Waste Carbon Research Articles

Adsorption of Phosphate from Aqueous Solution Using Hydrochar Produced from Agricultural Wastes

Excess phosphorus (P) in agricultural runoff can cause eutrophication in nearby waterbodies. Therefore, it is crucial to remove P from agricultural runoff before it reaches aquatic environments. This study evaluated the P adsorption potential of adsorbents prepared via co-hydrothermal carbonization of multiple agricultural wastes, including dairy manure (DM), corn stover (CS), and eggshell (ES), followed by thermal activation. The performance of the prepared adsorbents was investigated by both batch and column experiments. The activated hydrochar (AHC) with a DM/CS/ES ratio of 1:0:1 showed the highest P adsorption capacity of 209 ± 0.6 and 65.97 ± 9.04 mg/g in batch and column experiments, respectively. The P adsorption mechanism was well described by the Langmuir isotherm model (R2 > 0.8802) and the pseudo-second-order kinetics model (R2 > 0.8989). The adsorbent indicated the longest breakthrough and exhaust time of 210 and 540 min, respectively, with an adsorbent dose of 1 g and an initial concentration of 25 mg P/L. The breakthrough curve was well described by the Thomas model (R2 > 0.971). Thus, this study indicates that AHC with eggshell has high potential for use as an adsorbent for P removal from agricultural runoff.

MrFeed Pro50 FF supplementation improves growth of Largemouth Bass fed a diet containing 160‐g/kg fish meal

AbstractObjectiveThis study aimed at evaluating the role of a novel commercial product, MrFeed Pro50 FF (MP50), as a functional ingredient with which to formulate low‐fish‐meal diets for Largemouth Bass Micropterus nigricans.MethodsSeven test diets were examined. A reference diet (RD) contained 400‐g/kg fish meal, and a control diet (C) was formulated by replacing 60% of the fish meal in RD with poultry by‐product meal. The other five diets were formulated by adding MP50 to C at 5.0 (D50), 7.5 (D75), 10.0 (D100), 12.5 (D125), or 15.0 (D150) g/kg. Fish (initial body weight = 9.2 ± 0.1 g) were fed the test diets for 8 weeks.ResultThe MP50 supplementation level significantly affected weight gain, final body weight, carbon retention efficiency, energy retention efficiency (ERE), hepatosomatic index (HSI), viscerosomatic index (VSI), the ratio of fish meal consumption to fish production (RCP), and carbon waste. The weight gain of fish fed D50, D75, and D100 was greater than that of fish fed C and D150. The ERE was greater in fish fed D50 and D100 than in fish fed C and D75. The HSI and VSI were greater and nitrogen and carbon wastes were lower for fish fed D50 and D100 than in fish fed C. Fish fed D50, D75, and D100 exhibited greater weight gain and lower RCP values compared with fish fed RD. The weight gain of fish fed RD did not significantly differ from the weight gain of fish fed C, D125, and D150, confirming that the minimum fish meal level could be reduced to 160 g/kg.ConclusionThis study indicates that MP50 at 5.0–10.0 g/kg can be used as a functional ingredient in low‐fish‐meal diets for Largemouth Bass.

Exploring the potential of waste carbon fiber reinforced epoxy for high‐performance electromagnetic interference shielding

