Carbonaceous Adsorbents Research Articles

Transformation of waste cornstalk into versatile porous carbon adsorbent for selective CO2 capture and efficient methanol adsorption

For the purpose of selective CO2 capture and efficient methanol adsorption, versatile porous carbon adsorbents are prepared from waste cornstalk by using hydrothermal carbonization treatment and the subsequent KOH activation process. The resultant adsorbents are characterized with different techniques, and the effects of activation degree on the porous structure and chemical components are discussed. The influence of porous texture and heteroatoms doping on the performance of CO2 capture and methanol adsorption has been systematically analyzed. For CO2 capture, the ultra-micropore is the dominant factor under 1 bar, while the heteroatoms N and O have important cooperation effect under 0.15 bar. The methanol adsorption uptakes under 95 mbar and 10 mbar are closely associated with the specific surface area and ultra-micropore volume, respectively. The adsorbents exhibit remarkable CO2 adsorption uptake of 3.97 mmol g−1 at 1 bar, and desirable methanol adsorption uptake of 18.88 mmol g−1 at 95 mbar, in the temperature of 25 °C. The adsorbents also feature excellent reusability and good selectivity for CO2 over N2, as well as methanol over water. This work provides a feasible approach to prepare low-cost porous carbon adsorbents, which may inspire new research interests and provide necessary theoretical guidance for the application and investigation of biomass-derived carbonaceous adsorbents for CO2 capture and methanol adsorption.

Coal Bottom Ash as a Potential Adsorbent for CO2 Capture

Coal bottom ash (CBA) is the solid residue produced from coal-fired power plant. It is classified as hazardous material, which can cause adverse effect to the environment and public health. In view of the situation, exploring and discovering possible utilization of these coal residues into value-added products has to be performed. Hence, the aim of this paper is to investigate the potential of raw CBA as an adsorbent for carbon dioxide (CO2) gas adsorption. The physicochemical characteristics of CBA were determined using ultimate and proximate analysis, nitrogen adsorption-desorption isotherm, scanning electron microscopy (SEM), and elemental diffraction x-ray (EDX) analysis. CO2 adsorption study was conducted using simulated flue gas by pressure swing adsorption process in a fixed-bed reactor to evaluate the suitability of CBA as an adsorbent material. High carbon content in CBA makes it’s become a good precursor for production of carbonaceous adsorbent. Trace elements like calcium, silica and alumina, indicating that the material had a good adsorption capacity. The result indicated that CBA was able to adsorb CO2 with the adsorption capacity of 0.000276 mol CO2/g CBA. As a conclusion, CBA has the potential to be an adsorbent for its application in gas phase especially in CO2 adsorption.

Biochar from the co-pyrolysis of Saccharina japonica and goethite as an adsorbent for basic blue 41 removal from aqueous solution

The effects of utilizing goethite (5%, 10%, and 20%) in co-pyrolysis with low-lignin macroalgae, Saccharina japonica, on the carbon sequestration potential, magnetic, physicochemical, and dye (basic blue 41, BB41) removal properties of the resulting biochar were investigated. Biochars exhibited more aromaticity, better magnetic properties, and insignificant alterations to their point of zero charges (11.07 ± 0.03 to 10.59 ± 0.01) with goethite increment. Optimum conditions for high organic matter conversion and carbon preservation occurred using 5% goethite. Adsorption experiments showed that BB41 adsorption was highly pH-dependent, equilibrated later (from 12 h to 24 h) after goethite modification, and was best fitted to the pseudo-second-order model (higher R2 and lower SSE values). Langmuir monolayer adsorption capacity for BB41 was the highest amongst carbonaceous adsorbents in the literature [1494 mg/g (pristine); 1216 mg/g (5% goethite)]; initial BB41 concentration of 2000 mg/L at 30 °C and pH 8. The main governing mechanisms involved ion exchanges, hydrogen bonding, π-π interaction and pore-filling. Overall, low goethite amount (5%), co-pyrolyzed with macroalgae, offers an economically and environmentally effective way to produce magnetic biochar with enhanced carbon sequestration potential and superb cationic dye removal performance for environmental remediation applications.

