Carbonaceous Sorbents Research Articles

Characterization and application of spherical carbonaceous materials prepared with the use of microwave radiation

A series of new synthetic spherical carbonaceous sorbents has been prepared by carbonization and physical activation of strongly acidic ion exchange resin - Wofatit RH. The carbonaceous materials were prepared using two different variants of thermal treatment - microwave and conventional heating. The samples obtained were characterized using various techniques, i.e. elemental analysis, determination of surface pH as well as the content of oxygen functional groups according to the Boehm titration method. The porous structures of all samples under investigation were characterized by low temperature nitrogen adsorption/desorption. Thermal properties of the spherical carbonaceous materials were investigated using thermogravimetric analysis as well as differential thermogravimetry. Kinetic and sorption studies of the removal of organic dye Bismarck Brown Y by adsorption on the carbonaceous adsorbents were carried out. In order to optimize the sorption effectiveness, the effects of contact time, initial dye concentration, pH of dye solution as well as temperature were studied.The products obtained were spherical carbonaceous materials of surface area ranging from 0.02 to 194 m2/g and pore volume from 0.0001 to 0.18 cm3/g. More favorable textural parameters were revealed by activated carbons obtained with the use of microwave radiation. It was found that the sorption capacity towards Bismarck Brown Y increased with the increasing initial concentration of the dye solution as well as the phases contact time.

Investigating the activation of hydrochar from sewage sludge for the removal of terbuthylazine from aqueous solutions

Hydrothermal carbonization offers the opportunity to reduce the issues related to the management of sewage sludge, enhancing dewaterability and avoiding thermal treatment prior landfill disposal or incineration, as water acts as a subcritical medium which catalyzes the process. The hydrochar obtained can find sustainable application as fuel, sorbent and soil amendment. Here, the effects of activation temperature (550–750 °C), time (1–4 h) and impregnation ratio potassium hydroxide: hydrochar (1–3), as well as their interactions, were investigated by Response Surface Methodology. The carbonaceous sorbent was then applied for the removal of terbuthylazine from aqueous solutions. Solid yields up to 32.31% were obtained, with corresponding ash content ranging from 13.05 to 35.06%. The combined effect of time and temperature significantly affects the ash content. An increase of impregnation ratio or temperature leads to low yields but high terbuthylazine adsorption, while the effect of the activation time on the pollutant removal is negligible. Up to 63.87% of the herbicide was adsorbed by the activated material, at terbuthylazine concentration of 2.5 mg L−1. The developed sorbent well fits the circular economy approach, offering a promising potential for sewage sludge management, as well as for water remediation.

One-pot synthesis and characterization of engineered hydrochar by hydrothermal carbonization of biomass with ZnCl2

Hydrochar, the product of hydrothermal carbonization of biomass, is a sustainable alternative to other carbonaceous environmental sorbents. However, its use has been limited due to its low surface area. A one-pot biomass/metal salt co-hydrothermal synthesis method might improve its sorptive properties while retaining its efficient production characteristic. Thus, bamboo sawdust and zinc chloride (ZnCl2) were combined in a hydrothermal reactor (200 °C, 7 h) for preparing modified hydrochar. Compared to the non-modified hydrochar, the hydrochar produced with the addition of ZnCl2 during hydrothermal treatment was more fully carbonized (C content increased from 54% to 64%), of higher surface area after acid washing (30 versus 1.7 m2 g−1), and enriched in O-containing functional groups and of greater aromaticity (according to FTIR and XRD analysis). Because of these improved properties, Methylene blue adsorption capacity of the modified hydrochar increased by nearly 90% and by 257% after it was rinsed with acid. This study highlights the potential of this one-pot co-hydrothermal treatment of biomass in presence of metal salt to provide a simple and effective hydrochar with properties suitable for environmental remediation and water treatment.

Production of a carbonaceous sorbent from the CO2 pyrolysis of hydraulic fracturing flowback and produced water solids

Hydraulic fracturing produces wastewater, referred to as flowback and produced water, which can be saline or brackish, and contain residual additives (e.g.: friction reducers, biocides) and chemicals from the formation water (brines) that may pose risks to the environment, if not properly managed and handled according to existing regulations. Here, we created a pyrolyzed product from flowback water and characterize the resulting material for the purpose of using it for contaminant sorption. The produced pyrolyzed flowback water solids were compositionally comparable to biochar and activated carbon samples, had a high pH value (9.6), surface area (92 m2/g), and sorption capacity (120 mg/g methylene blue), and showed relatively low concentrations of most metals and metalloids as compared to other charcoal materials. The new material was shown to perform better than activated carbon and biochar to remove metals from flowback water, demonstrating its potential use in flowback water treatment operations.

