Adsorption Capacity Of Adsorbent Research Articles

Monoethanol Amine Modified Zeolite 13X for CO2Adsorption at Different Temperatures

Zeolite 13X has been modified with monoethanol amine (MEA). MEA loadings of 0.5–25 wt % have been achieved using the impregnation method in different solvents. The mode of incorporation based on methanol with stirring at room temperature appears to be the most feasible. The adsorbent has been characterized for crystallinity, surface area, pore volume, and pore size. The thermal stability of the adsorbent is studied using a thermal analyzer. The CO2 adsorption capacity of adsorbents is evaluated using the breakthrough adsorption method with a packed column on a 10 g scale. The adsorption capacities of adsorbents are estimated in the temperature range 30–120 °C. The adsorbents show improvement in CO2 adsorption capacity over the unmodified zeolite by a factor of ca. 1.6 at 30 °C, whereas at 120 °C the efficiency improved by a factor of 3.5. For adsorption at these temperatures, different MEA loading levels were found to be suitable as per the governing adsorption phenomena, that is, physical or chemical. The adsorbent is also studied for CO2 selectivity over N2 at 75 °C. The MEA-modified adsorbent shows better CO2 selectivity, which was improved further in the presence of moisture.

High‐efficiency desulfurization by adsorption with mesoporous aluminosilicates

AbstractMesoporous aluminosilicate (MAS) was synthesized by hydrothermal method with zeolite NaY as precursor and CTMAB (cetyltrimethylammonium bromide) as structure directing agent. Desulfurization adsorbents were characterized with XRD, BET, FTIR and NH3‐TPD. FTIR results showed that Lewis acid sites act as adsorption centers for dibenzothiophene (DBT) molecules. The adsorption desulfurization ability of MAS was studied in model and hydrotreated diesel. For model oil containing 10mmol/L DBT, the adsorption capacity of adsorbents is NaY > MAS > MCM‐41. For hydrotreated diesel, MAS shows the largest adsorption capacity, MCM‐41 the second, and NaY shows the least adsorption capacity. The improvement of desulfurization ability of improvement of MAS by Cu(I) is more significant than that of MCM‐41. The physicochemical properties of fuels, such as viscosity and aromatics concentration had great influence on the desulfurization property of adsorbents. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Removal of Arsenic(V) from Aqueous Solutions Using Iron‐Oxide‐Coated Modified Activated Carbon

Removal of arsenic(V) from aqueous solutions was evaluated with the following three different sorption materials: coal-based activated carbon 12 x 40 (activated carbon), iron(II) oxide (FeO)/activated carbon-H, and iron oxide. The apparent characteristics and physical chemistry performances of these adsorbents were investigated by X-ray diffraction, nitrogen adsorption, and scanning electronic microscope. Also, batch experiments for arsenic removal were performed, and the effects of pH value on arsenic(V) removal were studied. The results suggest that the main phases of the iron oxide surface are magnetite, maghemite, hematite, and goethite; fine and uniform iron oxide particles can cover activated carbon surfaces and affect the surface area or pore structures of activated carbon; adsorption kinetics obey a pseudo-first-order rate equation; and adsorption capacities of adsorbents are affected by the values of pH. The optimum value of pH for iron oxide lies in a narrow range between 4.0 and 5.5, and arsenic(V) removal by FeO/activated carbon-H is ideal and stable in the pH range 3 to 7, while activated carbon has the lowest adsorption capacity in the entire pH range. Also, the adsorption characteristics of FeO/activated carbon-H composites and virgin activated carbon match well the Langmuir adsorption model, while those of iron oxide fit well the Freundlich adsorption model.

Removal of lead from aqueous solution using low cost abundantly available adsorbents

The removal of poisonous Pb (II) from wastewater by different low-cost abundant adsorbents was investigated. Rice husks, maize cobs and sawdust, were used at different adsorbent/metal ion ratios. The influence of pH, contact time, metal concentration, adsorbent concentration on the selectivity and sensitivity of the removal process was investigated. The adsorption efficiencies were found to be pH dependent, increasing by increasing the solution pH in the range from 2.5 to 6.5. The equilibrium time was attained after 120 min and the maximum removal percentage was achieved at an adsorbent loading weight of 1.5 gm. The equilibrium adsorption capacity of adsorbents used for lead were measured and extrapolated using linear Freundlich, Langmuir and Temkin isotherms and the experimental data were found to fit the Temkin isotherm model.

