Adsorption of Methyl Chloride on Molecular Sieves,Silica Gels,and Activated Carbon

Adsorption of methyl chloride (CH₃Cl or MeCl) on five different types of adsorbents was investigated experimentally at increasing pressures and room temperature. Prior to adsorption, all adsorbents were analyzed to assess their physical and chemical characteristics. The experimental data was then used to determine the adsorption isotherms, heats of adsorption, adsorption rates, and their respective theoretical models. The MeCl adsorption capacity was found to reasonably correlate with the adsorbent's surface area. The MeCl adsorption isotherm and adsorption rates were fitted for the first time to a Freundlich isotherm model and pseudo first-/second-order kinetic models, respectively. The range of heat of adsorption indicated a physisorption type of bonding; hence, the investigated adsorbents can potentially be regenerated for cyclic adsorption.     

Thermodynamics aspect of tannin sorption on polymeric adsorbents

Hypercrosslinked polydivinylbenzene and gel type poly(styrene-co-divinylbenzene) post-crosslinked with isocyanuric acid and macroporous crosslinked poly (N-vinyl acetamide) adsorbent were prepared for adsorbing tannin from aqueous. The sorption isotherms were measured and the isosteric enthalpy was quantitatively correlated with the fractional loading for the tannin sorption onto the three polymeric adsorbents. Surface energetic heterogeneity was observed for the three adsorbents and described with the functions of isosteric enthalpy. The causative factors of the surface heterogeneity of the adsorbents and the mechanism of tannin sorption onto the adsorbents from aqueous were discussed. It was suggested that multiply hydrogen bonding, π-π interaction and hydrophobic interaction were involved in tannin adsorption onto the polymeric adsorbents.     

蜂巢石改性及其对Mn~(2+)吸附试验研究

为探讨硫酸对蜂巢石吸附材料改性的影响因素,以及改性蜂巢石对Mn~(2+)的吸附特性,采用正交试验法研究了硫酸改性条件对蜂巢石比表面积、孔容、孔径的影响;对改性蜂巢石和未改性蜂巢石做了SEM和XRD对比分析;通过静态吸附试验探讨了硫酸改性蜂巢石对Mn~(2+)的最佳吸附条件。试验结果表明,硫酸浓度为0.50mol/L,改性时间为30 min,温度为35℃时改性最佳,改性后蜂巢石比表面积、孔容分别达到21.15 m2/g、0.053cm3/g左右,平均孔径为5 nm;SEM和XRD对比分析发现,改性后蜂巢石表面变得粗糙蓬松,微孔增加,空隙率和孔道通透性提高,出现了Ca SO4·2H2O单斜晶体;改性蜂巢石投加量和溶液的p H值是影响吸附效果的重要因素,当溶液p H值为5,改性蜂巢石投加量为4 g/L,Mn~(2+)初始质量浓度为5 mg/L时,对Mn~(2+)的去除率达85%以上,吸附量超过10.0 mg/g。     

Synthesis,characterization, and adsorption properties of collagen and attapulgite-filled copolymer biocomposites: Batch and column studies

Several biocomposites were synthesized by copolymerizing hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) at varied molar ratios in the presence of different wt% of collagen (CLG) and attapulgite (APG) clay. The structure and properties of the biocomposite adsorbents were characterized by Fourier transform infrared apectroscopy, nuclear magnetic resonance, X-ray photo electron spectroscopy, X-ray diffraction, scanning electron microscope, transfer electron microscopy, energy-dispersive X-ray analysis, differential thermal analysis–thermogravimetric analysis, point zero charge analysis, mechanical properties, and pH reversibility tests. The synthesis variables were optimized with a central composite design of response surface methodology (RSM). The biocomposite prepared with an optimized composition of 1.5 wt% CLG, 1.7 wt% APG, and 5:1 molar ratio of HEMA:IA showed an adsorption capacity (Q_e, mg/g) of 674.4/602.4 for methylene blue (MB)/Rose Bengal (RB) dye from a feed containing 200 mg/L of MB + RB dye mixture in batch mode. In a fixed bed in column mode, the optimized biocomposite showed a removal% of 82.8/71.3 for 100 mg/L inlet concentration, 20 ml/min flow rate, and 20 mm bed height with a breakthrough time of 23/31 min and a mass transfer coefficient (k_mtc × 10⁵ cm/s) of 8.36/7.67 for MB/RB as single dye solution.     