AbstractThe waste carbon fiber reinforced epoxy (WFRE) is difficult to recycle and high‐value reuse due to its irreversible cross‐linked structure. Currently, many recycling methods are flawed, rendering effective recycling unattainable and resulting in the waste of high‐value carbon fibers and increased environmental pollution. In this study, the production of high‐aspect‐ratio carbon fiber powder from WFRE was achieved through the application of solid‐state shear milling technology. The prepared EP/WFRE/CNT composites exhibited commendable mechanical properties and good electromagnetic interference (EMI SE) shielding efficiency, owing to the excellent dispersion and interfacial adhesion. The EMI SE value of EP/WFRE/CNT composites reached 21.9 dB, meeting the basic demand in the civil field. The flexural modulus of EP/WFRE/CNT composites reached 5914 MPa with the incorporation of 5 wt.% CNT. Moreover, the storage modulus of composite at 40°C increased from 2299 MPa for neat epoxy to 3006 MPa for composites. This research proposes a novel application of WFRE as good mechanical performance material for electromagnetic interference shielding, demonstrating the potential for commercial‐scale applications.Highlights Solid‐state shear milling can effectively peel epoxy resin. Solid‐state shear milling can preserve the high aspect ratio of carbon fiber. EP/WFRE/CNT has a flexural modulus of up to 5914.8 MPa. EP/WFRE/CNT has EMI SE that reaches 21.9 dB. CNT and carbon fiber synergistically formed conductive network.

The carbon crater: Comparing anthropogenic greenhouse gas emissions to historical planetary events

Equilibrium climate sensitivity modeling relies heavily on paleoclimate records that were affected by meteorite impacts and volcanic explosions. This paper conducts a thought experiment by re-assembling known data and theories to shed new light on anthropogenic carbon waste. Anthropogenic activity, meteorite impacts and volcanic explosions all extract material from the Earth’s crust and deposit it in the atmosphere. This thought experiment tests if the mass of anthropogenic greenhouse gas emissions from 1851 to 2021 is comparable to the mass of atmospheric emissions from historical planetary events. Approximately 3.60 trillion tons of anthropogenic carbon dioxide equivalents are converted into volume and then transformed into the shape of a meteorite impact structure named the “Carbon Crater.” The 35 km crater (bounded by 34%–68% confidence intervals of 25–45 km) would rank 23rd on the list of known impact structures. The 2.6 km projectile required to create the Crater would be a 10 on the 1–10 Torino hazard scale described as “. . .capable of causing global climatic catastrophe. . .” The estimated re-occurrence interval for a projectile of this size is 5.3 million years. An interval of this time in Earth’s recent history predates homo sapiens. The Crater’s volume is exponentially larger than the 1883 eruption of Krakatoa and ranks as an 8 (“mega-colossal”) on the 0–8 Volcanic Explosivity Index. The thought experiment indicates that the Carbon Crater’s scale is comparable with large historical biospheric events. These results likely confer few direct implications for the study of the paleoclimate in climate modeling but might change conceptual understandings of atmospheric human waste. Additional empirical research is required to understand the potential impact of the Carbon Crater on conceptual change.

Valorization of process water from hydrothermal carbonization of food waste by dark fermentation

Hydrothermal carbonization (HTC) of food waste produces hydrochar—a suitable biofuel—and process water (PW), which has a high organic content suitable for material and energy recovery. In this work, we study the effect of pH (4.8, 5.3, and 6.0) and organic loading rate (OLR; 2.5, 5.0, and 7.5 gCOD L−1 d−1) throughout the dark fermentation (DF) of PW from the HTC of food waste (180 °C, 1 h) in a continuous stirred tank reactor. The highest hydrogen yield (197.5 mL H2 L−1 d−1) was reached at pH 4.8 and OLR 5 gCOD L−1 d−1, associated with a prevalence of Clostridium bacteria. The highest volatile fatty acids concentration (10.2 gCOD·L−1) was achieved at pH 4.8 and OLR 7.5 gCOD L−1 d−1, with a dominance of Actinobacteria phylum. The integrated system HTC-DF allowed a potential energy recovery of 11.2 MJ kg−1.

