Carbon-based Sorbents Research Articles

TiO2/ZnO activated carbon composite for the removal of benzotriazole from water by a combination of sorption and photocatalytic processes

Organic xenobiotic substances are emitted into the environment from a number of preparations used in industry and households. Some are relatively persistent and difficult to biodegrade, so they pass relatively easily through wastewater treatment plants into the surface waters and contaminate drinking water sources. The goal of this study is to develop an innovative technological material that will effectively eliminate organic xenobiotics in water. The principle of our method is to combine carbon-based sorbent (biochar and Hydraffin) with a semiconductor layer (TiO2 or ZnO) to synthesize a photoreactive nanocomposite material which, in conjunction with UV/VIS exposure, can efficiently and safely degrade captured organic xenobiotics (benzotriazole, BTR in this study) in water through the processes of sorption and photocatalytic degradation. This nanocomposite should act as more effective alternative to the widely discussed composite biochar-TiO2. Specifically, the composite coated with ZnO provided the highest degradation efficiency of the photochemical process and it also had the highest sorption capacity for BTR because of the interactions with Zn.In this study, nevertheless, both types of composites are tested and compared their efficiency during removal of selected micropollutant representatives from waters.Graphical

Metal sulfide functionalized activated carbon for efficient capture of gaseous iodine

Emission control of gaseous elemental iodine discharged from nuclear industries is of extreme importance for ecological environment and human health. An obvious barrier hindering the extensive application of activated carbon-based sorbents primarily derives from the absence of active ligands with satisfactory binding towards iodine. To effectively face this challenge, copper sulfide (CuS) with high binding affinity for iodine was introduced and to graft on activated carbon matrix through a simple room-temperature precipitation method under mild conditions. The as-prepared CuS/AC sorbent exhibits favorable textual properties (large specific surface area and developed pore channel) and was enriched with abundant active sites including CuS components and hydroxy functional groups (–OH). Those excellent characteristics contributed to that the iodine uptake capacity of CuS/AC reached to 486 mg g−1. CuS with rich abundance and high accessibility was found to be main ligands accounting for the conversion and immobilization of gaseous iodine. The elemental iodine was reduced into iodine ions and reacted with CuS to form the ultimate adsorbate CuI, effectively avoid the secondary emission of vapor-phase iodine. The whole iodine adsorption process was synergetic controlled by physisorption and chemisorption. The goal of this work not only extends the performance enhancement of the carbon-based sorbents for iodine removal but also inspires further exploitation for the cost-effective and high-performance sorbents for iodine abatement from nuclear industries.

β-Lactoglobulin Enhances Clay and Activated Carbon Binding and Protection Properties for Cadmium and Lead.

The removal of heavy metals from wastewater remains a challenge due to the limitations of current remediation methods. This study aims to develop multicomponent composites as inexpensive and environmentally friendly sorbents with enhanced capture of cadmium (Cd) and lead (Pb). The composites are based on calcium montmorillonite (CM) and activated carbon (AC) because of their proven effectiveness as sorbents for diverse toxins in environmental settings. In this study, we used a combination of computational and experimental methods to delineate that β-lactoglobulin enhances CM and AC binding and protection properties for Cd and Pb. Modeling and molecular dynamics simulations investigated the formation of material systems formed by CM and AC in complex with β-lactoglobulin and predicted their capacity to bind heavy metal ions at neutral pH conditions. Our simulations suggest that the enhanced binding properties of the material systems are attributed to the presence of several binding pockets formed by β-lactoglobulin for the two heavy metal ions. At neutral pH conditions, divalent Cd and Pb shared comparable binding propensities in all material systems, with the former being consistently higher than the latter. To validate the interactions depicted in simulations, two ecotoxicological models (L. minor and H. vulgaris) were exposed to Cd, Pb, and a mixture of the two. The inclusion of CM-lactoglobulin (β-lactoglobulin amended CM) and AC-lactoglobulin (β-lactoglobulin amended AC) at 0.05-0.2% efficiently and dose-dependently reduced the severe toxicity of metals and increased the growth parameters. This high efficacy of protection shown in the ecotoxicological models may result from the numerous possible interaction pockets of the β-lactoglobulin-amended materials depicted in simulations. The ecotoxicological models support the agreement with computations. This study serves as a proof of concept on how computations in tandem with experiments can be used in the design of multicomponent clay- and carbon-based sorbent amended systems with augmented functionalities for particular toxins.

