Carbon Removal Research Articles

Bioremediation of dissolved organic compounds in produced water from oil and gas operations using Chlorella sorokiniana: a sustainable approach.

The sustainable treatment of petroleum-derived produced water (PW), a significant byproduct of oil and gas extraction, presents a persistent problem due to the presence of organic pollutants. This study examines the potential of the microalga Chlorella sorokiniana (C. sorokiniana) for the bioremediation of dissolved organic pollutants in PW. The primary objectives were to evaluate the efficacy of C. sorokiniana in decreasing the levels of dissolved organic contaminants while examining its growth and survival in such a complex environment. The cultivation of C. sorokiniana in photobioreactors containing synthetic produced water (SPW), supplemented with synthetic municipal wastewater (SMW) to provide essential nutrients, was carried out under controlled laboratory conditions. Parameters such as biomass growth, lipid content, and the microalgae's capacity to metabolize organic compounds are monitored over time. The results indicate that, except for 100% PW, maximum biomass output after 16 days ranged from 733 to 1077 mg/L. Total organic carbon (TOC) removal efficiency increased with rising PW concentrations, peaking at 85% for 50% PW. The cultivation period resulted in substantial nitrogen and phosphorus removal from the enriched PW media, achieving a maximum nitrogen removal of 87% at 10% PW and a phosphorus removal of 98.5% at 40% PW. Lipid content ranged from 12 to 16% during this period. In conclusion, C. sorokiniana offers a promising and sustainable approach for the bioremediation of dissolvedorganic compounds in PW. This method provides an eco-friendly option to reduce the ecological impact associated with petroleum-derived PW.

Thermodynamics of Electrochemical Marine Inorganic Carbon Removal.

In recent years, marine carbon removal technologies have gained attention as a means of reducing greenhouse gas concentrations. One family of these technologies is electrochemical systems, which employ Faradaic reactions to drive alkalinity-swings and enable dissolved inorganic carbon (DIC) removal as gaseous CO2 or as solid minerals. In this work, we develop a thermodynamic framework to estimate upper bounds on performance for Faradaic DIC removal systems. To assess the fundamental mass balances of these systems, we first define unit operations in the DIC/total alkalinity (TA) space. By coupling a seawater speciation model to an electrochemical framework, we provide a generalized comparison of gas evolution and mineralization DIC removal routes, focusing on asymmetric charge/discharge systems. We then show how this framework can be extended to other processes, such as those employing dilution schemes. Finally, we provide a minimum energetic assessment of mCDR pathways relative to direct air capture. Overall, this thermodynamic framework aims to guide system and process design and to drive material discovery and engineering for future electrochemical marine DIC removal systems.

Estimating CO2 flows in urban parks: knowns and unknowns

The life cycle climate impacts of urban parks are poorly known. Whereas vegetation and soils can be carbon sinks, building products, energy use, and processes cause emissions. Several studies acknowledge the need for further assessment of urban parks, especially regarding vegetation, soil organic carbon, management and design, together with the development of supportive tools for climate-wise planning. To deepen our understanding of carbon flows of urban parks, we applied life cycle assessment (LCA) and studied the carbon dioxide (CO2) emissions and removals of five urban parks in Helsinki, Finland. The components of the parks were divided into four categories: site preparation, covering and surface structures, vegetation and growing media, and systems and installations. According to our findings, CO2 emissions ranged from 27.08 to 61.45 kgCO2e/m2 and CO2 removals from 11.35 to 16.23 kgCO2e/m2 with uncertainty. Planted woody vegetation and existing forested areas had the highest CO2 uptake among the vegetation types. Moreover, growing media caused on average 35% of total CO2 emissions. As significant volumes of growing media remain necessary to support the growth and establishment of plantings, finding less emission intensive alternatives to peat-based growing medium becomes essential. Other main emissions sources included transportation, and replacements of surface materials, but their dominance is highly dependent on the design, use and maintenance of the park. LCA offers a robust assessment framework for the quantification of greenhouse gas emissions and is evolving towards the including of greenhouse gas removals and storages. However, the inclusion of living organisms would require changes in the mindset of LCA. The level of maturity in the assessment methods differs significantly between the park components. Data and methods are especially lacking for nursery production, maintenance and end-of-life phases of vegetation, soils, and mulches. We also identified uncertainties regarding the estimations of CO2 uptake by woody vegetation, lawns, and meadows due to software limitations and lack of data for local context. Simulating dynamic plantings raises additional questions, together with the forecast of accurate meteorological conditions of a changing climate. This research highlights the need for more holistic life cycle assessment of urban parks to inform low-carbon landscape industries.