Towards cleaner energy: An innovative model to minimize NOx emissions in chemical looping and CO2 capture technologies

The urgent global challenges of climate change and environmental issues have catalyzed the development of CO2-capture-ready technologies incorporating fluidization, such as fluidized bed (FB) and circulating fluidized bed (CFB) combustion under oxy-fuel conditions, chemical looping combustion (CLC), chemical looping with oxygen uncoupling (CLOU), in-situ gasification chemical looping combustion (iG-CLC), and calcium (or carbonate) looping (CaL) systems. While these technologies have the potential to reduce CO2 emissions significantly, the persistent presence of nitrogen oxides (NOx = NO + NO2) as pollutants remains a critical environmental concern.This paper introduces a comprehensive fuzzy logic-based model for predicting NOx emissions (FuzzyNOx model) from solid fuel combustion in fluidized beds of chemical looping systems. This innovative model takes into account a wide range of operating parameters, including fuel type, fuel particle size, fuel moisture content, air/fuel ratio, and temperature. It also explores advanced coal and biomass combustion modes, including air-firing, oxyfuel, iG-CLC, and CLOU. Furthermore, it delves into the intricacies of two distinct facilities: the 5 kWth dual-fluidized bed Chemical-Looping-Combustion of Solid-Fuels (DFB-CLC-SF) facility at Czestochowa University of Technology, Poland, and the calcium looping dual-fluidized bed (CaL DFB) facility at Niigata University, Japan.Bituminous coal, semi-anthracite, and wood chips are utilized as fuels. Moreover, three various oxygen carriers (OCs) for chemical looping combustion were employed, namely ilmenite, copper oxide (60 % wt.) supported by carbonate waste from ore flotation, and copper oxide (60 % wt.) supported by ilmenite (20 % wt.) and fly ash. Bituminous coal, semi-anthracite, and wood chips are utilized as fuels.The developed knowledge-based fuzzyNOx model allows the optimization of operating parameters to reduce NOx emissions from CO2 capture technologies.

Enhancing Hydrothermal Carbonization of Food Waste with Landfill Leachate: Optimization, Methane Recovery, and Sustainable Energy Generation

Enhancing Hydrothermal Carbonization of Food Waste with Landfill Leachate: Optimization, Methane Recovery, and Sustainable Energy Generation

Hydrothermal carbonization of woody waste: Changes in the physicochemical properties and the structural evolution mechanisms of hydrochar during this process

The Chinese medicine residue (CMR) is composed of wet woody waste, including licorice and ephedra, so using hydrothermal carbonization (HTC) to recover renewable energy from the CMR is a suitable treatment method. An in-depth analysis of the physicochemical properties and structural evolution mechanism of hydrochars is helpful in fundamentally promoting the energy utilization of traditional Chinese medicine waste residue. Therefore, this study analyzed the physicochemical properties and morphological structure of hydrochar produced under varying HTC conditions using multiple testing methods. The evolution of the hydrochar's structural characteristics can be categorized into three stages: component decomposition, structural rearrangement, and carbonization. During the component decomposition and carbonization stages, numerous nanoscale micropores form within the hydrochar. These micropores' specific surface area and pore volume can reach up to 113.420 m2/g and 0.01913 cm3/g, respectively. The highest fractal dimension values for D1 and D2 are 2.6354 and 2.5565, while the maximum values for the microcrystalline stacking height (Lc) and the average number of crystalline layers (Nave) are 0.3354 and 1.9968, respectively. Consequently, the hydrochar produced during these stages exhibits a rougher pore surface and a more complex structure, making it more suitable for adsorbing heavy metals from soil and sequestering CO2. During the structural rearrangement stage, the hydrochar exhibits higher contents of fixed carbon (FC), MgO, P2O5, and a higher C/N atomic ratio, with maximum values of 38.51%, 0.99%, 1.12%, and 28.49, respectively. Thus, the hydrochar produced during this stage is more suitable for soil remediation and nutrient recovery.

