Carbon Adsorption Systems Research Articles

Economic and carbon emission analysis of two typical denitrification systems for sintering process in the iron and steel industry

The transition of the Chinese iron and steel industry to ultralow emissions has accelerated the development of denitrification technologies. Considering the existing dual carbon targets, carbon emissions must be considered as a critical indicator when comparing denitrification systems. Consequently, this study provided a comprehensive cost-benefit model for denitrification in the steel industry, encompassing additional carbon emissions resulting from the implementation of denitrification systems. Activated-carbon adsorption and selective catalytic reduction (SCR) systems are two efficient techniques for controlling NOx emissions during sintering. Based on this model, a cost-benefit analysis of these two typical systems was conducted, and the results indicated that the unit flue-gas abatement costs of SCR and activated-carbon adsorption systems were 0.00275 and 0.0126 CNY/m3, and the unit flue-gas abatement benefits were 0.0072 and 0.0179 CNY/m3, respectively. Additionally, the effect of operational characteristics on operating costs, including duration and material prices, was analyzed. When treating the flue gas, the two systems released 0.0020 and 0.0060 kg/m3 of carbon dioxide, respectively. The primary sources of carbon emissions from the SCR and activated-carbon adsorption systems are the production of reducing agents and system operations, respectively. Furthermore, considering the features of the activated carbon adsorption system for simultaneous desulfurization, a SCR- wet flue gas desulfurization (WFGD) technology route was developed for comparison with the activated carbon adsorption system.

Correction to: Effective transport properties for the pyridine-granular activated carbon adsorption system

Correction to: Effective transport properties for the pyridine-granular activated carbon adsorption system

Reduction wastewater discharge in second-generation acetone-butanol-ethanol (ABE) fermentation process by adsorptive removal of organic acids toward the broth recycling system

The treatment of high chemical oxygen demand (COD) organic wastewater is one of the major technical bottlenecks for the industrialization of second-generation biobutanol production. An effective strategy to decrease the wastewater discharge in biobutanol fermentation process is broth recycling (BR). Nevertheless, the conventional BR process suffered from server organic-acid by-products inhibition, causing low butanol yield. In this study, to solve the barrier, active carbon (AC) adsorption system was hybrid with the acetone-butanol-ethanol (ABE) fermentation and ex-situ product separation (ESPR) units. After fermentation and pervaporation, organic acids that remaining in the ABE-separated broth were partially adsorbed onto AC so that improve the continuity and efficiency of the BR process. The physicochemical characterizations of different types of commercial ACs and the organic acids adsorption efficiency was evaluated by analyzing the static and dynamic adsorptions kinetics. When adopting the DD-type AC (code C299105), the better adsorbent for organic acids removal, 87.50% of fermentative wastewater can be saved whilst the ABE concentrations were also kept constantly at 15.22 ± 0.45 g L−1 in the following cycles of fermentation, and the ABE productivity was almost no changed (0.21 ± 0.01 g L−1 h−1) after 3 cycles of operation. Therefore, the AC assisted ESPR process is an attractive method for ABE production with low wastewater discharge.

Corrigendum to “Chemical Adsorption of Nitrogen Dioxide with an Activated Carbon Adsorption System” [Aerosol Air Qual. Res. 19: 2568-2575

The original version of this article omitted an affiliation for Chih-Hsiang Chen. The correct affiliations are listed below. Department of Finance, Ming Chuan University, Taipei 11103, TaiwanSchool of Software and Microelectronics, Peking University, Beijing 102600, China

Evaluation of Sand Filtration and Activated Carbon Adsorption for the Post-Treatment of a Secondary Biologically-Treated Fungicide-Containing Wastewater from Fruit-Packing Industries

