3,5-Dinitrosalicylic Acid Adsorption Using Granulated and Powdered Activated Carbons

Some nitroaromatic compounds are found in wastewater from industries such as the weapons industry or the wine industry. One of these compounds is 3,5-dinitrosalicylic acid (DNS), widely used in various tests and frequently found as an emerging pollutant in wastewater and to which the required attention has not been given, even though it may cause serious diseases due to its high toxicity. This study investigated the adsorption of DNS using granulated activated carbon (GAC) and powdered activated carbon (PAC) at different temperatures. The results show that in equilibrium, the adsorption takes place in more than one layer and is favorable for the removal of DNS in both GAC and PAC; The maximum adsorption capacity was obtained at 45 °C, with values of 6.97 mg/g and 11.57 mg/g, respectively. The process is spontaneous and exothermic. In addition, there was a greater disorder in the solid-liquid interface during the desorption process. The predominant kinetics using GAC (7.14 mg/g) as an adsorbent is Elovich, indicating that there are heterogeneous active sites, and when PAC (10.72 mg/g) is used, Pseudo-second order kinetics predominate, requiring two active sites for DNS removal. External mass transfer limitations are only significant in GAC, and ATR-FTIR studies in PAC demonstrated the participation of functional groups present on the adsorbent surface for DNS adsorption.     

Novel three-stage kinetic model for aqueous benzene adsorption on activated carbon

We propose a novel kinetic model for adsorption of aqueous benzene onto both granular activated carbon (GAC) and powdered activated carbon (PAC). The model is based on mass conservation of benzene coupled with three-stage adsorption: (1) the first portion for an instantaneous stage or external surface adsorption, (2) the second portion for a gradual stage with rate-limiting intraparticle diffusion, and (3) the third portion for a constant stage in which the aqueous phase no longer interacts with activated carbon. An analytical solution of the kinetic model was validated with the kinetic data obtained from aqueous benzene adsorption onto GAC and PAC in batch experiments with two different solution concentrations (C(0)=300 mg L(-1), 600 mg L(-1)). Experimental results revealed that benzene adsorption for the two concentrations followed three distinct stages for PAC but two stages for GAC. The analytical solution could successfully describe the kinetic adsorption of aqueous benzene in the batch reaction system, showing a fast instantaneous adsorption followed by a slow rate-limiting adsorption and a final long constant adsorption. Use of the two-stage model gave incorrect values of adsorption coefficients in the analytical solution due to inability to describe the third stage.     

Kinetics of adsorption and desorption of Pb(II) in aqueous solution on activated carbon by two-site adsorption model

The adsorption and desorption equilibrium and kinetics of lead ions from aqueous solutions on a granular activated carbon (GAC) were examined. Rapid increase followed by slow increase in Pb(II) amount on the GAC was observed as a function of time for the adsorption, while rapid decrease and consecutive very slow decrease was observed in desorption. Based on the experimental results, a two-site adsorption model was proposed for the adsorption and the desorption of Pb(II) under the study conditions. The Pb(II) adsorption on the GAC was estimated to have simultaneously occurred on the strong and the weak adsorption sites. Conventional Langmuir-type kinetic equations were introduced to quantitatively predict the adsorption and desorption with the two-site model by optimizing the parameters to fit the equilibrium and the kinetic experimental results. The equilibrium and kinetic experimental results could be represented by the equations by using one set of the common Langmuir parameters. Resultant kinetic parameters revealed that the adsorption equilibrium constant was two orders of magnitude greater for strong adsorption site than for weak adsorption site, though the maximum number of weak adsorption site was 1.5 times as great as that of strong adsorption site. The strong adsorption equilibrium constant resulted from a small desorption rate constant for the site. The equations were demonstrated to be applicable for predicting other desorption performances as well.     

