Different Types Of Adsorbents Research Articles

Adsorption of different types of surfactants on graphene oxide

The aim of this study was to improve the dispersibility of graphene oxide (GO) and pave the way for future research of proteins and nanosheets in our laboratory. The interactions of GO (with a concentration fixed at 0.10 g/L) with typical cationic, anionic, and neutral surfactants, dodecyl trimethylammonium bromide (DTAB), sodium dodecyl sulfate (SDS), and Triton X-100 (TX-100) were explored using several methods, including surface tension (ST), conductivity, ζ-potential, hydrogen nuclear magnetic resonance (1H NMR), and isothermal titration microcalorimetry (ITC). Several approaches were adopted to confirm the different adsorption behaviors between three surfactants with different charged head groups and the negatively charged GO in different aspects. After comprehensive consideration, it was deduced that the interaction between DTAB and GO was strongest mainly because of electrostatic attraction supplemented by hydrophobic interaction; this was followed the SDS-GO and TX-100-GO interactions for which the hydrophobic interaction played the main role in the adsorption process. The probable adsorption patterns of each surfactant-GO pair were proposed and are presented at the end of the paper.

Effect of impregnated activated carbon on carbon dioxide adsorption performance for biohydrogen purification

The challenge in biohydrogen (bio-H2) production is the presence of low hydrogen purity, which contains a high concentration of carbon dioxide (CO2). Bio-H2 purification systems are required to produce high-purity hydrogen for industrial applications, such as adsorption for CO2 removal. This study tested the effect of impregnated activated carbon (AC) and feed gas flow rate on CO2 adsorption performance. Different types of adsorbents were synthesized by impregnating the chemical on AC, such as potassium iodide, potassium hydroxide, copper (II) sulfate, sodium carbonate, and zinc acetate. The feed gas flow rate was varied in the range of 0.25–1.0 L min−1 by using synthetic bio-H2 gas, that is, mixing the gas with 50 vol.% H2 and 50 vol.% CO2. The CO2 adsorption performances of the synthesized adsorbents were evaluated in terms of breakthrough time and adsorption capacity. To evaluate the reusability of the adsorbents, adsorption–desorption cycles were conducted for several times. For desorption, atmospheric air was used to remove the adsorbed CO2 from the adsorbents. The effect of air flow rate on CO2 desorption was assessed by setting the air flow rate to be between 100 and 350 L min−1. The impregnated AC with zinc acetate displayed the highest adsorption capacity of 63.61 mg CO2/g adsorbent and the longest breakthrough time of 25.7 min. The optimum feed gas flow rate was 0.25 L min−1, thereby demonstrating that the lowest feed gas flow rate resulted in the highest adsorption capacity. Moreover, desorption was faster at higher air flow rates.

Removal of inert COD and trace metals from stabilized landfill leachate by granular activated carbon (GAC) adsorption

Landfills in Germany are currently approaching stabilization phase; as a result removal of inert organics and potentially toxic elements in the leachate is becoming a primary concern. Dissolved air floatation (DAF) at the secondary stage reduces only 27% of the residual chemical oxygen demand (COD) in the investigated treatment systems; downstream granular activated carbon (GAC) units are required to further reduce COD concentration by 40–56% to meet indirect discharge or direct discharge limits respectively. Therefore, in this study performance in terms of COD and trace metals adsorption of different types of granular activated carbon were compared over different contact times and dosages. GAC 1 with Brunauer-Emmett-Teller (BET) surface area of 719.5 ± 2.1 m2/g and average pore diameter (D) of 4.81 nm was identified to be inappropriate for treatment of leachate from this landfill. GAC 2 (with BET of 1513.7 ± 6.4 m2/g and D of 3.50 nm) was feasible for COD reduction from DAF-pretreated leachate, while GAC 3 (with BET of 644.5 ± 2.6 m2/g and D of 5.65 nm) can be coupled either with biological step alone, or as a tertiary step after the DAF unit. Moreover, as COD is the primary remaining contaminant of interest after secondary and tertiary treatment, spectrometer probes provide a close estimation of COD concentration for use in online monitoring. Beside COD removal, GAC 3 also confirmed the effectiveness of trace metals adsorption even at trace level, as it removed 66, 64, 48, 47, 43, and 25% of copper, cobalt, chromium, manganese, nickel, and zinc, respectively.