In this work, a sand filtration-activated carbon adsorption system was evaluated to remove the fungicide content of a biologically treated effluent. The purification process was mainly carried out in the activated carbon column, while sand filtration slightly contributed to the improvement of the pollutant parameters. The tertiary treatment system, which operated under the batch mode for 25 bed volumes, resulted in total and soluble COD removal efficiencies of 76.5 ± 1.5% and 88.2 ± 1.3%, respectively, detecting total COD concentrations below 50 mg/L in the permeate of the activated carbon column. A significant pH increase and a respective electrical conductivity (EC) decrease also occurred after activated carbon adsorption. The total and ammonium nitrogen significantly decreased, with determined concentrations of 2.44 ± 0.02 mg/L and 0.93 ± 0.19 mg/L, respectively, in the activated carbon permeate. Despite that, the initial imazalil concentration was greater than that of the fludioxonil in the biologically treated effluent (i.e., 41.26 ± 0.04 mg/L versus 7.35 ± 0.43 mg/L, respectively). The imazalil was completely removed after activated carbon adsorption, while a residual concentration of fludioxonil was detected. Activated carbon treatment significantly detoxified the biologically treated fungicide-containing effluent, increasing the germination index by 47% in the undiluted wastewater or by 68% after 1:1 v/v dilution.

Equilibrium and Kinetic Modelling of Aqueous Cadmium Ion and Activated Carbon Adsorption System

Despite their extensive and decade-long application in wastewater treatment, activated carbon remains one of the most viable adsorbents, with substantive practical application, due to their high pollutant binding capacity. In this study, commercially available activated charcoal was applied in the uptake of aqueous cadmium [Cd(II)] ion. The effect of some process variables on the Cd (II) uptake was investigated via batch mode. Furthermore, the adsorbents’ surface charge (pHPZC), surface morphology (using SEM) and available surface functional groups (using FTIR) were explained. The pH dependence of the present adsorption system was revealed, while the optimum pH was recorded at pH 5.0. Similarly, the Cd (II) uptake (mg/g) decreased with increasing adsorbent dosage due to possible active sites clogging, overcrowding and interference. Furthermore, the isothermal and kinetics analyses of the experimental data, which were aptly validated using the hybrid error model, respectively depicted the Langmuir isotherm and pseudo-second-order kinetic model as the best fit. A Langmuir adsorption capacity of 682.5 mg g−1 was also recorded in the study. Consequently, the present adsorption system was characterized by an equilibrium timeframe of industrial practicability; hence, the adsorbent was successfully applied for the aqueous Cd (II) uptake.

Managing siloxanes in biogas-to-energy facilities: Economic comparison of pre- vs post-combustion practices

Siloxanes present in small concentrations in biogas interfere with the operation of biogas-to-energy facilities. During biogas combustion, siloxanes form white deposits on engine components (engine heads, spark plugs, valves) in crystals or amorphous forms depending on the temperature. The purpose of this study was to evaluate the economic feasibility of biogas-to-energy systems for managing the operational challenges due to siloxanes in biogas. The facility maintenance cost data were compiled by a survey of biogas-to-energy facilities in the United States. Economic analyses were performed to compare the operational costs due to increased maintenance for removing the white deposits forming on the engine components and the installation of a pretreatment system (carbon adsorption) to remove siloxanes prior to combustion. Numerical analyses showed that for the facilities with operating capacities less than 1300 m3/h (750 scfm), the costs for installation and operation of the carbon adsorption system exceeded the maintenance costs for removal of deposits from the engine components. The maintenance costs correlated well with the reported maintenance needs which were between 120 and 800 man hours per year. On the basis of siloxane removal costs alone, it is not economically feasible to install a carbon adsorption system for siloxane removal prior to combustion for small facilities processing less than 1300 m3/h (750 scfm) of biogas. However, using a process for siloxane removal prior to gas engines (e.g., carbon adsorption) would be improve the overall performance of the gas engines and reduce maintenance need at all facilities.