Magnetic carbon nanotube sorbents with macropores formed by salts for oily wastewater treatment

The development of carbon-based sorbents that are simple to fabricate, possess high sorption capacity and are easily collected and reusable has been of great interest for oily wastewater remediation. A magnetic carbon nanotube (CNT) oil sorbent is proposed to cleanup of oily wastewater, offering effortless and complete recovery and enabling reusability. The sorbent, characterized by easy preparation of multi-walled CNT (MWCNT) with m-cresol for macronization, is coupled with a space-holder technique that employs salts for open pore formation for oil sorption. Four sorbents were prepared with varying ratios of sodium chloride (NaCl) and monosodium L-glutamate (MSG), resulting in surface open pores corresponding to salt particle sizes. The sorbents formed an extensive macropore network of more than 200 μm while enhancing the specific surface area. Their bulk densities ranged from 126 kg/m3 to 139 kg/m3, indicating CNT powder densification and suitability for wastewater oil absorption. With its elongated rectangle shape, the MSG-prepared sorbent, exhibited the widest specific surface area and diverse macropores, including those larger than 800 μm. The sorbents exhibited sorption capacities of 2.37–13.60 g of oil/g of sorbent and volume gains of 44–123 %, depending on the oil and solvent types. These values were comparable to or exceeded those of previous carbon-based sorbents. The sorption capacities of the sorbents remained consistent over ten sorption-heat treatment cycles, highlighting recyclability. Sorbents of MWCNT grown from iron catalysts exhibited easy recovery by a magnet after oil sorption, with surface magnetism. Despite their promise for oily wastewater treatment, CNT sorbents must address challenges related to capacity improvement, scalability, economic viability, and environmental impact to be practical for widespread application.

Separation trace amounts of copper ion by solid-phase extraction with carbon-based sorbent prior to flame atomic absorption spectrometry

ABSTRACT In this research, a carbon adsorbent modified with curcumin ligand was utilised in the solid-phase extraction procedure. This method was coupled with flame atomic absorption spectrometry to pre-concentrate and separate trace amounts of copper ions in aqueous solutions. Different experimental parameters, including pH, eluent type and concentration, adsorbent dose, extraction time and sample volume, were studied and optimised. The obtained optimum conditions for the proposed method were: pH of solution, 4.8; extraction time, 9 min; adsorbent dose, 0.01 g; type and concentration of eluent, 1:1 mixture of HCl and HNO3 0.5 mol L−1. Under optimal conditions, the pre-concentration factor of 400.0 and linear range values of the method were 0.031–1.875 µg/L and 12.5–750 µg/L for copper ions in the initial and final solutions, respectively. The relative standard deviation (RSD) for seven replicate detections of 0.05 µg L−1 of copper ion in initial solution was calculated as 2.2%. Furthermore, the detection limit of 0.008 µg L−1 was determined for the suggested method. In order to investigate the selectivity of modified carbon adsorbent, the influence of some interfering ions on the extraction and recovery of Cu (II) was studied. Finally, the present method was employed for the determination of copper ions in real water samples and standard alloys.

Nox impact on mercury removal based on TAC: A comprehensive DFT and XAFS analysis

The simplification of surface chemical reactions is crucial for comprehending the role of nitrogen oxides (NOx) in the adsorption behavior of elemental mercury (Hg0) onto carbon-based sorbents, thereby contributing to technological advancements in reducing mercury emissions. In this study, we developed two fundamental models for activated carbon and investigated the interactions among the carbon surface, NO/NO2, and Hg0 using density functional theory (DFT) calculations. Additionally, thermally-treated activated carbon (TAC) was utilized for Hg0 adsorption, and X-ray absorption fine structure (XAFS) analysis was conducted to examine the morphology and bonding environment of captured Hg. The results suggest that the carbon surface exhibits weak physisorption towards Hg0, but effectively adsorbs NO/NO2. Adsorption of NO/NO2 on the carbon surface with a zigzag edge leads to a decrease in the ADCH charge and surrounding electrostatic potential (ESP) of neighboring carbon vertices, thereby enhancing Hg0 adsorption in those regions through the Eley-Rideal reaction mechanism. The interaction between Hg0 and the surface with ZNO1, ZNO2, or ZNOO2 configurations involves electron transfer and subsequent formation of Hg-C ionic bonds, resulting in adsorption energies ranging from −91.33 to −87.56 kJ/mol. Notably, the adsorption of Hg0 onto the surface with ZNOO1 configuration results in a more extensive electron transfer, facilitating the formation of a robust Hg-O ionic bond and leading to a further reduction in Hg0 adsorption energy to −430.02 kJ/mol. XAFS analysis confirms that predominant formation of Hg-O species occurs following Hg0 adsorption on TAC under syngas containing NO2.