Mathematical modeling and numerical investigation of carbon capture by adsorption: Literature review and case study

The carbon capture by adsorption (CCA) is regarded as an available engineering technology because of its low energy-consumption, easy to control, and possible integration with renewable energy. The recent advances in CCA research comprises mainly about the performance improvement of adsorbents, design and optimization of engineering process. However, considering the time-consuming and intensive funding required for experimental investigation, the numerical simulation has been widely applied in CCA. In numerical simulation field of CCA, the adsorption process is commonly simplified into mathematical models group comprised of adsorption kinetics model, the adsorption equilibrium model, pressure drop model and heat transfer model. However, few studies’ focus is to provide a detailed review of the research methodology of mathematical modeling in CCA simulation.This paper presents a pathway map on CCA mathematical modeling through literature review and case study. An overview of model screening and modeling method of CCA is provided in the review part. This part also provides a short guided tour on how to combine the fundamental models about heat and mass transfer together to form a model group for various application scenarios in CCA. Then the pathway map on CCA modeling, which is summarized based on the review, is applied to a case study. In this part, the adsorption of CO2/N2 mixtures on activated carbon under the conditions of high temperature and low pressure is numerically investigated based on the established models. The performance indicators comprise gas temperature, mole fraction, and adsorbate amount of the fixed bed, are applied in the evaluation performance of CCA. Based on the proposed methodology, the CCA modeling demonstrates a more fluent design process relative to the real physical scenario, with a possible access to further optimization. Particularly, the simulation results showed that the optimized dimensionless velocity for the highest utilization efficiency of the fixed bed can be obtained and thus is proposed as 1.2–1.4 for the most suitable feed velocity to fit different size of fixed bed and different types of adsorbents for the engineering design.

Adsorption of hexavalent chromium on modified corn stalk using different cross-linking agents

In this study, four different types of adsorbents modified from corn stalk were synthesized after the reaction with epichlorohydrin, N,N-dimethylformamide, triethylamine and different cross-linking agents. The surface functional groups and thermal stability of modified corn stalk (MCSs) were characterized using FTIR and TG analysis, respectively. The feasibility of using MCSs to remove Cr(VI) were evaluated. Adsorption isotherms were determined and modeled with Langmuir, Freundlich and Temkin equations. The experimental results showed that MCS modified using diethylenetriamine (DETA) had the best modification effect, and the adsorption capacity of Cr(VI) reached as high as 227.27 mg/g at 323 K. Thermodynamic study showed that the Cr(VI) adsorption onto MCSs was endothermic processes. As a result, MCS by using DETA as cross-linking agent has good potential for the removal of Cr(VI) from aqueous solutions.

Identification of carotenoid isomers in crude and bleached palm oils by mass spectrometry

In this work, a method for identification of α- and β-carotene isomers in palm oil samples was developed by UHPLC-MS/MS. The fragmentation patterns of both isomers were studied and a diagnostic ion was assigned to α-carotene (m/z 388). The developed method was used to identify isomers in crude palm oils from two cultivars (E. guineensis, here so-called native oil and E. guineensis × E. oleifera, here so-called interspecific hybrid) and bleached oil with two types of commercial bleaching earths (neutral and acid activated). It was noticed that α- and β-isomers are present in both crude oils, nevertheless β-carotene is the most abundant. The reduction of α- and β-isomers in the bleached native oil was very similar after treatment with the two different types of adsorbents. For the interspecific hybrid oil, the acid adsorbent provided a reduction of the two forms, while the neutral adsorbent reduced mostly the β-form.