Chemical Adsorption of Nitrogen Dioxide with an Activated Carbon Adsorption System

ABSTRACT Nitrogen dioxide (NO2) is a pollutant that directly harm the human respiratory system, lead to inflammation, as well as to form the secondary aerosol pollutants. The main NO2 sources, combustion or thermal processes, were well controlled. However, the metal etching operation in semiconductor industry emits flue gases with reddish-brown NO2 fume that leads to visibility reduction, acidic odor, as well as negative effects on human health. In this study, a stream of flue gases with low NO2 (230 ± 10 ppm) and NO (50 ppm) concentrations were conducted to pass through an activated carbon-packed fixed bed for analyzing the adsorptive conversion behavior of NO2 by the activated carbon (AC) at room temperature. The repeated adsorption test was carried out by washing the regenerated waste carbon with a caustic solution and water and drying. Results propose that at the beginning of adsorption, nitrogen dioxide combined with carbon to form NO and desorbed from carbon surface. The net adsorptive conversion removal capacity of NO2 by the virgin AC and regenerated AC was 224 and 155 mg g–1 AC, respectively. Regeneration restored around 70–75% of effective surface area, pore volume, and adsorptive conversion capacity of the virgin AC. Leached caustic solution obtained from the carbon regeneration contained only nitrate and the phenomena indicates the adsorbed -C2(ONO2) hydrolyzed following the Eq. (2) -C2(ONO2) + H2O → 3 -C* + -C(O) + 2 HNO3, where -C* denotes active site on the carbon surface.

Metronidazole removal in powder-activated carbon and concrete-containing graphene adsorption systems: Estimation of kinetic, equilibrium and thermodynamic parameters and optimization of adsorption by a central composite design

ABSTRACTMetronidazole (MNZ) removal by two adsorbents, i.e., concrete-containing graphene (CG) and powder-activated carbon (PAC), was investigated via batch-mode experiments and the outcomes were used to analyze the kinetics, equilibrium and thermodynamics of MNZ adsorption. MNZ sorption on CG and PAC has followed the pseudo-second-order kinetic model, and the thermodynamic parameters revealed that MNZ adsorption was spontaneous on PAC and non-spontaneous on CG. Subsequently, two-parameter isotherm models, i.e., Langmuir, Freundlich, Temkin, Dubinin–Radushkevich and Elovich models, were applied to evaluate the MNZ adsorption capacity. The maximum MNZ adsorption capacities () of PAC and CG were found to be between 25.5–32.8 mg/g and 0.41–0.002 mg/g, respectively. Subsequently, the effects of pH, temperature and adsorbent dosage on MNZ adsorption were evaluated by a central composite design (CCD) approach. The CCD experiments have pointed out the complete removal of MNZ at a much lower PAC dosage by increasing the system temperature (i.e., from 20°C to 40°C). On the other hand, a desorption experiment has shown 3.5% and 1.7% MNZ removal from the surface of PAC and CG, respectively, which was insignificant compared to the sorbed MNZ on the surface by adsorption. The overall findings indicate that PAC and CG with higher graphene content could be useful in MNZ removal from aqueous systems.

Effective transport properties for the pyridine-granular activated carbon adsorption system

In this work, the kinetics of pyridine adsorption onto granular activated carbon was studied from the point of view of an up-scaling process by using the method of volume averaging. The pore and surface effective diffusivities were estimated by supposing simple microscale geometries (ordered media of cylinders and spheres) and those of images processed from SEM (Scanning Electron Microscopy) micrographs. In addition, as a rough estimate, the point surface diffusivity is reported. The results revealed that the up-scaled diffusional model satisfactorily interpreted the concentration decay curves and the effective diffusivity was found to be an increasing function of the concentration, mainly due to the contribution of surface diffusion. In general, the diffusivity coefficients involved in the adsorption system are related through the expression molecular diffusivity = 22 i‚' point surface diffusivity = 5/2 x‚' pore effective diffusivity = 1/12 x ‚' surface effective diffusivity.

Effect of Adsorbent Particle Layering on Performance of Conventional and Tapered Fixed-Bed Adsorbers

Experimental and modeling studies were conducted for the adsorption of phenol from aqueous solutions onto activated carbon in fixed beds with the adsorbent particles layered according to particle size. In the conventional stratified cylindrical adsorber (SCA), the particles were layered according to natural stratification, and increased in size with column depth. In the reverse stratified tapered adsorber (RSTA), the particle size decreased with column depth, and the fluid velocity decreased in the direction of flow. Experimental data indicate that for a uniform particle size distribution, the breakthrough time for the RSTA was about 60% higher than for the SCA under identical carbon loading and flow conditions. The homogeneous solid phase diffusion model with Linear-Freundlich isotherm was used to model the layered adsorbers. It provides excellent predictions for breakthrough curves at various column depths. Bed capacity utilization can be increased with the RSTA due to the sharpening of the solute front, and this will translate into lower capital and operating costs for the carbon adsorption system due to the smaller unit required, lower carbon inventory, and lower pumping costs.