Adsorption behavior of strontium on binary mineral mixtures of Montmorillonite and Kaolinite

The adsorption behavior of kaolinite and montmorillonite minerals and their mixtures in respect of Sr ion were studied by means of a batch method using 90Sr as a radio tracer. The effect of several parameters such as temperature, pH, Sr concentration and supporting electrolyte were investigated. Experimentally measured distribution coefficients showed a good agreement to within 98.5–99.7% with theoretically calculated values. The values of adsorption capacity of adsorbents and mean adsorption energy of adsorption were calculated by fitting the adsorption data to Dubinin–Radushkevich isotherm. The adsorption capacity of clay mixtures decreased as kaolinite fractions increased. The mean adsorption energy values of 8.0–9.5 kJ mol −1 showed that adsorption was governed by ion exchange. The Freundlich parameters were used to characterize a site distribution function for binary exchange between Sr and Na.

Removal of Arsenic(III) from Aqueous Solution by Activated Carbons Prepared from Solvent Extracted Olive Pulp and Olive Stones

The removal of As(III) from aquatic solutions at different concentrations and pH by using four types of activated carbons obtained from solvent extracted olive pulp and olive stone waste materials was studied. The adsorbents are obtained by chemical (K2CO3 and HNO3) activation and physical (water vapor) activation. The results show that carbons produced by chemical and physical activation of solvent extracted olive pulp and olive stones are efficient adsorbents for arsenic removal. Arsenic adsorption follows a Langmuir isotherm. The best results were obtained with the adsorbent, obtained from extracted olive pulp by pyrolysis in the presence of water vapor. The maximum removal was found to be 18.60 μmol/g. The adsorption capacity for adsorbents, obtained from extracted olive pulp and olive stones, is 11.42 and 9.85 μmol/g, respectively. The test showed that alkaline aqueous medium favored the removal of As(III). Some experiments were carried out to study the oxidation of arsenite to arsenate in the presen...

Modified hardwood sawdust as adsorbent of heavy metal ions from water

The sawdust of oak and black locust hardwood was found to have good adsorption capacities for heavy metal ions. The leaching of coloured organic matters during the adsorption can be prevented by each of the following pre-treatments of adsorbents: with formaldehyde in acidic medium, with sodium hydroxide solution after formaldehyde treatment, or with sodium hydroxide only. The studies indicated that the leaching of coloured matters from modified hardwood sawdust was less than that from unmodified hardwood sawdust, namely between 70 and 94%, dependent on wood species and the method of modification. At the same time, adsorption capacities of modified adsorbents were higher than unmodified adsorbents when sodium hydroxide was applied for modification. When formaldehyde was applied for modification, the adsorption capacities of adsorbents remained unchanged. Only the application of sodium hydroxide was recommended for modification of hardwood sawdust.

05/02294 Environmentally benign working pairs for adsorption refrigeration

Thermal heat driven adsorption systems using natural refrigerants have been focused on the recent energy utilization trend. However, the drawbacks of these adsorption systems are their poor performance in terms of system cooling capacity and coefficient of performance (COP). The objective of this paper is to improve the performance of thermally powered adsorption cooling system by selecting new adsorbent–refrigerant pair. Adsorption capacity of adsorbent–refrigerant pair depends on the thermophysical properties (pore size, pore volume and pore diameter) of adsorbent and isothermal characteristics of the pair. In this paper, the thermophysical properties of two PAN types of activated carbon fibers (FX-400 and KF-1000) are determined from the nitrogen adsorption isotherms. The standard nitrogen gas adsorption/desorption measurements on various adsorbents at liquid nitrogen of temperature 77.3 K were performed. Surface area of each adsorbent was determined by the Brunauer, Emmett and Teller (BET) plot of nitrogen adsorption data. Pore size distribution was measured by the Horvath and Kawazoe (HK) method. As of the adsorption/desorption isotherms, FX-400 shows very small hysteresis when the value of P/Po exceeds 0.4, while KF-1000 has no hysteresis in the whole range of P/Po. The adsorption capacity of FX-400 is about 30% higher than that of KF-1000. The adsorption equilibrium data of activated carbon fiber (ACF)-methanol are presented and correlated with simple equations. The adsorption equilibrium data of ACF (KF-1000)-water also presented in order to facilitate comparison with those of ACFs-methanol pair. The results will contribute significantly in designing the adsorber/desorber heat exchanger for thermally driven adsorption cooling system.

