Adsorption Capacity Of Activated Carbon Research Articles

Carboxymethyl cellulose/activated carbon/hydroxyapatite composite adsorbent for remediation of methylene blue from water media

In the present study, activated carbon (AC), activated carbon/hydroxyapatite (AC/HAp), and carboxymethyl cellulose/activated carbon/hydroxyapatite (CMC/AC/HAp) composite adsorbents were prepared to remediation of methylene blue (MB) from water media. The pyrolysis method used the Pine cone as a natural precursor to synthesize AC. FTIR, XRD, Raman, BET, TEM, and SEM-Dot mapping techniques were applied to characterize synthesized adsorbents. Experimental results demonstrated that the maximum removal efficiency of AC, AC/HAp, and CMC/AC/HAp adsorbents under optimum conditions of pH 8, adsorbent dose 1 g/L, contact time 60 min, initial concentration 10 mg/L, and temperature 25 °C was computed to be 98.75, 98.86, and 98.93 %, respectively. Kinetic and equilibrium data were well-fitted with pseudo-second-order and Langmuir models, respectively. The maximum monolayer adsorption capacity of AC, AC/HAp, and CMC/AC/HAp was determined to be 40, 44.248, and 43.86 mg/g, respectively. FTIR results showed that hydrogen bonding and electrostatic interactions are the main mechanisms of the adsorption process. Results of the thermodynamic study showed that the adsorption process is spontaneous and exothermic. Finally, AC, AC/HAp, and CMC/AC/HAp composite adsorbents can be used as promising adsorbents for the remediation of MB from wastewater.

Grape seeds waste activated carbon as an adsorber of paracetamol drug residue: Experimental and theoretical approaches

Activated carbon (AC) derived from grape seeds wastes and chemically activated with phosphoric acid was employed to remove paracetamol (PCT); from an aqueous solution; as a pharmaceutical compound model. The AC was characterized using several techniques, and a series of batch adsorption experiments were conducted. Additionally, a theoretical study investigated the interactions of PCT with various functional groups present on the AC surface. The results demonstrated that the developed AC possessed a well-developed pore structure and a high specific surface area (SBET = 543 m2/g). The AC also exhibited an acidic surface and a low pHpzc (2.5). Adsorption experiments revealed that the pseudo-second-order (PSO) and Freundlich models provided the best fits for experimental kinetic and equilibrium data, respectively. The maximum adsorption capacity of AC for PCT was found to be 17.3 mg/g. Thermodynamic analysis suggested endothermic, favorable, and spontaneous adsorption; with low enthalpy values (ΔH° = 8.099 kJ/mol), supporting physisorption. The DLPNO-CCDT(T)/6-311G(d,p) calculation method yielded the most reliable adsorption energy (Eads) and Gibbs free energy (ΔGads) values between PCT and functional groups on the carbon surface, indicating strong interactions between the acid phosphate group of AC and the acetamide fragment of PCT (ΔGads = −7.60 kcal/mol), and strong interactions between the ketone groups and lactone cycles with the hydroxyl (ΔGads = −3.40 kcal/mol), and acetamide (ΔGads = −1.91 kcal/mol) groups of PCT, respectively. The obtained results indicated, first, that the use of activated carbon from waste is an effective alternative adsorbent for the treatment of wastewater containing pharmaceutical compounds. Second, the application of theoretical computational methods in quantum chemistry provides a thorough understanding of the mechanism of the absorption of PCT at the carbon surface.

Efficient Catalytic Elimination of Toxic Volatile Organic Compounds via Advanced Oxidation Process Wet Scrubbing with Bifunctional Cobalt Sulfide/Activated Carbon Catalysts.