Adsorption performance of reduced graphene-oxide/cellulose nano-crystal hybrid aerogels reinforced with waste-paper extracted cellulose-fibers for the removal of toluene pollution

In recent years, with the progressive advancement of industries, an enormous amount of polluted effluent has been generated and discharged into the ecosystem. Thus, the aqueous environment has been affected by various kinds of pollution, which threatened the health of living organisms, especially human. Numerous procedures have been developed to eliminate the pollution from the environment, among which the adsorption has been known as an effective method. Up to this point, activated carbon was commercially available as an adsorbent for wastewater treatment. Lately, 3-Dimensional (3D) porous structures, such as Graphene Aerogels (GA) demonstrated supreme potentials of an ideal adsorbent, which introduced the next generation of carbonaceous adsorbents. Herein, we proposed a method based on a mild chemical reduction route to prepare reduced Graphene-Oxide (rGO)/Cellulose Nano-Crystal (CNC) hybrid aerogels. Cellulose Fibers (CFs) extracted from waste-papers were incorporated into the pore-structure as reinforcing agents. Moreover, CNCs were employed to enhance the mechanical stability of rGO sheets, resulting in a 280% increase in the compressive strength of the aerogels. Adsorption performance of the synthesized aerogels, according to ASTM F726-17, exhibited an adsorption capacity of 59 g g−1 for toluene uptake. Besides, the batch adsorption experiments confirmed the pseudo-second-order and Langmuir isotherms as the best-fitted models to explain the adsorption behavior of the adsorbent. The Langmuir isotherm revealed the maximum adsorption capacity of 454 mg g−1 for the removal of toluene from aqueous media. The study showed promising results for graphene-based aerogels to act as the new class of adsorbents.

Effectiveness of discarded cigarette butts derived carbonaceous adsorbent for heavy metals removal from water

Disposed cigarette butt is one of the biggest solid, non-biodegradable wastes across the world. Cigarette butts (CBs) made of cellulose acetate are good candidates for the initial raw materials of carbon materials synthesis, providing a possible way for waste CBs recycling. Herein a carbonaceous adsorbent derived from waste CBs was prepared for the heavy metals removal from aqueous solution. The product activated at 500 °C has a maximum adsorption capacity for lead ions, which has a favorable balance of high specific surface area and abundant O-containing functional groups, facilitating the adsorption of heavy metals ions. The adsorption experiments showed that the pH of the solution played a pivotal role in the adsorption of heavy metals by CBs-derived activated carbons and the optimal pH for the adsorption was around 5. Effective adsorption of chromium (Cr3+), cobalt (Co2+), nickel (Ni2+), lead (Pb2+) and cadmium (Cd2+) demonstrated that the prepared materials can be used for multiple heavy metal ions removal. The prepared materials were able to adsorb Pb2+ within ten minutes, and the adsorption process can be well described by the pseudo-second order model, indicating that the chemical adsorption is the rate determining step for the adsorption process. The equilibrium data followed the Langmuir isotherm model and the corresponding maximum adsorption capacity for Pb2+ was 249.3 mg g−1. Considering the merits of low cost, easy synthesis pathway and excellent removal ability of heavy metals, CBs-derived carbonaceous adsorbent exhibits potential application in the fields of heavy metal contaminated water treatment.

Sustainable carbonaceous biochar adsorbents derived from agro-wastes and invasive plants for cation dye adsorption from water

This study investigated methyl orange (MO) dye adsorption using three biochars produced from agro-waste and invasive plants; the latter consisted of wattle bark (BA), mimosa (BM), and coffee husks (BC). BC had the lowest specific surface area (2.62 m2/g) compared to BA (393.15 m2/g) and BM (285.53 m2/g). The adsorption efficiency of MO was stable at pH 2–7 (95%–96%), whilst it had reduced stability at pH 7–12. Between 0 and 30 min, MO adsorption efficiency was >82%, and at 120 min, representative adsorption equilibrium had occurred. The maximum adsorption capacity of the biochars was 12.3 mg/g. The underlying adsorption mechanisms of the three biochars were governed by electrostatic adsorption and pore diffusion. There was an abundance of active sites for adsorption in BA and BM, while chemical adsorption appeared to be more vital for BC, as it contained more functional groups on its surface. The highest MO adsorption efficiency occurred with BM. BC was not recommended for MO removal, as it was observed to stain the water when a dose exceeding 5.0 g/L was utilized.