Study on adsorption refrigeration cycle utilizing activated carbon fibers. Part 1. Adsorption characteristics

Thermal heat driven adsorption systems using natural refrigerants have been focused on the recent energy utilization trend. However, the drawbacks of these adsorption systems are their poor performance in terms of system cooling capacity and coefficient of performance (COP). The objective of this paper is to improve the performance of thermally powered adsorption cooling system by selecting new adsorbent–refrigerant pair. Adsorption capacity of adsorbent–refrigerant pair depends on the thermophysical properties (pore size, pore volume and pore diameter) of adsorbent and isothermal characteristics of the pair. In this paper, the thermophysical properties of two PAN types of activated carbon fibers (FX-400 and KF-1000) are determined from the nitrogen adsorption isotherms. The standard nitrogen gas adsorption/desorption measurements on various adsorbents at liquid nitrogen of temperature 77.3 K were performed. Surface area of each adsorbent was determined by the Brunauer, Emmett and Teller (BET) plot of nitrogen adsorption data. Pore size distribution was measured by the Horvath and Kawazoe (HK) method. As of the adsorption/desorption isotherms, FX-400 shows very small hysteresis when the value of P/ P o exceeds 0.4, while KF-1000 has no hysteresis in the whole range of P/ P o. The adsorption capacity of FX-400 is about 30% higher than that of KF-1000. The adsorption equilibrium data of activated carbon fiber (ACF)-methanol are presented and correlated with simple equations. The adsorption equilibrium data of ACF (KF-1000)-water also presented in order to facilitate comparison with those of ACFs-methanol pair. The results will contribute significantly in designing the adsorber/desorber heat exchanger for thermally driven adsorption cooling system.

Sorbent characteristics influence on the adsorption of PAC: I. PAH adsorption with the same number of rings

The aim of this paper is to study the abatement of three-ring polycyclic aromatic hydrocarbons (PAHs) from hot gas emissions during energy generation in coal combustion. The three-ring PAHs are one of the most abundant PAH groups emitted during coal combustion. Four of them—Acenaphthene (Ac), Phenanthrene (Phe), Fluorene (Fu) and Anthracene (An)—have been listed by US EPA as priority pollutants. The three-ring PAH adsorption capacities are related to the textural properties of the 16 sorbents used in this work. Single and multiple linear regressions —principal component regression (PCR)—were applied in this study. The main conclusions reached are two: (1) the micropore volume is the most determinant parameter for these PAH removal; (2) the adsorption of three-ring PAH by sorbents from waste hot gas emissions is inversely proportional to their volatility: the lower the PAH volatility, the higher the adsorbent adsorption capacity. The adsorption isotherms show that Phe and An, both examples of PAHs with three aromatic rings, behave similarly. However, their behaviour differs from that of Ac and Fu, compounds where only two of their three rings exhibit an aromatic nature.

Three-ring PAH removal from waste hot gas by sorbents: influence of the sorbent characteristics.

Three-ring polycyclic aromatic hydrocarbons (PAH) are one of the most abundant PAH groups emitted during coal combustion. Four of them-acenaphthene (Ac), phenanthrene (Phe), fluorene (Fu), and anthracene (An)-have been listed by the U.S. EPA as priority pollutants. The aim in this paper is to study the abatement of this particular group of three-ring PAH from hot gas emissions during energy generation in coal combustion. The three-ring PAH adsorption capacities are related to the morphological and chemical properties of the 16 sorbents used in this work. Single and multiple linear regressions-principal component regression (PCR)-were applied in this study. The main conclusions reached are, first, that the micropore volume is the most determinant parameter for removal of these PAHs and, second, that the adsorption of three-ring PAH by sorbents from waste hot gas emissions is inversely proportional to their volatility: the lower the PAH volatility, the higher the adsorbent adsorption capacity. The adsorption isotherms show that Phe and An, both examples of PAH with three aromatic rings, behave similarly. However, their behavior differs from that of Ac and Fu, compounds in which only two of their three rings exhibit an aromatic nature.