Advanced oxidation process (AOP) wet scrubber is a powerful and clean technology for organic pollutant treatment but still presents great challenges in removing the highly toxic and hydrophobic volatile organic compounds (VOCs). Herein, we elaborately designed a bifunctional cobalt sulfide (CoS2)/activated carbon (AC) catalyst to activate peroxymonosulfate (PMS) for efficient toxic VOC removal in an AOP wet scrubber. By combining the excellent VOC adsorption capacity of AC with the highly efficient PMS activation activity of CoS2, CoS2/AC can rapidly capture VOCs from the gas phase to proceed with the SO4•- and HO• radical-induced oxidation reaction. More than 90% of aromatic VOCs were removed over a wide pH range (3-11) with low Co ion leaching (0.19 mg/L). The electron-rich sulfur vacancies and low-valence Co species were the main active sites for PMS activation. SO4•- was mainly responsible for the initial oxidation of VOCs, while HO• and O2 acted in the subsequent ring-opening and mineralization processes of intermediates. No gaseous intermediates from VOC oxidation were detected, and the highly toxic liquid intermediates like benzene were also greatly decreased, thus effectively reducing the health toxicity associated with byproduct emissions. This work provided a comprehensive understanding of the deep oxidation of VOCs via AOP wet scrubber, significantly accelerating its application in environmental remediation.

Integrated Constructed Wetland–Microbial Fuel Cell Systems Using Activated Carbon: Structure-Activity Relationship of Activated Carbon, Removal Performance of Organics and Nitrogen

This study designed integrated constructed wetland–microbial fuel cell (CW–MFC) systems using activated carbon (AC) as both CW substrates and MFC anodes and investigated the structure-activity relationship of six kinds of commercial columnar AC, as well as the organics and nitrogen removal, microbial activity and diversity of CW–MFCs. Results showed that the nitrogen adsorption by AC tended to be a linear process in which physical adsorption played a leading role and micropores made great contributions. A higher specific surface area, developed mesopores, and oxygen functionalities were conducive to the capacitance properties of AC, while a higher specific surface area and developed micropores were conducive to reduce material resistance and improve ion permeability. Coconut-shell-based AC had both excellent nitrogen adsorption capacity and electrochemical properties, making it ideal as both CW substrates and MFC anodes for CW–MFCs. The electricity generation, coulombic efficiency, internal resistance, and organics and nitrogen removal of CW–MFCs were positively correlated with the total depth of AC anodes. The total depth of AC anodes can be determined based on the influent organics/nitrogen loadings and organics/nitrogen removal load of AC, and a relatively smaller depth of a single AC anode (5 cm) was recommended. The MFC effectively improved the enzymatic activity (by 10.33% dehydrogenase, 8.72% catalase, and 7.35% ammonia monooxygenase), nitrification/denitrification intensity (by 9.53%/6.68%), and microbial diversity (by 1.64–4.07%) of AC (MFC anodes) in CW–MFCs, while the depth of a single AC anode barely influenced the microbial activity and diversity. MFCs increased COD and NH3-N removal in CW–MFCs by 11.60% and 3.4%, respectively. The increased total adsorption capacity of AC with the increase of its total depth narrowed the difference in COD removal resulting from the promotion of MFCs on organics degradation. MFCs increased TN removal in CW–MFCs by 5.29% through promoting denitrification in cathodes and enhancing NH3-N assimilation in anodes. The phyla of EAB (Proteobacteria, Bacteroidetes, Firmicutes, and Acidobacteria) and genera of EAB (Citrobacter, Geobacter, and Pseudomonas) accounted for 85–86% and 15.58–16.64% of the microbial community on AC anodes in CW–MFCs, respectively.

Predicting apparent adsorption capacity of sediment-amended activated carbon for hydrophobic organic contaminants using machine learning

In-situ stabilization of hydrophobic organic compounds (HOCs) using activated carbon (AC) is a promising sediment remediation approach. However, predicting HOC adsorption capacity of sediment-amended AC remains a challenge because a prediction model is currently unavailable. Thus, the objective of this study was to develop machine learning models that could predict the apparent adsorption capacity of sediment-amended AC (KAC,apparent) for HOCs. These models were trained using 186 sets of experimental data obtained from the literature. The best-performing model among those employing various model frameworks, machine learning algorithms, and combination of candidate input features excellently predicted logKAC,apparent with a coefficient of determination of 0.94 on the test dataset. Its prediction results and experimental data for KAC,apparent agreed within 0.5 log units with few exceptions. Analysis of feature importance for the machine learning model revealed that KAC,apparent was strongly correlated with the hydrophobicity of HOCs and the particle size of AC, which agreed well with the current knowledge obtained from experimental and mechanistic assessments. On the other hand, correlation of KAC,apparent to sediment characteristics, duration of AC-sediment contact, and AC dose identified in the model disagreed with relevant arguments made in the literature, calling for further assessment in this subject. This study highlights the promising capability of machine learning in predicting adsorption capacity of AC in complex systems. It offers unique insights into the influence of model parameters on KAC,apparent.