Carbon removal potentials in agricultural systems – participatory scenario modelling with farmers in Sweden

Estimates of theoretical climate change mitigation potentials in agriculture need to be complemented with investigations of factors that influence deployment. This study introduces a framework for landscape-level assessment of climate change mitigation in agriculture that accounts for existing land uses, soil carbon stocks, and farmers’ preferences concerning specific mitigation options. The framework is used in an assessment of the deployment potentials for selected mitigation options in an agricultural landscape in Sweden, in which arable land covers approximately one-third of the land area. Three options were found to be preferable by farmers: biochar as soil amendment, cover crops, and (an increased) cultivation of ley crops in crop rotations. Cultivation of cover crops and leys was found to increase SOC stocks by 1.9 and 1.6 MgC ha−1 over three decades, respectively. About 10.2 MgC ha−1 is sequestered in soils over three decades when biochar is added as a soil amendment, if 50% of available residues are collected and utilized. This can be compared with GHG emissions from agriculture from the studied area, estimated at 1.6 Mg CO2-eq ha−1 yr−1 (GWP100). The framework was found useful for assessing mitigation options in the agriculture sector, underlining farmer involvement to identify actionable strategies.

A high-rate A2O bioreactor with airlift-driven circulation and anoxic hybrid growth for enhanced carbon and nutrient removal from a nutrient rich wastewater.

Within this research, a one-stage hybrid dual internal circulation airlift A2O (DCAL-A2O) bioreactor was designed and operated to simultaneously remove carbon, nitrogen and phosphorous (CNP) from milk processing wastewater (MPW) in different operational circumstances. The substantial operating variables monitored in this work were including hydraulic retention time (HRT), airflow rate (AFR) and aeration volume ratio (AVR) ranged from 7-15 h, 1-3 L/min and 0.324-0.464, respectively. From the view point of economics and process function, the optimum conditions were obtained at the HRT, AFR and AVR of 10 h, 2 L/min and 0.464, respectively. At the optimum conditions TCOD, TN, TP removal efficiencies and effluent turbidity were reported to be 97 %, 90 %, 92 % and 9 NTU, respectively. The impact of wastewater biodegradability (BOD5/COD) was evaluated on the bioreactor performance using two other wastewaters i.e. soft drink (SDW) and soybean oil plant wastewaters (SOW) in comparison with the MPW. Removal efficiencies for TCOD and TN exceeding 80 % were observed. The feeding location revealed a prominent impact on the TN and phosphorous removal efficiencies (both ≥ 80 %) related to the availability degree of the readily biodegradable organic substrate to denitrifiers and PAOs. The rise in HRT, AFR and AVR resulted in reducing microbial secretions as SMP present in sludge and bioreactor effluent as well as loosely bounded EPS (LB-EPS), reported to be 26, 28, 32.5 and 194.4 mg/L TOC, respectively. Different bacteria species were present at optimum conditions confirming concurrent CNP removal in a single body. Finally, the operating cost evaluation verified the effectiveness of the hybrid airlift A2O treating the MPW.

Proposing Oxalic Acid as Chemical Storage of Carbon Dioxide to Achieve Carbon Neutrality.