Using L. minor and C. elegans to assess the ecotoxicity of real-life contaminated soil samples and their remediation by clay- and carbon-based sorbents

Toxic substances, such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals, can accumulate in soil, posing a risk to human health and the environment. To reduce the risk of exposure, rapid identification and remediation of potentially hazardous soils is necessary. Adsorption of contaminants by activated carbons and clay materials is commonly utilized to decrease the bioavailability of chemicals in soil and environmental toxicity in vitro, and this study aims to determine their efficacy in real-life soil samples. Two ecotoxicological models (Lemna minor and Caenorhabditis elegans) were used to test residential soil samples, known to contain an average of 5.3, 262, and 9.6 ppm of PAHs, lead, and mercury, for potential toxicity. Toxicity testing of these soils indicated that 86% and 58% of soils caused ≤50% inhibition of growth and survival of L. minor and C. elegans, respectively. Importantly, 3 soil samples caused ≥90% inhibition of growth in both models, and the toxicity was positively correlated with levels of heavy metals. These toxic soil samples were prioritized for remediation using activated carbon and SM-Tyrosine sorbents, which have been shown to immobilize PAHs and heavy metals, respectively. The inclusion of low levels of SM-Tyrosine protected the growth and survival of L. minor and C. elegans by 83% and 78%, respectively from the polluted soil samples while activated carbon offered no significant protection. These results also indicated that heavy metals were the driver of toxicity in the samples. Results from this study demonstrate that adsorption technologies are effective strategies for remediating complex, real-life soil samples contaminated with hazardous pollutants and protecting natural soil and groundwater resources and habitats. The results highlight the applicability of these ecotoxicological models as rapid screening tools for monitoring soil quality and verifying the efficacy of remediation practices.

High organic sulfur coal derived carbon-based sorbent for Hg0 capture from coal-fired flue gas

To develop the high value utilization of high organic sulfur coal instead of combustion as well as save the cost of mercury pollution control, we attempted to transmute the inherent sulfur of high organic sulfur coal, in the case of LF coal (which is from Linfen city, China), to active sulfur species for mercury capture by doping metal oxides, and CuO performed best among various metal oxides. The sorbent (or activated sample) prepared from LF coal with doping CuO is labelled LF+Cu-A, around which a series of experiments were conducted. Firstly, the effects of operational conditions, including GHSV (gas hourly space velocity), temperature and flue components, on the mercury capture performance of LF+Cu-A were thoroughly investigated, and results showed that LF+Cu-A had an excellent mercury capture performance. The average mercury capture efficiency is 97.8 % during a two-hour test under N2+O2+H2O+SO2+NO atmosphere with GHSV of 240000 h−1 and temperature of 120 °C. Secondly, the experimental data were fitted by four kinetic models, and it is found that the mercury adsorption process under low temperatures (60, 90, 120 °C) and high temperature (150 °C) are in the best agreement with the pseudo-first-order model and the intra-particle diffusion model respectively. Last, the mercury capture mechanisms of LF+Cu-A were revealed by Hg-TPD (Hg-temperature programed desorption) experiment, Raman analysis and XPS (X-ray photoelectron spectrometer) spectra, and it is indicated that the multiple sulfur species and Cu2+ play roles in the mercury capture process, during which elemental mercury are oxidized to HgS and fixed on the surface of LF+Cu-A.