A Study on the Influence and Mechanism of Temperature and Dosage on PCDD/Fs Adsorption via Coal-Based Activated Carbon

Using a trace polychlorinated-ρ-dibenzodioxins and dibenzofurans (PCDD/Fs) stabilizing generator, an experimental study related to the influence of temperature (150, 165, and 180 °C) and activated carbon (AC) dosage (0.10, 0.15, and 0.20 g) on the adsorption effect of gas-phase PCDD/Fs via coal-based AC was conducted. Increasing the AC dosage is the most efficient method to improve the PCDD/Fs adsorption efficiency from 65.8% (0.10 g) to 93.0% (0.20 g) at 150 °C in an exponential trend. Both the polychlorinated-ρ-dibenzodioxins (PCDD)/polychlorinated dibenzofurans (PCDF) ratio and the Cl-PCDD/Fs value showed positive correlations, with the AC dosage under the same temperature. Increasing adsorption temperature declined the adsorption capacity of AC, resulting in the exponentially decreased average I-TEQ value adsorbed per gram of AC, from 131.3 ng TEQ/Nm3 (150 °C) to 55.9 ng TEQ/Nm3 (180 °C). The coal-based AC used in this study preferred to adsorb lower chlorinated PCDD/Fs, tetrachlorianted dibenzo-p-dioxin and dibenzofurans (TCDD/Fs), and pentachlorianted dibenzo-p-dioxin and dibenzofurans (PeCDD/Fs) than highly chlorinated PCDD/Fs, heptachlorianted dibenzo-p-dioxin and dibenzofurans (HpCDD/Fs), hexachlorinated dibenzo-p-dioxin and dibenzofurans (HxCDD/Fs), and octachlorianted dibenzo-p-dioxin and dibenzofurans (OCDD/Fs), which was aggravated by the increasing temperature. The characterization of the surface properties of AC revealed that slight oxidation occurred on the AC surface during the adsorption process, introducing oxygen to the competitive adsorption. In addition, it was found in this study that an increased temperature led to a higher content of hydrophilic carboxyl and anhydride groups and weakened π-π interactions, which were also partly responsible for the negative impact of the increasing temperature on the AC adsorption capacity. The results of this study can contribute to the operation optimization for controlling PCDD/F emissions from municipal solid waste incineration (MSWI).

Feasibility study on the removal of toluene from the air stream by activated carbon/zeolite imidazolate framework composite material

In the present study, a porous composite material (activated carbon (AC)@ zeolitic imidazolate framework-8 (ZIF-8)) was synthesized by in situ method to remove toluene from the gas phase. The adsorption capacity, initial removal efficiency, breakthrough time, pressure drop, desorption and regeneration of this adsorbent were compared with those of ZIF-8 and AC to determine the most suitable adsorbent. The adsorption performance of the adsorbents for toluene was also evaluated in a laboratory scale system based on BS EN ISO 10121–1:2014 and previous studies. The toluene adsorption capacities of AC, ZIF-8 and AC@ZIF-8 were 1278.7, 2828.91 and 4538.09 mg/g, respectively, at 30.5 °C, 10 mg adsorbent mass, flow rate of 300 mL/min and relative humidity of 33%. In addition, the initial removal efficiencies of AC @ZIF-8, ZIF-8 and AC were 99.51%, 88.67% and 86.01%, respectively. The 50% breakthrough time of the composite was 16045 s, which was 3.5 times that of AC and 1.6 times that of ZIF-8. Moreover, the composite retained a 99.93% capacity after six reuse cycles. The in situ synthesis of AC @ZIF-8 composite was an efficient method and the adsorbent was successfully synthesized. This composite material exhibited high adsorption capacity for the removal of toluene from the air stream. In addition, the adsorbent proved to be cost-effective, maintaining a 99.93% capacity after several reuse cycles (99.93%). Considering the high cost of MOF synthesis and the drawbacks of AC, such as low selectivity, the synthesized AC @ZIF-8 composite can be used for air purification and adsorption processes.

