Kinetic Adsorption Capacity Research Articles

Anthracite coal-based activated carbon for elemental Hg adsorption in simulated flue gas: Preparation and evaluation

Mercury (Hg) is one of the major airborne emissions from coal combustion sources. Mercury emissions can be a serious pollution issue that is harmful to human health. Activated carbon (AC) is one of the most promising sorbents for Hg adsorption to date. Due to its high cost of chemical preparation, an affordable alternative activated carbon with a high Hg-capturing capacity would be beneficial to environmental security. This study focused on investigating the use of anthracite coal-based activated carbon (ACAC) prepared by a chemical activation method to remove elemental Hg from simulated flue gas. An activation process was developed by evaluating different carbonization temperatures, reagent/coal mass ratios and treating environments. The sample with the highest surface area was selected for synthesizing a bromide-impregnated ACAC. The ACAC sample prepared with KOH at a carbonization temperature of 800 °C, KOH/anthracite mass ratio of 1:1, and activated in an N2 environment yielded a surface area of 527.43 m2/g. Mercury adsorption experiments using synthesized ACAC in simulated flue gas were conducted at two different temperatures, 20° and 100 °C, with exposure times of 2.5 and 1 h, respectively. The kinetic adsorption capacity was found to increase with decreasing temperature. Specifically, at the Hg-laden gas temperature of 20 °C, with 2.5 h exposure time, the adsorbent can achieve the maximum adsorption capacity of 476.51μ g/g. The bromide-impregnated ACAC was also investigated under two different temperatures of 20 °C and 100 °C and exposure of 5 h. The adsorption capacity of the bromide-impregnated ACAC was found to be higher at elevated temperatures.

Remediation of hydrocarbons polluted water by hydrophobic functionalized cellulose

Remediation of water bodies from petroleum hydrocarbons is of the utmost importance due to health risks related to the high toxicity, mutagenicity and carcinogenicity of the hydrocarbons components that may enter into the food chain. Though several methods were proposed to face up this challenge, they are generally not easily feasible at a contaminated site and quite costly. Here we propose a green, cost-effective technology based on hydrophobized Spanish Broom (SB) cellulose fiber. The natural cellulose fiber was extracted by alkaline digestion of the raw vegetable. The hydrophilic cellulose surface was transformed into a hydrophobic one by the reaction with 4,4′–diphenylmethane diisocyanate (MDI) forming a very stable urethane linkage with the hydroxyl groups of cellulose emerging from the fibers surface. Chemical functionalization was performed with a novel solvent-free technology based on a home-made still reactor were the fiber was kept under vortex stirring and the MDI reactant then spread onto the fiber surface by nebulizing it in form of micrometer-sized droplets.The functionalized fiber, characterized by means of WCA measurements, XPS and ATR-FTIR spectroscopy, shows fast adsorption kinetics adsorption capacity as high as 220 mg/g, among the highest ever reported so far in the literature for cellulosic materials.

Interaction models on sand surface of natural adsorbent with adsorbate Cd+2 metal ions in solution with batch operation

The interaction type of metal ion with the adsorbent surface in adsorption operation was evaluated in this study. The binary metal ions in solution was mixed with the sand then shaken in 100 rpm. The kinetics adsorption capacity was than measured with the pseudo order model to evaluate the interaction type from the r2 indicator. The result found that the Cd ions with r2 = 0.9656 and r2 = 0.9989 for first and second order respectively, for black sand and r2 = 0.9070 and r2 = 0.999 for first and second order respectively, for white sand. It was indicated that the interaction type of metal ions on sand surface was occurred together as physical and chemical interaction.