Hg0 removal performance of magnetic raffinate slag-based sorbents: Mechanism study on oxidation modification

The sulfur-containing carbon-based sorbent was regarded as potential sorbent for the removal of toxic elemental mercury (Hg0). However, due to its lower reaction temperature and the stronger Hg0 oxidation capacity of oxides at higher temperature, oxidation modification on sulfur-containing raffinate slag-based sorbents was proposed in the study. The effects of O2, H2O2 and KMnO4 oxidation modification on Hg0 removal performance and physicochemical properties of sorbents were investigated. The oxidation modification had little effect on pore structure of sorbents, but mainly affected the content and valence state of sulfur and oxygen elements. Compared with H2O2 oxidation, KMnO4 oxidation was more conducive to forming active lattice oxygen (Oα). The valence state of manganese bound with Oα influenced Hg0 capture a lot, and Oα in MnO2 showed strong oxidation capacity to Hg0. Active S22−and Oα in A850-0.1KMnO4-12h sorbent could both promote the Hg0 removal with HgS and HgO formed in used sorbent. The saturated magnetization of A850-0.1KMnO4-12h sorbent was 5.39 emu·g−1, making it possible to separate mercury-containing sorbents from fly ash. It showed good resistance to low concentration of SO2, and NO could promote its Hg0 removal ability. Meanwhile, KMnO4 oxidation successfully improved the Hg0 removal performance at higher reaction temperature and gas hourly space velocity.

The adsorption mechanism of arsenic in flue gas over the P-doped carbonaceous adsorbent: Experimental and theoretical study

The utilization of carbon-based sorbent has gained extensive attention for arsenic removal from flue gas due to their high specific surface area, sufficient active sites and abundant sources. This study proposes that the addition of phosphorous could be used as an effective promoter for the activation and modification of carbonaceous sorbent to enhance their arsenic fixation capacity. Both experimental and density functional theory (DFT) methods were employed to systematically investigate the adsorption characteristics of arsenic over different carbon based sorbents. The results reveal that the modification of H3PO4 generated C-O-P, C-P-O, and C3-P-O functional groups on the surface of activated carbon, and the adsorption ability of H3PO4-modified activated carbon for gaseous arsenic was significantly improved compared with the untreated activated carbon. DFT calculations indicate that unsaturated C atoms on carbonaceous surface served as active sites during arsenic adsorption, the electronegativity of which could be enhanced by phosphorous functional group, thereby facilitating the adsorption of gaseous arsenic species. Additionally, the positive effect of the phosphorous functional group on arsenic adsorption is more pronounced on zigzag carbonaceous surface than on armchair carbonaceous surface. This work provides a theoretical basis of the development of high-performance biochar preparation for arsenic adsorption by explaining the promoting effect of phosphorous functional group on gaseous arsenic adsorption on carbonaceous surface.

Amine functionalized lignin-based mesoporous cellular carbons for CO2 capture

Amine-impregnated mesoporous carbon sorbents have been considered one of the most promising sorbents for CO2 capture from streams with low CO2 concentrations. In this work, a series of novel solid amine adsorbents were prepared by impregnating polyethyleneimine (PEI) on mesoporous carbons using low-cost bio-waste material “lignin” as a carbon precursor via a facile templating method. Our results demonstrated that the mesoporous carbon with 3D interconnected porous structure and large pore size and pore volume exhibited excellent CO2 adsorption capture of 2.90–3.13 mmol/g at a temperature operating window of 75–90 °C under CO2 partial pressure of 0.15 bar, being significantly higher than PEI impregnated sorbents prepared by using mesoporous carbon with 2D porous structures and also many amine-impregnated carbon-based sorbents reported in previous studies. The well-developed 3D interconnected mesoporous structure, high pore volume (up to 1.80 cm3/g), and large pore size permit the facile dispersion and immobilization of PEI within their pores and high availability of amine groups, which significantly improves both the CO2 adsorption capacity and kinetics. In addition, the cyclic adsorption–desorption test showed that the PEI-impregnated sorbents exhibit superior thermo-stability. These results indicate that the PEI-impregnated mesoporous adsorbents are promising ideal candidates for post-combustion CO2 capture. This work provide a potential strategy to prepare advancved amine impregnanted mesoporous carbons from lignin for efficient carbon capture.

