Variation Of Adsorption Capacity Research Articles

Post‐combustion carbon dioxide adsorption of concurrent activated and surface modified palm kernel shell‐derived activated carbon

AbstractThis research applied a concurrent activation and surface modification (CAM) process to synthesize palm kernel shell‐derived activated carbon (PKSdAC) to obtain CO2 affinity surface functionalization. The CAM process is a simplified activated carbon activation process that is cost‐effective. The CAM process used in this study integrates sulphuric acid activation and barium chloride functionalization. The formation of barium sulphate is targeted to incorporate barium through a reduction process with carbon‐containing material at elevated temperatures into PKSdAC to obtain basic metal surfaces functional group for chemical adsorption. The optimal temperature for CAM‐PKSdAC CO2 adsorption performance was at 40–60 °C, established through temperature‐programmed desorption of CO2 (TPD‐CO2) analysis. The CAM‐PKSdAC adsorption performance was tested using a lab‐scale adsorption system. The bed CO2 content was determined using gas chromatography coupled with a thermal conductivity detector (GC‐TCD) by manual syringe injection. CAM‐PKSdAC exhibited a high CO2 adsorption capacity of 0.89 mmol g−1 from TPD‐CO2, and 1.91 mmol g−1 from GC‐TCD at 40 °C and 1 bar. It showed comparable CO2 adsorption capacity to conventional surface modified‐activated PKSdAC (1.96 mmol g−1) while higher than commercial and modified ACs (1.14–1.60 mmol g−1), but lower than potassium hydroxide modified ACs (1.81–2.10 mmol g−1) at 40 °C and 1 bar. Barium promoted chemisorption of CO2 as supplementary reaction, which increases adsorption capacity. The non‐linear Dubinin Radushkevich model strongly correlates with the experimental adsorption data for CAM‐PKSdAC adsorption, indicating the physisorption process via micropore filling on CAM‐PKSdAC. CAM‐PKSdAC showed moderate reusability with negligible variation in adsorption capacity after 10 adsorption–desorption cycles. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Adsorption-desorption behavior of florpyrauxifen-benzyl on three microplastics in aqueous environment as well as its mechanism and various influencing factors

Microplastics (MPs) and pesticides are two categories contaminants with proposed negative impacts to aqueous ecosystems, and adsorption of pesticides on MPs may result in their long-range transport and compound combination effects. Florpyrauxifen-benzyl, a novel pyridine-2-carboxylate auxin herbicide has been widely used to control weeds in paddy field, but the insights of which are extremely limited. Therefore, adsorption and desorption behaviors of florpyrauxifen-benzyl on polyvinyl chloride (PVC), polyethylene (PE) and disposable face masks (DFMs) in five water environment were investigated. The impacts of various environmental factors on adsorption capacity were evaluated, as well as adsorption mechanisms. The results revealed significant variations in adsorption capacity of florpyrauxifen-benzyl on three MPs, with approximately order of DFMs > PE > PVC. The discrepancy can be attributed to differences in structural and physicochemical properties, as evidenced by various characterization analysis. The kinetics and isotherm of florpyrauxifen-benzyl on three MPs were suitable for different models, wherein physical force predominantly governed adsorption process. Thermodynamic analysis revealed that both high and low temperatures weakened PE and DFMs adsorption, whereas temperature exhibited negligible impact on PVC adsorption. The adsorption capacity was significantly influenced by most environmental factors, particularly pH, cations and coexisting herbicide. This study provides valuable insights into the fate of florpyrauxifen-benzyl in presence of MPs, suggesting that PVC, PE and DFMs can serve as carriers of florpyrauxifen-benzyl in aquatic environment.

Characteristics and adsorption behavior of typical microplastics in long-term accelerated weathering simulation.

Microplastics can function as carriers in the environment, absorbing various toxins and spreading to diverse ecosystems. Toxins accumulated in microplastics have the potential to be re-released, posing a threat. In this study, two typical plastics, namely polyethylene (PE) and polystyrene (PS), along with the degradable plastic poly(butylene adipate-co-terephthalate) (PBAT), were subjected to a long-term ultraviolet alternating weathering experiment. The study investigated the variations in the weathering process and pollutant adsorption of microplastics of different particle sizes. Furthermore, the adsorption capacity of microplastics for various pollutants was assessed. The findings indicate that particle size significantly influences weathering, leading to variations in adsorption capacity. The weathered PE displays a higher adsorption capacity for azo dyes. Additionally, the adsorption capacity of PBAT for neutral red is double that of antibiotics. Importantly, the maximum adsorption capacity of PBAT for pollutants after aging is approximately 10 times greater than that of PE. Consequently, degradable plastics undergoing weathering in the natural environment may pose a higher ecological risk than traditional plastics.

