Carbonaceous Sorbents Research Articles

Facile synthesis of phosphorus-doped porous biochars for efficient removal of elemental mercury from coal combustion flue gas

• An efficient sorbent was synthesized for Hg 0 removal through heteroatom doping. • More pore networks and functional groups were formed on the biochar after P doping. • The Hg 0 adsorption capacity of biochar was increased by 411 times after P doping. • The C-P = O, C = O, and O-C = O groups served as active sites for Hg 0 removal. Heteroatom doping is an effective method to modify carbonaceous sorbents and improve their chemical reactivity. In this study, P-doped biochars (PBCs) derived from one-step pyrolysis of H 3 PO 4 -laden biomass were developed for elemental mercury (Hg 0 ) removal from coal-fired flue gas. Sample characterization showed that there were massive micropores and slit-shaped mesoporous in the PBCs. The specific surface area and pore volume of PBCs was obviously enhanced after P doping. In addition, more organic functional groups were generated on the PBCs surface, particularly the C-P=O and C=O groups. The PBCs presented far higher mercury removal efficiency compared with raw biochars (BCs). The influences of pyrolysis temperature (700 °C-1000 °C), adsorption temperature (25 °C-180 °C), and various flue gas components (NO, SO 2 , O 2 , HCl, and H 2 O) on mercury removal performance were also analyzed. At the optimum temperature (100 °C), the Hg 0 adsorption capacity of PBC 900 was increased by more than 400 times compared with BC 900 , which was also higher than that of a commercial brominated activated carbon. The mechanism responsible for Hg 0 removal was further revealed. The results suggested that chemisorption dominated the Hg 0 removal process, where the C-P=O, C=O, and O-C=O groups could serve as electron acceptors, accelerating the electron migration process for Hg 0 oxidization.

Sorbent extraction behavior of cesium and strontium from nitric acid solutions using a new high thermal stability material

In this study a new low-cost carbonaceous material was prepared from husks of opuntia-ficus-indica as a starting material (precursor) which was accomplished by chemical activation route using H3PO4 impregnation. The material has been identified by different analytical tools. The sorption performance of Cs(I) and Sr(II) from HNO3 solutions was examined through batch system. Variations of the distribution coefficients (Kd) as a function of HNO3 concentration in the range 0.001–5.0 M were presented. Some of separation probabilities were suggested. The results attained signals that the Sr(II) selectivity is higher than that of Cs(I) at high molarities. The retention capacity (qe) of Cs(I) and Sr(II) ions increased with growing temperature. The capacities at 0.001 M HNO3 are 34 and 108 mg/g for Cs(I) and Sr(II), respectively. Whereas, at 2.0 M HNO3 capacities were about 4 and 37 mg/g for each of Cs(I) and Sr (II), respectively. This studies demonstrates that the prepared carbonaceous sorbent is an economically effective sorbent for retention of Cs(I) and Sr(II) species from HNO3 solutions. Cs(I) and Sr(II) removal potential was tested from simulated low- and intermediate-level radioactive waste samples.

Sustainable sorbent derived from discarded cigarette butts for elimination of tobacco specific nitrosamines carcinogen

In order to control the increasingly serious pollutions of tobacco specific nitrosamines (TSNA) and discarded cigarette butts (DCB) that caused by smoking, new sustainable carbonaceous sorbent was prepared to follow the new idea of “cleaning environment with recycle of waste”. For this propose, DCB was used as the carbon source and aluminum nitrate as the pore-forming agent to form the sorbent with a developed porosity and the well-exposed metal oxides. One-pot synthesis was adopted without template and washing, in order to recycle waste with a sustainable technology. New sorbent could selectively capture 25% of TSNA among hundreds of components in tobacco extract solution or 35 mg g − 1 of 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK) in aqueous solution, quite better than activated carbon and zeolite NaZSM-5. In addition, the sorbent was able to catalyze the degradation of the adsorbed NNK in 472–584 K to eliminate the environment carcinogen at relative low temperature. Moreover, cell test demonstrates that the sorbent derived from DCB was cell-safe and therefore widely available. The application of this new sorbent will control both pollutions of TSNA and DCB at the same time, which will protect environment and public health effectively. • Recycle of waste to clean environment was demonstrated in this paper. • Using discarded cigarette butts as the raw material to prepare new sorbent. • One-pot synthesis of the alumina doped carbon without template and washing. • Sustainable sorbent effectively capture tobacco specific nitrosamines carcinogen. • New sorbent is cell-safe and therefore widely available.