Physical and chemical properties of carbon-based sorbents that affect the removal of per- and polyfluoroalkyl substances from solution and soil

Removal of per- and polyfluoroalkyl substances (PFASs) from water or their immobilization in soil using carbon-based sorbents is one of the cost-effective techniques. Considering the variety of carbon-based sorbents, identifying the key sorbent properties responsible for PFASs removal from solution or immobilization in the soil can assist in the selection of the best sorbents for management of contaminated sites. This study evaluated the performance of 28 carbon-based sorbents including granular and powdered activated carbon (GAC and PAC), mixed mode carbon mineral material, biochars, and graphene-based materials (GNBs). The sorbents were characterized for a range of physical and chemical properties. PFASs' sorption from an AFFF-spiked solution was examined via a batch experiment, while their ability to immobilize PFASs in soil was tested following mixing, incubation and extraction using the Australian Standard Leaching Procedure. Both soil and solution were treated with 1 % w/w sorbents. Comparing different carbon-based materials, PAC, mixed mode carbon mineral material and GAC were the most effective in sorbing PFASs in both solution and soil. Among the different physical characteristics measured, the sorption of long-chain and more hydrophobic PFASs in both soil and solution was best correlated with sorbent surface area measured using methylene blue, which highlights the importance of mesopores in PFASs sorption. Iodine number was found to be a better indicator of the sorption of short-chain and more hydrophilic PFASs from solution but was found to be poorly correlated with PFASs immobilization in soil for activated carbons. Sorbents with a net positive charge performed better than those with a net negative charge, or no net charge. This study showed that surface area measured by methylene blue and surface charge are the best indicators of sorbent performance with respect to sorption/reducing leaching of PFASs. These properties may be helpful in selecting sorbents for PFASs remediation of soils/waters.

Molecular simulation on carbon dioxide capture performance for carbons doped with various elements

Among the different types of CO2 capture technologies for post-combustion, sorption CO2 capture technology with carbon-based sorbents have been extensively explored with the purpose of enhancing their sorption performance by doping hetero elements due to the rapid reaction kinetics and low costs. Herein, sorption capacity and selectivity for CO2 and N2 on carbon-based sorbents doped with elements such as nitrogen, sulfur, phosphorus, and boron, are evaluated and compared using the grand canonical Monte Carlo (GCMC) method, the universal force field (UFF), and transferable potentials for phase equilibria (TraPPE). The sorption capacities of N-doped porous carbons (PCs) at 50 °C were 76.1%, 70.7%, 50.6%, and 35.7% higher than those of pure PCs, S-doped PCs, P-doped PCs, and B-doped PCs, respectively. Its sorption selectivity at 50 °C was approximately 14.0, nearly twice that of pure PCs or other hetero-element-doped PCs. The N-doped PCs showed the largest sorption heat at 50 °C among all the PCs, approximately 20.6 kJ·mol−1, which was 9.7%−25.5% higher than that of the pure PCs under post-combustion conditions. Additionally, with the product purity of 41.7 vol.%−75.9 vol.% for vacuum pressure swing sorption, and 53.4 vol.%−83.6 vol.% for temperature swing sorption, the latter is more suitable for post-combustion conditions than pressure-swing sorption.

Stabilisation of PFAS in soils: Long-term effectiveness of carbon-based soil amendments

Immobilisation/stabilisation is one of the most developed and studied approaches for treating soils contaminated with per- and poly-fluoroalkyl substances (PFAS). However, its application has been inhibited by insufficient understanding of the effectiveness of added soil sorbents over time. Herein, we present results on the effectiveness of select carbon-based sorbents, over 4 years (longevity) and multiple laboratory leaching conditions (durability). Standard batch leaching tests simulating aggressive, worst-case scenario conditions for leaching (i.e., shaking for 24–48 h at high liquid/solid ratios) were employed to test longevity and durability of stabilisation in clay-loam and sandy-loam soils historically contaminated with PFAS (2 and 14 mg/kg ∑28 PFAS). The different sorbents, which were applied at 1–6% (w/w), reduced leaching of PFAS from the soils to varying degrees. Among the 5 sorbents tested, initial assessments completed 1 week after treatment revealed that 2 powdered activated carbon (PAC) sorbents and 1 biochar were able to reduce leaching of PFAS in the soil by at least 95%. Four years after treatment, the performance of the PAC sorbents did not significantly change, whilst colloidal AC improved and was able to reduce leaching of PFAS by at least 94%. The AC-treated soils also appeared to be durable and achieved at least 95% reduction in PFAS leaching under repetitive leaching events (5 times extraction) and with minimal effect of pH (pH 4–10.5). In contrast, the biochars were affected by aging and were at least 22% less effective in reducing PFAS leaching across a range of leaching conditions. Sorbent performance was generally consistent with the sorbent's physical and chemical characteristics. Overall, the AC sorbents used in this study appeared to be better than the biochars in stabilising PFAS in the long term.