Valorization of carbon soot ash for the selective capture of lead ions from industrial waste water–A waste to resource approach

Landfills are struggling to accommodate the increasing amounts of carbon soot ash waste from oil refineries. Due to extensive industrial productions, large quantities of lead ions are released into the environment, which not only pollutes the environment but also affects flora and fauna. In this work, these urgent environmental issues will be tackled by studying the use of modified carbon soot ash for specific heavy metal adsorption. Carbon soot ash modified with chemical leaching and physical ball-milling was loaded onto the surface of graphene oxide. This adsorbent was found to selectively adsorb and remove toxic lead ions (>99%) from a mixed heavy metal solution. The adsorption efficiency was found to increase with temperature (20–60 °C) and pH (2–8). Langmuir isotherm and pseudo-second order kinetics were found to fit the adsorption process through curve fitting, where the adsorbent reached a maximum capacity of 194.55 mg/g. Potential mechanisms for lead adsorption and metal specificity are also discussed here. This work aligns with the waste-to-resource pathway, where waste carbon soot ash is diverted from landfilling and is formulated as a specific heavy metal adsorbent, that shows promise for environmental remediation.

Tangerine peel-derived nitrogen-doped carbon dots incorporated chitosan/pullulan-based active packaging film for bread packaging

Citrus peel waste carbon dots based on nitrogen-doped (N-TanCD) were developed by a hydrothermal strategy to deliver active packaging fillers and characterized by transmission electron microscopy, photoluminescence, and Fourier transform infrared analyses. The addition of N-TanCD into chitosan-pululan (CS/Pul@N-TanCD) polymer blend amplified the tensile strength of the composite film by 22.8%, whereas the antioxidant activities against DPPH and ABTS reached 62.7% and 91.6%, respectively. The proposed film showed blocked 98.8% of UV-A and 100% of UV-B without affecting the film’s transparency. The CS/Pul@N-TanCD film lowered the contamination of L. monocytogenes and E. coli by more than 4 and 5log CFU/mL, respectively. Sliced bread was packaged using CS/Pul-based films and stored for 12 days at 50% relative humidity and 25 °C to investigate changes in the quality of the bread. It was found that bread packaged with CS/Pul film integrated with N-TanCD maintained excellent bread quality relating to appearance, moisture content, hardness, weight loss, and total viable bacterial count.

Preparation of Ti3AlC2 MAX-phase as a precursor material using industrial waste carbon flex for MXene synthesis

MAX phase represents a new class of solids that combine some of the best attributes of metals and ceramics, exhibiting unusual, mechanical, electrical, and thermal properties. Further Ti3AlC2 MAX phase is exfoliated to create 2D nanosheet material called Ti3C2 MXene and both have unmatched qualities for difficult and unusual applications. The Ti3AlC2 MAX phase powder is the precursor material to synthesize the Ti3C2 MXene nanosheets, but the cost effective synthesis of Ti3AlC2 powder is still a challenging problem which ultimately decides the quality and cost of Ti3C2 MXene. In this paper, we present the novel synthesis of Ti3AlC2 MAX phase using carbon flex generated as an industrial waste from aluminum, Steel, and other metal industries in composites production. To the best of our knowledge we first time novely report the use of Industrial waste carbon flex as a base carbon material to partially replace commercial graphitic carbon powder in Ti3C2 synthesis. The effect of adding carbon flexes precursor to synthesizing Ti3AlC2 MAX phase solving many current challenges. In present work we comparatively report the physicochemical study of the MAX phase synthesized with three different carbon precursors to establish the role of industrial waste carbon flex in the quantitative growth of Ti3C2MXene as the final product.

Co-hydrothermal carbonization of lignocellulosic biomass and swine manure: Optimal parameters for enhanced nutrient reclamation, carbon sequestration, and heavy metals passivation