Separation of PET and PS from PET/PS/PP plastic mixture and their use in synthesis of composite floating sorbent materials for dyes removal

AbstractBACKGROUNDThe large production of polymeric materials worldwide and the difficulty of their decomposition make recycling necessary for both economic and environmental reasons. In this study, the separation of polyethylene terephthalate (PET) and polystyrene (PS) from ternary mixtures (polyethylene terephthalate/polystyrene/polypropylene, PET/PS/PP) and their subsequent utilization as sorbent materials was carried out. The carbonaceous sorbent materials based on polymeric matrices that were synthesized and characterized have low densities, resulting in ease of removal by flotation.RESULTSWetting agents polyvinyl alcohol (PVA) and dodecylamine (DA) were used to selectively wet PET and PS, respectively, and the effect of the wetting agents' concentration and pH on the effectiveness of the separation were studied. The recovered polymers were then utilized to prepare carbon composite materials that were used to remove of a test dye, Reactive Black dye, from aqueous solutions.CONCLUSIONThe results show effective dye removal (nearly 98%) for both composite materials. The sorbents may then be regenerated for further wastewater treatment. © 2021 Society of Chemical Industry (SCI).

Can porous carbons be a remedy for PFAS pollution in water? A perspective

Per- and polyfluoro alkyl substance (PFAS) is a class of emerging pollutants in various water streams in many countries of the world. PFAS compounds present a wide range of hazards and there is an increasing concern about the health impacts of humans. Several approaches have been proposed to remove PFAS from water and one of the approaches is its adsorptive removal in porous carbons. Many experiments suggested the promising features of porous carbons in successfully removing PFAS from water, however, there are some bottlenecks to fully implement this material for PFAS removal purposes. In this perspective article, we have discussed the advantages of porous carbons in the PFAS removal process and compared its performance with other adsorbents. Based on the hypothetical interactions between surface functionalities of carbon and PFAS, we recommended the modified and customized structures of porous carbons that are expected to demonstrate better performance. We emphasized that incorporation of hierarchical porosity, and enhancement of affinity towards PFAS molecule by incorporating fluorophilicity, hydrophobicity and positive charge on the surface would facilitate the better adsorption of PFAS by carbonaceous sorbents. We also incorporated the computational analysis that may reveal the interactions between the PFAS and the porous carbon in the atomic level and ultimately assist in designing a better variety of porous carbons with superior performance towards PFAS removal.

Methods of Obtaining and Physicochemical Properties of Modified Carbonaceous Sorbents

The variety of practical problems solved in recent years with the help of sorption methods requires expanding the range of used adsorbents. Active carbons are very promising porous adsorbents. Due to a whole complex of valuable properties of a highly developed porous structure, a variety of the chemical nature of the surface, special electrophysical properties, as well as chemical, thermal and radiation resistance, various active carbons are widely used for the absorption of gaseous and dissolved substances. The peculiar nature of carbon adsorbents contributes to the fact that solutes on coal can be adsorbed by completely different; mechanisms, their sorption may be due to the different nature of the forces involved in the adsorption process. The purpose of the work is to obtain multipurpose sorbents; to study methods of modification of carbonaceous sorbents from ash waste, as well as their physicochemical properties

Self-assembled fungus-biochar composite pellets (FBPs) for enhanced co-sorption-biodegradation towards phenanthrene

Sorption and biodegradation are two major applicable techniques for organic pollutants removal. However, the desorption risk following the sorption process and the low bioavailability of trace pollutants to microbes are still hindering the efficient removal of pollutants. To take full advantages of both sorption (for contaminant accumulation) and microbial degradation, here we introduce a self-assembly method combining carbonaceous sorbents (i.e., biochars: RS350, RS500, and RS700) with fungal hyphae (Phanerochaete chrysosporium) which can efficiently degrade phenanthrene (PHE), one of the typical polycyclic aromatic hydrocarbons. By cultivating Phanerochaete chrysosporium in biochar-containing medium, fungus-biochar composite pellets (FBPs) were successfully synthesized with a 3D macrostructure of abundant hyphae and uniform pellet size (~2.5 mm in diameter). Benefiting from the high sorption ability of biochars, such FBPs showed up to triple sorption ability and 70 folds faster biodegradation rate than pure fungal pellets. The PHE concentration remaining in solution receiving co-sorption-degradation treatment after 22 d was only one third of that receiving sorption treatment alone. Continuous removal experiment indicated that these composite pellets could hold their removal ability of above 90 % in the first 4 cycles. This study points out a simple and promising self-assembly approach that could be easily scaled up to manufacture FBPs with high removal efficiency, fast biodegradation rate, easy separation ability and long-term stability.