Increasing emissions of carbon dioxide into the atmosphere due to the use of fossil fuels and ongoing deforestation are affecting the global climate. To reach the Paris climate agreement, in the coming decades low emission technologies must be developed, which allow for carbon removal on a Gt per year-scale. In this regard, we propose the electrochemical conversion of carbon dioxide to oxalic acid as a potentially viable pathway for large scale CO2 utilization and storage. Combined with water oxidation, in principle this transformation does not need stoichiometric amounts of co-reagents and minimize the necessary electrons for the reduction of carbon dioxide.

Мaterial composition and thermal properties of chrysotile asbestos enrichment tailings of the Kiembaevsky deposit

The article discusses the issues of carbon removal in a circulating vacuum unit. It is shown that in order to achieve an ultra-low carbon content (less than 0.002 %), it is necessary to take into account the wear of the lining of steel ladles. When replacing periclase-carbon products in the walls and bottom of the steel ladle with carbon-freeones, carbon intake into the melt can be significantly reduced. Additionally, rational technological parameters of steel processing in a circulating vacuum unit were determined.

Optimization and performance evaluation of a novel nano-zeolite amended pure oxygen-driven membrane aerated biofilm reactor (Z-PO-MABR) for enhanced carbon and nitrogen removal from high-strength wastewater

High-strength wastewater presents significant environmental challenges. Membrane-aerated biofilm reactor (MABR) technology, enhanced by pure oxygen, improves treatment efficiency. Additionally, nano-zeolite-based techniques have shown promise. This study introduces a novel nano-zeolite amended pure oxygen-based MABR system (Z-PO-MABR), combining the benefits of pure oxygen and nano-zeolite. A bench-scale Z-PO-MABR was developed and tested under various conditions to optimize the operation. Optimization achieved high removal rates of organic carbon (98 %) and total nitrogen (96.9 %) with 72 g/Lr of nano-zeolite after 9 h. The Z-PO-MABR system outperforms conventional and pure oxygen-based MABRs, demonstrating greater efficiency in continuous and batch flow modes. The optimized parameters maximize carbon degradation and support microbial growth, offering an eco-sustainable solution for high-strength wastewater treatment. The Z-PO-MABR system is proposed as a promising method for efficient carbon removal and complete nitrogen release. Thus, the study strongly nominates the Z-PO-MABR as an effective treatment system.

Nanocellulose in Polyvinylidene Fluoride (PVDF) Membranes: Assessing Reinforcement Impact and Modelling Techniques

In this study, polyvinylidene fluoride (PVDF)-based nanocomposite membranes reinforced with cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF) were fabricated using the phase inversion method. The effects of 0.5wt% and 1wt% CNC and CNF on structural, mechanical, and filtration properties were examined. Membranes reinforced with 1wt% CNF exhibited the highest distilled water flux, increasing from 445.91 to 476.17L/m².h, and showed improved antifouling ability and higher total organic carbon (TOC) removal compared to unreinforced membranes. Mechanical properties were modelled using five numerical methods, with finite element and Mori-Tanaka models showing the best agreement with experimental data. Modelling results indicated that finite element and Mori-Tanaka methods were the most accurate in predicting the modulus of elasticity. The reinforcement significantly enhanced the membranes' performance in terms of flux recovery, fouling resistance, and mechanical strength, making this a novel interdisciplinary investigation of nanocomposite membranes focusing on both mechanical and filtration capabilities.

Insight into the ferrate(VI)/ozone process: Multiple oxidation systems promote the elimination of electron-deficient pollutants