Hydrochar, the primary product of hydrothermal carbonization (HTC) of wet organic waste, is recognized as a versatile, carbon-abundant material with diverse applications. However, optimizing its performance for specific uses remains challenging. Therefore, this study introduced a co-HTC process involving carbon-rich lignocellulosic materials and ash-rich livestock manure [i.e., Zanthoxylum bungeanum branch residue (ZB) and swine manure (SM), respectively]. The impacts of HTC temperature (i.e., 180 °C, 220 °C, and 240 °C) and mass ratios (i.e., 1:0, 7:3, 5:5, 3:7, and 0:1) on hydrochar properties (e.g., pH, EC, nutrient contents, heavy metal content and availability, chemical stability, etc) and the characteristics of process water were evaluated. Results reveal that co-HTC dramatically improved the quality of hydrochars compared with that derived from a single feedstock. Notably, the ZB:SM ratio had a more substantial impact on total nutrient content, carbon stability, and heavy metal accumulation and mobility. Additionally, the synergistic effects of ZB and SM were greatly dependent on the HTC temperature. By adjusting the feedstock mass ratio and HTC temperature, a highly-functionalized hydrochar can be produced. For example, hydrochars produced at 240 °C with a 7:3 ZB to SM ratio (HC240-7) is optimal for degraded soil amendment, enhancing carbon sequestration and nutrient supplementation. Results from this study could provide valuable insights for improving waste management through HTC and expanding the environmental and agricultural application of hydrochar.

Grave-to-cradle dry reforming of plastics via Joule heating

Both plastics and CO2 are waste carbon resources, and their accumulation in nature has led to severe environmental pollution. However, simultaneously converting plastic waste and CO2 into value-added chemicals remains a challenge. Here we demonstrate a catalytic reforming process that converts plastics and CO2 into syngas over an electrified FeCrAl heating wire. The temperature of the electrified heating wire can quickly exceed 800 °C, facilitating the decomposition of polyethylene into gaseous hydrocarbons. The high-temperature heating wire promote the CO2 deoxygenation, resulting in the generation of CO, as well as the dehydrogenation of gaseous hydrocarbons. Significantly, the additional O species from CO2 and the carbon species from hydrocarbons can react to form CO, maintaining the high catalytic activity of the electrified heating wire. This novel approach is of paramount to achieving a circular economy in addressing the ongoing environmental crisis caused by the accumulation of plastic waste and excessive CO2 emissions.

Identification of mechanisms and experimental implementation for enhancing the interfacial force between oxygen functionalized waste carbon fibers and polyamide resin

To recycle waste carbon fibers (CFs) and utilize them as a composite material with polyamide–6 (PA–6), the oxidation of the carbon surface is crucial for enhancing its bonding with PA–6 without damaging the waste CFs. However, the most effective oxygen-containing functional group (O–group) was hitherto unknown. In this study, computational simulations demonstrated that incorporating O–groups enhanced the interfacial bonding force via hydrogen bonding between the oxygen of the O–groups and hydrogen (N–H) of PA–6. Among various O–groups, the bonding of lactone groups to PA–6 was energetically most favorable, corroborated by different oxidation treatments such as acid, heat, and plasma. As the reaction time or temperature increased, the amount of O–groups, such as lactones, increased. Regardless of the oxidation treatment type, an increase in the amount of O–groups increased the interfacial force, and this tendency was predominantly observed in lactone groups. However, excessive surface oxidation introduced defects on the surface of CFs, which reduced the interfacial force. The modification of waste CFs by identifying the proposed mechanisms lays the groundwork for synthesizing high-quality waste CF composites.

Visible Light‐Switchable Lattice Oxygen Sites for Selective C−H and C(O)−C Bond Electrooxidation

Lattice‐oxygen is highly oxidizable, ideal for electrocatalytic C−H oxidation but insufficient alone for C(O)−C bond cleavage due to the non‐removable nature of lattice sites. Here, we present a visible light‐assisted electrochemical method of in‐situ formulating removable lattice‐oxygen sites in a nickel‐oxyhydroxide (ESE‐NiOOH) electrocatalyst. This catalyst efficiently converts aromatic alcohols and carbonyls with C(O)−C fragments from lignin and plastics into benzoic acids (BAs) with high yields (83–99%). Without light irradiation, ESE‐NiOOH’s intrinsic lattice‐oxygen is non‐removable and inert for C(O)−C bond cleavage. In‐situ characterizations show light‐induced lattice‐oxygen removal and regeneration via OH– refilling. Theoretical calculations identify the nucleophilic oxygen attack on ketone‐derived carbanion as a rate‐determining step, which can be remarkably facilitated by removable lattice‐oxygen to activate α‐C−H bonds. As a proof‐of‐concept, an “electrochemical funnel” strategy is developed for high‐efficiency upgrading aromatic mixtures with C(O)−C moieties into BA with up to 94% yield. This in‐situ removal‐regeneration approach for lattice sites opens an avenue for the tailored design of interfacial electrocatalysts to selectively upcycle waste carbon sources into valuable products.

