Kinds Of Adsorbents Research Articles

Magnetized bentonite by Fe3O4 nanoparticles treated as adsorbent for methylene blue removal from aqueous solution: Synthesis, characterization, mechanism, kinetics and regeneration

In this work, we carried out the adsorption of methylene blue (MB) onto a kind of adsorbent, which was magnetized bentonite by Fe3O4 nanoparticles (MBF) using a quick, efficient and low-cost one-pot method. The characterization of the adsorbent conducted via SEM, EDS, VSM, XRD, BET and FT-IR spectroscopy. The adsorption trend follows the pseudo-second order kinetics model and the equilibrium could be established within 20 min. Factors affecting the adsorption of MB such as pH, adsorbent dosage, contact time, and initial concentration of MB were investigated. The role of ─OH functional group in this adsorption process was discussed. MBF showed a high adsorption capacity and an efficient adsorption toward MB in aqueous medium and implies the great potential application in the treatment of colored wastewaters. Regeneration of the saturated adsorbent was easily carried out with gamma-irradiation of a certain dose.

Micro- and nano-sized bentonite filled composite superabsorbents of chitosan and acrylic copolymer for removal of synthetic dyes from water

Bentonite clay, chitosan and acrylic copolymer gels have been separately reported for the adsorption of dyes. In the present work these three kinds of adsorbents were combined to make composite hydrogels. The hydrogels were characterized by FTIR, XRD, DTA–TGA and SEM. The swelling, diffusion and network parameters of the hydrogels were also evaluated. These composite hydrogels were used for the removal of malachite green and methyl violet dyes from water. The composite hydrogels showed high adsorption and removal% of both of these dyes. The mass transfer coefficient, diffusion coefficient and thermodynamic parameters of the dye adsorption were also determined.

흡착제를 이용한 참기름의 벤조피렌 저감화

This study was conducted to reduce benzo(a)pyrene in sesame oil by addition of several kinds of absorbents (active carbon, diatomaceous earth, kaolin, acid clay, perlite, and silicate). Sesame oil containing 4.1 ppb benzo(a)pyrene was stirred with 0.2% (w/w) several kinds of adsorbents at 40°C for 30 min. Active carbon resulted in the highest reduction of benzo(a)pyrene in sesame oil among the investigated adsorbents, and decolorization was observed only by using silicate. Reduction of benzo(a)pyrene was optimized by controlling amount the of active carbon, stirring time, and stirring temperature. Futher, 4.1 ppb benzo(a)pyrene in sesame oil was reduced by up to 0.91 ppb by adding 0.5% (w/w) active carbon and stirring for 30 min at 70°C. Optimized conditions were applied to sesame oil (2.14～4.11 ppb) purchased from a Gyeonggi traditional market, and benzo(a)pyrene in sesame oil was reduced by up 0.43～0.86 ppb.

The Influence of Hydrothermal Temperature on CaO-based Adsorbents Synthesized by Sol-Gel-Hydrothermal Method

To capture carbon dioxide (CO2), a major green house gas from flue gas, several kinds of adsorbents have been synthesized, characterized and tested. In this study, CaO-based adsorbents were synthesized via sol-gel-hydrothermal method and different hydrothermal temperatures (100, 120, 140 and 160°C) have been investigated in order to verify their influence on the CaO-based adsorbents. Experimental results showed that the Ca(OH)2 adsorbent with a mixture of CaCO3 synthesized at 120°C hydrothermal treatment possesses high CO2 adsorption capacity (0.52 g-CO2/g-sorbent) and at 160°C hydrothermal treatment, CaC2O4.H2O adsorbent was observed and its CO2 adsorption capacity was 0.46 g-CO2/g-sorbent for first carbonation/calcination cycle.

Capture of carbon dioxide from flue gas on TEPA-grafted metal-organic framework Mg2(dobdc)

Carbon dioxide (CO2) adsorption on a standard metal-organic framework Mg2(dobdc) (Mg/DOBDC or Mg-MOF-74) and a tetraethylenepentamine (TEPA) modified Mg2 (dobdc) (TEPA-Mg/DOBDC) were investigated and compared. The structural information, surface chemistry and thermal behavior of the adsorbent samples were characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), thermogravimetric analysis (TGA) and nitrogen adsorption-desorption isotherm analysis. CO2 adsorption capacity was measured by dynamic adsorption experiments with N2-CO2 mixed gases at 60°C. Results showed that the CO2 adsorption capacity of Mg/DOBDC was significantly improved after amine modification, with an increase from 2.67 to 6.06 mmol CO2/g adsorbent. Moreover, CO2 adsorption on the TEPA-Mg/DOBDC adsorbent was promoted by water vapor, and the adsorption capacity was enhanced to 8.31 mmol CO2/g absorbent. The adsorption capacity of the TEPA-Mg/DOBDC adsorbent dropped only 3% after 5 consecutive adsorption/desorption cycles. Therefore, this kind of adsorbent can be considered as a promising material for the capture of CO2 from flue gas.