Facile synthesis of imprinted submicroparticles blend polyvinylidene fluoride membranes at ambient temperature for selective adsorption of methyl p-hydroxybenzoate

We developed a simple phase inversion technique to prepare molecularly imprinted membrane (MIM) at room temperature for membrane selective adsorption and separation of methyl p-hydroxybenzoate (M4HB). The prepared SMIP-MIM was characterized by SEM, FT-IR, TGA. Compared with non-imprinted membrane (NIM1-5) adsorbent, SMIP-MIM1-5 adsorbent with high specific surface area and showed higher binding capacity, faster kinetic and better selectively adsorption capacity for M4HB. The maximum isotherm adsorption capacity for M4HB of SMIP-MIM4 was 3.519mg·g−1, and the experimental data was well fitted to the slips model by multiple analysis. The maximum kinetic adsorption capacity and equilibrium adsorption time for SMIP-MIM4 were 1.335mg·g−1 and 160 min, respectively. The mechanism for dynamic adsorption of M4HB onto SMIP-MIM4 was found to follow pseudo-first-order model and pseudo-second-order model. Additionally, the permeability separation factor of SMIP-MIM4 for M4HB compared to a structural analogues methyl 2-hydroxybenzoate (M2HB) could reach 2.847. The adsorption capacity of SMIP-MIM4 for M4HB and M2HB was 0.549mg·cm−2 and 1.563mg·cm−2, respectively. The adsorption behavior of M4HB through SMIP-MIM4 followed the retarded permeation mechanism.

Effect of electrostatic interaction on the methylene blue and methyl orange adsorption by the pristine and functionalized carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were functionalized with cysteamine groups by several percentage of mass as adsorbents, then kinetics adsorption capacity was investigated for methylene blue (MB) and methyl orange (MO) as anionic and cationic dyes adsorbate molecules, respectively. The effect of temperature (from 283 to 303K), contact time and initial concentration of the MB and MO dyes in a solution (10 to 40ppm) was considered. The optimal contact time was found to be about 60min. Some kinetics model such as pseudo-first-order, pseudo-second-order, intra-particle diffusion and the Elovich were tested. The adsorptions of MB dye on the pristine and functionalized MWCNT surfaces were found to be the intra-particle diffusion and the pseudo-second-order kinetic model, respectively and for adsorption of MO dye by the pristine and low functionalized MWCNTs and highly functionalized tubes, found to be the pseudo-second-order and intra-particle diffusion kinetic model, respectively, based on the chi-square statistic (X2) and also high correlation coefficient (R2) values.

Ion-Imprinted Polymers Based on Hollow Silica with Yeasts as Sacrificial Supports for Sr2+ Selective Adsorption

Surface ion-imprinting technique combined with a sacrificial support process was applied to synthesize Sr2+ ion-imprinted polymers (Sr-IIPs) in which yeast cells were used as sacrificial supports. The synthesized polymers were characterized by Fourier transmission infrared spectrometry, scanning electron microscope, transmission electron microscope and nitrogen adsorption–desorption analysis. The results indicated that Sr-IIPs possessed a relatively good dispersion and large surface area. Batch mode adsorption experiments were carried out to investigate the specific adsorption equilibrium, kinetics and selective recognition properties of Sr-IIPs. Sr-IIPs exhibited a fast kinetics adsorption capacity and high selectivity for adsorption of Sr2+. Under optimal experimental conditions, the adsorption of Sr2+ onto Sr-IIPs followed the pseudo-second-order kinetics model and was well-described by the Langmuir isotherm model. The monolayer adsorption capacity at 318 K was 60.61 mg g−1 for Sr-IIPs, which is over three-times that of NIPs. Thermodynamic parameters confirmed that the adsorption of Sr2+ onto Sr-IIPs was a spontaneous and endothermic process within the studied temperature range (298–318 K).