Stabilization of arsenic and fluoride bearing spent adsorbent in clay bricks: Preparation, characterization and leaching studies

The presence of arsenic and fluoride in groundwater has been observed throughout the world. Many technologies have been developed by various research groups in order to tackle this problem. Adsorption has emerged as one of the best possible technique for the removal of arsenic, fluoride and many other pollutants from drinking water. Although a considerable amount of work has been published on the adsorptive removal of arsenic and fluoride, the area related to the management of spent adsorbent is not well explored. Present paper deals with the adsorptive removal of arsenic and fluoride from aqueous solution by three different types of adsorbents, namely, thermally treated laterite (TTL), acid-base treated laterite (ABTL) and aluminum oxide/hydroxide nanoparticles (AHNP). Under the experimental conditions in batch operation, the adsorption capacities of TTL, ABLT and AHNP for arsenic are found to be 6.43 μg/g, 9.25 μg/g and 48.5 μg/g respectively, whereas for fluoride, these values are found as 0.21 mg/g, 0.85 mg/g and 4.65 mg/g respectively. After adsorption, the spent adsorbents have been stabilized in the form of clay bricks. The effects of spent adsorbent concentration on the properties of bricks and their leaching properties are investigated. The bricks have been tested for various properties like density, percentage water absorption, shrinkage, compressive strength and efflorescence. The maximum values of density and shrinkage of the bricks formed are found as 2.3 g/cm3 and 10.2%, whereas the percentage water absorption and compressive strength of the bricks are found between 11 and 14% and 35 to 150 kgf/cm2 respectively. All the test results are in accordance with the criteria set by Indian Standards. The leaching test of arsenic and fluoride from the bricks reveals that their maximum values in leachate are 510 μg/L and 2.1 mg/L respectively, which are below the permissible limits of USEPA standards.

An Integrated Two-Stage P/VSA Process for Postcombustion CO2 Capture Using Combinations of Adsorbents Zeolite 13X and Mg-MOF-74

An integrated two-stage pressure/vacuum swing adsorption (P/VSA) process for postcombustion CO2 capture from dry flue gas has been simulated and optimized. In the first stage CO2 is concentrated to 40–60% at almost atmospheric pressure, and in the second stage it is further concentrated to 95%. A two-bed six-step cycle configuration was employed in the first stage, while a two-bed five-step cycle configuration was used in the second stage. All possible combinations of two different types of adsorbents (zeolite 13X and Mg-MOF-74) have been employed to study the effect of adsorbent type on key process performance indicators of the process under consideration. The results from systematic comparative simulations demonstrate that the combination of adsorbents zeolite 13X–Mg-MOF-74 has the best process performance, in terms of CO2 purity and CO2 recovery, followed by the use of zeolite 13X at both stages of the process. Furthermore, process optimization studies employing the above combinations of adsorbents have been performed to minimize energy consumption for specified minimum requirements in CO2 purity and in CO2 recovery. The optimization results indicate that the minimum target of 95% in CO2 purity and 90% in CO2 recovery is met for the integrated two-stage P/VSA process, for both combinations of adsorbents at different operating conditions, resulting in different energy requirements and CO2 productivities.

A low pressure cryogenic trap for cleaning of feed stream in dilution refrigerator

Cryogenic traps are frequently used for removing impurities from gases and conventionally use the cryo-adsorption technique with activated carbon adsorbents. Such purification instruments are often operating at high pressure to aid the adsorption process to its maximum extent. In a system which operates at low pressure and low gas flow rates the residual concentration of the adsorptive gas is determined only by its vapor pressure in relation to the total pressure. In a dilution refrigerator the process gas circulates at sub-atmospheric pressure and it becomes a challenge to remove impurities by cryogenic trap at substantially low pressures. In this paper we describe a simple one column liquid nitrogen cooled cryogenic trap for entrapment of O2 and N2 from the circulating process gas. Two different types of adsorbents, LiLSX and activated carbon were investigated using volumetric adsorption approach and break-through studies.