The utilization of ferrate(VI) (Fe(VI)) is constrained by its limited efficacy in removing electron-deficient pollutants. This study provided insights into the enhanced removal of such pollutants by employing a blend of ozone (O3) and Fe(VI). The removal of electron-deficient pollutants by individual Fe(VI) (50 μM) or O3 (25 μM) ranged from 5 % to 50 % at pH 8.0. The synergistic Fe(VI)/O3 process enhanced the removal to a range of 60 %-95 %, while the pollutants removal rate constant showed a significant increase ranging from 3 to 14 times. The Fe(VI)/O3 process exhibited an increase in total organic carbon removal by 40–90 %. Multiple enhanced oxidation systems were constructed by intermediates derived from the Fe(VI) and O3. The self-decomposition of Fe(VI) released H2O2, which coupled with O3 to form ·OH. Revealed through XPS analysis, the Fe(III) flocs derived from Fe(VI) decomposition contained structures of Fe2O3 and FeOOH. The combined flocs/O3 processes facilitated the production of both ·OH and Fe(IV)/Fe(V). Product analysis and Fukui function calculation demonstrated that, many hydroxylated initial products were exclusively found in the Fe(VI)/O3 process. ·OH initially transforms electron-deficient pollutants into electron-rich products, rendering them more susceptible to electrophilic attack by Fe(IV)/Fe(V). The employment of the Fe(VI)/O3 method demonstrates a concurrent increased production of ·OH and Fe(IV)/Fe(V), presenting a potential resolution for tackling the issue related to stubborn electron-deficient pollutants.

Future land carbon removals in China consistent with national inventory

China’s commitment to carbon neutrality by 2060 relies on the Land Use, Land-Use Change, and Forestry (LULUCF) sector, with forestation targets designed to enhance carbon removal. However, the exact sequestration potential of these initiatives remains uncertain due to differing accounting conventions between national inventories and scientific assessments. Here, we reconcile both estimates and reassess LULUCF carbon fluxes up to 2100, using a spatially explicit bookkeeping model, state-of-the-art historical data, and national forestation targets. We simulate a carbon sink of −0.24 ± 0.03 Gt C yr−1 over 1994–2018 from past forestation efforts, aligned well with the national inventory. Should the official forestation targets be followed and extended, this could reach −0.35 ± 0.04 Gt C yr−1 in 2060, offsetting 43 ± 4% of anticipated residual fossil CO2 emissions. Our findings confirm the key role of LULUCF in carbon sequestration, but its potential will decline if forestation efforts cease, highlighting the necessity for emission reductions in other sectors to achieve carbon neutrality.

Application of waste iron in wet flue gas desulfurization (WFGD) wastewater treatment.

The wet flue gas desulfurization (WFGD) procedure results in wastewater containing a complex mixture of pollutants, including heavy metals and organic compounds, which are hardly degradable and pose significant environmental challenges. Addressing this issue, the proposed approach, incorporating waste iron shavings as a heterocatalyst within a modified Fenton process, represents a sustainable and effective solution for contaminants degrading in WFGD wastewater. Furthermore, this study aligns with the Best Available Techniques (BAT) regulations by meeting the requirement for compound oxidation-replacing the chlorine utilization with the generation of highly reactive radicals-and coagulation, which completes the treatment process. This method introduces an innovative use of waste-derived iron shavings in a BAT-compliant technology, providing a sustainable and cost-effective alternative to conventional treatments. The study focuses on process kinetics and optimization parameters, achieving approximately 48% total organic carbon (TOC) removal in 90min at an optimal pH 3, using 1998 mgL-1 H2O2 under UV light. Analysis of variance revealed that the process efficiency depended more significantly on pH than time duration or the H2O2 dose. Catalyst's characterization, including the use of microscopic techniques, including electron microscopy, laser diffraction, X-ray fluorescence, Raman spectroscopy, and UV spectroscopy, indicates its stability and great reusability with consistent TOC decrease across three process cycles. This research demonstrates a cost-effective, environmentally friendly approach to wastewater treatment, advancing sustainable methodologies through the repurposing of waste materials and underscoring the catalyst's reuse potential.