Adsorption and desorption of gaseous naphthalene on carbonaceous sorbents: Insights into advantageous pore sizes and morphologies

Capturing and recovering naphthalene as a profitable chemical from hot flue gas are of significance in terms of environmental protection with economic benefits, for which the adsorption technology using high-performance sorbents provides the key step for success in practical applications. Carbonaceous materials with hydrophobic natures have been shown to render high affinities with non-polar naphthalene, but remain challenging due to difficulties in tackling the trade-off between adsorption and desorption. This work reports a systematic investigation with deeper insights into adsorption equilibria, kinetics and regenerabilities of gaseous naphthalene on typical carbonaceous sorbents originated from different texture properties, including ordered mesoporous carbons (CMK-3, CMK-5 and FDU-15), carbon nanotubes (SWCNT and MWCNT) and a coconut-shell-based activated carbon (AC). The adsorption isotherm and breakthrough curves at wide feed concentration ranges and temperature programmed desorption curves for each sorbent were obtained along with series of theoretical model fitting. FDU-15 and CMK-5 were demonstrated as superior sorbents with high maximum adsorption capacities (1.13 and 1.735 mmol/g) and low desorption activation energy (62.66 and 72.68 kJ/mol), respectively exhibiting advantages of the 3-dimensional diffusion-controlled desorption upon a hexagonal pore arrangement and the efficient adsorption upon a reasonable mesopore-micropore hierarchical structure, in contrast to poor kinetics on pure microporosity (AC) and 1-dimensional topologies (CNTs). Deeper insights into the morphology-affinity relationship revealed advantageous naphthalene transport behaviors over 3-dimensional ordered mesoporosities with appropriate coexisting microporosities and narrower primary size (2–5 nm) or diverse forms of mesopore, which contribute toward reaching comprehensive balances of sorption performances.

Sorption of benzo[a]pyrene by Chernozem and carbonaceous sorbents: comparison of kinetics and interaction mechanisms

Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon, highly persistent and toxic and a widespread environmental pollutant. Although various technologies have been developed to remove BaP from the environment, its sorption through solid matrixes has received increasing attention due to cost-effectiveness. The present research compares the adsorption capacity of Haplic Chernozem, granular activated carbon and biochar in relation to BaP from water solution. Laboratory experiments with different initial BaP concentrations in the liquid phase and different ratios of the solid and liquid phases show that Freundlich model describes well the adsorption isotherms of BaP by the soil and both sorbents. Moreover, the BaP isotherm sorption by the Haplic Chernozem is better illustrated by the Freundlich model than the Langmuir equation. The results reveal that the sorption capacity of the carbonaceous adsorbents at a ratio 1:20 (solid to liquid phases) is orders of magnitude higher (13 368ngmL-1 of activated carbon and 3 578ngmL-1 of biochar) compared to the soil (57.8ngmL-1). At the ratio of 0.5:20, the adsorption capacity of the carbonaceous sorbents was 17-45 times higher than that of the soil. This is due to the higher pore volume and specific surface area of the carbonaceous sorbents than soil particles, assessed through scanning electron microscopy. The sorption kinetic of BaP by Chernozem was compared with the adsorption kinetics by the carbonaceous sorbents. Results indicate that the adsorption dynamic involves two steps. The first one is associated with a fast BaP adsorption on the large available surface and inside macro- and meso-pores of the sorbent particles of the granular activated carbon and biochar. Then, the adsorption is followed by a slower process of BaP penetration into the microporous space and/or redistribution into a hydrophobic fraction. The effectiveness of the sorption process depends on both the sorbent properties and the solvent competition. Overall, the granular activated carbon and biochar are highly effective adsorbents for BaP, whereas the Haplic Chernozem has a rather limited capacity to remove BaP from contaminated solutions.