Preparation of Sulfur-impregnated Carbonaceous Adsorbent Using Mechanochemical Treatment

Preparation of Sulfur-impregnated Carbonaceous Adsorbent Using Mechanochemical Treatment

Adsorption of methylene blue on corncob charcoal: Thermodynamic studies

To obtain the thermodynamic properties of adsorption of methylene blue (MB) on corncob carbonaceous adsorbents - untreated (UCC) and acid treated (TCC) - their equilibrium adsorption was determined between 10 o– 40o C at different pH conditions. The adsorption isotherms were fitted to Freundlich, Langmuir and Temkin isotherm models. The point of zero charge of each of the adsorbents was also determined. The point of zero charge was 10.58 ±0.09 for TCC, and 7.55 ± 0.10 for UCC. Only Freundlich model could account for the observed thermodynamic properties of MB adsorption by the adsorbents, though Temkin and Langmuir models have higher correlation coefficients. MB adsorption by TCC was an entropically driven process which depends on pH;ΔSo at pH 10.5 < ΔSo at pH 8.0 <ΔSo at pH 12.0. The ΔHo of the endothermic process at pH 12 is > ΔHo at pH 8 > ΔHo at pH 10.5. The results suggest that MB adsorption by the adsorbents occur by physisorption and is optimum when the pH is around the point of zero charge. It is important to ensure that in addition to fitting and equilibrium adsoption data by an isotherm model, the fit of the relevant equilibrium parameter should also be good and give thermodynamic quantities that could satisfactorily account for the observed adsorption properties of the system. Deciding the suitability of an isotherm model for fitting adsorption equilibrium experiment based on compared error function of the fitted curves or lines through single temperature isotherm could lead to erroneous conclusion.
 Keywords: adsorption, adsorbent; methylene blue; enthalpy; entropy; Freundlich

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.

Adsorption Isotherms, Thermodynamics, and Kinetic Modeling of Methylene Blue onto Novel Carbonaceous Adsorbent Derived from Bitter Orange Peels

This work reports the production of activated carbons (AC) from bitter orange peel by using ZnCl2 or H3PO4 as activating agent at two different carbonization temperatures (450 °C and 550 °C). Surface morphology analyses of produced bitter orange activated carbons (BOACs) were done by SEM. The surface areas of the produced BOACs, functional groups on the AC surfaces and compositions, were determined by using BET, FT-IR, and TGA analyses. Furthermore, their application for the removal of methylene blue (MB) was studied. The parameters affecting adsorption, such as pH and temperature, were evaluated. BOAC produced with ZnCl2 at 550 °C, exhibits the highest surface area (1450.6 m2 g−1), whereas BOAC produced with ZnCl2 at 450 °C yielded with the highest adsorption capacity (108.9 m2 g−1). Langmuir isotherm shows a good fit for the BOACs. Adsorption kinetics were studied and follows pseudo-second-kinetic model. The thermodynamic parameter studies indicate that the adsorption process is endothermic and spontaneous.

Carbonaceous materials-supported polyethylenimine with high thermal conductivity: A promising adsorbent for CO2 capture

A new three-dimensional (3-D) interconnected elastic scaffold with high thermal conductivity was prepared from hydroxylated graphene (HG) and hydroxylated carbon nanotubes (HCNTs). Then, polyethyleneimine (PEI) was uniformly covalently grafted to the surfaces of the scaffold, to give a HG-HCNTs-PEI nanocomposite as a superior CO2 adsorbent. The resulting nanocomposites possess high amine loading (9.46 mmol N g−1) and high adsorption capacity in simulated flue gas (up to 4.43 mmol CO2 g−1). Due to the excellent thermal conductivity (5.1 W/mK), the adsorbents exhibit superior cyclic stability even in harsh desorption temperature (135 °C), Thus, these carbonaceous materials-supported adsorbents make the CO2 capture process practical and promising.