A Novel Electrochemical Sensor Based on Molecularly Imprinted Solid-Phase Extraction for Rapid Determination of Ractopamine in Pig Urine

A new absorbent (polymer) for solid-phase extraction of ractopamine (RAC) was synthesized on the multi-walled carbon nanotubes (MWCTs) using grafting technique and surface imprinting methods. The superficial characteristics of the polymer were studied by scanning electron microscopy (SEM) and UN spectrometry was applied to investigate the static and kinetic adsorption capacity of the new absorbent. After the experimental conditions for the solid-phase extraction of RAC were optimized, a sensing system for the determination of RAC was established by connecting the solid-phase extraction column with a portable amperometric sensing system. The SEM study showed that numbers of imprinted micro-pores were exhibited on the surface of the imprinted polymers, and the absorption experiments indicated that the molecularly imprinted absorbent possessed satisfactory kinetics for the adsorption of ractopamine. The current response of the amperometric sensor demonstrated a linear correlation to the concentration of RAC over the range of 50 to 450 nM (r = 0.998) and the detection limit was 15 nM. Satisfactory sensitivity and stability was also presented under the optimized experimental conditions. The recoveries of RAC samples reached 87.3–94.8% in urine sample.

Experimental Study on Adsorption of Carbon Dioxide by 5A Molecular Sieve for Helium Purification of High-Temperature Gas-Cooled Reactor

A fixed-bed apparatus with the dynamic two-route proportional gas mixing system was designed to investigate the adsorption behavior of carbon dioxide on 5A molecular sieve for designing the helium purification system of high-temperature gas-cooled reactors (HTGR). Experiments were performed at near atmospheric pressure, and the dynamic column breakthrough method was used to derive the single-component adsorption equilibrium of carbon dioxide with helium as the carrier gas. The breakthrough curves and the desorption curves were measured at low carbon dioxide partial pressure of 10−150 Pa and temperatures of 5−35 °C. By analyzing the breakthrough curve, both the equilibrium adsorption capacity and the kinetic adsorption capacity at the breakthrough point were determined. The effects of superficial velocity, temperature, gas feed concentration, adsorption pressure, and regeneration temperature on the adsorption capability were studied. The CO2 single-component adsorption isotherm at 10 °C was obtained and fi...

The effect of vapor polarity and boiling point on breakthrough for binary mixtures on respirator carbon.

This research evaluated the effect of the polarity of a second vapor on the adsorption of a polar and a nonpolar vapor using the Wheeler model. To examine the effect of polarity, it was also necessary to observe the effect of component boiling point. The 1% breakthrough time (1% tb), kinetic adsorption capacity (W(e)), and rate constant (kv) of the Wheeler model were determined for vapor challenges on carbon beds for both p-xylene and pyrrole (referred to as test vapors) individually, and in equimolar binary mixtures with the polar and nonpolar vapors toluene, p-fluorotoluene, o-dichlorobenzene, and p-dichlorobenzene (referred to as probe vapors). Probe vapor polarity (0 to 2.5 Debye) did not systematically alter the 1% tb, W(e), or kv of the test vapors. The 1% tb and W(e) for test vapors in binary mixtures can be estimated reasonably well, using the Wheeler model, from single-vapor data (1% tb +/- 30%, W(e) +/- 20%). The test vapor 1% tb depended mainly on total vapor concentration in both single and binary systems. W(e) was proportional to test vapor fractional molar concentration (mole fraction) in mixtures. The kv for p-xylene was significantly different (p < or = 0.001) when compared according to probe boiling point; however, these differences were apparently of limited importance in estimating 1% tb for the range of boiling points tested (111 to 180 degrees C). Although the polarity and boiling point of chemicals in the range tested are not practically important in predicting 1% tb with the Wheeler model, an effect due to probe boiling point is suggested, and tests with chemicals of more widely ranging boiling point are warranted. Since the 1% tb, and thus, respirator service life, depends mainly on total vapor concentration, these data underscore the importance of taking into account the presence of other vapors when estimating respirator service life for a vapor in a mixture.

Effects of adsorbed water vapor on the adsorption rate constant and the kinetic adsorption capacity of the Wheeler kinetic model.