Influence of carbon-containing and mineral sorbents on the toxicity of soil contaminated with benzo[a]pyrene during phytotesting.

Benzo[a]pyrene (BaP) is a member of polycyclic aromatic hydrocarbons known for high persistency and toxicity. Technologies of BaP sorption through solid matrixes have received relatively more attention. The present study was devoted to the phytotesting investigations of two different groups of sorbents, such as carbonaceous, including biochar and granulated activated carbon (GAC), and mineral, including tripoli and diatomite. Evaluation of the BaP removing efficiency was carried out using the phytotesting method with spring barley in Haplic Chernozem contaminated with different levels of contamination (200 and 400μgkg-1 BaP). The sorbents' efficiency for BaP remediation was estimated in the sorbents doses from 0.5 to 2.5%per kg of soil. It was shown that biochar and GAC decreased the soil toxicity class to a greater extent than mineral sorbents ones. The effect intensified with an increase in applying sorbents doses. The optimal dose of carbonaceous sorbents into the soil contaminated with 200µgkg-1 was 1%, decreasing the BaP content up 57-59% in the soil. Simultaneously, the optimal dose of the mineral sorbents was found to be 1.5%, which decreased the BaP content in the soil up 41-48%. Increasing the BaP contamination level up to 400µgkg-1 showed the necessity of a sorbent dose increasing. In these conditions, among all applied sorbents, only 2% GAC could reduce the soil toxicity class to the normal level up to 0.91-1.10. It was shown that BaP tended to migrate from the soil to the roots and further into the vegetative part of barley.

New environmental selective micro-mesoporous carbonaceous sorbent for eliminating tobacco specific nitrosamines and lead ion

New selective carbonaceous sorbent is one-pot fabricated using microburst of bi-metal salts in order to eliminate carcinogens in environment. We used discarded cigarette butts as carbon source, aluminum nitrate and ferrous acetate as pore-forming agents to prepare the versatile sorbent with a developed porosity and the well-exposed metal oxides in order to replace zeolites for the selective adsorption in environment protection. Numerous finely divided porous particles endowed the composite a surface area of over 350 m2g-1, enabling it to be the best sorbent of tobacco specific nitrosamines (TSNA) to date in solution. It adsorbed 41% of TSNA among hundreds of components in tobacco extract solution or 142 mg g−1of 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK) in aqueous solution, and rapidly trapped Pb(Ⅱ) at the S/L of 0.2 within 10 min with a capacity of 153 mg g−1. Moreover, new sorbent could catalyze the degradation of NNK in mild conditions, which is rare but is very important for environmental protection.

Determining the Thermal Properties of Buckypapers Used in Photothermal Desorption.

Volatile organic compounds (VOCs) pose an occupational exposure risk due to their commonplace usage across industrial and vocational sectors. With millions of workers annually exposed, monitoring personal VOC exposures becomes an important task. As such, there is a need to improve current monitoring techniques by increasing sensitivity and reducing analysis costs. Recently, our lab developed a novel, preanalytical technique known as photothermal desorption (PTD). PTD uses pulses of high-energy, visible light to thermally desorb analytes from carbonaceous sorbents, with single-walled carbon nanotube buckypapers (BPs) having the best overall performance. To apply this new technology most effectively for chemical analysis, a better understanding of the theoretical framework of the thermal phenomena behind PTD must be gained. The objectives of the present work were 3-fold: measure the thermal response of BPs during irradiation with light; determine the best method for conducting such measurements; and determine the thermal conductivity of BPs. BPs were exposed to four energy densities, produced by light pulses, ranging from 0.28 to 1.33 J/cm2, produced by a xenon flash lamp. The resulting temperature measurements were obtained via fast response thermocouple (T/C) mounted to BPs by three techniques (pressing, adhering, and embedding). Temperature increase measured by T/C using the adhering and pressing techniques resulted in similar values, 29.2 ± 0.8 to 56 ± 3 °C and 29.1 ± 0.9 to 50 ± 5 °C, respectively, while temperature increase measured by embedding the T/C into the BP showed statistically larger increases ranging from 35.2 ± 0.9 to 76 ± 4 °C. Peak BP temperatures for each mounting technique were also compared with the temperatures generated by the light source, which resulted in embedded BPs demonstrating the most temperature conversion among the techniques (74–86%). Based on these results, embedding T/Cs into the BP was concluded to be the best way to measure BP thermal response during PTD. Additionally, the present work modeled BP thermal conductivity using a steady-state comparative technique and found the material’s conductivity to be 10.6 ± 0.6 W/m2. The present work’s findings will help pave the way for future developments of the PTD method by allowing calculation of the energy density necessary to attain a desired sorbent temperature and providing a means for comparing BP fabrication techniques and evaluating BP suitability for PTD before conducting PTD trials with analytes of interest. Sorbents with greater thermal conductivity are expected to desorb more evenly and withstand higher energy density exposures.