Visible Light-Switchable Lattice Oxygen Sites for Selective C-H and C(O)-C Bond Electrooxidation.

Lattice-oxygen is highly oxidizable, ideal for electrocatalytic C-H oxidation but insufficient alone for C(O)-C bond cleavage due to the non-removable nature of lattice sites. Here, we present a visible light-assisted electrochemical method of in-situ formulating removable lattice-oxygen sites in a nickel-oxyhydroxide (ESE-NiOOH) electrocatalyst. This catalyst efficiently converts aromatic alcohols and carbonyls with C(O)-C fragments from lignin and plastics into benzoic acids (BAs) with high yields (83-99%). Without light irradiation, ESE-NiOOH's intrinsic lattice-oxygen is non-removable and inert for C(O)-C bond cleavage. In-situ characterizations show light-induced lattice-oxygen removal and regeneration via OH- refilling. Theoretical calculations identify the nucleophilic oxygen attack on ketone-derived carbanion as a rate-determining step, which can be remarkably facilitated by removable lattice-oxygen to activate α-C-H bonds. As a proof-of-concept, an "electrochemical funnel" strategy is developed for high-efficiency upgrading aromatic mixtures with C(O)-C moieties into BA with up to 94% yield. This in-situ removal-regeneration approach for lattice sites opens an avenue for the tailored design of interfacial electrocatalysts to selectively upcycle waste carbon sources into valuable products.

Pemanfaatan Limbah Karbon-Aktif Melalui Reaktivitasi Termal Sebagai Adsorben Ion Kadmiun pada Lindi TPA

The leachate produced at the Kawatuna landfill, managed without proper waste treatment systems, has been found to contain heavy metals like cadmium (Cd), which contaminate groundwater and pose significant health risks. This study investigates the reduction of Cd ions in leachate through adsorption using activated carbon (AC) waste. The AC waste was reactivated via thermal methods, including phosphoric acid immersion, heating, and washing. Morphological analysis was conducted using scanning electron microscopy (SEM), and adsorption efficacy was evaluated with atomic absorption spectroscopy (AAS). The findings indicate that AC waste with a pore diameter of 2.95 µm can be effectively reused as an adsorbent through thermal reactivation. Specifically, AC treated with H3PO4 immersion and heating exhibited a pore diameter of 3.24 µm, while heating and washing resulted in a pore diameter of 2.29 µm. The Cd concentration in leachate treated with AC immersed in H3PO4 followed by heating showed a modest reduction, whereas the heating and washing treatment led to a significant decrease in Cd levels, achieving an adsorption capacity of 3.92 mg/L within 50 min. This method presents a viable alternative for managing landfill leachate at the Kawatuna site.

Effect of Carboxymethyl Cellulose and Polyvinyl Alcohol on the Dispersibility and Chemical Functional Group of Nonwoven Fabrics Composed of Recycled Carbon Fibers.