Preparation of modified silica for heavy metal removal

2-hydroxy-5-nonyl-acetophenoneoxime, di-2,4,4-trimethylpentyl phosphinic acid, and a tertiary amine were bound on the silica surface after surface modification. The adsorption of the metal chelating agents appears to be due to physical attraction such as van der Waals interactions and not covalent bonding. Stability tests show that the adsorbents are stable under acidic conditions. Batch tests were conducted for heavy metal ion adsorption and elution. Heavy metal ions which were adsorbed to the surface of the adsorbents could be recovered by elufion with 0.1 M HC1.     

Hydrogen adsorption on metal-organic framework (MOF-5) synthesized by DMF approach

Metal-organic frameworks (MOFs), especially MOF-5, are believed to be promising new porous materials for hydrogen adsorption. A comparative study of material synthesis, characterization and hydrogen adsorption was performed to examine the effects of different synthesis conditions on crystal structure, pore textural property and hydrogen adsorption performance of MOF-5 materials. Three MOF-5 samples synthesized with dimethyl formamide (DFM) as solvent and slightly different procedures have shown similar phase structure and chemical composition, diverse crystal structures, varying pore textural properties and different hydrogen adsorption performance. It was established from the experimental results that higher order of crystallinity in the MOF-5 materials generates better adsorbents with larger crystal size, higher specific surface area, uniform pore size distribution (PSD), larger hydrogen adsorption capacity and faster hydrogen diffusion rate in MOF-5 adsorbents. The best MOF-5 sample synthesized in this work (MOF-5(γ)) has a Langmuir specific surface area of 1157 m²/g; it can adsorb 0.5 wt.% of hydrogen at 77 K and 800 mmHg; and results in hydrogen diffusivity inside MOF-5 crystal of 2.3 × 10⁻⁹ cm²/s. The density functional theory reasonably predicts the presence of mesopores and macropores in all three MOF-5 samples synthesized in this work.     

Rapid adsorption of alcohol biofuels by high surface area mesoporous carbons

Surfactant templated mesoporous carbons were evaluated as biofuel adsorbents through characterization of equilibrium and kinetic behavior for both ethanol and n-butanol. Variations in synthetic conditions enabled facile tuning of specific surface area (500-1300 m²/g) and pore morphology (hexagonally packed cylindrical or BCC spherical pores). n-Butanol was more effectively adsorbed than ethanol for all mesoporous carbons, suggesting a mechanism of hydrophobic adsorption. The adsorbed alcohol capacity increased with elevated specific surface area of the adsorbents, irrespective of pore morphology. While adsorption capacity of these mesoporous carbons is comparable to commercially-available, hydrophobic polymer adsorbents of similar surface area, the pore morphology and structure of mesoporous carbons greatly influenced adsorption rates, enhancing them by up to 1-2 orders of magnitude over commercial polymer adsorbents. Multiple cycles of adsorbent regeneration did not impact the adsorption equilibrium or kinetics. The high chemical and thermal stability of mesoporous carbons provide potential significant advantages over other commonly examined biofuel adsorbents, such as polymers and zeolites.     