A review on the removal of antibiotics by carbon nanotubes

Increasing concerns have been raised regarding the potential risks of antibiotics to human and ecological health due to their extensive use. Carbon nanotubes (CNTs) have drawn special research attention because of their unique properties and potential applications as a kind of adsorbents. This review summarizes the currently available research on the adsorption of antibiotics on CNTs, and will provide useful information for CNT application and risk assessment. Four different models, the Freundlich model (FM), Langmuir model (LM), Polanyi-Mane model (PMM), and Dubinin-Ashtakhov model (DAM), are often used to fit the adsorption isotherms. Because different mechanisms may act simultaneously, including electrostatic interactions, hydrophobic interactions, π-π bonds, and hydrogen bonds, the prediction of organic chemical adsorption on CNTs is not straightforward. Properties of CNTs, such as specific surface area, adsorption sites, and oxygen content, may influence the adsorption of antibiotics on CNTs. Adsorption heterogeneity and hysteresis are two features of antibiotic-CNT interactions. In addition, CNTs with adsorbed antibiotics may have potential risks for human health. So, further research examining how to reduce such risks is needed.

Dust removal and purification of calcium carbide furnace off-gas

A large amount of CO contained in calcium carbide furnace off-gas can be recycled and used as an important raw material for C1 (one carbon) industrial chemical manufacturing. The key to the recovery is the removal of dust and gaseous impurities from the off-gas. For this purpose, an industrial device has been used for removing the dust. This consists of a laboratory-scale fixed-bed reactor with two kinds of adsorbents, prepared in our laboratory, for removing HCN and COS. The results show that the dust content after the dedusting process was less than 20mg/m3. The dust particles are composed of microspheres, with an obvious tendency to agglomerate, and with an average diameter of about 6.71μm. After adsorption, the outlet concentrations of both HCN and COS were less than 1mg/m3. In order to remove HCN, activated carbon (AC) was used, impregnated with 0.15mol/L Cu(CH3COO)2 solution. The optimum calcination temperature was 350°C. The AC, modified with Cu(CH3COO)2, was examined by means of N2-BET and X-ray photoelectron spectroscopy (XPS) before and after off-gas treatment. The results indicate that the chemisorption products were mainly present in the AC micropores and mesopores, with radius 0.81–1.51nm. After dust removal and purification, the calcium carbide furnace off-gas is fit for use as a raw material in the C1 chemical manufacturing industry.

Study of a New Kind of Adsorbent for Removal of Nitric Oxides

A new kind of adsorbent is prepared in the present study, which is expected to capture NOx with high efficiency. NaOH, Ca(OH)2, carbide slag, diatomite, activated alumina are chosen as the major material with a small amount of surfactants and dispersants as the additive. Different recipes were characterized by SEM and N2 adsorption-desorption method. The result showed that the optimum adsorbent has the largest surface area of 95.67m2/g which is Ca(OH)2: NaOH: activated alumina=4:1:1. The test on removal of NOx is conducted. The result showed that the adsorbent is capable of removal efficiency exceeding 98% in 10minutes.

Application of multi-sorbent tubes filled with modified multi-walled carbon nanotubes for determining volatile organic compounds in a wide range of polarity

New adsorbent M101 was obtained by loading multi-walled carbon nanotubes (MWCNTs) on 101 white support, and 3-aminopropyl silica gel–MWCNTs (APSG-MW) were prepared by chemical modification. Based on the early research, 15 kinds of adsorbents were tested to adsorb sulfide and amine compounds. Then 4 combinations of multi-sorbent tubes were prepared including Tenax TA/M101/Carbopack B (TMB), Tenax TA/M101/Carboxen 564 (TM564), Carbopack B/M101/Silica gel (BMS) and Carbopack B/APSG-MW/Silica gel (BAMS). The adsorption and desorption recoveries for alkanes, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, esters, ketones, sulfides and amines were determined. The results showed that the recoveries of multi-layer adsorbents BMS and BAMS were above 90% for most of the target compounds, and 80% for amines. Then the influence of humidity on the sampling, storage stability and sampling precision of BMS and BAMS was tested. The results indicated that BMS and BAMS were more suitable for sampling both polar and non-polar compounds in the air.