A study on the performance of a novel adsorbent UiO-66 modified by a nickel on removing tetracycline in wastewater

In the present study, Ni-UiO-66 was synthesized to improve the adsorption efficiency of tetracycline (TC) in wastewater treatment. To this end, nickel doping was performed in the preparation process of UiO-66. The synthesized Ni-UiO-66 was characterized by XRD, SEM and EDS, BET, FTIR, TGA, and XPS for obtaining the lattice structure, surface topography, specific surface area, surface functional groups, and thermostability. More specifically, Ni-UiO-66 has a removal efficiency and adsorption capacity of up to 90% and 120 mg g−1, respectively, when used to treat TC. The presence of ions HCO3−, SO42−, NO3− and PO43− slightly affects the TC adsorption. A 20 mg L−1 humic acid reduces the removal efficiency from 80% to 60%. The performed analyses revealed that Ni-UiO-66 had similar adsorption capacity in wastewater with different ion strengths. The variation of adsorption capacity with the adsorption time was fitted using a pseudo-second-order kinetic equation. Meanwhile, it is found that the adsorption reaction occurs only on the monolayer of the UiO-66 surface so the adsorption process can be simulated using the Langmuir isotherm model. The thermodynamic analysis indicates that the adsorption of TC is an endothermic reaction. Electrostatic attraction, hydrogen-bond interaction, and π-π interaction might be the main reasons for the adsorption.The synthesized Ni-UiO-66 has well adsorption capacity and stable structure. Accordingly, it is expected to achieve a good prospect in industrial applications and wastewater treatment plants.

Effect of microstructure in mesoporous adsorbents on the adsorption of low concentrations of VOCs: An experimental and simulation study

This study evaluated the adsorption of five volatile organic compounds (VOCs) on Opoka, precipitated silica, and palygorskite, to elucidate the effect of their pore size on VOCs adsorption. The adsorption capacity of these adsorbents is not only highly correlated with their surface area and pore volume, but also notably improved by the presence of micropores. The variation in adsorption capacity for different VOCs was primarily influenced by their boiling point and polarity. Palygorskite, which had the smallest total pore volume (0.357 cm3/g) but the largest micropore volume (0.043 cm3/g) among the three adsorbents, exhibited the highest adsorption capacity for all tested VOCs. Additionally, the study constructed slit pore models of palygorskite with micropores (0.5 and 1.5 nm) and mesopores (3.0 and 6.0 nm), calculated and discussed the heat of adsorption, concentration distribution, and interaction energy of VOCs adsorbed on different pore models. The results revealed that the adsorption heat, concentration distribution, total interaction energy, and van der Waals energy decrease with increasing pore size. The concentration of VOCs in 0.5 nm pore was nearly three times that in 6.0 nm pore. This work can also provide guidance for further research on using adsorbents with mixed microporous and mesoporous structures to control VOCs.

Removal of lead ion from aqueous solutions by adsorption onto phosphate-functionalized treated waste papers (PF-TWPs)

Waste papers, although known as a potential global concern, could be used as an adsorbent for removal of lead ions from the aqueous medium, following some degrees of modifications. The present study deals with the adsorption of Pb(II) ion from aqueous solution by using phosphate-functionalized treated waste papers (PF-TWPs). Batch adsorption study was performed based on contact time, pH, adsorbent dose, and temperature. There was logical coordination of experimental data with Freundlich and Langmuir isotherms. The results of this study showed that the percentage of Pb(II) adsorption on the PF-TWPs increased with increasing pH of approximately 5.5, higher or lower pHs showed no remarkable variation in adsorption capacity. The kinetics analysis showed a substantial correlation between the experimental adsorption data with the pseudo-second-order model. Besides, thermodynamic studies were conducted to explore the adsorption of Pb(II) onto PF-TWPs, regarding the influence of temperature on this process. The spontaneity and endothermicity of the Pb(II) adsorption process were identified based on the negative free energy value and positive enthalpy change. The result of the present study showed that the PF-TWPs could be used as a cost-effective adsorbent for Pb(II) removal from industrial effluent.