Adsorptive interaction of bisphenol A with mesoporous titanosilicate/reduced graphene oxide nanocomposite materials: FT-IR and Raman analyses

Nanocomposite materials containing graphene oxide have attracted tremendous interest as catalysts and adsorbents for water purification. In this study, mesoporous titanosilicate/reduced graphene oxide composite materials with different Ti contents were employed as adsorbents for removing bisphenol A (BPA) from water systems. The adsorptive interaction between BPA and adsorption sites on the composite materials was investigated by Fourier transform infrared (FT-IR) and Raman spectroscopy. Adsorption capacities of BPA at equilibrium, q _e (mg/g), decreased with increasing Ti contents, proportional to the surface area of the composite materials. FT-IR observations for fresh and spent adsorbents indicated that BPA adsorbed onto the composite materials by the electrostatic interaction between OH functional groups contained in BPA and on the adsorbents. The electrostatic adsorption sites on the adsorbents were categorized into three hydroxyl groups: Si-OH, Ti-OH, and graphene-OH. In Raman spectra, the intensity ratios of D to G band were decreased after the adsorption of BPA, implying adsorptive interaction of benzene rings of BPA with the sp² hybrid structure of the reduced graphene oxide.     

Beta-cyclodextrin adsorbents to remove water pollutants—a commentary

Beta-cyclodextrin-based adsorbent is a promising adsorbent because it has unique characteristics and able to form host-guest complexes with various organic compounds. Adsorption using beta-cyclodextrin-based adsorbent has continuously improved by various preparation strategies and crosslinking agents. This commentary aims to highlight the preparation strategies, properties, and adsorption mechanisms of beta-cyclodextrin-based adsorbents. The adsorbents can be generally classified according to the preparation methods and display high adsorption capacity especially for dyes. Particularly, composite/nanocomposite beta-cyclodextrin-based adsorbents exhibit outstanding adsorption capacity even though the surface area is lower than that of porous and magnetic beta-cyclodextrin-based adsorbents. The beta-cyclodextrin/chitosan functionalized graphene oxide hydrogel with specific surface of 17.6 m²·g^–1 yields an extraordinarily maximum adsorption capacity of 1499 mg·g^–1 methylene blue, while beta-cyclodextrin/chitosan modified with iron(II, III) oxide nanoparticles displays a much greater maximum adsorption capacity at 2780 mg·g^–1. The hydrophobic interaction, functional groups, hydrogen bonding, and electrostatic interaction govern the adsorption to a greater capacity. Although this commentary is not exhaustive, the preparation strategies and illustrated mechanisms provide useful insights into the adsorbent–adsorbate interactions, cost-effective analysis, challenges, and future directions of beta-cyclodextrin-based adsorbents in wastewater treatment.     

Water vapor adsorption and the microporous structures of carbonaceous adsorbents

The principal role in adsorption of almost all vapors organic and inorganic substances on nonporous and microporous carbonaceous adsorbents is played by dispersion interactions. They are characterized by a considerable increase in adsorption potentials as a result of superposition of the fields of the opposite pore walls. This effect determines the entire specifics of adsorption in micropores and, in particular, the substantial increase in adsorbability. A theoretical estimate of the adsorption potentials of benzene and water in adsorption on graphite, and a comparison of the differential heats of adsorption of water vapors on a non-porous carbon black previously heated in a vacuum at 950°C and on an active carbon show that water adsorption is due to the formation of hydrogen bonds both between the oxygen complexes on the surface of carbonaceous adsorbents and between the adsorbed molecules themselves. Dispersion interactions are weak and can be neglected to a first approximation. It has been shown for microporous structures and the slitlike model that one can calculate, from the parameters W₀ and E₀ of the adsorption equation of the theory of volume filling of micropores (determined from the adsorption isotherm of a standard vapor, benzene) the volume of the micropores, their halfwidth, and the specific surface area of the micropore walls. The latter are in good agreement with the specific surface areas of the micropores, as estimated by the independent method of similarity of the adsorption isotherms of water in micropores and on the surface of a nonporous carbonaceous adsorbent. The application of the BET and t-methods to microporous carbonaceous adsorbents is physically unsubstantiated.     