3D Monolayer Silanation of Porous Structure Facilitating Multi-Phase Pollutants Removal.

Activated carbon (AC) is widely used to removing hazardous pollutantsfrom air and water, owing to its exceptional adsorption properties. However, the high affinity of water molecules with the surface oxygen-containing functional groups can adversely affect the adsorption performance of AC. In this study, a facile and efficient method is presented for fabrication of hydrophobicAC through surface monolayer silanation. Compared to initialAC, the hydrophobicAC improves thewater contact angle from 29.7°to 123.5°while maintaining high specific surface area and enhances the removal capacity of multi-phase pollutants (emulsified oiland toluene).Additionally, the hydrophobicAC exhibits excellent adsorption capabilityto harmful algal bloom species (Chlorella) (97.56%) and algal organic matter(AOM)(96.23%) owing to electrostatic interactionsand surface hydrophobicity.Thestudy demonstrates that this method of surface monolayer silanation can effectively weaken the effect of water molecules on AC adsorption capacity, which has significant potential for practical use in air and water purification, as well as in the control of harmful algal blooms.

Various carbon-based MgAl2O4 adsorbents and their removal efficiency of CR dye and antibiotics in aqueous media: High selective adsorption capacity, performance prediction and mechanism insight

Various carbon -based MgAl2O4 (MAO) adsorbents were synthesized by a simple ultrasound irradiation technology with the activated carbon (AC), carbon quantum dots (CQDs), C3N4 (CN) and graphene oxide (GO) as carbon sources. The optimum synthesis conditions for the carbon -based MAO adsorbents were determined by the study of the addition of different types of carbon and different mass ratios of mVarious carbon: mMAO = 2.5%, 5.0%, 7.5% and 10%. The carbon -based MAO adsorbents were used for the adsorption of Congo red (CR) dye, tetracycline hydrochloride (TCH), oxytetracycline hydrochloride (OCH), ciprofloxacin (CIP), naproxen sodium (NPS) and tetrabromobisphenol A (TBBPA) and the seven factors affecting the adsorption behavior were discussed, including the type of carbon, AC content, initial dye concentration (CCR), adsorbent dosage (Ccarbon -based MAO adsorbents), adsorption time (At), pH value and reaction temperature (T). The corresponding adsorption isotherm models such as Langmuir, Tempkin, Koble-Corrigan, Toth and Freundlich models and thermodynamics of carbon -based MAO adsorbents for the adsorption of CR dye were also studied. When pH = 7.8, CCR = 200 mg/L, At = 90 min, T = 287 K and CAC 5.0 wt%-MAO = 1 g/L, the removal rate of CR dye reaches 89.7%. The back propagation (BP) neural network model was used to predict the adsorption percentage of carbon-based MAO adsorbents, which was consistent with the experimental results. The high adsorption capacity of AC 5.0 wt%-MAO adsorbents for the adsorption of CR dye can be assigned to the synergistic effects of electrostatic interaction, intermolecular force, n-π interaction and hydrogen bonding, while for the adsorption of TCH, OCH and CIP can be ascribed to the electrostatic interaction. This study demonstrated a huge potential of carbon -based MAO adsorbents as an eco-friendly adsorbent for the adsorption of dyes and drugs.

Characterization of physicochemical properties of activated carbons prepared from penicillin mycelial residues and its adsorption properties for VOCs

In this study, adhering to the concept of "treat waste with waste", the physicochemical properties of activated carbons (ACs) prepared from penicillin mycelial residues (PMR) was characterized, and the adsorption performance of ACs for VOCs was explored. The results showed that AC230–1 exhibited the largest specific surface area (2187.50 m2/g), while AC290–0.5 exhibited the largest microporous surface area (1624.81 m2/g). With the increase of KOH ratio, microporous surface area of ACs decreased gradually, and the pore size distribution of ACs gradually developed to large micropores and mesopores. XRD and Raman results showed that AC290–0.5 had better graphite microcrystalline structure and stability. FT-IR results showed that ACs had similar surface functional groups, and XPS results indicated that AC290–0.5 contained more CO, C-OH, and abundant N-containing functional groups, which could effectively improve the adsorption capacity of ACs for VOCs. AC290–0.5 exhibited the highest dichloromethane (DCM) saturation adsorption capacity (204.83 mg/g), trichloroethylene (TCE) saturation adsorption capacity (732.59 mg/g) and chlorobenzene (CLB) saturation adsorption capacity (735.90 mg/g). The Y–N model could perfectly fit the adsorption breakthrough curve of ACs for VOCs, and adsorption kinetics indicated that the adsorption of ACs for VOCs was mainly physical adsorption. The microporous and surface chemical group of AC were the main factors that determined its adsorption capacity for VOCs.