Soaps, shampoos, and detergents

Heavy metals are pollutants that are naturally produced by human activities. Due to heavy metals' amount and toxicity in aqueous media, they are considered extremely harmful to human life. Therefore, it is necessary to find effective and efficient methods, as a severe challenge for reducing these pollutants to a permissible level. Among the various removal methods, the adsorption process has received much attention due to its benefits like low cost, ease of operation, high selectivity, and high removal efficiency. So far, various adsorbents such as activated carbon, agricultural waste, minerals, nanoparticles, and other inexpensive adsorbents have been used. Surface modification of these adsorbents by surfactants improves the adsorption properties, and as a result, enhances the adsorption capacity of adsorbents. This research has tried to discuss the use of surfactant-modified adsorbents to remove metal ions from aqueous media. In this study, heavy metals and various methods for removing them will also be studied. Also, isotherm, thermodynamic and kinetic behaviors of the sorption process are considered. The addition of anionic and cationic surfactants to the adsorbents can strongly alter the adsorbent's surface charge and directly affect the optimal pH value. Also, the maximum sorption efficiency using surfactant-modified adsorbents has been obtained at low temperatures (25 °C), which can be economically viable. According to previous studies, two surfactants such as SDS and CTAB, have shown a high ability to improve the adsorption efficiency and adsorption capacity of adsorbents. To this end, DNPH/SDS/Fe3O4 and CTAB/yeast adsorbents showed the highest removal efficiency (99.5%), which were able to remove Cr(VI) and CrO42− ions, respectively. Moreover, both adsorbents showed significant adsorption capacity.

Carbon Fiber Adsorption Using Quantitative Structure-Activity Relationship

Adsorption capacities of adsorbents are necessary for selecting and designing adsorption systems for separation and removal processes, such as air quality control devices, because they are indicators of service life. This paper describes the use of the Dubinin-Radushkevich (DR) equation and the quantitative structure-activated relationship to predict the equilibrium adsorption of select organic vapor by activated carbon fiber (ACF) adsorbents. The DR isotherm parameter, k, depends on the adsorbate as well as the adsorbent, and the prediction for k can be obtained indirectly from the affinity coefficient. A correlation is developed to compute the affinity coefficient from the modified, first-order, valence molecular connectivity index. This method provides an improved way to predict equilibrium adsorption capacities for select volatile organic compound adsorbates and activated carbon fiber adsorbents.

Adsorption of Chlorophyll and Pheophytin from Alkali-Refined Rapeseed and Soybean Oils with Attapulgite and Sepiolite.

Bleaching efficiency, amount adsorbed, k-value and equilibrium amount adsorbed were measured to determine maximum adsorption capacity of adsorbent for the removal of chlorophyll (Chl) derivatives. Cosmetic-grade attapulgite (A5) was equivalent to standard activated clay (SAC) in optimum clay dose for bleaching alkali-refined rapeseed and soybean oils. The dose was 2.0% wt/wt for rapeseed and 1.5% wt/wt for soybean. Adsorption capacity should be evaluated based on the equilibrium amount adsorbed from the adsorption isotherm but not on the bleaching efficiency, amount adsorbed or k-value. A5 was the same as SAC in equilibrium amounts of pheophytins (Phy) a/b adsorbed at low and high residual concentrations. A5 is thus useful for the adsorption removal of Chl and Phy as well as SAC.

Dynamics of pressurization and blowdown of an adiabatic adsorption bed: 4. Intraparticle diffusion/convection models

Abstract The importance of intraparticle mass transfer during pressurization and blowdown steps of PSA processes in an adiabatic adsorption bed was assessed by comparing intraparticle diffusion/ convection and intraparticle diffusion models. Film mass/heat transfer resistances are also considered in the model. The film heat transfer resistance is more important than the heat transfer resistance inside the particle; it can be assumed to be negligible in PSA processes when the temperature variation is not very large, otherwise it leads to serious errors when the adsorption capacity of adsorbents is high and the heat capacity of the system is not high. Intraparticle convection improves the mass transfer inside the particle and leads to faster heat releases into and out of the adsorbents.

A basic study of column adsorption chromatography : Part I. Standardization of adsorbent

The method of measuring f(I) values is proposed as a measure of the adsorption capacity of adsorbents. The f(I) value, a characteristic figure for a particular system, can be obtained chromatogiaphically by measuring the progression rate of zone and the degree of packing of the column. For a system involving a unit concentration of trasns- p-methoxyazobenzene in benzene as standard solution and alumina as adsorbent, optimum conditions for the measurement of f(I) were established. The effects of day-light, pretreatment of column, temperature, flow rate of solution, amount of adsorbent and degree and mode of packing were studied Under optimum conditions, the value of f(I) was reproducible within ±2%.