Controllable Adsorption of CO2 on Smart Adsorbents: An Interplay between Amines and Photoresponsive Molecules

Photoresponsive adsorbents for CO2 capture attract significant attention, because the variation of adsorption capacity can be tailored conveniently by light irradiation. However, all photoresponsive adsorbents reported until now capture CO2 via physical interaction (weak sites). Thus, the selectivity of CO2 over other gases like CH4 is low, and the variation of CO2 adsorption capacity originates from pure structural change via isomerization of photoresponsive units. Despite great challenges, photoresponsive adsorbents for CO2 capture based on chemical interaction (strong sites) are extremely desirable. Here, we report for the first time the construction of photoresponsive adsorbents with chemical adsorption sites for CO2. The control of adsorption capacity is based on the interplay between active amine sites {A, [3-(methylamine)propyl]trimethoxysilane} and photoresponsive azobenzene molecules [P, 4-(3-triethoxysilylpropyl-ureido)azobenzene]. Density functional theory (DFT) calculations reveal that the neg...

Effect of multifactors interaction on competitive adsorption of Zn2+ and Cd2+ by response surface methodology

The problem associated with multi-metals contaminated soils has generated increasingly more attention. Thus, it is necessary within the field to study the mutual influence of environmental factors on competitive adsorption. The majority of studies carried out to date have concentrated on the variation of adsorption capacity or the removal efficiency, with only a single factor changed (including pH, ionic strength, and metal concentration). However, the interaction effect among various environmental factors was ignored in these studies. The purpose of this study was mainly aimed toward the investigation of the interaction of two influential factors, as well as the influential degree of each factor (such as the initial pH, ionic strength, initial metal concentration, and the competitive metal concentration) on competitive adsorption using the response surface method. These results demonstrated that the influential degree of each factor studied on the competitive adsorption of Zn2+ and Cd2+ followed the trend of having the initial concentration of the target metal > initial pH > concentration of competitive metal > ionic strength. When the metal concentration was held constant, we found that the competitive adsorption of Zn2+ initially increased, followed by a decrease with increasing initial pH. However, this was found to change minimally with increasing ionic strength. When the initial pH or ionic strength was held constant, the competitive ability was observed to increase with increasing Zn2+ concentration. However, with increasing Zn2+ or Cd2+ concentrations, the variation degree of the competitive adsorption was found to become smaller. These results provide novel information toward a better understanding of the effect of multifactors on the competitive adsorption of Zn2+ and Cd2+.

Properties of modified crude clay by iron and copper nanoparticles as potential hydrogen sulfide adsorption

The present work aimed at modifying original kaolin with iron and copper chlorides in order to introduce active centers for hydrogen sulfide (H2S) adsorption. In the first modification, interlayer sodium cations were exchanged with two metals. In the second one, iron oxide (FeOx) was introduced to the clay surface. Kaolin and modified kaolin were analyzed using ICP, X-ray diffraction (XRD), Infrared Ray, Fluorescence-X, BET surface area analysis and SEM. The modified clay samples were tested as hydrogen sulfide adsorbents. Iron-doped and copper-doped samples showed a significant improvement in the capacity for H2S removal, despite a noticeable decrease in microporosity compared to the initial pillared clay. The smallest capacity was obtained for the clay modified with FeOx. Variations in adsorption capacity are likely due to differences in the chemistry of metals species, degree of their dispersion on the surface, and accessibility of small pores for H2S molecule. Results suggest that on the surface of metal-modified clay, hydrogen sulfide reacts with Cu2+ and Fe+3 ions to form sulfides or can be catalytically oxidized to SO2 on iron (hydro) oxides. Subsequent oxidation may lead to sulfate formation.

Effect of formation pH, molar ratio and calcination temperature on the synthesis of an anionic clay based adsorbent targeting defluoridation

Calcined Ca Al (NO3) LDH, an anionic clay based adsorbent, was synthesized at different process conditions. The influence of formation pH, molar ratio, and calcination temperature on the physicochemical characteristics of this adsorbent was assessed. The response surface methodology (RSM) was applied to optimize the adsorption capacity by employing a 33 factorial design. Characterization of the adsorbent was conducted through XRD, FTIR, EDX, SEM and N2 adsorption desorption analysis. A significant variation in adsorption capacity (6.4 to 12.5mg/g) was observed for the experimental points designed. XRD results demonstrated that the increase in formation pH enhances the crystallinity of the LDH material. The defluoridation capacity was observed to decrease with increasing pH or molar ratio, as the aluminum content in LDH structure was found to be inversely correlated with both the factors. The fluoride adsorption capacity was found to attain optima at a calcination temperature of approximately 500°C. The reconstruction of the original structure from the calcined product of LDH through a ‘memory effect’ may enhance its adsorption capacity. The maximum adsorption capacity by the Langmuir isotherm model was estimated to be 108.69mg/g.