Characteristics of activated carbon derived from Camellia oleifera cake for nickel ions adsorption

This study used Camellia oleifera cake to prepare activated carbon (AC) for nickel removal from aqueous solutions. After carbonization at 700 °C for 2h, activation was subsequently carried out with four different activators (Na2CO3, KOH, NaOH, H3PO4). The results showed that the four ACs had well-developed microporous structures. The AC with NaOH activation had the highest specific surface area of 512.18 m2 g−1, and the largest pore volume of 0.356 cm3 g−1. The adsorption of Ni(II) on the ACs showed that the removal ratio of Ni2+ reached 95.7% at 25 °C on AC with Na2CO3 activation when the input amount was 5 g L−1, while AC with NaOH as activator had the highest Ni2+ removal ratio of 86.75% when the input amount was 1g L−1 at 25 °C. In addition, the adsorption capacity of AC was increased when the temperature rose between 25 and 60 °C. Compared to pseudo-first-order (PFO) model, the adsorption of Ni2+ on ACs is better suited by pseudo-second-order (PSO) model, and the ion precipitation in chemical adsorption is proved as adsorption mechanism.

Regeneration of granular activated carbon clogged in the treatment of leachates.

Landfill leachates are highly contaminated liquids and complex to treat. Two of the processes which are promising for the treatment are the advanced oxidation and adsorption methods. With the combination of the Fenton and adsorption methods, practically all the organic load of leachates can be removed; however, this combination of processes is limited due to the soon clogging of adsorbent material, which leads to high operation costs. In the present work, the results of the regeneration of clogged activated carbon are shown after the application of the Fenton/adsorption process in leachates. This research consisted of four stages: sampling and leachate characterization, clogging of the carbon through the Fenton/adsorption process, carbon regeneration through the oxidative Fenton process, and lastly, evaluation of regenerated carbon adsorption through jar and column tests. In the experiments, HCl 3M was used, and different concentration of hydrogen peroxide (0.15M, 0.2M, 0.25M) were tested at different times (16h and 30h). The activated carbon regeneration through the Fenton process and the optimal peroxide dosage was 0.15M for 16h. The regeneration efficiency was obtained from comparing the adsorption efficiency between regenerated and virgin carbon, reaching 98.27% and can be applied up to 4 times without losing regeneration efficiency. These results prove that it is possible to restore the clogged activated carbon adsorption capacity during the Fenton/adsorption process.

Activated carbon adsorbent derived from waste biomass, “Croton caudatus” for efficient removal of 2-chlorophenol from aqueous solution: Kinetics, isotherm, thermodynamics and DFT simulation

The present study aims to prepare an activated carbon (AC) adsorbent developed from Croton caudatus biomass material for the adsorption of 2-chlorophenol (2CP) from wastewater. Activated carbon was prepared by KOH activation at 2:1 impregnation ratio and 700 °C temperature using a muffle furnace under self-generated atmosphere for 2 h. Several techniques and methodologies such as proximate analysis, ultimate (CHNS) analysis, BET, SEM, FT-IR, XRD and point of zero charge (pHpzc) have been used to determine physicochemical properties of the activated carbon. Batch adsorption studies were conducted for 2-chlorophenol adsorption and the optimum adsorbent dose, initial concentration, pH, reaction time and temperature were found to be 0.15 g/L, 80 mg/L, 4, 60 min and 298 K, respectively. The equilibrium isotherm study for 2-chlorophenol adsorption was fitted well to the Langmuir model with the adsorption capacity of 53.619 mg/g, while the adsorption kinetics was best described by pseudo-second order model. Thermodynamic parameters demonstrated a negative ΔH (exothermic) and negative ΔG (spontaneous) values. Studies on regeneration have shown that saturated carbon can be recycled up to five times with considerable removal efficiency. Besides, density functional theory (DFT) simulation revealed that the adsorption of 2-chlorophenol onto AC adsorbent is favorable. Among the oxygen-containing functional groups, the carboxyl group appeared to have a greater influence on the adsorption process than the hydroxyl and carbonyl groups with the highest negative Eadsorption of − 42.16 kJ/mol. Furthermore, the inclusion of three oxygen-containing functional groups improves the adsorption capacity of AC towards 2CP relative to a single functional group.

