake (q_e), phase distribution factor (K_d), and percentage recovery (R). Under identical liquid–solid ratios, the Lewatit SP112H matrix exhibited superior affinity toward dissolved scandium, achieving q_e = 179.82 mg/g and K_d = 172.41 mL/g. Equilibrium fitting procedures revealed that scandium uptake by Purosorb SAC140H conforms to monolayer-type retention described by the Langmuir formalism (R² = 0.9786), whereas sorption on Lewatit SP112H proceeds over energetically non-uniform sites and is more adequately represented by Freundlich and Dubinin–Radushkevich approximations. The observed retention characteristics establish a selection framework for ion-exchange media applicable to scandium concentration from acidic chloride hydrometallurgical streams. Full article

Jojoba oil is a well-established skin-beneficial liquid wax with high value in topical formulations. Bigels, as preferred semi-solid dosage forms, serve as versatile platforms by incorporating hydrogels and oleogels to leverage their advantages and address their limitations. In this study, jojoba oil bigels were developed using sorbitan monostearate (20%, w/w) as an oleogelator and different hydrophilic bases, 1% Carbomer 940, 6% methylcellulose, or 20% Poloxamer 407 gel, with all concentrations expressed relative to the corresponding phase. Nine bigels were obtained by varying hydrogel-to-oleogel ratios (90:10–70:30). They were evaluated in terms of their organoleptic, microstructural, and textural characteristics. Both the hydrogel matrix type and the phase proportion impacted the studied properties. Carbomer bigels displayed the highest spreadability, methylcellulose formulations showed the greatest adhesiveness, and poloxamer systems exhibited maximum firmness and cohesiveness, with a comparatively more homogeneous phase distribution. The increase in oleogel content enhanced firmness and cohesiveness while modulating spreadability and adhesiveness in a hydrogel-dependent manner. Moreover, all designed formulations remained physically stable after centrifugation, but only those containing 80% carbomer gel or 70% or 80% poloxamer gel preserved their mechanical characteristics without significant changes after freeze-thawing. Besides identifying three promising biphasic dermal drug delivery platforms, these findings reinforce the tunability of bigels through the careful component selection. Full article

This study addresses the challenge of achieving efficient separation of vanadium and chromium from vanadium–chromium slag (VCS) while simultaneously tackling issues related to artificial granite waste residue (AGWR), such as its substantial stockpiling and associated air pollution. AGWR was used as a substitute calcination additive for calcium carbonate to achieve efficient separation through a calcination-leaching process. Orthogonal experiments were conducted to investigate the effects of AGWR addition amount, calcination temperature, and calcination time on the leaching behavior of vanadium and chromium. During calcination, vanadium reacts with CaO (a decomposition product of AGWR) to form acid-soluble calcium vanadate. Concurrently, chromium hydroxide decomposes into chromium oxide, which is poorly soluble in dilute acid. Subsequent leaching of the calcination product with dilute sulfuric acid leaches vanadium (V) into the solution, while chromium (Cr) remains in the residue, thus achieving separation. The experimental results showed that under the conditions of 30% AGWR addition; calcination at 850 °C for 1 h; leaching at 90 °C for 2 h with a liquid-to-solid ratio of 10:1 and a sulfuric acid concentration of 50 g·L⁻¹; the leaching rate of vanadium reached 85.68%, whereas that of chromium was only 2.34%. These results demonstrate highly efficient separation of vanadium and chromium, offering valuable insights for resource recovery from both VCS and AGWR. Full article

The Aspen Plus process simulation with techno-economic assessment was used to evaluate the industrial-scale feasibility of enzymatic hydrolysis of corn stover. Choline chloride (ChCl)-based deep eutectic solvents containing lactic acid (LA), formic acid (FA), and acetic acid (AA) as hydrogen bond donors were used to pretreat the corn stover. Optimal pretreatment conditions (140 °C and a solid-to-liquid ratio of 1:30) achieved high levels of lignin (77.3%, 72.9% and 73.5%) and xylan (90.2%, 93.5% and 90.5%) removal for ChCl/LA (1:5), ChCl/FA (1:5) and ChCl/AA (1:5), respectively, while retaining significant levels of glucan (81.3%, 76.2% and 82%). Subsequent enzymatic hydrolysis at 10% substrate loading yielded glucose at 93.7%, 91.2% and 82.7%, respectively. The DES pretreatment and solvent recovery units accounted for 41.9% of capital costs at a solid-to-liquid ratio of 1:30. Increasing the solid-to-liquid ratio to 1:10 reduced total capital investment by 41.6%. Operational costs were heavily influenced by DES solvent consumption (81.2–92.7% of raw material costs). Of the DESs, the ChCl/FA (1:5) pretreatment process offered the best economic performance, achieving a minimum selling price (MSP) of USD 988.2 per ton. Sensitivity analysis identified glucose yield as the most critical cost driver (±20% variation caused a ±25% change in the MSP, followed by DES recycling efficiency. Fluctuations in DES prices had a limited impact (±20% variation caused a change in MSP of only 2.4–3.8%) due to the solvent recycling mechanism. This study demonstrates the potential of DES pretreatment for industrial application through process optimization, solvent recycling and valorization of by-products. Full article