Heavy metal removal from aqueous solution by tannins immobilized on collagen

Abstract Different recycled materials, which were derived from leather manufacturing processes, were used as adsorbents for the treatment of synthetic wastewater containing heavy metal ions. Three pelt scraps samples (P-M, P-Z and P-P), one shaving scrap (S) and one trimming scrap (T) were used as recycled adsorbents. Removal efficiency of Cu(II), Cd(II), Zn(II), Pb(II) and Cr(III) was evaluated by a laboratory-scale batch reactor at different solution pH. For all adsorbents except T sample, the adsorption of heavy metal ions begins between pH 2 and 4 and reaches near complete adsorption within the next 3–4 pH units, showing a typical cationictype of adsorption. Removal trend of Cr(III) was quite similar without depending on the kind of adsorbents. From the kinetic experiments of Cu(II) by S adsorbent, adsorption of Cu(II) was bett er described by second-order reaction than first-order reaction. The initial removal rate of Cu(II) by S adsorbent was 7143 mg/kg·h. Adsorption isotherm of Cu(II) onto S adsorb...

Selective separation of biobutanol from acetone–butanol–ethanol fermentation broth by means of sorption methodology based on a novel macroporous resin

The traditional distillation method for recovery of butanol from fermentation broth is an energy-intensive process. Separation of butanol based on adsorption methodology has advantages in terms of biocompatibility and stability, as well as economy, and therefore gains much attention. However, the application of the commercial adsorbents in the integrated acetone-butanol-ethanol (ABE) fermentation process is restricted due to the low recovery (less than 85%) and the weak capability of enrichment in the eluent (3-4 times). In this study, we investigated the sorption properties of butanol onto three kinds of adsorbents with different polarities developed in our laboratory, that is, XD-41, H-511, and KA-I resin. The sorption behaviors of single component and ABE ternary mixtures presented in the fermentation broths on KA-I resin were investigated. KA-I resin had higher affinity for butanol than for acetone, ethanol, glucose, acetic acid, and butyric acid. Multicomponent ABE sorption on KA-I resin was modeled using a single site extended Langmuir isotherm model. In a desorption study, all the adsorbed components were desorbed in one bed volume of methanol, and the recovery of butanol from KA-I resin was 99.7%. The concentration of butanol in the eluent was increased by a factor of 6.13. In addition, KA-I resin was successfully regenerated by two bed volumes of water. Because of its quick sorption, high sorption capacity, low cost, and ease of desorption and regeneration, KA-I resin exhibits good potential for compatibility with future ABE fermentation coupled with in situ recovery product removal techniques.

Preconcentration of trace lead and iron on activated carbon functionalized by o-Anisic acid derivatives prior to their determination in environmental samples

Two solid-phase adsorbents (phase I and phase II) were synthesized successfully that o-Anisic acid derivatives were evenly functionalized on the surface of activated carbon. It was certified that the two adsorbents were applied to preconcentrate and separate trace levels of Pb(II) and Fe(III) from natural liquid samples with satisfactory results. It can be found that the adsorption capacity of the ions adsorbed on phase I and phase II was 48.3 and 85.7mgg−1 for Pb(II), 39.5 and 72.5mgg−1 for Fe(III), respectively. The detection limit (3σ) of the method separated on phase I and phase II was 0.12 and 0.09ngmL−1 for Pb(II), 0.23 and 0.17ngmL−1 for Fe(III), respectively. The relative standard deviation (R.S.D.) of the method was lower than 3.0%.The adsorption and desorption property of two kinds of adsorbents was comparatively studied, respectively. The adsorption selectivity of heavy metal ions at certain pH, the adsorption kinetics, the condition of complete elution, the effect of coexisting ions, the adsorption capacity and adsorption isotherm modes were examined. Based on the experimental datum determined by inductively coupled plasma optical emission spectrometry (ICP-OES), it was certified that the adsorption on the surface of adsorbents was in strict accordance with the monolayer adsorption principle. The structural features of series of multidentate ligand modified on adsorption matrix had been obtained. These conclusions can provide reference for synthesizing an efficient adsorbent which is specific to remove a particular kind of contaminant.