Improved removal of Cr(VI) by starch functionalized iron oxide nanoparticles

We investigate the effect of starch functionalization of iron oxide nanoparticles on their adsorption of Cr(VI) from aqueous solutions. Iron oxide nanoparticles (IONPs) are synthesized by alkaline hydrolysis of FeCl3. The rate of addition of the base determines the time of aging of the reaction mixture at increasing pH values. This affects the iron oxide phase composition, nanoparticle sizes and their distribution. The purpose of this study is to first understand the effect of phase composition of such IONPs on their adsorption of Cr(VI) from aqueous solutions. Then to further investigate the effect of starch functionalization of these IONPs on their Cr(VI) adsorption capacity from aqueous medium. The results show that adsorption capacity changes with the phase composition. Further, for a given phase composition, starch functionalized iron oxide nanoparticles (SIONPs) exhibit significant improvement in adsorption capacities for Cr(VI) as compared to IONPs. Adsorption capacity is dependent on the pH value and at a given Cr(VI) concentration the adsorption capacity is found to be highest at pH 2 for all SIONPs and IONPs samples. The variation of adsorption capacity with pH depends on the nanoparticle phase composition as well as its starch functionalization. The removal of Cr(VI) by all SIONPs and IONPs follow Langmuir adsorption isotherm. The highest monolayer saturation adsorption capacity as obtained from the Langmuir adsorption isotherm for SIONPs is 9.02mg/g.

Competition among Mixed Adsorbates Affecting the Adsorption of Gaseous Methyl Ethyl Ketone by Hydrophobic Molecular Sieve

Internal circulation cabinets, equipped with adsorbents for emitted volatile organic compounds (VOCs), are extensively used to store organic solvents in Taiwanese university and hospital laboratories. This work evaluates how ketone and isopropanol (IPA) respectively influence the methyl ethyl ketone (MEK) adsorption capacity of a hydrophobic molecular sieve (MS) with a high Si/Al ratio of 1000, HiSiv 1000, manufactured by UOP LLC Corporation, USA. Experimental results for MEK at concentrations from 113 to 2815 ppm reveal that the MEK adsorption capacity is linearly expressed as the natural logarithm of adsorption time (ln (t)) at the constant temperature 27 o C and relative humidity 72 ± 3%. The variations in the simulated MEK equilibrium adsorption capacity (Qe, g MEK/g MS) and concentration (C, ppm) are closely fitted using a Langmuir isotherm. Lower VOC concentration ratios less than 0.17 for mixing acetone and IPA respectively with MEK rarely affect the MEK adsorption by HiSiv 1000. However, the effect of competitive adsorption, which evidently reduces the adsorption capacity of MEK, is related to the higher mixture concentration ratio (> 0.80) of IPA to MEK. The experimental results show that the hydrophobicity characteristics of MEK, acetone and IPA were responsible for variation in adsorption capacity of hydrophobic molecular sieve. Working parameters of adsorbent materials in the internal circulation cabinet have been also provided for preventing breakthrough of VOC adsorption by the molecular sieve.

Adsorption of Formaldehyde on Treated Activated Carbon and Activated Alumina

Formaldehyde is extensively used for disinfection and antisepsis in medical facilities and especially in textile and paint industries as a solvent. Owing to the higher concentration of formaldehyde, both in waste effluents and local environment of medical facilities and industries, it has been reported to cause cancer and as an irritant to eyes and skin. The removal efficiency and the adsorption mechanism of formaldehyde onto the treated activated carbons and activated alumina were studied to analyze the effect of modified surface chemistry of adsorbents. The adsorption capacities of all the selected adsorbents were investigated in batch study at varying contact time and initial concentration of formaldehyde at STP. It was found that commercially implemented activated alumina, treated with effective nucleophile, showed significant formaldehyde adsorption with less variation in adsorption capacity even with decrease in initial concentration of adsorbate. These set of experiments indicate that acidity of formaldehyde can be exploited for its removal from waste effluent and air. The optimization studies were carried out to find out the optimum conditions for this adsorption process with adsorption model fitting and kinetic studies. The investigation results were evaluated on per gram of adsorbent basis to predict feasibility of scaling up at commercial level.

Operational aspects of adsorption air-conditioner used in diesel locomotive

A locomotive cabin adsorption air-conditioner has been equipped in #DF4B-2369 locomotive; and has been successfully run for 2 years. It is powered by waste heat from the exhaust of the diesel engine. The influence on heat transfer is described by the equivalent heat transfer coefficient or thermal resistance of components inside the adsorber. The variation of adsorption capacity is expressed by a non-equilibrium adsorption function. The dynamic heat transfer process of adsorption air-conditioning system is treated with the lumped parameter method. Some typical running experimental results are present. The diesel engine rotating speed and locomotive speed influenced on the refrigeration system are discussed. The maximum mean refrigeration power is regarded as an objective function. Based on experiments and theoretical analysis, the running characteristics of the air-conditioning system are optimized. Some techniques of performance improvement are suggested as well. Copyright © 2006 John Wiley & Sons, Ltd.