Highway Runoff In Situ Treatment: Copper and Zinc Removal through MOGFC

AbstractThe primary objective of this study is to develop and evaluate multifunctional open-graded friction course (MOGFC) for use as an in situ treatment technique to remove Cu and Zn from highway runoff. First, the conventional porous pavement, open-graded friction course (OGFC), was prepared with varying air voids. Five different types of adsorbents were selected based on cost, applicability, and availability. Second, MOGFC was prepared by adding different adsorbents into the void of OGFC. A series of laboratory tests were conducted to evaluate the adsorption capacity of the adsorbents and metal removal efficiency of MOGFC. The tests included air void content, permeability, moisture susceptibility of OGFC and MOGFC, batch adsorption study of adsorbents, and metal removal by MOGFC. Results showed that three adsorbents have moderate to high adsorption capacity for copper (Cu) and zinc (Zn) removal from its aqueous solution. With these adsorbents, MOGFC could also considerably reduce metal concentration f...

Adsorption study of Ammonia Nitrogen by watermelon rind

The utilization of fruit waste for low-cost adsorbents as a replacement for costly conventional methods of removing ammonia nitrogen from wastewater has been reviewed. The adsorption studies were conducted as a function of contact time and adsorbent dosage and it were carried out on four different adsorbents; fresh watermelon rind and modified watermelon rind with sodium hydroxide (NaOH), potassium hydroxide (KOH) and sulphuric acid (H2SO4). Adsorbents were tested for characterization by using zeta potential test and all samples shows negative values thus makes it favourable for the adsorption process. The batch experimental result showed that adsorption process is rapid and equilibrium was established within 40 minutes of contact time. The ammonia nitrogen removal rate amounted in range of 96% to 99%, and the adsorption capacities were in range of 1.21 to 1.24 mg/g for all four different types of adsorbents used.

Establishment of in vitro Culture of Rubber (Hevea brasiliensis) from Field-derived Explants: Effective Role of Silver Nanoparticles in Reducing Contamination and Browning

The development of in vitro methods to produce high quality clonal planting materials of c for replanting and new planting is highly essential. The establishment of in vitro cultures of challenging woody plant species like H. brasiliensis has frequently been hampered by persistent microbial contamination, phenolic production, phase change and low response to media. Therefore, the overall goal of this study was to establish an efficient in vitro propagation method for H. brasiliensis through solving those persistent problems. In determining the most suitable method of reducing explant contamination, different concentrations of sodium hypochlorite, mercuric chloride and nano silver (NS) at different immersion times were assessed on explants derived from three physiological leaf stages (bronze, light green and stable green leaf stages) of preculture and non-preculture treated plants. The highest percentage of survival (94.44%) was from explants derived from the light green leaf stage of preculture treated plants immersed in 10 ppm NS for 20 min. Different types of adsorbents which were silver nitrate, activated charcoal and NS were assessed in controlling browning of in vitro cultures of H. brasiliensis. NS at 4 ppm significantly produced the highest percentage of explant survival (87.03%) with a low percentage of browning (10%). In determining the most suitable medium for in vitro culture of H. brasiliensis explants, Murashige and Skoog (MS) medium, Woody Plant medium (WPM) and Enjalric and Carron (MB) medium in combination with 3%, 6% and 9% sucrose concentrations were assessed. After 16 weeks of culture, the highest percentage of shoot formation (80%) was on MB medium supplemented with 6% sucrose.

TREATMENT OF NATURAL GAS BY ADSORPTION OF CO2

Apart from burning, one of the possible uses of natural gas is as a fuel for motor vehicles. There are two types of fuel from natural gas — CNG (Compressed Natural Gas) or LNG (Liquefied Natural Gas). Liquefaction of natural gas is carried out for transport by tankers, which are an alternative to long-distance gas pipelines, as well as for transport over short distance, using LNG as a fuel for motor vehicles. A gas adjustment is necessary to get LNG. As an important part of the necessary adjustment of natural gas to get LNG, a reduction of CO<sub>2</sub> is needed. There is a danger of the carbon dioxide freezing during the gas cooling. This work deals with the testing of adsorption removal of CO2 from natural gas. The aim of these measurements was to find a suitable adsorbent for CO<sub>2</sub> removal from natural gas. Two different types of adsorbents were tested: activated carbon and molecular sieve. The adsorption properties of the selected adsorbents were tested and compared. The breakthrough curves for CO<sub>2</sub> for both adsorbents were measured. The conditions of the testing were estimated according to conditions at a gas regulation station — 4.0MPa pressure and 8 °C temperature. Natural gas was simulated by model gas mixture during the tests. The breakthrough volume was set as the gas volume passing through the adsorber up to the CO<sub>2</sub> concentration of 300 ml/m3 in the exhaust gas. The thermal and pressure desorption of CO<sub>2</sub> from saturated adsorbents were also tested after the adsorption.