Deep Learning Neural Network Approach for Predicting the Sorption of Ionizable and Polar Organic Pollutants to a Wide Range of Carbonaceous Materials.

Most contaminants of emerging concern are polar and/or ionizable organic compounds, whose removal from engineered and environmental systems is difficult. Carbonaceous sorbents include activated carbon, biochar, fullerenes, and carbon nanotubes, with applications such as drinking water filtration, wastewater treatment, and contaminant remediation. Tools for predicting sorption of many emerging contaminants to these sorbents are lacking because existing models were developed for neutral compounds. A method to select the appropriate sorbent for a given contaminant based on the ability to predict sorption is required by researchers and practitioners alike. Here, we present a widely applicable deep learning neural network approach that excellently predicted the conventionally used Freundlich isotherm fitting parameters log KF and n (R2 > 0.98 for log KF, and R2 > 0.91 for n). The neural network models are based on parameters generally available for carbonaceous sorbents and/or parameters freely available from online databases. A freely accessible graphical user interface is provided.

Comparative environmental assessment of end-of-life carbonaceous water treatment adsorbents

This study evaluates and compares the environmental impacts arising from the disposal of different carbonaceous sorbents used for wastewater treatment. Three different adsorption materials were considered, i.e. activated carbon, biochar and hydrochar, and three end-of-life management approaches, i.e. incineration, regeneration and landfilling. The highest overall environmental impact was of Carcinogenic effects and Freshwater Ecotoxicity due to emissions of heavy metals during production of all types of sorbents. The use of materials with higher adsorption capacities and regeneration of carbonaceous materials were considered and shown to be an efficient way for reducing the overall environmental impacts of the different adsorbents. The compensation of fossil fuel incineration by using recovered heat led to negative impacts in all categories. Recirculation of HTC process water reduced the impact on Freshwater Ecotoxicity and Eutrophication.

Evaluation of Sorbent Sampling and Analysis Procedures for Acetone in Workplace Air: Variations of Concentration and Relative Humidity.

This study experimentally evaluates the performance of different sorbent tubes for sampling acetone vapor in workplace air. A dynamic atmosphere system produced an acetone alone and a mixture with other analytes containing ~73, 483, and 1898 µg acetone mass loading at 25, 50, and 75% relative humidity (RH) at 25°C. Sorbent samples were analyzed in accordance with OSHA Method 69 (Carbosieve S-III) and NMAM 1501, modified to use Anasorb 747 sorbent. Both methods were modified to include the additional analytes. Additional extraction procedures with and without 1% dimethylformamide and anhydrous magnesium sulfate were included in the modified NMAM 1501 using Anasorb 747. Silica gel sorbent tubes analyzed according to NMAM 2027 were included. There were significant reductions in the recovery of acetone from both Anasorb 747 and Carbosieve S-III collected from air at 75% RH, relative to collection at 25 or 50% RH at very low loading compared with that of samples collected at mid to high loading. Silica gel provided a consistent recovery of acetone at all RHs and in the presence of other chemical interferences at 75% RH. The likely cause of mass dependence may arise from the humidity effect on acetone adsorption onto both beaded active carbon and carbon molecular sieve either in sampling or in analysis. The present study confirms not only previous observations but also adds to the literature showing carbonaceous sorbents are not well suited for sampling ketones at high humidity and low concentration.

Electrokinetic effects on the interaction of phenanthrene with geo-sorbents.

Interactions with solid matrices control the persistence and (bio-)degradability of hydrophobic organic chemicals (HOC). Approaches influencing the rate or extent of HOC interactions with matrices are thus longed for. When a direct current (DC) electric field is applied to a matrix immersed in an ionic solution, it invokes transport processes including electromigration, electrophoresis, and electroosmotic flow (EOF). EOF is the surface charge-induced movement of pore fluids. It has the potential to mobilize uncharged organic contaminants and, hence, to influence their interactions with sorbing geo-matrices (i.e. geo-sorbents). Here, we assessed the effects of weak DC electric fields on sorption and desorption of phenanthrene (PHE) in various mineral and carbonaceous geo-sorbents. We found that DC fields significantly changed the rates and extent of PHE sorption and desorption as compared to DC-free controls. A distinct correlation between the Gibbs free energy change (ΔG°) and electrokinetic effects such as the EOF velocity was observed; in case of mineral sorbents EOF limited (or even inhibited) PHE sorption and increased its desorption. In strongly sorbing carbonaceous geo-sorbents, however, EOF significantly increased the rates of PHE sorption and reduced PHE desorption by > 99% for both activated charcoal and exfoliated graphite. Based on our findings, an approach linking ΔG° and EOF velocity was developed to estimate DC-induced PHE sorption and desorption benefits on mineral and carbonaceous sorbents. We conclude that such kinetic regulation gives rise to future technical applications that may allow modulating sorption processes e.g. in response to fluctuating sorbate concentrations in contaminated water streams.