A recent trend in occupational safety and health has focused on the use of respiratory protective equipment to supplant engineering controls as the primary means of protecting workers from toxic substances. Respirator adsorbent cartridges have been demonstrated to have a finite capacity to adsorb toxic vapors. The knowledge of when this limit is approached or has been exceeded is crucial to the user. The Wheeler kinetic breakthrough model has been shown to describe accurately organic vapor penetration through beds of activated carbon. The model, however, does not account for competitive adsorption of water vapor or other organic vapors. The investigations reported here demonstrate the effect of adsorbed water vapor on the kinetic adsorption parameters (kinetic rate constant and kinetic saturation capacity) of the Wheeler equation. Adsorbent beds were equilibrated at varying concentrations of water vapor and then challenged with carbon tetrachloride vapor-laden air. Dry carbon had an initial rate constant of 62.5 s-1 and a kinetic adsorption capacity of 0.36 g of adsorbed CCl4/gram (g/g) of adsorbent. These parameters decreased in proportion to the amount of water vapor adsorbed, with the minimum predicted values occurring at 100% relative humidity. The minimum experimental value for the kinetic rate constant was 17.6 s-1, a decrease of 73% from the dry carbon values. The minimum predicted value for the kinetic adsorption capacity was 0.16 g/g, a decrease of 45%.

Effects of Adsorbed Water Vapor on the Adsorption Rate Constant and the Kinetic Adsorption Capacity of the Wheeler Kinetic Model

Effects of Adsorbed Water Vapor on the Adsorption Rate Constant and the Kinetic Adsorption Capacity of the Wheeler Kinetic Model

Organic vapor (OV) respiratory cartridge testing--potential Jonas model applicability.

More efficient methods of characterizing organic vapor (OV) respirator performance against the wide range of compounds and environmental conditions found in industrial settings are needed to improve respiratory protection in the workplace. One method, based on Jonas' kinetic model, has potential application for evaluating OV cartridges and more efficiently utilizing available research, testing and certification resources. Jonas has shown that the kinetic adsorption capacity and gas adsorption rate of a small packed charcoal sorbent bed is described by the linear relationship between gas breakthrough time and sorbent weight as predicted by the modified Wheeler equation. This research is based on the hypothesis that characterizing sorbent performance against a reference compound will allow prediction of breakthrough times, and therefore prediction of cartridge life, for other compounds under similar conditions. Baseline data on dried cartridges at dry conditions are presented that demonstrate that the linear relationship between breakthrough time and and sorbent weight that Jonas showed for small sorbent columns also holds when commercially manufactured respiratory cartridges are stacked in series to resemble a packed column of varying bed length and sorbent weight. This suggests the potential applicability of the Jonas model for characterizing and evaluating commercially available OV respirator cartridges.

The kinetics of adsorption of organo-phosphorus vapors from air mixtures by activated carbons

The adsorption characteristics of activated carbons for the vapors of dimethyl methylphosphonate (DMMP) and of isopropyl methylphosphonofluoridate (IMPF) were studied under kinetic flow conditions. The carbon granules were packed to a reproducible bulk density in beds of uniform cross-sectional area and subjected to constant inlet vapor concentration, volume flow rate, and temperature but varying bed weights. The breakthrough time of the vapor through the bed, at an exit concentration equal to 1 per cent of the inlet concentration, was determined for each bed weight, and plotted as a straight line in accordance with the equation for adsorption kinetics. The kinetic saturation capacity of the carbon for each vapor was determined from the slope and the pseudo first order adsorption rate constant from the intercept. Kinetic equations were constructed for each vapor and, when solved simultaneously, showed that the breakthrough time for IMPF could be correlated with that of DMMP in accord with the equation t b (IMPF) = 0.911 t b (DMMP)−8.86 for activated carbon and t b (IMPF) = 1.084 t b (DMMP)−4.32 for the same carbon after impregnation with copper, silver, and chromium salts. The close agreement between the relationships of these organophosphorus vapors on the two carbons suggests that the prediction of adsorption of one vapor based upon prior characterization with a reference vapor, originally applicable only under equilibrium, can be extended for use under kinetic conditions. A method is presented for calculating the kinetic adsorption capacity of an activated carbon for IMPF from the experimental DMMP value using equilibrium relationships, and shown capable of predicting the capacity within 4.1 per cent.