Adsorption of dimeric surfactants in lamellar silicates

The adsorption of different types of cationic surfactants in lamellar silicates changes their surface character from hydrophilic to hydrophobic. This study was undertaken to obtain lamellar silicates modified by a series of novel dimeric (gemini) surfactants of different length alkyl chains and to characterise these organophilised materials. Synthetic sodium montmorillonite SOMASIF® ME 100 (M) and enriched bentonite of natural origin (Nanoclay – hydrophilic bentonite®) were organophilised with dimeric (gemini) surfactants (1,1′-(1,4-butanediyl)bis(alkoxymethyl)imidazolium dichlorides). As a result of surfactant molecule adsorption in interlamellar space, the d-spacing (d001) increased from 0.97nm (for the anhydrous structure) to 2.04nm. A Fourier transform infrared spectroscopy (FTIR) analysis of the modified systems reveals bands assigned to the stretching vibrations of the CH2 and CH3 groups and the scissoring vibrations of the NH group from the structure of the dimeric surfactants. Thermogravimetric (TG) and derivative thermogravimetric (DTG) studies imply a four-stage process of surfactant decomposition. Scanning electron microscopy (SEM) images provide information on the influence of dimeric surfactant intercalation into the silicate structures. Particles of the modified systems show a tendency toward the formation of irregularly shaped agglomerates.

Investigation of the adsorption behaviour of different types of dyes on MIL-100(Fe) and their removal from natural water

Metal–organic framework MIL-100(Fe) microcrystals were explored for the selective adsorption of different types of dyes from aqueous solution.

Adsorption-Desorption of Heavy Metal Ions

Adsorption and desorption studies on different types of adsorbents, including natural materials such as teak tree bark powder, rice husk, natural bentonite, different algae like Ecklonia maxima, Escherichia coli, Ascophyllum nodasum, Rhizopus nigricans, Cladophora fascicularis, goethite and soils of three nuclear power plant and artificial materials such as Fe oxide-coated sand, goethite pretreated with phosphate, dithizonemodified sodium trititanate whisker, modified nanometre sized TiO 2 , Chromosorb 102 resins and poly(m-phenylenediamine) are summarized. The kinetics, thermodynamics, sorption/desorption mechanism of different metal ions on different adsorbents under different experimental conditions are discussed. It is found that desorbing agent is greatly dependent on the adsorbate used. All the metal ions are desorbed using acids like HCl, HNO 3 and H 2 SO 4 in most of the cases, except Cr(VI). EDTA can be used to remove Pb 2+ and Zn 2+ in addition to acids. Since Cr(VI) is present in anionic form; it can be eliminated from the loaded adsorbents using bases like NaOH, Na 2 CO 3 or NaHCO 3 .

Efficiency of Low Cost Adsorbents for the Removal of Arsenic from Water

Adsorption is one of the primary processes for removing arsenic from drinking water. This study focuses on developing inexpensive and effective adsorbents to remove arsenic from ground water. Eight different types of adsorbents were prepared. Some of these materials were chemically modified. The efficiency of percentage adsorption of arsenate, As (+III) on different materials were investigated at different pH, contact time and initial concentrations. Out of eight different types of adsorbents, the iron-loaded x ant hated orange waste (Fe-XOW) showed high efficiency for the removal of arsenic. It was found that approximately 83 % of arsenate, As (+III) and 87% of arsenate, As (+V) removal could be achieved at optimum pH of 10 and 4respectively. The significant effect of pH was in the range of 9 to12 for As (+III) and 3 to 5 for As (+V). Time dependency experiments for the arsenite uptake showed that the adsorption rate on Fe-XOW was fast initially for 1 hour, followed by slow attainment of equilibrium at 2.15 hour. Adsorption isotherm test showed that equilibrium adsorption data were better represented by Langmuir model than the Freundlich model and the maximum adsorption (qmax) for As (+III) onto Fe-XOW was found to be 53.47 mg/gm. The concentration of arsenic in water sample was determined by standard silver diethyldithiocarbamate spectrophotometric method (SDDC method).