CO2 Adsorption Performance on Surface-Functionalized Activated Carbon Impregnated with Pyrrolidinium-Based Ionic Liquid

The serious environmental issues associated with CO2 emissions have triggered the search for energy efficient processes and CO2 capture technologies to control the amount of gas released into the atmosphere. One of the suitable techniques is CO2 adsorption using functionalized sorbents. In this study, a functionalized activated carbon (AC) material was developed via the wet impregnation technique. The AC was synthesized from a rubber seed shell (RSS) precursor using chemical activation and was later impregnated with different ratios of [bmpy][Tf2N] ionic liquid (IL). The AC was successfully functionalized with IL as confirmed by FTIR and Raman spectroscopy analyses. Incorporation of IL resulted in a reduction in the surface area and total pore volume of the parent adsorbent. Bare AC showed the largest SBET value of 683 m2/g, while AC functionalized with the maximum amount of IL showed 14 m2/g. A comparative analysis of CO2 adsorption data revealed that CO2 adsorption performance of AC is majorly affected by surface area and a pore-clogging effect. Temperature has a positive impact on the CO2 adsorption capacity of functionalized AC due to better dispersion of IL at higher temperatures. The CO2 adsorption capacity of AC (30) increased from 1.124 mmol/g at 25 °C to 1.714 mmol/g at 40 °C.

Micropollutants Removal from Water and Activated Carbon Regeneration by Combining Adsorption and Electro-Fenton

The presence of micropollutants in municipal wastewater effluents is a topic of major concern, as these pollutants end up in surface and ground waters. Currently, adsorption on activated carbon (AC) is used to remove these recalcitrant compounds. When saturated, the AC is generally either thermally regenerated or disposed of. Thermal regeneration is expensive and negatively affects the structure and adsorptive properties of the AC.Over the last decade, considerable attention has been directed towards the electrochemical advanced oxidation processes (eAOPs), due to their ability to remove a large range of organic pollutants from water even at very low concentrations [1]. eAOPs rely on the in-situ generation of powerful oxidants, such as HO• by electron transfer at the anode surface. However, these processes are limited by mass transfer and require high energy consumption.In this study, combined adsorption on granular activated carbon (GAC) and electro Fenton process (EF) is applied. The purpose of this coupled process is to overcome the mass transfer issue by pre-concentrating the compounds on AC and proposing a new AC regeneration method. During the EF the AC can directly be used as a cathode. Due to the electrostatic repulsions and oxidation process, the compounds are desorbed from the AC and oxidized by the HO• generated in the bulk. Material and Methods The adsorption cycles and EF experiments were performed in batch mode using deionized water (DW) and simulated wastewater (SWW) with caffeine as a model compound. Similar experimental steps and conditions as described in [2] are followed, using 1g of GAC, with pH=3, Fe2+= 0.15 mM, Na2SO4= 50mM, and a current intensity of 200 mA. To assess the degradation and mineralization of the caffeine, HPLC and TOC measurements were used, respectively. The regeneration efficiency was calculated by comparing the adsorption capacity of the AC after each regeneration cycle with its initial adsorption capacity. Results and Conclusions The efficiency of the process was discussed as regards (i) desorption of organic compounds and regeneration efficiency in DW and SWW, (ii) degradation and mineralization of organic compounds, and (iii) stability of GAC for several successive regeneration cycles. During the regeneration, over 80% of desorbed caffeine was degraded and 75% was mineralized due to the formed HO• by Fenton reaction and at the BDD anode surface (Fig.1). Furthermore, a recovery of the AC adsorption capacity by up to 50 % in PW and 37% in SWW was observed. These regeneration percentages decreased to 25% during the second cycle and then remained stable during the third and the fourth cycle. The incomplete regeneration is most likely due to remaining caffeine molecules at the AC [3], or a blockage of the carbon adsorption sites by formed degradation molecules. Hence, a longer treatment time might lead to higher efficiency. These hypotheses will be taken into consideration in future work to draw a clear conclusion on the regeneration phenomenon. The similar regeneration efficiencies and mineralization rates obtained during the 2nd,3rd, and 4th cycles indicate the stability of the GAC electrode.In conclusion, the results from this study illustrate that combined adsorption and EF is a suitable process for the removal of caffeine and regeneration of AC. The advantage of such a process is that part of the AC can be regenerated while over 75% of the desorbed compounds from the AC are mineralized, thus avoiding toxic effluents. This process is currently implemented as a continuous e-cell for sequential adsorption and EF regeneration.