Modeling and Thermodynamics of Methylene Blue and Acid Blue 80 Adsorption onto Potato Residue Based Activated Carbon

A study was made on the adsorption kinetics and thermodynamics of methylene blue(MB) and acid blue 80(AB80) onto powder of activated carbon(PAC) prepared by chemical method from dry potato residue(DPR). The PAC was characterized by N₂ adsorption-desorption isotherms analysis and scanning electron microscopy. The ma- ximum adsorption capacities of PAC for MB and AB80 at 303 K are 532.19 and 156.22 mg/g, respectively. The results indicate that the adsorption kinetics of the selected dyes on PAC is well-described by the pseudo-second order model. And their thermodynamic data were analyzed via the isotherms of Langmuir, Freundlich, Redlich-Peterson, Toth and Sips, and the thermodynamic parameters were calculated. The results show that PAC is a fast and effective adsorbent for removing the cationic dyes from aqueous solutions.     

Perchlorate removal by granular activated carbon coated with cetyltrimethyl ammonium bromide

In this study, granular activated carbon (GAC) coated with cetyltrimethyl ammonium bromide (CTAB) (GAC-CTAB) was synthesized to remove perchlorate from water via adsorption. Laboratory-scale batch experiments were performed to study the factors affecting the perchlorate adsorption by GAC-CTAB, including the CTAB content and solution pH, and explore the mechanisms behind the adsorption phenomenon. The novel GAC-CTAB material was characterized by scanning electron microscopy (SEM), zeta potential measurement and Brunauer-Emmett-Teller (BET) analysis. The characterization tests showed that CTAB was deposited on the GAC surface, pH(pzc) of the material was between 2.0 and 3.0, and the BET specific surface area was reduced from 925 to 729 m(2)/g with the increasing CTAB content from 0 to 0.034 mmol CTAB/g GAC. The adsorption process was better described by a pseudo-second-order kinetics model and the Freundlich adsorption model. The CTAB content and solution pH significantly influenced the kinetics and chemical equilibrium of the adsorption. When the CTAB content was increased from 0.0.023 to 0.135 mmol CTAB/g GAC, the K in the Freundlich adsorption isotherm increased from 0.071 to 0.19 mmol/g. The optimal adsorption typically occurred at pH 2-3, close to the pH(pzc) of the solution. Finally, the mechanisms for the adsorption of perchlorate on GAC-CTAB were associated with surface complexation, electrostatic interaction and ion exchange.     

Experimental and Theoretical Study of MTBE Adsorption from Polluted Water on GAC and PAC in Continuous Process

Methyl tertiary butyl ether (MTBE) is an organic compound thatis used to increase the gasoline octane number. At the beginning of 1980s, by discovering the undesirable effects of tetra ethyl lead usage in fuel, MTBE began to be used worldwide. But gradually the undesirable effects of MTBE on environment had been revealed. Adsorption is the most conventional and economical technology for MTBE removal from polluted water. In this research, some experiments have been done for studying the adsorption of MTBE on different solid adsorbent in continuous processes. In continuous experiments, the water polluted with known initial MTBE concentration passes through an adsorption column containing two kinds of adsorbent including granular activated carbon (GAC), powdered activated carbon (PAC). By measuring MTBE concentration in exit flow at different times the effect of different operating parameters such as temperature, pH, and flow rate have been studied and the optimum condition have been determined. The batch experimental results have been used to calculate the constant parameters of Langmuir adsorption isotherm equations. A dynamic simulation of MTBE adsorption on activated carbon in an adsorption column has been proposed. The comparison of the experimental data with the values given by the proposed model for similar operating conditions, verifies the accuracy of the proposed mathematical model.      