Removal of Lead Ions from Aqueous Solutions by Different Types of Industrial Waste Materials: Equilibrium and Kinetic Studies

Abstract

A comparative study of the adsorbents prepared from several industrial wastes for the removal of Pb²⁺ has been carried out. Fertilizer industry waste viz. carbon slurry and steel plant wastes viz. blast furnace (B.F.) slag, dust, and sludge were investigated as low‐cost adsorbents after proper treatment in the present study. The adsorption of Pb²⁺ on different adsorbents has been found in the order: B.F. sludge>B.F. dust>B.F. slag>carbonaceous adsorbent. The least adsorption of Pb²⁺ on carbonaceous adsorbent even having high porosity and consequently greater surface area as compared to other three adsorbents, indicates that surface area and porosity are not important factors for Pb²⁺ removal from aqueous solutions. The adsorption of Pb²⁺ has been studied as a function of contact time, concentration, and temperature. The adsorption has been found to be exothermic, and the data conform to the Langmuir equation. The kinetic results reveal that the present adsorption system follows Lagergren's first order rate equation. Since all three waste products from the steel industry show higher potential to remove lead from water, therefore, it is suggested that these metallurgical wastes can be fruitfully employed as low‐cost adsorbents for effluent treatment containing toxic metal ions.     

Optimized and functionalized paper sludge activated with potassium fluoride for single and binary adsorption of reactive dyes

The yield and adsorption uptake of optimized paper sludge activated carbon (PSAC) prepared using potassium fluoride as alternative chemical activation agent was investigated. The PSAC was functionalized with ethylenediamine (FPSAC) and both adsorbents were used for single and binary adsorption of Reactive orange 16 (RO16) and Reactive blue 19 (RB19). Effect of pH on the adsorption process, equilibrium, kinetics, isotherm and thermodynamic studies were carried out. Optimum PSAC preparation parameters were: activation temperature, X₁ = 810 °C; activation time, X₂ = 105 min; and impregnation ratio, X₃ = 0.95 which gave adsorption uptake of 178 and 158 mg/g for RO16 and RB19, respectively.     

Larger pore volume tetraphenyladamantane-based hybrid porous polymers: Facile Friedel–Crafts preparation,CO2 capture,and Rhodamine B removal properties

Synthesis of covalently linked porous polymers with high surface area and larger pore volume for two or more task-specific functionalities is always a big challenge. In this article, the facile Friedel–Crafts reaction is employed to construct the hierarchical hybrid porous polymers (HPPs) from tetraphenyladamantane and octavinylsilsesquioxane. The resulting polymers, HPP-1 to HPP-3, possessed the surface areas from 1356 to 1511 m² g⁻¹, and the pore volumes from 2.05 to 2.67 cm³ g⁻¹. All these polymers feature micropores, mesopores, and macropores in nature. The resultant polymers exhibit high CO₂ adsorption capacity up to 2.0 mmol g⁻¹ (8.82 wt %), at 273 K, 1.0 bar, and the maximum Rhodamine B (RB) sorption capacity of 653.6 mg g⁻¹. To illustrate the adsorption process, the effects of factors, contact time, initial concentration, temperature, and pH value on the adsorption capacity of RB were studied. The adsorption equilibrium data displayed a better fitting to the Langmuir isotherm model than the Freundlich model and the adsorption kinetics fitted well with the pseudo-second-order kinetic model. The recycle experiments displayed that the capacity recovery was still higher than 95% after four cycles. Theses polymers are promising to be the adsorbents for capturing CO₂ and removing RB. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 136, 48572.     

Removal of acid blue 113 and reactive black 5 dye from aqueous solutions by activated red mud

Removal of acid blue 113 (AB113) and reactive black 5 (RB5) dyes from aqueous solutions by activated red mud was investigated at different reaction parameters. Activated red mud has higher removal efficiency for AB113 than that for RB5. This can be explained by a greater molecular size of RB5 than that of AB113 and by different binding affinity with the surface of the activated red mud. Equilibrium data was fitted well with Freundlich isotherm and the kinetic data followed a pseudo second-order model. Maximum adsorption capacity was 83.33 mg/g and 35.58 mg/g at pH 3 for AB113 and RB5, respectively.     