Enhanced capacitive deionization properties of activated carbon doped with carbon nanotube-bridged molybdenum disulfide

The shortage of freshwater supplies has restricted societal development. Capacitive deionization (CDI) is an emerging technology for desalination of seawater or brackish water, the performance of which is highly dependent on electrode materials. In this work, a molybdenum disulfide/carbon nanotube composite (CNTs-b-MoS2) with high capacitance was successfully synthesized using a hydrothermal method. The composite exhibited a specific capacitance of 112.79 F g−1. To reduce costs and determine the practicality of using CNTs-b-MoS2 for CDI, we combined activated carbon (AC) with CNTs-b-MoS2 as a CDI electrode. The research demonstrated that after doping with 5% (mass ratio) CNTs-b-MoS2, the specific capacitance and electrosorption capacity of AC were significantly improved and the maximum desalination capacity of CNTs-b-MoS2/AC reached 8.19 mg g−1. The low dosage of CNTs-b-MoS2 combined with the high specific surface area of AC avoided the shortcomings of CNTs-b-MoS2, namely low specific surface area and high cost. Moreover, the outstanding conductivity of CNTs-b-MoS2 improved the conductivity and enhanced the adsorption capacity of AC, giving CNTs-b-MoS2/AC potential as an advanced, low-cost CDI electrode material.

Performance evaluation and prediction of activated carbon for VOCs via experiments and LFER methods

Due to the diversity and fluidity of volatile organic compounds (VOCs), it is difficult to conduct experimental studies on activated carbon (AC) used to capture VOCs in industry. Therefore, predicting the adsorption capacity of AC for VOCs is of great significance for evaluating the adsorption performance of AC and developing its promising applications. Herein, based on the experimental data of dynamic adsorption, the poly parameter linear free energy relationship (pp-LFER) model was developed to quantify the interactions between VOCs and AC. Through the dynamic adsorption curves of 25 VOCs on a fixed bed packed with the AC, the partition coefficient (PC) and adsorption capacity (q) of AC for VOCs were calculated, and the pp-LFER equations used to predict them were established. For the PC values, the pp-LFER model consists of the excess molar refractive index (E), molar polarizability (S), hydrogen-bond acidity (A), and logarithmic hexadecane-air partition coefficient (L), and the R2 of it was 0.86. For the ln q values, the developed model can predict it in R2 of 0.83, and the increased adsorption capacity was predominantly attributed to the dispersive interaction (lL). Finally, the internal and external validation results confirmed that the developed models have reliability, robustness, and predictability.

Adsorption of Hexavalent Chromium Using Activated Carbon Produced from Sargassum ssp.: Comparison between Lab Experiments and Molecular Dynamics Simulations.