Adsorption and biotransformation of 17β-estradiol in biological activated carbon adsorbers

As the first systematic study dealing with the adsorption of estrogens by granular activated carbon (GAC), the removal behavior of 17β-estradiol (E2) and its biotransformation product of estrone (E1) in fixed GAC columns was examined using four biological activated carbon (BAC) columns (BAC-1～BAC-4) generated by coating four GAC columns with detached microorganisms from the riverbed sediment of a representative drinking river water source containing lower content of natural organic matter (NOM). For comparison, parallel adsorption experiments were also performed using another four GAC columns (GAC-1～ GAC-4) packed by strictly following the configurations of four BAC columns. Adsorption experimental results obtained by intermittently spiking E2 over a total running period about 350 days into the river water mixed with or without a peaty water containing higher content of NOM showed that E2 was readily removed by adsorption and the combined adsorption/biodegradation. The vertical profiles of E2 and E1, which have great significance for better understanding and optimization of the adsorption process for removal of human estrogens, were also obtained.     

Preparation of a novel magnetic powder resin for the rapid removal of tetracycline in the aquatic environment

Magnetic powder resin Q150 with high specific surface area of 1074 m~2/e was prepared by the membrane emulsificationsuspension polymerization technique.Adsoption of tetracycline on the obtained sorbent Q150 was evaluted by using the granule resin(GR) XAD-4,the powder activated carbon(PAC) 1240AC and the granule activated carbon(GAC) HD4000 for comparison.It was found that Q150 had a larger adsorption capacity,faster kinetic and easier regeneration under alkaline condition.The results suggested that the powder resin(PR) Q150 would be a promising sorbent for removing antibiotics and even other organic micropollutants from the aquatic environment.     

Competitive adsorption of the herbicide fluroxypyr and tannic acid from distilled and tap water on activated carbons and their thermal desorption

A study was conducted on batch and column competitive adsorption of fluroxypyr (FLX) and tannic acid (TA) from distilled (DW) and tap water (TW) on activated carbon cloth (ACC) and granular activated carbon (GAC). Thermal desorption of the adsorbates from the spent ACC was also studied. FLX adsorption was higher from TW than from DW at low FLX equilibrium concentrations, and the inverse was observed at high FLX concentrations. The presence of TA diminished the amount of FLX adsorbed from both solvents due to partial blocking of the microporosity, but the same trends as before were observed at low and high FLX concentrations. Carbon consumption, obtained from the breakthrough curves, was lower as a function of superficial contact time with ACC than with GAC. The presence of TA increased carbon consumption, which was related to the microporosity of the adsorbents. Thermal desorption profiles of the spent ACC showed two peaks and one peak after adsorption from DW and TW, respectively. Desorption peaks shifted to higher temperatures with an increase in the heating rate, allowing the apparent activation energies and pre-exponential factors of the desorption processes to be determined.     

Modeling breakthrough curves of volatile organic compounds on activated carbon fibers

Granular activated carbon (GAC) and more recently activated carbon fibers (ACF) are used for the treatment of volatile organic compounds (VOC) in industrial processes. The purpose of this study was to investigate the adsorption kinetics of ACF to eliminate VOC from polluted air. This approach is carried out by modeling experimental breakthrough curves with two kinds of models: an equilibrium model and a mass transfer model based on a linear driving force (LDF) in conjunction with the Langmuir equilibrium model. The results show the influence of the intraparticle diffusion on the adsorption kinetics of ACF, in spite of their small fiber diameter. Moreover, external diffusion kinetics is fast because of the influence of the large external surface area of ACF on the VOC mass transfer.     

Adsorption of phenol by oil-palm-shell activated carbons

Steam activated carbons from oil-palm shells were prepared and used in the adsorption of phenol. The activated carbon had a well-developed mesopore structure which accounted for 45% of the total pore volume. The BET surface area of the activated carbon was 1183 m²/g and a total pore volume of 0.69 cm³/g using N₂ adsorption at 77 K. The adsorption capacity of the activated carbon for phenol was 319 mg/g of adsorbent at 298 K. The adsorption isotherms could be described by both the Langmuir-Freundlich and the Langmuir equations. The adsorption kinetics consisted of a rapid initial uptake phase, followed by a slow approach to equilibrium. A new multipore model is proposed that takes into account of a concentration dependent surface diffusion coefficient within the particle. This model is an improvement to the traditional branched pore model. The theoretical concentration versus time curve generated by the proposed model fitted the experimental data for phenol adsorption reasonably well. Phenol adsorption tests were also carried out on a commercial activated carbon known as Calgon OLC Plus 12×30 and the agreement between these adsorption data and the proposed model was equally good.     