Removal of oxidized sulfur compounds using different types of activated carbon, aluminum oxide, and chitosan-coated bentonite

The adsorption of benzothiophene sulfone and dibenzothiophene sulfone from diesel using six different types of adsorbents were investigated. Adsorbents used were commercial adsorbents granular-activated carbon (GAC), aluminum oxide (ALU), novel adsorbents chitosan-coated bentonite (CHB), and metal-ion impregnated activated carbons, where there types of metal ions, Cu2+, Fe3+, and Ni2+, were loaded (Cu2+/AC, Fe3+/AC, Ni2+/AC). Kinetic studies conducted showed that the adsorption process followed a pseudo-second-order kinetics. Equilibrium studies indicated that the heterogeneous and homogenous monolayer adsorption and are present in the process. Moreover, based on the results of sulfone removal using the synthetic diesel fuel, increasing removal efficiencies of Benzothiophene sulfone followed the order of ALU < GAC < Cu2+/AC < < Fe3+/AC < CHB, while for dibenzothiophene sulfone (DBTO) removal, increasing DBTO removed efficiencies followed the order of GAC < CHB < ALU < Cu2+/AC ≈ Fe3+/AC ≈ Ni2+/AC.

Enhancing and reducing the Rashba-splitting at surfaces by adsorbates: Na and Xe on Bi/Cu(111)

The surface alloy Bi/Cu(111) shows a paradigmatic free-electron-like surface state with a very large Rashba-type spin–orbit splitting. Using angle-resolved photoemission we investigate how adsorbates of different chemical nature influence the size of the spin splitting in this system. We find that the adsorption of small amounts of monovalent Na atoms leads to an enhancement of the spin splitting while an overlayer of the closed-shell rare gas Xe causes a reduction. The latter result is in contrast to the Au(111) surface for which an increased splitting size after Xe-adsorption was observed. We discuss these experimental findings in terms of the characteristic differences of the surface state wave functions and their spatial deformation in the presence of different types of adsorbates. Our results provide insight into the complex interplay of atomic and interface potential gradients governing the Rashba effect.

Adsorptive drying of CO2 using low grade heat and humid, ambient air

Adsorptive separation of water from CO2 is an appealing alternative to liquid absorbers for post-combustion capture systems. In all cases, the purified CO2 stream from a PCC system will have a high moisture content and, due to equipment corrosion issues and the risk of hydrate formation, the CO2 stream must be rigorously dried prior to being compressed. This work reports the first study on solid adsorbent selection for CO2 drying using low grade heat and ambient air as a regeneration gas. Different types of adsorbents, chosen for their range of water adsorption characteristics, have been investigated for the desiccation of a pure CO2 stream. When destined for sequestration the CO2 product gas has little value and so the drying process should require no supporting process operations and should consume little additional energy. However, due to the costs and complexity of separating and purifying CO2 from a flue gas stream, the drying process should return as much CO2 as possible to the compression stage. An ideal desiccant for CO2 drying should have a high moisture capacity and selectivity and should be regenerable using waste heat and ambient, humid air. The CO2 drying performance of Na-, Ca-, and Ca/H- forms of ETS-10 were compared to that of commercial silica and 4A zeolite. Ca-ETS-10 was found to have the highest moisture capacity using a temperature swing of 30–70°C and a CO2 feed stream of 50–100% relative humidity. Due to the intrinsic selectivity for water over CO2 on solid adsorbents, all desiccants tested had a CO2 recovery greater than 95%.