Miscellaneous organic NESHAP compliance for a new countermeasure flare production facility at the Milan Army Ammunition Plant

AbstractFR Countermeasures, Inc. (FRC), a division of Flight Refuelling Ltd. of the United Kingdom, has sited a countermeasure flare production facility at the Milan Army Ammunition Plant (MLAAP) in Milan, Tennessee. Franklin Engineering Group, Inc. (Franklin Engineering) worked in cooperation with FRC to develop an air permitting strategy that would allow expedited regulatory review and approval to meet an aggressive construction schedule. This strategy addressed eventual compliance with the 40 CFR, Subpart FFFF (Miscellaneous Organic NESHAP (MON) standard) by permitting the facility as a conditional major source to allow for construction, start‐up, and initial operation with eventual operation as a major source (i.e., Title V) at full processing rates.The facility was modeled after Flight Refuelling Ltd.'s North Stockbridge, U.K., manufacturing facility, with several important distinctions. First, the regulatory standards for air emissions from this type of facility in the United States, in combination with a higher production capacity, necessitated a higher level of control for hazardous air pollutants (HAPs). Additionally, FRC had to address increased volume of effluent water from the solvent recovery process and carbon regeneration process. Finally, this effluent water had to meet the Sewer Use Agreement, which required additional acetone removal prior to discharge to the sewer. The selection of an integrated air pollution control system to achieve these environmental objectives required special consideration of safety issues inherent to energetics manufacturing.After consideration of several air pollution control technologies, FRC and Franklin Engineering selected an activated carbon adsorption system for treatment of combined gases from two main batch sources: mixing and drying processes. This system will achieve greater than 95 percent recovery of HAPs from these processes, as required for regulatory purposes. Carbon beds are regenerated via steam stripping to yield two streams: recovered hydrocarbons and a recondensed aqueous stream. Recovered solvents are reused or sold. The aqueous stream is combined with water from the batch wash process and steam stripped for solvent recovery. Crucial to assuring safe operation of the air pollution control system was the utilization of a flame isolation valve with gas cartridge actuators to eliminate potential flame/deflagration passage between each process unit. © 2004 Wiley Periodicals, Inc.

Capture of Organic Vapors Using Adsorption and Electrothermal Regeneration

Activated-carbon-fiber cloth (ACFC) is an alternative adsorbent to granular activated carbon (GAC) for removing and recovering organic vapors from gas streams. Electrothermal desorption (ED) of ACFC provides rapid regeneration while requiring less energy compared to traditional regeneration techniques used with GAC. This paper provides proof-of-concept results from a bench-scale ACFC adsorption system. The automated system captured 1,000 ppmv of hazardous air pollutants/volatile organic compounds (HAPs/VOCs) from air streams and demonstrated the use of ED, using ac voltage, to recover the HAP/VOC as a pure liquid. The desorbed HAP/VOC condensed onto the inner walls of the adsorber and was collected at the bottom of the vessel, without the use of ancillary cooling. Seventy percent of the HAP/VOC was collected per cycle as condensate, with the balance being retained in the regenerated adsorber or recycled to the second adsorber. ED with in-vessel condensation results in minimal N\d2 consumption and short regeneration cycle times allowing the process to be cost competitive with conventional GAC-based adsorption processes. This technology extends the application of carbon adsorption systems to situations that were previously economically and physically impractical.