Insight into the effect of Tubificidae on dynamic membrane reactor: Membrane fouling mitigation and Tubificidae-ASM3-dynamic membrane coupled model

To gain insights into the effects of Tubificidae on dynamic membrane sequencing batch reactor (DMSBR), 4 identical DMSBRs were operated with different Tubificidae densities (i.e., 0, 1, 2, 3 g ww/L). Experimental results showed that Tubificidae had a minimal effect on carbon and nitrogen removal but varied effluent turbidity and sludge characteristics. An appropriate density (2 g ww/L) of Tubificidae significantly decreased effluent turbidity and mitigated membrane fouling, which was attributed to the minimized mixed liquor suspended solids (MLSS) and the maximized particle size. A Tubificidae-ASM3-dynamic membrane coupled model was developed by combining the biological model with the dynamic membrane resistance model, incorporating the extracellular polymeric substances (EPS) to characterize its contribution to membrane pore fouling, and introducing an inhibitory function to limit the unrestricted growth of membrane resistance. The model can be considered as a first attempt to describe the observed Tubificidae effects on dynamic membrane reactor.

Degradation of the Antibiotic Sulfamethoxazole by Ozonation: A Comprehensive Review

ABSTRACTSulfamethoxazole (SMX) is an antibiotic widely used for the treatment of several diseases, especially respiratory and urinary. Due to its widespread use, its presence in the environment has been on the rise. This study discusses the degradation of the antibiotic SMX through the ozonation process. SMX is preferentially degraded by the direct action of O3 on the molecule, starting by breaking the double bonds in the aromatic ring. Through ozonation it is possible to obtain complete SMX degradation within 10 min, but the mineralization of the solution is not achieved, reaching total organic carbon removal efficiencies of 5%–60%, depending on the reaction time. Factors such as the presence of organic matter (OM) and the pH of the solution interfere with the degradation of SMX. The OM acts as a radical scavenger, decreasing the efficiency of degradation, while the pH interferes with the decomposition of O3 into radicals and the dissolution of the oxidant in the medium, in addition to influencing the state of ionization of the SMX making it more or less prone to reactions. In general, most other remediation processes are carried out on a laboratory scale. To increase the level of these processes to a full scale, more pilot‐scale studies are needed. In addition, it is necessary to focus on the practice of reusing materials, avoiding the generation of secondary pollution, and increasing the useful life of the material. The review also discusses the reaction mechanisms, intermediate compounds formed, mineralization of the solution, and factors that influence the process, which can help in making decisions for future studies to be carried out in the area. Prospects in the research area revolve around using metal–organic frameworks as molecular imprinting technology to modify heterogeneous catalysts, integration of external energy, bimetallic systems, and evaluation of deactivation mechanisms.

A new global carbon flux estimation methodology by assimilation of both in situ and satellite CO2 observations

Accurate estimation of carbon removal by terrestrial ecosystems and oceans is crucial to the success of global carbon mitigation initiatives. The emergence of multi-source CO2 observations offers prospects for an improved assessment of carbon fluxes. However, the utility of these diverse observations has been limited by their heterogeneity, leading to much variation in estimated carbon fluxes. To harvest the diverse data types, this paper develops a multi-observation carbon assimilation system (MCAS), which simultaneously integrates both satellite and ground-based observations. MCAS modifies the ensemble Kalman filter to apply different inflation factors to different types of observation errors, addressing the heterogeneity between satellite and in situ data. In commonly used independent validation datasets, the carbon flux derived from MCAS outperformed those obtained from a single source, demonstrating a 20% reduction in error compared to existing carbon flux products. We use MCAS to conduct ecosystem and ocean carbon flux inversion for the period of 2016–2020, which reveals that the 5-year average global net terrestrial and ocean sink was 1.84 ± 0.60 and 2.74 ± 0.49 petagrams, absorbing approximately 47% of human-caused CO2 emissions together, which were consistent with the global carbon project estimates of 1.82 and 2.66 petagrams. All these facts suggest MCAS is a better methodology than those for assimilating single-source observation only.