Adsorption of lead ions on carbonaceous sorbents of nutshell obtained from secondary raw material

Adsorption of lead ions on carbonaceous sorbents of nutshell obtained from secondary raw material

Water caltrop shell-derived nitrogen-doped porous carbons with high CO2 adsorption capacity

Adsorption via sorbents is considered an attractive technology that can effectively separate CO2 from flue gas. Optimal adsorption performance can be achieved through the utilization of specific sorbents with superior CO2 adsorption capacity. This work demonstrates the conversion of water caltrop shell into N-doped porous carbons for CO2 capture, which involves a three-step procedure, i.e., carbonization of water caltrop shell, post-nitriding by melamine, and KOH activation. The developed adsorbents possess plentiful porous structures and high nitrogen content, with BET surface area up to 2384 m2 g−1 and N content of 8.48 wt%, respectively. CO2 adsorption measurements show that the studied sorbents have good CO2 adsorption abilities, as high as 4.22 and 6.06 mmol g−1 at 25 and 0 °C under ambient pressure, respectively. A comprehensive investigation found that CO2 uptake of as-synthesized adsorbents is dictated by the synergistical interplay of N content and narrow microporous volume. Additionally, they exhibit fast CO2 adsorption kinetics, excellent reversibility and stability, good CO2/N2 selectivity, applicable heat of adsorption and high dynamic CO2 adsorption capacity. This work provides a general method of the preparation of N-doped porous carbonaceous sorbents from waste biomass. The inexpensiveness precursors along with simple preparation procedure highlight the great potential of biomass-based carbons in CO2 capture and many other applications.

Highly Efficient Nitrogen-Doped Porous Carbonaceous CO2 Adsorbents Derived from Biomass

In this manuscript, N-doped porous carbonaceous CO2 sorbents were synthesized using biomass waste hazelnut shell as the raw materials, melamine as the nitridation agent, and KOH as the porogen. The...

Efficient nitrogen doped porous carbonaceous CO2 adsorbents based on lotus leaf

In this work, the waste biomass lotus leaf was converted into N-doped porous carbonaceous CO2 adsorbents. The synthesis process includes carbonization of lotus leaf, melamine post-treatment and KOH activation. For the resultant sorbents, high nitrogen content can be contained due to the melamine modification and advanced porous structure were formed by KOH etching. These samples were carefully characterized by different techniques and their CO2 adsorption properties were investigated in detail. These sorbents hold good CO2 adsorption abilities, up to 3.87 and 5.89 mmol/g at 25 and 0°C under 1 bar, respectively. By thorough investigation, the combined interplay of N content and narrow microporous volume was found to be responsible for the CO2 uptake for this series of sorbents. Together with the high CO2 adsorption abilities, these carbons also display excellent reversibility, high CO2/N2 selectivity, applicable heat of adsorption, fast CO2 adsorption kinetics and good dynamic CO2 adsorption capacity. This study reveals a universal method of obtaining N-doped porous carbonaceous sorbents from leaves. The low cost of raw materials accompanied by easy synthesis procedure disclose the enormous potential of leaves-based carbons in CO2 capture as well as many other applications.