Using organoclays to enhance carbon filtration

Organoclays have found increased acceptance as pre-treatment for activated carbon adsorption systems in both groundwater and wastewater cleanup. The reason is that activated carbon tends to become quickly blinded by large organic molecules of low solubility, particularly oils. However, it is also well established that activated carbon is more efficient at low concentrations of organic contaminants than at higher ones, i.e. at less than 1 ppm. With organoclays it is exactly the opposite, they are better at removing organics at higher concentrations, above 3 ppm. Therefore it is cost effective in these applications to use two or more vessels in series, the first one filled with organoclay, the remainder with activated carbon. The economics make sense, even though the organoclay is not regenerated, because of the reduction in down time every time a carbon vessel has to be changed out. Use of organoclays increases the volume treated by carbon in many applications seven to nine fold. In the case of other organic contaminants, as the aqueous solubility increases, the efficiency decreases, except in the case of methylene chloride, which it removes at far higher efficiency then carbon. This article presents the results of a series of tests, including K d determinations, jar tests, and mini-column tests. These tests determined the adsorption capacity and efficiency of organoclay and activated carbon for the removal of benzene, toluene, xylene and naphtalene from water. These tests were followed by adding the four compounds into one container to see if the combination of organoclay, followed by carbon, would be more efficient then each sorbent alone. The tests also compared the efficiency of organoclay versus carbon for the removal of various oils from water.

Photocatalytic pretreatment of contaminated groundwater for biological nitrification enhancement

AbstractThe sequential photocatalytic/biological treatment of a contaminated groundwater from a local industrial site was studied. The ground water contained approximately 100 mg dm−3 ammonia, as well as mg dm−3 levels of nitrification‐inhibiting organics such as chlorobenzene. An existing treatment system uses carbon adsorption pretreatment to remove the nitrification inhibitors before the water is treated in a biological nitrification system. Photocatalysis, using a corrugated plate photoreactor, was studied as an alternative to the carbon adsorption system for inhibitor removal. Photocatalytic pretreatment was found to significantly enhance the extent of biological nitrification. An optimal pretreatment time appeared to exist, since further pretreatment resulted in accumulation of nitrite. Although further study is required, there appears to be a potential for using photocatalysis to remove inhibitors from biological nitrification systems.© 2002 Society of Chemical Industry

Comparison of a single grain activated carbon and column adsorption system

Results from a single grain activated carbon adsorption study indicate that the effective diffusion coefficient was from 0.65×10 −6 to 7.4×10 −6 cm 2/s for H 2S in the concentration range of 20–300 ppmv at 23 °C for both virgin activated carbon (FAC) and impregnated-regenerative activated carbon (IRAC). The effective diffusivity of the IRAC was nearly two times the FAC for H 2S adsorption. The surface reaction of H 2S-impregnated regenerative activated carbon was faster than that of H 2S and virgin activated carbon. The single grain activated carbon kinetic curve and a time scale conversion method were used to predict the breakthrough curve and the adsorption capacity of the column adsorption system. The single grain activated carbon adsorption system measured the breakthrough curve more efficiently than column adsorption. The prediction error was between 10 and 30%. Improvement can be further achieved by enhanced experimental approaches. It has a great potential for scale-up.

STUDY OF THE ADSORPTION/REMOVAL EFFICIENCY OF WOVEN AND NONWOVEN ACTIVATED CARBON FABRICS FOR MEK

The initial gaseous contaminant removal efficiency and adsorption characteristics for various commercially available activated carbon fabrics were determined at air flow rates, air temperature and pressure drop typical of an indoor air residential or small office environment. Methyl ethyl ketone (MEK) was used as the hazardous air pollutant for the laboratory tests. For the range of MEK concentrations tested, the initial fabric adsorption efficiency decreased as concentration increased, although the total adsorption capacity (g/g) increased. Initial fabric efficiencies were also higher at a lower air flow rate. The pure activated carbon nonwoven felt had higher adsorption capacity as well as higher initial adsorption efficiencies than the woven carbon fabrics tested. In all of the fabrics which were tested, the maximum adsorption efficiency was achieved initially, lasted only momentarily, then steadily decreased until adsorption capacity was reached. It was also observed that fabrics that had reached capacity, but were then subjected to the same air flow conditions as occurred during the adsorption process (except without the MEK present), immediately began to desorb the adsorbed MEK. This raises concern about the application of carbon adsorption systems for indoor environments, if concentrations are highly variable due to the potential of desorption from the fabric.