The need for carbon-emissions-driven climate projections in CMIP7

Abstract. Previous phases of the Coupled Model Intercomparison Project (CMIP) have primarily focused on simulations driven by atmospheric concentrations of greenhouse gases (GHGs), for both idealized model experiments and climate projections of different emissions scenarios. We argue that although this approach was practical to allow parallel development of Earth system model simulations and detailed socioeconomic futures, carbon cycle uncertainty as represented by diverse, process-resolving Earth system models (ESMs) is not manifested in the scenario outcomes, thus omitting a dominant source of uncertainty in meeting the Paris Agreement. Mitigation policy is defined in terms of human activity (including emissions), with strategies varying in their timing of net-zero emissions, the balance of mitigation effort between short-lived and long-lived climate forcers, their reliance on land use strategy, and the extent and timing of carbon removals. To explore the response to these drivers, ESMs need to explicitly represent complete cycles of major GHGs, including natural processes and anthropogenic influences. Carbon removal and sequestration strategies, which rely on proposed human management of natural systems, are currently calculated in integrated assessment models (IAMs) during scenario development with only the net carbon emissions passed to the ESM. However, proper accounting of the coupled system impacts of and feedback on such interventions requires explicit process representation in ESMs to build self-consistent physical representations of their potential effectiveness and risks under climate change. We propose that CMIP7 efforts prioritize simulations driven by CO2 emissions from fossil fuel use and projected deployment of carbon dioxide removal technologies, as well as land use and management, using the process resolution allowed by state-of-the-art ESMs to resolve carbon–climate feedbacks. Post-CMIP7 ambitions should aim to incorporate modeling of non-CO2 GHGs (in particular, sources and sinks of methane and nitrous oxide) and process-based representation of carbon removal options. These developments will allow three primary benefits: (1) resources to be allocated to policy-relevant climate projections and better real-time information related to the detectability and verification of emissions reductions and their relationship to expected near-term climate impacts, (2) scenario modeling of the range of possible future climate states including Earth system processes and feedbacks that are increasingly well-represented in ESMs, and (3) optimal utilization of the strengths of ESMs in the wider context of climate modeling infrastructure (which includes simple climate models, machine learning approaches and kilometer-scale climate models).

A simple formula to fabricate high performance lithium metal capacitors

Energy storage technologies that are low-cost, with long cyclability, high rate-capability as well as high energy and power densities are under intensive investigation for sustainable clean energy transition. In this paper, we report a high-performance lithium metal capacitor (LMC) achieved by a simple slurry modification during the cathode film preparation. We show that a mere substitution of ~0.4 wt% conductive carbon by single walled carbon nanotubes (SWCNTs) increased the specific energy of LMCs by 22 %. Porous carbon cathode in this study was obtained from a non-edible biomass (coconut rachis); the optimized sample showed desirable surface characteristics (surface area ~1933 m2⸱g−1 and pore diameter ~2.0 nm) as well as high edge-plane fraction (ratio between relative density of edge and basal plane ~0.4). Cathode with no SWCNTs show a specific capacitance (CS) of ~133 F·g−1@0.1 A·g−1 in the potential window 2.0–4.0 V in the Li//LiPF6//AC device configuration. Removal of conductive carbon by SWCNTs up to ~0.6 wt% increased electrical conductivity of the cathode; however, the charge storability enhancements were only up to ~0.4 wt%. The optimum device delivered a CS ~188 F·g−1@100 mA·g−1 in the potential window 2.0–4.0 V with improved rate capability and cycling stability. Electrochemical impedance spectroscopy was used as a tool to understand the charge kinetics at the electrode; these studies collectively validated the observed enhancements in the charge storability. The device hereby developed showed superior specific capacity than most of the reported lithium-ion capacitors and comparable to some of the LMBs. The perceived 22 % increase in the specific energy by a mere 0.4 wt% SWCNT substitution is a step forward in fabricating the high-performance LMCs in addition to support the sustainability agenda through the carbon-negative precursors.