Superhigh selective capture of volatile organic compounds exploiting cigarette butts-derived engineering carbonaceous adsorbent

Herein, we develop cost-efficient superhigh-performance of engineering carbonaceous adsorbent from cigarette butts using combined wet-impregnated and re-dispersed method of KOH, which optimizes the implant approach of activator, breaking the restriction of selective capture of toluene using traditional activated carbon. The Brunauer-Emmett-Teller (BET) surface area and pore volume of targeted adsorbent can attain 3088 m2·g−1 and 1.61 cm3·g−1, respectively, by optimizing the temperature-dependent synthetic factor effect of the adsorbent. The adsorption capacity of resultant adsorbent for presenting volatile benzene and toluene shows a positive correlation with increasing carbonization temperature of carbon precursor. Besides, we demonstrated the unsmoked and smoked butts derived adsorbents afford feeble difference in saturated adsorbed capacity of volatile organic compounds (VOCs). The highest adsorption capacity of sample CF-800 for benzene and toluene in CF group is as high as 1268.1 and 1181.6 mg·g−1 respectively, slightly higher than that of sample UF-800, but far outperforming reported other adsorbents. The predicted adsorption selectivity of CF-800 and UF-800 for C7H8/H2O (g) using the DIH (Difference of Isosteric Heats) equation reach up to ca. 3800 and 7500 respectively, indicating the weak adsorbability of water vapor on the developed adsorbent and greater superiority of the smoked butts derived adsorbents in selective capture of VOCs at low relative humidity in the competitive adsorption process for practical mixed VOCs.

Flower-like structures of carbonaceous nanomaterials obtained from biomass for the treatment of copper ion-containing water and their re-use in organic transformations

In the present work, raw waste material obtained from polluting dried tree fibres (raw TF) as a source of natural carbon was used for the removal of contaminating copper ions in water. Through two sequential steps of oxidation, carbonaceous adsorbent materials were obtained. Namely, tree fibre activated carbon treated with sulphuric acid (TFSA) and oxidised activated carbon modified using Hummer's method (TFHM). These materials were then characterized using techniques such as SEM, TEM, XRD, FTIR, XPS, TGA, Raman, and BET. The surface areas were found to have an increase from 0, 0.3109 and 55.0107 m2/g for raw TF, TFSA, and TFHM, respectively. The carbonaceous adsorbents were then used in batch adsorption studies for the removal of copper ions in a test water solution. The maximum adsorption capacities determined by non-linear estimation models at the optimum pH 6, were 11.04 and 80.19 mg/g for TFSA and TFHM, respectively. Furthermore, copper is known to facilitate many organic transformations such as reduction and cyclisation, thus, the spent carbonaceous adsorbents were re-used in cyclocondensation and catalytic reduction reactions to avoid discarding these into the environment and creating secondary pollutants. The initial catalytic studies of cyclocondensation of benzamine lead to 96% and 98% yield of desired product via recrystallization while catalytic reduction of 4-nitrophenol was obtained 92% within 22 min.

Carbonaceous Adsorbents Derived from Agricultural Sources for the Removal of Pramipexole Pharmaceutical Model Compound from Synthetic Aqueous Solutions

The aim of the present study was to synthesize various samples of activated carbon (AC) from different agricultural sources as precursors, like orange peels, tea stalks, and kiwi peels, as well as sucrose. The synthesis of AC was achieved with chemical activation using H3PO4 and KOH. The produced AC samples were tested as adsorbents for the removal of a pharmaceutical model compound, pramipexole dihydrochloride (PRM), from synthetic aqueous synthetic solutions. The produced-from-sucrose AC presented the higher yield of synthesis (~58%). The physicochemical features of the materials were analyzed by FTIR spectroscopy, N2 physisorption, and SEM imaging. More specifically, the AC sample derived from sucrose (SG-AC) had the highest specific surface area (1977 m2/g) with the total pores volume, mesopores volume, and external surface area being 1.382 cm3/g, 0.819 cm3/g, and 751 m2/g, respectively. The effect of the initial pH and PRM concentration were studied, while the equilibrium results (isotherms) were fitted to Langmuir and Freundlich models. The maximum adsorption capacities were found to be 213, 190, 155, and 115 mg/g for AC samples produced from sucrose, kiwi peels, orange peels, and tea stalks, respectively.