Optimizing Cell Preparation Technique to Enhance Adsorption Capacity of Pseudomonas Putida 5-X to Heavy Metal Ions

A heavy metal accumulation bacterium Pseudomonas putida 5-x isolated from electroplating effluent was used as biosorbent for heavy metal removal from wastewater. In order to compete with physical adsorbent, the optimization of the cell preparation technique for further improving its heavy metal adsorption capacity was conducted. Experimental results showed that the variation of medium compositions and cell growth age, and different cell pre-treating technique would result in the variation of the cell surface components and structural, hence the variation of adsorption capacity of the cell to heavy metal ions. With optimum cell culture conditions and pretreatment technique, the Cu2 + adsorption capacity of the cell was obviously increased from 51.2 mg g− 1 to 89.6 mg g− 1. The optimised P. putida 5-x cell could be reused at least five cycles to remove heavy metal ions from electroplating effluent with about 95% removal efficiency.

Adsorption of hydrogen sulfide on montmorillonites modified with iron

Sodium-rich montmorillonite was modified with iron in order to introduce active centers for hydrogen sulfide adsorption. In the first modification, interlayer sodium cations were exchanged with iron. In another modification, iron oxocations were introduced to the clay surface. The most elaborated modification was based on doping of iron within the interlayer space of aluminum-pillared clay. The modified clay samples were tested as hydrogen sulfide adsorbents. Iron-doped samples showed a significant improvement in the capacity for H 2S removal, despite of a noticeable decrease in microporosity compared to the initial pillared clay. The smallest capacity was obtained for the clay modified with iron oxocations. Variations in adsorption capacity are likely due to differences in the chemistry of iron species, degree of their dispersion on the surface, and accessibility of small pores for H 2S molecule. The results suggest that on the surface of iron-modified clay hydrogen sulfide reacts with Fe +3 forming sulfides or it is catalytically oxidized to SO 2 on iron (hydro)oxides. Subsequent oxidation may lead to sulfate formation.

Adsorption studies with gmelinite zeolites containing mono-, di- and tri-valent cations

Synthetic gmelinite zeolites are prepared via (i) hydrothermal conversion of strontium-containing zeolite Y and (ii) the use of a DABCO (1,4-diazabicyclo [2,2,2] octane) polymer structure-directing agent. The synthetic materials are compared to a sample of natural gmelinite. The adsorption capacities of the three gmelinites after ion exchange with Na +, Sr 2+ and La 3+ for adsorbates such as water, methanol, ethanol, propanol, nitrogen, n-hexane and cyclohexane are presented. It is shown on each type of gmelinite and independent of the degree of faulting, the adsorption capacities of nitrogen, propanol, n-hexane and cyclohexane increase when monovalent cations are replaced by multivalent cations. However, adsorbates such as water, methanol and ethanol do not show significant variations in adsorption capacity with exchangeable ion valency.

Phosphorus sorption capacity of low activity clay soils of South Western Nigeria and its usefulness in evaluating P requirement of rice

Field and laboratory experiments were conducted on 15 low activity clay soils in Ogun State of Nigeria to evaluate the relationships between P sorption capacity and some soil properties and the use of sorption indices in evaluating the P requirement of rice. Langmuir adsorption capacity (b) varied from 30.9 to 414.3 µg g−1. Although adsorption capacity was related significantly to a number of soil properties, citrate dithinonite bicarbonate (CDB) extractable Fe was the most important variable accounting for 99% of the variation in adsorption capacity. The solution P concentration (SPC) required to achieve 95% maximum grain yield of rice varied from 0.03 in a sandy clay soil to 0.19 µg ml−1 in a sandy soil, while the quantity of fertilizer P required to attain the solution P concentration (Standard Phosphate requirement, SPR) varied from 14.1 to 88.7 kg ha−1. Highly significant power function relationships were obtained between SPC and b (r=0.93) and between SPR and b (r=0.93). The P buffering capacity (PBC) of the soils indicated that the soils are moderately buffered. However, SPR accounted best for the variation in grain yield of rice on the field (R2=0.90). The use of P sorption indices in estimating P needs of rice appears superior to the use of chemical extractants.