Theoretical Investigations on the Healing of Monovacancies in Single-Walled Carbon Nanotubes by Adsorption of Carbon Monoxide

The outstanding properties of single-walled carbon nanotubes (CNTs) are often impaired by the presence of structural defects, such as vacancies, as consequence of peculiar growth techniques or electron irradiation. However, the changes in the electronic structure due to the presence of defects can also induce the formation of sites at the sidewall exhibiting unusual reactive properties. In particular, monovacancies constitute active reaction sites toward the addition of different kinds of adsorbates, which can potentially cure the defects and restore the properties of pristine nanotubes. In this work, the interaction of carbon monoxide with monovacancies on single-walled CNTs is investigated by means of an integrated approach, based on density functional theory, consisting of both static and molecular dynamics calculations for the evaluation of potential-energy minima and free-energy barriers. Our simulations suggest viable reaction routes for the healing of single vacancies on the sidewall by subsequent interaction with two CO molecules, leading to the restoration of a perfect hexagonal carbon-atom network. The outlined results clarify the role of CO as precursor for the growth of nanotubes both as carbon source and as active chemical species for the formation of a defect-free sidewall.

Property Analysis of Solid-Adsorption Desiccant System

Based on the concept of independent dehumidification, a system which can test the dehydration property of both the adsorbent bed and the adsorbent has been designed. As the adsorbent, the activated alumina and the 4A molecular sieve are used to test the dehydration property of the whole adsorbent bed with two kinds of adsorbent. Finally, three new evaluation indexes about the dehumidification efficiency based on the experimental data are proposed in this paper.

Editorial - TiO?2-Based Materials for Heterogeneous Photocatalytic Applications

From the data of the Worldwatch Institute, a foundation annualy publish a report “The Condition of Earth”. Each year the country members of the European Economic Community, produce about 2200 millions metric tons of residues (close to 18 Kg. by person, daily). From this quantity, 150 millions metric tons are listed as industrial residues. In addition, from these between 20 and 30 millions metric tons are residues catalogued as toxics and dangerous. According to the data of the Environment Protection Agency (EPA), in the United States of America, the quantity of toxics and dangerous remainders has increased upto 275 millions metric tons each year. These residues cause a great problem because most of them are directly casting out to public river beds through industry residual waters, with the concomitant contamination of such waters. Other part of the residues goes to weirs, which, is the storage problem. Different methodologies have been employed for the treatment of polluted water and air, such as biodegradation,chloration, ozone with UV-activation, and several combinations of these with activated carbon and other kinds of adsorbents and filters. However, in addition to some operative problems, all these methodologies have very important limitations, principally the type of pollutant and its concentration in the water or gaseous phases, and therefore, all them separately show relatively moderate efficiency. Therefore, it is very important to develop appopriate systems for the control and depuration of the great diversity of compounds in polluted waters and air. This problem has been satisfactory resolved by one of the most remarkable applications of the materials sciences, Heterogeneous Photocatalysis, particularly by using photoactive semiconductors as TiO2 because it has been shown, up to now, the best photoactivity under UV-irradiation in the photodegradation reactions of organic pollutants, mainly aromatics molecules with cancerous a and mutagenic characteristics. This is the main objective of this special issue, to show some approaches of TiO2-based materials in heterogeneous photocatalytic applications regarding water and air pollution.

Preparation of MgCl<sub>2</sub>-Coated Activated Carbon and its Adsorption Behavior of Azo Dye from Aqueous Solution

The preparation of MgCl2/AC composite and its adsorption behavior of azo dye from aqueous solution were investigated. The pore size of the new kinds of adsorbent increased with increasing the dosage of MgCl2 solution, while specific surface area decreased. The removal rate of Weak Acid Red 2R from aqueous solution on the MgCl2/AC composite was 93.4 % at the optimum conditions of the preparation: activated carbon with 2 M MgCl2 solution at 110°C for 2 h.

Adsorption of fluoride from aqueous solution by magnesia‐amended silicon dioxide granules