Effect of soil organic matter on the plant uptake of perfluorooctanoic acid (PFOA) and perfluorooctanesulphonic acid (PFOS) in lettuce on granular activated carbon-applied soil.

The presence of perfluorooctanoic acid (PFOA) and perfluorooctanesulphonic acid (PFOS) in crops is an important consideration for food safety. The soil organic matter (SOM) content may affect the adsorption potential of PFOA and PFOS in water and soil and their subsequent uptake in crops. To better understand these dynamics, the adsorption and uptake of PFOA and PFOS in lettuce were investigated using granular activated carbon (GAC)-treated soils with varying SOM content. The adsorption potential of GAC was investigated, with maximum adsorption capacities for PFOA and PFOS calculated to be 9.091mgg-1 and 27.778mgg-1, respectively. These values decreased to 5.208mgg-1 and 17.241mgg-1, respectively, after the addition of 0.04 wt% humic acid. The average plant uptake factor (PUF) in low and high perfluoroalkyl and polyfluoroalkyl acid (PFAA)-contaminated soils with 4.0 wt% SOM was restricted to 0.353 for PFOA and 0.108 for PFOS. The PUFs were approximately two times lower than those for soil with 2.6 wt% SOM. Addition of 1 wt% GAC to the soil successfully reduced the PUF by up to 99.4%, with values of 0.006 (PFOA) and 0.005 (PFOS) in 2.6 wt% SOM-treated soil and 0.079 (PFOA) and 0.023 (PFOS) in 4.0 wt% SOM-treated soil. Although the PUF in the GAC-treated soil was drastically decreased, the PUF of the soil with 4.0 wt% SOM was at least four times higher than that with 2.6 wt% SOM. Therefore, SOM content is an important consideration in the remediation of PFOA- and PFOS-contaminated farmland soil using carbonaceous adsorbent.

Chemically modified carbonaceous adsorbents for enhanced CO2 capture: A review

The rapidly-increasing concentration of atmospheric carbon dioxide (CO 2 ) gas has become one of the most pressing environmental concerns in recent years. CO 2 capture has become a vital technical solution to minimize environmental CO 2 emissions from various sources. The development of advanced adsorbents for effective CO 2 adsorption is a growing area that has gained significant attention in the materials science field. Hence, in this review we systematically discuss carbonaceous materials including carbon allotropes (carbon nanotubes (CNTs) and graphene oxide (GO)), carbon aerogels (CAs), biochar, polymer-derived carbons, microporous carbons, and mesoporous carbons that are extensively utilized for CO 2 uptakes. The functionalization of carbon materials that have also been reviewed here involved physical/chemical activations using activating agents (KOH, NaOH, K 2 CO 3 , and ZnCl 2 ), doping (N, O, and S), amine modification, carboxylation (-COOH), hybrid/composites formation, and metal oxide impregnation. Studies demonstrated that these all modifications play a very essential role in enhancing the CO 2 adsorption performance as compared to pristine carbons. It is well-acknowledged that the existence of extremely microporous network with ultra-high specific surface area exhibits a dominant role in enhanced CO 2 capture. Among various functionalized carbon-based adsorbents, modified porous activated carbons proved an excellent adsorbent for efficient CO 2 uptakes because of their brilliant textural properties and economical nature. Additionally, modified carbonaceous adsorbents possessed feasible isosteric heat of adsorption, excellent regeneration ability, and shows efficient selective CO 2 adsorption over N 2 . Besides, these studies also summarize future challenges and prospective research pathway that could be commenced for developing effectual adsorbent for an efficient CO 2 storage application by considering various factors. • Carbonaceous materials as adsorbents for CO 2 capture are highlighted. • Functionalization of carbon-based adsorbents for CO 2 capture has been studied. • Recyclability and selective CO 2 adsorption capacities are also discussed. • Chemical modification extensively enhanced the CO 2 adsorption capacities.