Removal of ionic liquids and ibuprofen by adsorption on a microporous activated carbon: Kinetics,isotherms, and pore sites

Ionic liquids (ILs) are considered as emergent pollutants as their synthesis and further use at a large scale might generate environmental problems. The adsorption on activated carbons represents one of the most effective methods to remove ionic liquids and other micropollutants from wastewater. In this work, the adsorption properties on an activated carbon cloth of two pyridinium ionic liquids (4-tert-butyl-1-propylpyridinium bromide (IL1) and 4-tert-butyl-1-(2-carboxyethyl)pyridinium bromide (IL2)) newly synthesized, were compared with the ones of ibuprofen. The adsorption kinetics and isotherms were studied at pH 3 and 7.5. The adsorption thermodynamic parameters calculated from the isotherms indicate an exothermic process, typical of physisorption. The adsorption kinetics of a mixture of the molecules show a competition between ibuprofen and IL2. The location of each adsorbed ionic liquid and ibuprofen into the porosity of the activated carbon cloth was determined from N₂ (at 77 K) and CO₂ adsorption isotherms (at 273 K). The purification process of an effluent containing the ionic liquids and the ibuprofen in mixture or in single solute could be workable by adsorption on an activated cloth.     

Kinetics of adsorption of di-n-butyl phthalate (DBP) by four different granule-activated carbons

The kinetics of the adsorption of an endocrine disruptor, di-n-butyl phthalate (DBP), by four different granulated-activated carbons (GACs) is presented in this paper. Results showed that adsorption of DBP by the four GACs followed first-order kinetics and the adsorption constant of the four GAC was found to follow the order: nut shell>coconut shell>Coaly carbon 1.0>Coaly carbon 1.5. Batch adsorption studies were also conducted to investigate the effect of pH on the adsorption process. The optimum pH for the removal of DBP from aqueous solutions under the experimental conditions used in this work was found to be 5.0. The characterization of the carbon surfaces was conducted by using scanning electron microscopy (SEM). Furthermore, results from infrared spectroscopic (IR) studies showed that physical adsorption plays an important role in the adsorption of DBP by the four selected GACs.     

Water adsorption with hysteresis effect onto microporous activated carbon fabrics

Understanding the adsorption of water vapor onto activated carbons is important for designing processes to remove dilute contaminants from humid gas streams, such as providing protection against chemical warfare agents (CWAs), or against toxic industrial compounds (TICs) used in a terrorist chemical attack. Water vapor isotherms for Calgon BPL granular activated carbon (GAC), military ASZM-TEDA GAC, electrospun activated carbon nanofibers (ACnF), Calgon Zorflex^™ activated carbon cloth, and Novoloid-based activated carbon fiber cloth (ACFC) are presented. Of particular interest are the ACFC isotherms, which exhibit an unusually high degree of hydrophobicity. The ACFC isotherms also show a correlation between water vapor adsorption hysteresis and the level of activation. Water vapor isotherm models from the literature are compared.     

Adsorption equilibrium and kinetics of copper ions and phenol onto modified adsorbents

The adsorption equilibrium and kinetics of single and binary component copper ions and phenol onto powdered activated carbon (PAC), alginate beads and alginate-activated carbon beads (AAC) were studied. Adsorption equilibrium data for single component copper ions and phenol onto the adsorbents could be represented by the Langmuir equation. Multicomponent equilibrium data were correlated by the extended Langmuir and ideal adsorbed solution theory (IAST). The IAST gave the best fit to our data. The amount of copper ions adsorbed onto the AAC beads in the binary component was greater than that of phenol. The internal diffusion coefficients were determined by comparing the experimental concentration curves with those predicted from surface diffusion and pore diffusion model.     