Adsorption is one of the most successful physicochemical approaches for removing heavy metal contaminants from polluted water. The use of residual biomass for the production of adsorbents has attracted a lot of attention due to its cheap price and environmentally friendly approach. The transformation of Sargassum—an invasive brown macroalga—into activated carbon (AC) via phosphoric acid thermochemical activation was explored in an effort to increase the value of Sargassum seaweed biomass. Several techniques (nitrogen adsorption, pHPZC, Boehm titration, FTIR and XPS) were used to characterize the physicochemical properties of the activated carbons. The SAC600 3/1 was predominantly microporous and mesoporous (39.6% and 60.4%, respectively) and revealed a high specific surface area (1695 m2·g−1). To serve as a comparison element, a commercial reference activated carbon with a large specific surface area (1900 m2·g−1) was also investigated. The influence of several parameters on the adsorption capacity of AC was studied: solution pH, solution temperature, contact time and Cr(VI) concentration. The best adsorption capacities were found at very acid (pH 2) solution pH and at lower temperatures. The adsorption kinetics of SAC600 3/1 fitted well a pseudo-second-order type 1 model and the adsorption isotherm was better described by a Jovanovic-Freundlich isotherm model. Molecular dynamics (MD) simulations confirmed the experimental results and determined that hydroxyl and carboxylate groups are the most influential functional groups in the adsorption process of chromium anions. MD simulations also showed that the addition of MgCl2 to the activated carbon surface before adsorption experiments, slightly increases the adsorption of HCrO4− and CrO42− anions. Finally, this theoretical study was experimentally validated obtaining an increase of 5.6% in chromium uptake.

Adsorption of Phthalate Acid Esters by Activated Carbon: The Overlooked Role of the Ethanol Content.

Ethanol has great effects on the adsorption of phthalate acid esters (PAEs) on activated carbon (AC), which are usually overlooked and hardly studied. This study investigated the overlooked effects of ethanol on the adsorption of PAEs in alcoholic solutions. The adsorption capacities of dibutyl phthalate (DBP) on AC in solutions with ethanol contents of 30, 50, 70, and 100 v% were only 59%, 43%, 19%, and 10% of that (16.39 mg/g) in water, respectively. The ethanol content increase from 50 v% to 100 v% worsened the adsorption performances significantly with the formation of water–ethanol–DBP clusters (decreasing from 13.99 mg/g to 2.34 mg/g). The molecular dynamics simulation showed that the DBP tended to be distributed farther away from the AC when the ethanol content increased from 0 v% to 100 v% (the average distribution distance increased from 5.25 Å to 15.3 Å). The PAEs with shorter chains were more affected by the presence of ethanol than those with longer chains. Taking DBP as an example, the adsorption capacity of AC in ethanol (0.41 mg/g) is only 2.2% of that in water (18.21 mg/g). The application results in actual Baijiu samples showed that the adsorption of PAEs on AC had important effects on the Baijiu flavors.

Adsorptive desulfurization using period 4 transition metals oxide: A study of Lewis acid strength derived from the adsorbent ionic-covalent parameter

Pearson’s Hard and Soft Acids and Bases (HSAB) principle has been widely utilized in describing the adsorption trend of sulfur compounds when using transition metal/metal oxides as adsorbents. This study is the first to report on the use of the ionic covalent parameter (ICP) for explaining the adsorption trend of sulfur compounds. Period 4 transition metal oxides (Zn-oxide, Cr-oxide, Mn-oxide, Co-oxide, Fe-oxide, Cu-oxide, Ni-oxide), which act as intermediate Lewis acids, were incorporated into activated carbon (AC), and used in the adsorptive desulfurization (ADS) of model and commercial diesel samples. The study findings show that desulfurization activity in model diesel increased in proportion to the concentration of adsorbent Lewis acid sites. With commercial diesel, the loading of metal oxides significantly enhanced the sulfur adsorption capacity of AC and increased its selectivity for steric sulfur compounds. The results showed a poor correlation between sulfur removal and the Pearson hardness ηth of the intermediate metal oxide cations. However, a strong inverse linear relationship was observed: sulfur removal decreased as the ICPth of the adsorbent metal oxide increased. The study findings suggest a novel concept, i.e. that the ICP is a more accurate measure of the Lewis acidic strength of transition metal oxides with varying crystal structures and metal geometries, and their subsequent desulfurization performance. Kinetic modelling showed that chemisorption was the controlling mechanism. The fixed-bed ADS of commercial diesel when using unmodified AC is best described by the Yoon-Nelson and Thomas models. Adsorption when using the Ni-oxide/AC adsorbent was correlated to the filtration advection–dispersion equation.