Preparation of low-cost activated carbons from amazonian nutshells for CO2 storage

Low-cost carbonaceous adsorbents with microporous structures and a moderate specific surface area (up to 1630 m2 g−1) were prepared from different amazonian nutshells by one-step chemical activation with KOH for CO2 storage. In-depth micropore structure analysis and surface characterization were performed using adsorption isotherms at 298 K and carbon dioxide isotherms at 273 K. The Brazilian nutshell and Cascara Capuassau exhibit a remarkable CO2 uptake capacity of 5.14 mmol g−1 and 5.13 mmol g−1 at 273 K, respectively up to 1 atm. The highest CO2 adsorption at 298 K equal to 3.67 mmol g−1 was observed on activated carbon produced from Cascara Capuassau. The low-pressure CO2 capacities are well correlated with the volume of small micropores (<0.7 nm) rather than the total micropore volume and surface area. The great mesoporosity of activated carbons is beneficial to ensure higher CO2 capture at high uptake pressure.

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.

Understanding the synergy between N-doped ultra-microporous carbonaceous adsorbent and nitrogen functionalities for high performance of CO2 sorption

Porous carbonaceous adsorbents are believed to encourage contenders to CO2 uptake however their high production cost has urged researchers towards cheap renewable. In this study, nitrogen-doped carbonaceous adsorbents with high ultra-microporous structure were synthesized by carbonization and activation of chitosan along with urea and KOH simultaneously at various temperatures (600−900 °C). The effects of temperature, urea modification, and chemical activation on nitrogen functionalities and development of porous structure were analyzed. Results showed that porous carbons synthesized with urea and KOH modification at 700 °C exhibit the highest CO2 adsorption value (5.92 mmol g−1 at 0 °C and 4.45 mmol g−1 at 25 °C). Enhanced adsorption by NCABC-700 was found due to synergistic effect of nitrogen as well as high specific surface area (1404 m2 g−1) and micropore volume (0.68 cm3 g−1), respectively. Furthermore, best fitting of Freundlich isotherm model explained heterogeneous nature of adsorbent. Isosteric heat of adsorption with a value of 42.2 kJ mol-1, also indicated the presence of N containing functional groups and a high number of micropores that created a strong interaction between adsorbent and adsorbate, helping in high CO2 uptake.

Carbonaceous Adsorbent Derived from Sulfur-Impregnated Heavy Oil Ash and Its Lead Removal Ability from Aqueous Solution

A novel carbonaceous adsorbent was prepared from sulfur-impregnated heavy oil ash via pyrolysis using potassium sulfide (K2S) solution, and its ability to remove lead (Pb2+) from aqueous solutions was examined. It was compared with an adsorbent synthesized by conventional pyrolysis using potassium hydroxide (KOH) solution. Specifically, the raw ash was immersed in 1 M K2S solution or 1 M KOH solution for 1 day and subsequently heated at 100–1000 °C in a nitrogen (N2) atmosphere. After heating for 1 h, the solid was naturally cooled in N2 atmosphere, and subsequently washed and dried to yield the product. Regardless of the pyrolysis temperature, the product generated using K2S (Product-K2S) has a higher sulfur content than that obtained using KOH (Product-KOH). Moreover, Product-K2S has a higher lead removal ability than Product-KOH, whereas the specific surface area of the former is smaller than that of the latter. Product-K2S obtained at 300 °C (Product-K2S-300) achieves the highest lead adsorption and a high selective lead removal from a ternary Pb2+–Cu2+–Zn2+ solution. The equilibrium capacity of Product-K2S-300 was found to fit the Langmuir model better than the Freundlich model, and its calculated maximum adsorption capacity is 0.54 mmol/g. From the ternary Pb2+–Cu2+–Zn2+ solution, the order of adsorption by Product-K2S-300 is Pb2+ &gt; Cu2+ &gt; Zn2+, and the removal of Pb2+ and Cu2+ increases as the pH of the solution increases.