Investigation into Recycling of Iron Oxide Scale on H13 Steel by Low‐Temperature Carbothermal Reduction Method

The current method for recovering iron oxide scale in the steel industry is not economically optimal, especially for high‐alloy scales found in alloyed steel. This study focuses on iron oxide scale containing valuable metals like chromium (Cr), molybdenum (Mo), and vanadium (V). The required carbon addition is calculated based on the iron and chromium oxides in the scale. The effects of varying carbon additions and reduction temperatures on reduction efficiency are thoroughly examined. Kinetic studies show that as temperature and carbon increase, the rate‐limiting step shifts from interfacial diffusion to interfacial reaction. Reduction experiments assess carbon utilization, metallization rate, deoxidation rate, and removal of harmful elements. Results show that high temperatures hinder sulfur (S) and phosphorus (P) removal, and excess carbon reduces carbon utilization efficiency. Optimal conditions are a carbon ratio of 0.2174 and a temperature of 1150 °C. The carbothermic reduction product requires further refinement through conventional ladle slag systems to meet the quality standards for metallic materials. Over 65% of alloying elements are recovered, though phosphorus content remains slightly higher than in finished alloy steel. The materials from this study are suitable as high‐quality intermediates for alloy steel production.

Exploring the Sustainable Utilization of Deep Eutectic Solvents for Chitin Isolation from Diverse Sources.

Deep eutectic solvents (DES) represent an innovative and environmentally friendly approach for chitin isolation. Chitin is a natural nitrogenous polysaccharide, characterized by its abundance of amino and hydroxyl groups. The hydrogen bond network in DES can disrupt the crystalline structure of chitin, facilitating its isolation from bioresources by dissolving or degrading other components. DES are known for their low cost, natural chemical constituents, and recyclability. Natural deep eutectic solvents (NADES), a subclass of DES made from natural compounds, offer higher biocompatibility, biodegradability, and the lowest biotoxicity, making them highly promising for the production of eco-friendly chitin products. This review summarized studies on chitin isolation by DES, including reviews of biomass resources, isolation conditions (raw materials, DES compositions, solid-liquid ratios, temperature, and time), and the physicochemical properties of chitin products. Consequently, we have concluded that tailoring an appropriate DES-based process on the specific composition of the raw material can notably improve isolation efficiency. Acidic DES are particularly effective for extracting chitin from materials with high mineral content, such as crustacean bio-waste; for instance, the choline chloride-lactic acid DES achieved purity levels comparable to those of commercial chemical methods. By contrast, alkaline DES are better suited for chitin isolation from protein-rich sources, such as squid pens. DES facilitate calcium carbonate removal through H+ ion release and leverage unique hydrogen bonding interactions for efficient deproteination. Among these, potassium carbonate-glycerol DES have demonstrated optimal efficacy. Nonetheless, further comprehensive research is essential to evaluate the environmental impact, economic feasibility, and safety of DES application in chitin production.

Oxidative hydrothermal carbonization to fabricate versatile magnetic biochar for Fenton-like degradation of phenolic compounds

Magnetic biochar (MBC) has drawn great attention as a versatile catalyst for advanced oxidation elimination of pollutants from aqueous solution with synergy of iron species and carbon matrix. Herein, an MBC was manufactured by oxidative hydrothermal carbonization employing potassium ferrate as precursor and internal oxidant for Fenton-like degradation of phenols in aqueous solution. This unique oxidative hydrothermal carbonization allowed multiple iron species to be introduced with persistent free radicals (PFRs), providing diverse catalysis sites for activating H2O2 into reactive oxygen species (ROSs) for efficient degradation of phenols. Moreover, graphite structure was generated with abundant oxygen functional groups, benefiting to accelerating Fe3+/Fe2+ cycle by electron shuttle and transfer. The catalysis degradation efficiency was up to 99.74 % with 44.4 % of total organic carbon (TOC) removal rate for 75 mg L−1 of phenol using 0.2 g L−1 MBC dosage. Satisfactory recyclability was achieved for the MBC as the catalysis degradation efficiency slightly decreased from 99.74 % to 87.95 % after five times recycling. Moreover, the MBC catalysis system exhibited extensive applicability in real water matrices and for degradation of different phenols with high efficiency. Serving as a demonstration of oxidized magnetic biochar for efficient Fenton-like degradation of phenols, this work highlighted the great potential of oxidative hydrothermal carbonization in preparation of high performance magnetic biochar.