USING ORGANOCLAYS TO ENHANCE CARBON FILTRATION

Organoclays have found increased acceptance as pre-treatment for activated carbon adsorption systems in both groundwater and wastewater cleanup. The reason is that activated carbon tends to become quickly blinded by large organic molecules of low solubility, particularly oils. However, it is also well established that activated carbon is more efficient at low concentrations of organic contaminants than at higher ones, i.e. at less than 1 ppm. With organoclays it is exactly the opposite, they are better at removing organics at higher concentrations, above 3 ppm. Therefore it is cost effective in these applications to use two or more vessels in series, the first one filled with organoclay, the remainder with activated carbon. The economics make sense, even though the organoclay is not regenerated, because of the reduction in down time every time a carbon vessel has to be changed out. Use of organoclays increases the volume treated by carbon in many applications seven to nine fold. In the case of other organic contaminants, as the aqueous solubility increases, the efficiency decreases, except in the case of methylene chloride, which it removes at far higher efficiency then carbon. This article presents the results of a series of tests, including Kd determinations, jar tests, and mini-column tests. These tests determined the adsorption capacity and efficiency of organoclay and activated carbon for the removal of benzene, toluene, xylene and naphtalene from water. These tests were followed by adding the four compounds into one container to see if the combination of organoclay, followed by carbon, would be more efficient then each sorbent alone. The tests also compared the efficiency of organoclay versus carbon for the removal of various oils from water.

Treatment of chlorinated ethenes in groundwater with ozone and hydrogen peroxide

AbstractA study was conducted to enhance the performance of an advanced oxidation process in treating chlorinated ethenes in groundwater at IBM's groundwater treatment system at its Essex Junction, Vermont facility. A model describing the reaction kinetics and mass transfer of a co‐current ozone injection process is presented. This model, in conjunction with experiments, demonstrates that the treatment performance of the ozone treatment process at a given ozone/air concentration and ozone mass flowrate cannot be improved by varying process operating parameters such as number of ozone injectors utilized, use of a static mixer, or variation of groundwater flowrate through each injector. This is because dissolved ozone reaches equilibrium with the injected ozone/air mixture within two seconds of initial contact. Also, the Venturi‐type ozone injection system presently in use destroys nearly half of the injected ozone.Injection of hydrogen peroxide in conjunction with ozone increases the overall tetrachloroethylene (PCE) treatment efficiency by a factor of four (in comparison to ozone alone) at a H2O2/O3 mass ratio of between 1 and 2. Treatment of trichloroethylene (TCE) is enhanced by a factor of two. This enhancement of the oxidative treatment process results in a reduction in solvent mass load to a granular activated carbon (GAC) adsorption system located downstream, thus potentially reducing the usage GAC and regeneration of spent GAC. However, residual hydrogen peroxide and/or hydroxyl free radicals from the oxidation process effluent may interact adversely with certain grades of GAC; the causes of this interaction and methods to attenuate it (i.e., the use of more resistant grades of GAC) are discussed. Overall O3/H2O2/GAC system operating costs can potentially be reduced significantly (up to $ 20K annually). An economic analysis and system operation/cost optimization study are presented.

Competitive Interactions among Components of Humic Acids in Granular Activated Carbon Adsorption Systems: Effects of Solution Chemistry

The adsorption by activated carbon of a humic acid extracted from Laurentian soil and polystyrene sulfonate, a synthetic polymer, was investigated. Size-exclusion chromatography was used to study competitive interactions among humic components by measuring the changes in molecular weight distributions of molecules remaining in solution after adsorption. The adsorption of humic substances was governed, in large part, by molecular size distribution in relation to adsorbent pore sizes. We demonstrate that the extent of adsorption increases with increasing ionic strength and calcium content. Increases in the extent of adsorption are due, in part, to a decrease in macromolecule size; our data suggest that these changes occur in solution prior to adsorption. The results of analyses employing size-exclusion chromatography demonstrate that low molecular weight fractions of humic material are preferentially removed from solution. Increases in the extent of adsorption correspond to shifts in the adsorbed molecular ...