This study investigated a feasible recycling and detoxification process for waste tire ash containing hazardous Zn and Al using acid leaching, followed by layered double hydroxide (LDH) synthesis. The novelty of this work is the direct conversion of a Zn/Al/Fe/Ca-rich real waste system into a phosphorus removal material, in which LDH-related uptake and secondary hydroxyapatite formation cooperatively immobilize phosphorus. Waste tire ash mainly consists of Zn, Al, Fe, Ca, and Si, most of which can be effectively leached with hydrochloric acid (HCl). The optimum leaching conditions for high extraction efficiency involved treatment with 10 M HCl for 10 min at 20 °C (solid–liquid ratio: 50 g/L). Under these conditions, the elution concentrations of Zn and Al from the residue decreased to 0.3 and 0.17 mg/L, respectively, meeting the Japanese leaching standards, whereas the raw ash showed significantly higher values. From the leached solution, LDH-containing products with high phosphorus removal capacity were synthesized at 40 °C for 2 h by adjusting the pH to 11.5. A phosphorus removal performance of 2.0 mmol/g was obtained owing to the formation of hydroxyapatite. The combined process of HCl leaching and LDH synthesis enables the detoxification of waste tire ash and the production of an environmental purification material. Full article

Hedera helix (HE) contains diverse bioactive constituents, including triterpenoid saponins, flavonoids, and phenolic acids, which exhibit various pharmacological activities. In this study, ultrasound-assisted extraction (UAE) combined with natural deep eutectic solvent (NADES) was employed to enhance the extraction efficiency and elucidate the underlying mechanisms. Among the tested formulations, a ternary system composed of malonic acid (Mal), N,N′-dimethylurea (DMU), and 1,4-butanediol (1,4-BDO) achieved the highest efficiency for extracting eight target compounds from the HE leaves. In addition, the key interactions among NADES components were confirmed by Fourier-transform infrared (FT-IR) spectroscopy, providing valuable insights into the extraction mechanism. The UAE process was systematically optimized through single-factor experiments. Subsequently, response surface methodology (RSM) identified the optimal conditions as ultrasonic time of 45 min, solid/liquid ratio of 1:54 g/mL, and ultrasonic temperature of 42 °C. Scanning electron microscopy (SEM) elucidated the microstructural alterations in plant cell walls induced by NADES-UAE, alongside the enhanced penetration and disruption mechanisms. In vitro bioactivity revealed that the NADES-extracted HE exerted strong inhibitory effect on HT-29 colon cancer cells. Overall, these findings demonstrate the high effectiveness and sustainability of NADES-UAE for extracting HE bioactive compounds and provide valuable implications for the industrial-scale production of plant-based functional products. Full article

Pursuing the so-defined biorefinery approach, residual biomass, such as agro-industrial wastes, should first be exploited for the extraction and production of high-value-added products and then processed for energy valorisation through anaerobic digestion (AD). However, the treatments applied to achieve the first goal could impact biogas yield. This problem can be solved by co-digesting the treated biomass with others. In this study, Brewery’ Spent Grain (by itself, a good biogas producer) was treated with an ionic liquid (IL) composed of triethylamine and sulfuric acid [TEA][HSO₄] for lignin removal. The residual biomass (pulp, BSGp) was then used for biogas production. The tests revealed a marked reduction in the total quantity of biomethane (per unit of volatile solid—VS). In detail, 6.82 × 10⁻⁴ Nm³CH₄/gVS of biomethane was produced with BSGp, against 1.31 × 10⁻³ Nm³CH₄/gVS with BSG. The lack of organic nitrogen after the IL-based treatment prevented biogas production, resulting in a shorter production period. To compensate for the nitrogen deficiency and restore the optimal C/N ratio, BSGp was mixed with Lemna minor (LM), an aquatic weed with a high nitrogen content. By itself, LM cannot be considered a good biogas producer as proven in this study. However, the co-digestion of LM with BSGp extended the production period and kept the daily production close to that registered in test made with the sole BSGp, thus achieving a total biomethane production equal to 1.83 × 10⁻³ Nm³CH₄/gVS, even higher than the one registered with untreated BSG. Full article