Preparation of Fe3O4-Reduced Graphene-Activated Carbon from Wastepaper in the Dispersive Solid-Phase Extraction and UHPLC-PDA Determination of Antibiotics in Human Plasma

In this work, a sorbent was prepared from wastepaper samples enriched with iron oxide particles and graphene oxide and used in the solid phase extraction of antibiotics. The precursor underwent a carbothermal reduction to promote the formation of paramagnetic phases useful for the recovery of the sorbent during the analysis, and to disperse and fix graphene and the iron oxide in a durable way throughout the cellulose structure. Characterizations were carried out to evaluate the composition (Raman, XRD and EDX) and the morphological structure (SEM) of the material. A UHPLC-PDA method was developed for the simultaneous determination of antibiotics from different drug families (carbapenems, fluoroquinolones, β-lactams) using a 120 SB-C 18 poroshell column (50 × 2.1 mm I.D., 2.7 um particle size) and a mobile phase consisting of 10 mM acetate buffer at pH 5 (Line A) and acetonitrile (Line B) both containing 0.1% of triethylamine. A gradient elution was used for the separation of the analytes, while for the quantitative analysis each analyte was determined at its maximum wavelength. Several experiments were carried out to evaluate the influence of different parameters involving the dispersive magnetic solid phase extraction of these analytes. Samples were extracted using 25 mg of sorbent at pH 5 and desorbed in 5 min using methanol. We report herein on some of the outstanding advantages of using carbon-based sorbent, such as lower toxicity, scalability, improved absorption capacity, target selectivity and stability in acidic medium. Moreover, from the results obtained it is evident that, despite the use of some recycled materials, the performances obtained were comparable or even superior to the methods reported in the literature.

Bar Adsorbent Microextraction with Carbon-Based Sorbent Layers for the Identification of Pharmaceutic Substances

Thirteen carbon materials were tested as sorbent layers in bar adsorbent microextraction (BA μE) to monitor hint amounts of 10 common pharmaceutical compounds (PhCs) in surface and groundwater matrices such as surface and groundwater, saltwater, spring water, and sewage. The persistence of trace amounts of three organophosphate insect repellent and cis and trans permethrin (PERM) in water quality matrices is suggested using bar adsorptive microextraction in conjunction with microliquid dissolution accompanied by significant volume injection-gas chromatography-mass spectroscopic analysis able to operate in the particular ion monitoring acquisition mode. Using BA μE to compare several sorbent coatings (five porous carbon and six polymers), it was discovered that activated carbon (AC2) was the optimum compromise among specificity and effectiveness. 17-estradiol, estrone, sulfamethoxazole, diclofenac, triclosan, gemfibrozil, 17-ethinylestradiol, mefenamic acid, and clofibric acid were chosen as system drugs to represent different treatment groups. Despite their lower porosity, statistics revealed that low-T-activated hydrochars, made from carbohydrates and a eutectic salt mixture at constant temperature (e.g., 180°C) and autogenerated pressures, could compete at the top level commercially carbonaceous materials in this purpose. These L-T-activated hydrochars had the best overall recovery (between 21.8 and 83.5 percent) for the simultaneous analysis of ten targeted PhCs with very different physical and chemical possessions, utilizing higher-efficiency liquid chromatography diode array identification.

Life cycle assessment applied on alternative production of carbon-based sorbents – A comparative study

Carbon-based sorption materials have excellent performance in numerous applications, and for their high porosity and sorption performance, these materials are irreplaceable in the industry; however, their manufacturing is demanding and usually fossil-dependent. This comparative study applies the life cycle assessment (LCA) analysis on the alternative production of carbon-based sorption materials and highlights its environmental benefits. The chosen raw materials are softwood pellets (SWP) and solid recovered fuel (SRF) from the local municipal waste collector. The analysis showed interesting equality of these two materials in terms of primary energy demand, specific energy consumption, and environmental impact. The overall favour of the SWP over the SRF is nearly negligible and not always damning. Also, the matter of emissions into the air was hardly distinguishable, with the most significant deviation equal to 1.7% (inorganics into the air). A similar statement applies to environmental impact determination using two life cycle impact assessment methodologies: ReCiPe 2016v 1.1 (H) and Environmental Footprint 3.0. Specific energy consumption of each process was also investigated and compared to better understand the requirements and environmental impact of the selected route of alternative sorbent production. As a result, gasification (3 kWh∙kg−1) appears to be less energy-demanding than hot-steam activation (4.5 kWh∙kg−1) due to scaling and the ability to process excessive amounts of material. The analysed procedure suggests a promising alternative for sorbent manufacturing toward sustainability and a lesser environmental footprint.