In this study, recycled carbon fibers (rCFs) recovered from waste carbon composites were used to manufacture wet-laid nonwoven fabrics. The aim was to improve dispersibility by investigating the changes in the dispersibility of carbon fibers (CFs) based on the content of the dispersant carboxymethyl cellulose (CMC) and the binder polyvinyl alcohol (PVA), and the length and basis weight of the CFs. In addition, the chemical property changes and oxygen functional group mechanisms based on the content of the CMC dispersant and PVA binder were investigated. The nonwoven fabrics made with desized CFs exhibited significantly improved dispersibility. For nonwoven fabrics produced with a fixed binder PVA content of 10%, optimal dispersibility was achieved at a dispersant CMC concentration of 0.4%. When the dispersant CMC concentration was fixed at 0.4% and the binder PVA content at 10%, the best dispersibility was observed at a CF length of 3 mm, while the maximum tensile strength was achieved at a fiber length of 6 mm. Dispersibility remained almost consistent across different basis weights. As the dispersant CMC concentration increased from 0.2% to 0.6%, the oxygen functional groups, such as carbonyl group (C=O), lactone group (O=C-O), and natrium hydroxide (NaOH), also increased. However, hydroxyl group (C-O) decreased. Moreover, the contact angle decreased, while the surface free energy increased. On the other hand, when the dispersant CMC concentration was fixed at 0.4%, the optimal binder PVA content was found to be 3%. As the binder PVA content increased from 0% to 10%, the formation of hydrogen bonds between the CMC dispersant and the PVA binder led to an increase in C=O and O=C-O bonds, while C-O and NaOH decreased. As the amount of oxygen increased, the contact angle decreased and the surface free energy increased.

Introduction, Types, Properties, and Applications of Switchable Solvents: A Review

AbstractSwitchable solvents (SS) are a class of liquids with the unique ability to significantly alter their physical properties in response to external stimuli such as changes in temperature or the introduction or removal of CO2 gas. This reversible behaviour allows them to return to their original state with minimal changes, making them highly advantageous for various applications. A notable example of a switchable solvent is waste carbon dioxide gas, which is non‐toxic, non‐flammable, and cost‐effective. The versatility of switchable solvents extends to their polarity and physical states, which can be modified through molecular adjustments, opening new pathways for research and industrial applications. This review provides a comprehensive overview of switchable solvents, including their classification, history, properties, and applications, with a particular focus on their role in green chemistry. The types of switchable solvents discussed include Switchable‐Polarity Solvents (SPS), Switchable‐Hydrophilicity Solvents (SHS), and Switchable Water. Each type is examined in terms of synthesis, chemical properties, and development. The desirable properties of switchable solvents, such as their efficiency and recyclability, make them suitable alternatives to traditional solvents in various fields. Their applications range from water treatment and oil extraction to cleaning solid particles and recovering residual motor oil. Additionally, switchable solvents have proven effective as reaction media and in recovering polystyrene from foam. This paper also highlights the environmental benefits of switchable solvents, emphasizing their role in reducing the ecological impact of chemical processes. The potential for future developments in this field is significant, with ongoing research aimed at enhancing their performance and expanding their applications. By providing a detailed analysis of switchable solvents, this review aims to support researchers and industry professionals in developing more sustainable and efficient chemical processes.

Hydrothermal carbonization of combined food waste: A critical evaluation of emergent products

Hydrothermal carbonization (HTC) increasingly appears as an eco-friendly method for managing food waste (FW). In this work, a combination of FW was subjected to HTC, and products were critically evaluated. This involved a lab-scale pressure reactor and optimization of HTC conditions: temperature (220–340 °C) and residence time (90–260 min) via central composite design type of response surface methodology (CCD-RSM). Results showed varying temperatures and residence time to impact the hydrochar (HC) and hydrothermal carbonization aqueous phase (HTC-AP) properties. Although HC produced through HTC exhibited lower ash content (<2%) despite higher fixed carbon (>55 %) with respect to the raw FW, the heating value of HC ranged from 19.2 to 32.5 MJ/kg. Temperature primarily influenced FW conversion, affecting carbonaceous properties. Saturated fatty acids (SFA) were found to be predominant in the HTC-AP under all tested operating conditions (77.3, 48.4, and 37.1 wt% for HTC at 340, 280, and 220 °C in 180 min, respectively). Total phosphorus recovery in HC and HTC-AP respectively peaked at 340 °C and 220 °C in 180 min. The study concludes that HTC holds promise for energy-dense biofuel production, nutrient recovery, and fostering a circular economy.