Preparation of biomass-derived porous carbons by a facile method and application to CO2 adsorption

In this work, a facile KOH activation was explored to prepare porous carbonaceous CO2 adsorbents using water chestnut shell as the raw material. This strategy integrates the carbonization and activation process together, which can avoid tedious multiple-step synthesis. The resultant adsorbents possess highly developed porous structures, which leads to good CO2 uptake under 1 bar, up to 3.61 and 5.23 mmol/g at 1 bar, 25 °C and 0 °C, respectively. Additional investigation was conducted to point out the main factors that determine the CO2 uptake of as-synthesized adsorbents. It is found that in addition to the volume of narrow micropores, pore size and pore size distribution of the sorbents play indispensable roles in their CO2 adsorption capacities. Thus, carbonaceous sorbents with high CO2 uptake should have the features of high amount of narrow micropores, together with small and narrow-distributed pore size. Aside from large CO2 uptake, these water chestnut shell-based carbons also hold stable recyclability, good CO2/N2 selectivity, suitable heat of adsorption, fast adsorption kinetics, and fair dynamic adsorption capacity. This study hopes to provide useful information that might profit the CO2 capture by biomass-derived carbons in realistic application.

Guanine condensates as covalent materials and the concept of cryptopores

Simple thermal treatment of guanine at temperatures ranging from 600 to 700 °C leads to C1N1 condensates with unprecedented CO2/N2 selectivity when compared to other carbonaceous solid sorbents. Increasing the surface area of the CN condensates in the presence of ZnCl2 salt melts enhances the amount of CO2 adsorbed while preserving the high selectivity values and C1N1 structure. Results indicate that these new materials show a sorption mechanism a step closer to that of natural CO2 caption proteins and based on metal free structural cryptopores.

Aqueous Mercury Removal with Carbonaceous and Iron Sulfide Sorbents and Their Applicability as Thin-Layer Caps in Mercury-Contaminated Estuary Sediment

This study aimed to investigate the Hg removal efficiency of iron sulfide (FeS), sulfurized activated carbon (SAC), and raw activated carbon (AC) sorbents influenced by salinity and dissolved organic matter (DOM), and the effectiveness of these sorbents as thin layer caps on Hg-contaminated sediment remediation via microcosm experiments to decrease the risk of release. In the batch adsorption experiments, FeS showed the greatest Hg2+ removal efficiencies, followed by SAC and AC. The effect of salinity levels on FeS was insignificant. In contrast, the Hg2+ removal efficiency of AC and SAC increased as increasing the salinity levels. The presence of DOM tended to decrease Hg removal efficiency of sorbents. Microcosm studies also showed that FeS had the greatest Hg sorption in both freshwater and estuary water; furthermore, the methylmercury (MeHg) removal ability of sorbents was greater in the freshwater than that in the estuary water. Notably, for the microcosms without capping, the overlying water MeHg in the estuary microcosm (0.14−1.01 ng/L) was far lesser than that in the freshwater microcosms (2.26−11.35 ng/L). Therefore, Hg compounds in the freshwater may be more bioavailable to microorganisms in methylated phase as compared to those in the estuary water. Overall, FeS showed the best Hg removal efficiency, resistance to salinity, and only slightly affected by DOM in aqueous adsorption experiments. Additionally, in the microcosms, AC showed as the best MeHg adsorber that help inhibiting the release of MeHg into overlying and decreasing the risk to the aqueous system.

Natural Bitumen as an Available Low Cost Sorbent for Remediation of Heavy Metal Cations

Natural bitumen was implemented as a cheap, green, available and efficient sorbent for removal of Pb(II), Cu(II) and Cd(II) ions. The effect of important parameters including time, sorbent dosage, pH and temperature was explored on adsorption process. Maximum removal for all three cations present at pH = 6.0 and 30 min for Pb(II) and Cd(II) cations and 60 min for Cu(II) cation. Also, %Removal for all three cations was decreased by increasing the temperature which is an indication of exothermic adsorption process. However, adsorption isotherms for all three cations were interpreted by Langmuir model. Also, experimental data of all three cations follows pseudosecond-order kinetic model which indicate chemisorption process. Thermodynamic parameters including ∆G, ∆H and ∆S were calculated for all three cations which present spontaneous nature of reaction. Finally, natural bitumen was presented highly adsorption–desorption property and used successfully for removal of Pb(II), Cu(II) and Cd(II) ions in wastewater real sample. Natural bitumen contains mostly carbon and oxygen elements and its good performance as a sorbent probably is due to its similar composition with other carbonaceous sorbents such as activated carbon.