Development of a New Polar Organic Chemical Integrative Sampler for 1,4-dioxane Using Silicone Membrane as a Diffusion Barrier.

Efficient monitoring methods must be developed for 1,4-dioxane, which is suspected to be carcinogenic to humans and is highly mobile in aquatic environments. In this regard, polar organic chemical integrative samplers (POCIS) have been utilized extensively as passive samplers for determining time-weighted average concentrations of hydrophilic organic compounds. However, POCIS are difficult to apply to extremely hydrophilic known organic compounds with negative log octanol-water partition coefficient (Kow ) values due to their limited kinetic sampling time. Using an activated carbon-based sorbent with a high adsorption capacity and a bilayer of silicone and polyethersulfone membranes that inhibit mass transfer to the sorbent, we developed a POCIS device to measure 1,4-dioxane (log Kow -0.27) in the present study. Permeation and field calibration tests demonstrated that the use of silicone membranes effectively reduces the water-to-sorbent mass transfer rate. The sampling rate and kinetic sampling period determined by field calibration tests were 1.4 ml day-1 and >14 days, respectively. Finally, the developed POCIS device was applied to a landfill treatment plant to determine the 1,4-dioxane concentrations. Environ Toxicol Chem 2023;42:296-302. © 2022 SETAC.

Improving CO2 capture in porous 3D-graphene by cationic nitrogen doping

The highly porous three-dimensional (3D) graphene is a promising solid sorbent for carbon capture and storage. However, generally, the selectivity of a carbon-based sorbent for CO2 in a gas mixture (such as the post-combustion flue gas in a power plant) is only moderate (∼10–20), which limits its applications. Here, using the Grand Canonical Monte Carlo (GCMC) simulation, we investigate a new type of nitrogen doping (N-doping) in graphene that contains cationic nitrogen sites for CO2 adsorption. We found that due to the favorable electrostatic interaction both CO2 adsorption and selectivity are improved substantially for the porous 3D graphene with the cationic N-doping and are at least an order of magnitude higher than those for the ones without N-doping or with neutral N-doping (such as graphitic, pyridinic, and pyrrolic ones). Our results highlight the possibility for this modified porous 3D graphene to possess both high selectivity and large adsorption for carbon capture, enhancing its commercial viability.

Physical-Chemical Characterization of Different Carbon-Based Sorbents for Environmental Applications.

Biochar has been used in various applications, e.g., as a soil conditioner and in remediation of contaminated water, wastewater, and gaseous emissions. In the latter application, biochar was shown to be a suitable alternative to activated carbon, providing high treatment efficiency. Since biochar is a by-product of waste pyrolysis, its use allows for compliance with circular economics. Thus, this research aims to obtain a detailed characterization of three carbonaceous materials: an activated carbon (CARBOSORB NC 1240®) and two biochars (RE-CHAR® and AMBIOTON®). In particular, the objective of this work is to compare the properties of three carbonaceous materials to evaluate whether the application of the two biochars is the same as that of activated carbon. The characterization included, among others, particle size distribution, elemental analysis, pH, scanning electron microscope, pore volume, specific surface area, and ionic exchange capacity. The results showed that CARBOSORB NC 1240® presented a higher specific surface (1126.64 m2/g) than AMBIOTON® (256.23 m2/g) and RE-CHAR® (280.25 m2/g). Both biochar and activated carbon belong to the category of mesoporous media, showing a pore size between 2 and 50 nm (20–500 Å). Moreover, the chemical composition analysis shows similar C, H, and N composition in the three carbonaceous materials while a higher O composition in RE-CHAR® (9.9%) than in CARBOSORB NC 1240 ® (2.67%) and AMBIOTON® (1.10%). Differences in physical and chemical properties are determined by the feedstock and pyrolysis or gasification temperature. The results obtained allowed to compare the selected materials among each other and with other carbonaceous adsorbents.