Carbon-based sorbents and their nanocomposites for the enrichment of heavy metal ions: a review.

This review (with 168 refs) summarizes the progress that has been made on the field of microextraction of heavy metal ions using carbonaceous materials. Following an introduction into the features of such materials, we discuss the various kinds of sorption-based microextraction techniques (like solid phase extraction, micro solid phase extraction, solid phase microextraction, magnetic solid phase extraction, and dispersive solid phase extraction). The next section covers specific methods based on the use of carbon-based adsorbents (with subsections on uses of carbon nanotubes, graphene, fullerenes, activated carbon, carbon nanohorns, carbon nanofibers, graphitic carbon nitride, and their composites). The concluding section addresses current challenges, and gives an outlook on potential future trends. Graphical abstract Schematic of the variety ofapplications of carbonaceous sorbents in sorptive extraction methods including SPE, SPME, SBSE, DSPE, μSPE, D-μSPE, and MSPE for the extraction and enrichment of different heavy metals.

CO2 Adsorption on Hazelnut-Shell-Derived Nitrogen-Doped Porous Carbons Synthesized by Single-Step Sodium Amide Activation

In this paper, using carbonized hazelnut shells as the raw material and sodium amide as both activator and nitridation agent, N-enriched carbonaceous sorbents were successfully made by an one-step ...

Surface modification and characterization of carbonaceous adsorbents for the efficient removal of oil pollutants.

In this study, the impact of different oxidizing agents on the structural integrity of activated carbon (AC) and multiwalled carbon nanotubes (MWCNTs) was studied for the removal of BTX from aqueous solution. Seven different combinations of green oxidizing agents (mild organic acids) in conjugation with NaOCl (basic oxidizing agent) were used. The modified adsorbents were analyzed by Brunauer, Emmett, and Teller (BET) surface area analyzer, Fourier transform infrared spectroscopy (FTIR), Boehm titration, Raman spectroscopy, thermal gravimetric analysis (TGA), x-ray diffraction (XRD), zeta potential, and variable pressure field emission scanning electron microscope (VPFESEM). The results suggested that the carbonaceous sorbents modified with combination of citric acid tartaric acid, malic acid and salicylic acid (CTMS-I) showed increased surface area (O-AC: 871.67 m2/g, O-MWCNTs: 336.37 m2/g) and total pore volume (O-AC: 0.59 cm3/g, O-MWCNTs: 0.04 cm3/g), with the significantly improved thermal stability. Preliminary batch adsorption experiments conducted using the present prepared O-AC and O-MWCNTs, showed an improved performance towards the adsorption of BTX, compared with other available reported adsorbents in the literature.

Structure and adsorptive property of carbon materials derived from thermal and mechanochemical reaction of CaC2 and chlorinated polymers

In this study, calcium carbide-derived carbon materials (CMs) were prepared by reacting CaC2 with chlorinated polymers via mechanochemical (CMs-M) and thermochemical (CMs-T) reaction in a planetary ball mill and tubular reactor, respectively. Their composition, structure, and adsorptive properties for dibenzothiophene (DBT) in oil and Hg2+ in water were studied, and the reaction mechanism was analyzed. In comparison with CMs-T, CMs-M possess higher specific area (600 ± 30 m2·g−1) and rich acetylenic and O-containing functional groups, and accordingly higher adsorptivity. Its saturated adsorbance is as high as 291.2 mg-Hg2+·g−1, and the adsorption isotherm can be well represented by Langmuir model, which manifests the chemisorption arising from the unique interaction between Hg2+ and the functional groups. CMs-M is one of the best carbonaceous sorbents for Hg2+ removal considering its high adsorption rate and capacity, high partition coefficient (21.8 mg·g−1·μM−1 at equilibrium concentration of 0.18 ppm), high selectivity w.r.t other heavy metal ions, and excellent recyclability. The mechanochemical method is more suitable for massive production of CMs in view of its mild operation condition and controllable reaction process. This study also sheds a light on the resource utilization of abundant highly chlorinated polymers, like polyvinylchloride (PVC) and chlorinated PVC (CPVC), for the manufacture of CMs-M.