AbstractBACKGROUND: A new kind of adsorbent, magnesia‐amended silicon dioxide granules (MAS), has been prepared by wet impregnation of silicon dioxide with magnesium chloride solution. The physicochemical properties were characterized using X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) and Brunauer, Emmett, Teller (BET) studies. The porous structure and high surface area of these granules make them suitable for sorption. The aim of this study was to show the possibility of defluoridation of water using MAS and to demonstrate the advantage of its use compared with silicon dioxide.RESULTS: XRD and FT‐IR analysis showed that amorphous magnesia was loaded on silicon dioxide after treating with magnesium chloride solution and calcining at 500 °C. Batch sorption experiments indicated that MAS is more effective than silicon dioxide for fluoride adsorption. The sorption capacities of MAS decreased as the solution pH rose. At pH 3, the maximum defluoridation capacity of MAS was 12.6 mg g−1. The adsorption process fitted the Dubinin–Radushkevich isotherm and kinetic studies revealed that the adsorption followed second‐order rate kinetics.CONCLUSION: The results indicate that it is feasible to modify both the physical and chemical properties of silicon dioxide with magnesia so that it can be used as a potential adsorbent to adsorb fluoride from aqueous solution. Copyright © 2009 Society of Chemical Industry

Adsorption/desorption behavior of protein on nanosized hydroxyapatite coatings: A quartz crystal microbalance study

Protein separation relates closely to the interactions between proteins and various kinds of adsorbents. To obtain a direct and comprehensive understanding of the protein interaction at the solid/solution interface, quartz crystal microbalance (QCM) technique was employed to in situ investigate the adsorption process of bovine serum albumin (BSA) on nanosized hydroxyapatite coatings, and factors affecting its adsorption such as pH, solution ionic strength and temperature were discussed in detail. The adsorption kinetic parameter and the desorption of adsorbed BSA caused by phosphate buffer solution (PBS) introduction were investigated and discussed as well, and an adsorption/desorption mechanism has been proposed. The obtained information suggests that QCM is a useful method for monitoring the adsorption/desorption behavior of BSA on nanosized hydroxyapatite coating.

Hemimicelle capped functionalized carbon nanotubes-based nanosized solid-phase extraction of arsenic from environmental water samples

The end functionalization of CNTs can introduce oxygen-containing negatively functional groups such as –COOH, –OH, or –C O on their surface site. If cationic surfactant such as cetyltrimethylammonium chloride (CTAC) was added to the functionalized CNTs, then interactions such as hydrophobic and ionic may lead to formation of hemimicelle/admicelle aggregates on the CNTs, a new kind of adsorbents, namely, the hemimicelle capped CMMWCNTs, is obtained. The application of the hemimicelle capped carbon nanotubes-based nanosized solid-phase extraction (SPE) adsorbents in environmental analysis is reported for the first time using arsenic as model target. The effect of adsorption and desorption conditions for arsenic including the amount of surfactant, initial pH of sample solution, the ultrasonic time of sample solution, the amount of electrolyte, flow rate, eluent and its amount were investigated and optimized prior to its determination by atomic fluorescence spectrophotometry (AFS). Arsenic can be quantitatively retained on the hemimicelle capped CMMWCNTs at pH 5–6 from sample volume up to 500 mL and then eluted completely with 2 mol L −1 HNO 3 in the presence of 10 mg L −1 CTAC. The method detection limit for arsenic determination with AFS detection was 2 ng L −1, and the relative standard deviation (RSD, n = 11) was 5.3% at the 0.5 μg L −1 level. The recoveries of arsenic in the spiked environmental water samples ranged from 94% to 104.29% with 500 mL of water sample. The proposed method has been applied successfully to the analysis of arsenic in aqueous environmental samples, which demonstrates the hemimicelle capped CMMWCNTs can be an excellent SPE adsorbents for arsenic pretreatment and enrichment from real water samples.

Comparative study of the removal of phenolic compounds by biological and non-biological adsorbents

The ability of biological and non-biological adsorbents to remove 2-nitrophenol (2-NP) and 2-chlorophenol (2-CP) from aqueous solutions in batch experiments at room temperature was compared. The marine seaweeds Macrocystis integrifolia Bory (S1) and Lessonia nigrescens Bory (S2) were cross-linked with CaCl 2 to enhance their mechanical properties. Natural bentonite was chemically exchanged with hexadecyltrimethylammonium bromide (B1) and bencyltriethylammonium chloride (B2) to increase their affinity towards organic compounds as well. The adsorption capacity of all of the adsorbents strongly depends on solution pH, whereas equilibrium assays showed a mixed mechanism according to the Langmuir and Freundlich isotherms. The maximum adsorption capacity of 2-NP follows the trend: S1 > S2 > B2 > B1 within the range of 97.37 and 18.64 mg g −1 whereas for 2-CP, it ranged between 24.18 and 9.95 mg g −1 with the trend: S1 > S2 > B2 ≈ B1. The importance of the octanol–water partition coefficient as the main factor on the adsorption of these compounds on two different kinds of adsorbents is discussed.