Equilibrium uptake and sorption dynamics for the removal of a basic dye (basic red) using low-cost adsorbents

Waste carbon slurries (generated in fertilizer plants) and blast furnace slag (generated in steel plants) have been converted into low-cost potential adsorbents. The adsorbents have been characterized and tried for the removal of the dye basic red from wastewater. Studies were performed at different pH to find the pH at which maximum adsorption occurs. Equilibrium isotherms were determined to assess the maximum adsorption capacity of the adsorbents. Adsorption capacities are compared for activated carbon developed from fertilizer waste and activated slag developed from blast furnace waste. The adsorption data are correlated with Freundlich and Langmuir isotherms in each system. The kinetics of adsorption depends on the adsorbate concentration and the physical and chemical characteristics of the adsorbent. Studies were conducted to delineate the effect of pH, temperature, initial absorbate concentration, particle size of the adsorbent, and solid-to-liquid ratio. The adsorption of basic red was found to be endothermic and first-order in nature.     

Theoretical and Experimental Study on the Adsorption and Desorption of Methane by Granular Activated Carbon at 25 ℃

A theoretical and experimental study was conducted to accurately determine the amount of adsorption and desorption of methane by various Granular Activated Carbon(GAC)under different physical conditions.To carry out the experiments,the volumetric method was used up to 500 psia at constant temperature of 25℃.In these experiments,adsorption as well as desorption capacities of four different GAC in the adsorption of methane,the major constituent of natural gas,at various equilibrium pressures and a constant temperature were studied.Also,various adsorption isotherm models were used to model the experimental data collected from the experiments.The accuracy of the results obtained from the adsorption isotherm models was compared and the values for the regressed parameters were reported.The results shows that the physical characteristics of activated carbons such as BET surface area,micropore volume,packing density,and pore size distribution play an important role in the amount of methane to be adsorbed and desorbed.     

Quantifizierung organischer Substanzen in Aktivkohleextrakten mit Hilfe der Gas-Chromatographie/Massenspektrometrie

Summary Use of activated carbon plays a significant role in water technology and analytical chemistry. Therefore determination of substances adsorbed on activated carbon is of special interest. As an example, granulated activated carbon (GAC) from a water treatment plant was serially extracted with different organic solvents. Quantitative determination of some selected compounds in the combined extracts was done by gas chromatography/mass spectrometry. The method of internal standard addition and calibration by response factors was used. The determined compounds (all of substituted benzene type) were extracted from the GAC in the concentration range from 0.2 mg/100 g (m-dichlorobenzene) to 5 mg/100 g (nitrobenzene). Relative standard deviation for double determination of five independent samples from the GAC filter was less than ±20%Spike experiments were performed to determine recovery efficiences. As expected, substance specific differences appeared and the recoveries were between 36% (m-dichlorobenzene) and 80% (nitrobenzene). A significant limitation for quantitative determination results from lack of available substances for calibration.     

介孔碳CMK-3对苯酚的吸附动力学和热力学研究

研究了介孔碳CMK-3对苯酚的吸附性能, 与传统商用活性碳(CAC)进行了比较, 结果表明, CMK-3比CAC的吸附量大、吸附速率快、达到平衡时间短, 是一种较好的吸附剂. 同时探讨了介孔碳CMK-3对苯酚的吸附热力学和动力学特征. CMK-3对苯酚的吸附行为可用Langmuir和Freundlich等温式进行描述, 相关性都较好, 但更符合Freundlich经验公式. 分别采用模拟一阶反应和二阶反应模型考察了吸附动力学, 并计算了这些动力学模型的速率常数. 模拟二级反应模型和实验数据之间有较好的相关性. 分别计算了热力学参数ΔG0, ΔS0和ΔH0, 结果表明, CMK-3对苯酚的吸附过程是吸热和自发的.