Nitrogen enriched porous carbons from d-glucose with excellent CO2 capture performance

In this study, nitrogen-enriched porous carbonaceous sorbents were successfully prepared by co-hydrothermal treatment of d-glucose and urea, followed by KOH activation under different conditions. Using this new synthesis strategy, the as-prepared adsorbents show a high nitrogen content ranging from 6.20 to 12.17 wt%. In addition, these sorbents also have highly developed porous texture including high narrow microporosity. The optimal sample exhibits the high CO2 uptake of 4.26 and 6.70 mmol/g at 25 and 0 °C, respectively, at 1 bar. Additional study finds that both narrow micropores and nitrogen content are important in deciding the CO2 adsorption ability for these adsorbents under ambient conditions. Besides the high CO2 adsorption ability, these adsorbents also demonstrate stable recyclability, high selectivity of CO2 over N2, suitable heat of adsorption, rapid adsorption kinetics, as well as excellent dynamic CO2 uptake. The above-mentioned excellent CO2 adsorption performance together with the low cost of precursor and facile synthesis strategy prove that these glucose-based porous carbonaceous sorbents are a potential candidate for industrial capture of CO2.

Single-Step Synthesis of Nitrogen-Doped Porous Carbons for CO2 Capture by Low-Temperature Sodium Amide Activation of Petroleum Coke

In this work, highly efficient nitrogen-doped porous carbonaceous CO2 sorbents were synthesized by sodium amide activation of petroleum coke at a temperature range of 400–500 °C. The as-obtained so...

Effects of oxygen functional complexes on arsenic adsorption over carbonaceous surface.

The adsorption mechanism of As2O3 on carbonaceous surface modified with oxygen functional complexes was studied using density functional theory to understand the effect of oxygen functional complexes on arsenic adsorption. Full-parameter geometrical optimization and single point energy were calculated on B3LYP/def2-SVP and B3LYP/def2-TZVP level. Results showed that As2O3 adsorption on bare carbonaceous surface took place in physical as well as chemical way. The adsorption energies were between -2.07 kJ/mol to -480.20 kJ/mol. Compared to armchair model, zigzag model was more suitable as a carbonaceous sorbent. The participation of oxygen functional complexes greatly promoted the surface activity of carbonaceous surface and its adsorption capacity on arsenic. The adsorption energies of arsenic on carbonaceous surface with oxygen functional complexes were between -111.56 kJ/mol to -669.46 kJ/mol. The promotion order of oxygen functional complexes on surface activity was: phenol > lactone > carbonyl > semiquinone > carboxyl. Oxygen functional complexes promoted adsorption capacity of carbonaceous surface through enhancing the activities of neighboring carbon atoms rather than directly providing active sites. Mayer bond order was a reliable way to understand the adsorption process of arsenic on carbonaceous surface. This study provides a new idea for using modified carbonaceous sorbent to remove arsenic pollution from power stations.

Efficient CO2 Adsorption on Nitrogen-Doped Porous Carbons Derived from d-Glucose

The synthesis of carbonaceous CO2 adsorbents doped with nitrogen were carried out via a hydrothermal reaction of biomass d-glucose, followed by urea treatment and K2CO3 activation. These carbons display high uptake of CO2 at 1 bar and 25 and 0 °C, up to 3.92 and 6.23 mmol g–1, respectively. Additionally, the as-synthesized materials exhibit superior reusability, high CO2/N2 selectivity, fast CO2 adsorption kinetics, and excellent dynamic capture capacity at the experimental conditions used. The synthetic effect of the nitrogen content and narrow microporosity decide the capture capacity for CO2 at 1 bar and 25 °C for these N-enriched carbonaceous adsorbents. This study provides a viable method to prepare high-performance CO2 carbonaceous sorbents without using caustic KOH. In addition, this work gives further insights into the CO2 adsorption mechanism for nitrogen-doped porous carbon sorbents and, hence, inspires ways to synthesize novel carbonaceous materials for removing CO2 from combustion exhaust gases.

Theoretical Study on Hg0 Adsorption and Oxidation Mechanisms over CuCl2-Impregnated Carbonaceous Material Surface

CuCl2-modified carbonaceous materials have been regarded as a kind of mercury sorbent, but the Hg0 reaction mechanism over CuCl2-impregnated sorbent surface is still unclear. In this work, the binding mechanism of Hg0 on CuCl2-impregnated carbonaceous material surface was investigated using hybrid density functional theory (DFT). The results indicate that the dissociation mechanism is responsible for CuCl2 adsorption over carbonaceous material sorbent surface. The active chlorine species generated from CuCl2 adsorption can significantly enhance mercury adsorption over carbonaceous material sorbent surface. Hg0 adsorption over CuCl2-impregnated carbonaceous material surface is dominated by a chemisorption mechanism. Surface Cl and C atoms are identified as the active sites for Hg0 adsorption on CuCl2-impregnated carbonaceous material surface. CuCl2 plays an important role in mercury adsorption on CuCl2-impregnated carbonaceous materials. CuCl2 includes the following roles: (1) CuCl2 can increase the reacti...

Efficient carbonaceous sorbent based on the waste sludge of oil extraction industry for purifying wastewater from petroleum products

The opportunity to use the oil extraction industry waste kieselghur sludge as a raw stuff for carbonaceous sorbent for purifying wastewater from petroleum and petroleum products has been researched. It has been demonstrated that the thermal modification of the waste sludge results in oxidation of organic matter and the formation of a carbon layer on the surface of kieselghur (diatomite), as well as the formation of the obtained material’s porous structure. The maximum values of oil-absorption and petroleum-absorption of the carbonaceous sorbent samples, obtained at various temperatures of the initial waste product treatment, have been determined. The highest petroleum saturation (2 g/g) is observed in the first 5 minutes of the sorbent’s contact with the pollutant and is characteristic of the material, obtained at temperature 500°С. The highest oil saturation (3.6 g/g) is shown by the sorbent, obtained at temperature 450°С. This value was achieved after 30 minutes of the sorbent’s contact with oil. The efficiency of clarifying water-oil emulsion with the concentration 1.5 g/dm3 by using carbonaceous sorbents of various thermal pre-history has been determined. The highest degree of emulsion clarification – 91% was achieved at using the sorbent, obtained as a result of the waste sludge modification at temperature 450°С.

Greatly enhanced reactivity of CaC2 with perchloro- hydrocarbons in a stirring ball mill for the manufacture of alkynyl carbon materials

Calcium carbide (CaC2) is a potential feedstock for various alkynyl chemicals, but its actual activity is very low due to its high lattice energy and insolubility. A stirring ball mill was used here to intensify its reaction with perchloro-hydrocarbons (PCHCs), namely hexachlorobenzene (HCB), hexachloroethane (HCE), tetrachloroethene (TCE) and tetrachloromethane (TCM), forming corresponding alkynyl carbon materials (ACMs), viz. ACMHCB, ACMHCE, ACMTCE and ACMTCM, respectively. The reaction intensification may be ascribed to the activation of CaC2 and its effective collision with PCHCs by the intensive impingement of the milling balls. The as-prepared ACMs were characterized by XRD, Raman, elemental analysis, XPS, SEM and BET analysis, and their adsorption performance was evaluated. These ACMs are mesoporous materials with over 70% carbon content, varying amount of acetylenic groups, rich micro-pores and high specific areas ranging from 270 to 970 m2 g−1. ACMHCB is found to be a promising sorbent with adsorption capacity of 514.7 mg-Hg g−1 for HgCl2 aqueous solution and 24.4 mg-S g−1 for DBT oil, which is much superior to most of carbonaceous sorbents due to its rich micro-porosity and abundant acetylenic groups.

Highly efficient CO2 adsorption by nitrogen-doped porous carbons synthesized with low-temperature sodium amide activation

This work provides a simple and cost-effective way to synthesize carbonaceous sorbents with superior CO2 capture performance under ambient conditions. Using a carbonized commercial phenolic resin as carbon precursor and NaNH2 as both activation agent and nitridation reagent, nitrogen-doped porous carbons were synthesized by a single-step reaction at 400-500 °C. The resulting carbons were highly microporous with large amounts of nitrogen content and CO2 uptake capacities up to 4.64 and 7.13 mmol/g, at atmospheric pressure and, respectively, 25 °C and 0 °C. A systematic study showed that the synergetic effect of narrow microporosity and nitrogen content determines the sorbents' CO2 capture capability. In addition, these phenolic-resin-derived porous carbons demonstrate excellent recyclability, stability, and dynamic CO2 capture capacity, as well as reasonable heat of adsorption and CO2/N2 selectivity. The multiple merits of these cost-effective phenolic-resin-based carbons combined with a single-step and low-temperature preparation procedure reveal that they are excellent candidates for CO2 capture.