吸附法净化室内甲醛研究进展

吸附法技术成熟、操作简单、现有系统完善,且一次性固定投资小,被广泛应用于室内气相污染物的净化处理。本文简单综述了吸附法在净化室内甲醛方面的研究,从原生碳吸附剂、改性碳吸附剂、无机非碳基吸附剂和有机非碳基吸附剂几个方面介绍了不同类型吸附剂的研究现状,对比了吸附性能,简要介绍了甲醛与吸附剂表面的作用机理,并详细总结了影响吸附效果的主要因素。指出整体上改性碳吸附剂性能最优,其他类型吸附剂之间差异不大,并与商品吸附剂没有明显差别;吸附剂结构和表面物化性质是影响吸附效果的首要因素,其织构特征、表面酸碱性、表面含氧/含杂原子官能团以及表面第二相等均对吸附效果产生重要影响。评述了吸附条件如甲醛浓度、吸附温度和湿度、吸附剂粒径等同样影响最终吸附效果。     

Multilayer single-solute adsorption from dilute solutions on energetically heterogeneous solids

The isotherm equations for multilayer single-solute adsorption from dilute solutions on energetically heterogeneous solids are derived by solving the integral equation for different energy distributions and local adsorption isotherm of BET-type. This procedure is analogous to that used in multilayer gas adsorption on heterogeneous solid surfaces. The equations, obtained for quasi-gaussian energy distribution, are examined using the adsorption data of n-valeric acid, n-amyl alcohol, aniline and cyclohexanol from dilute aqueous solutions on different types of carbon adsorbents of specific surface areas from 18.4m₂/g to 124m₂/g. The best equation for describing the above data is the modified Langmuir-Freundlich one, denoted in the paper by k-LF equation.     

Role of microporosity and surface chemistry in adsorption of 4,6-dimethyldibenzothiophene on polymer-derived activated carbons

Two carbon samples derived from poly(4-styrenesulfonic acid-co-maleic acid) based polymer by carbonization between 700 and 800 °C were oxidized to two different levels of surface acidity. The surfaces of resulting adsorbents were characterized by potentiometric titration, adsorption of nitrogen, FTIR, SEM/EDAX and thermal analysis. The materials were used as adsorbents of 4,6-dimethyldibenzothiophene (4,6-DMDBT) from hexadecane with initial concentration of sulfur between 10-150 ppmw. Although it was found that pores with diameter less than 10 Å govern the amount of 4,6-DMDBT adsorbed, that amount is enhanced when acidic groups are present in the larger pores owing to the contributions of specific interactions. Surface chemistry plays an important role in reactive adsorption and deposition of the products of surface reactions in the pore system.     

Removal of phosphorus by poorly ordered clays as influenced by heating and grinding

Phosphorus adsorption isotherms show that, among volcanic ash and pumice clay materials, proto-imogolite allophane has the highest ability for P adsorption, followed by allophane with two-dimensionally polymerized SiO₄ tetrahedra, and lastly, imogolite. The difference was considered to be owing to differences in the SiO₂/Al₂O₃ ratio (amount of Al atoms), and in chemical structure (bonding status of Al atoms) among the components. An increase in P adsorption by proto-imogolite allophane was observed after heating at 200°–400°C or grinding for 2–5 min, and it was attributed to the formation of the new P adsorption sites as a result of the breakdown of the Si---O---Al linkages in the structure of proto-imogolite allophane.The experimental results suggest that amorphous or poorly ordered clay materials of weathered volcanic ash and pumice which are mainly composed of proto-imogolite allophane are most effective in the removal of P. These clay materials may be used to cover bottom sediments to hinder the release of P from the sea- and fresh-water sediments. The effectiveness of these clays as scavengers for P can be improved by heating or grinding.     

The adsorption of sulphate, hydrogenchromate and dihydrogenphosphate anions on surfactant-modified clinoptilolite

The adsorption of sulphate, hydrogenchromate and dihydrogenphosphate anions on surfactant-modified clinoptilolite (SMC) was investigated. The SMCs were prepared by the adsorption of cis-1-aminoctadecen-9 (oleylamine) on both modified and unmodified natural clinoptilolite tuff. The properties of the modified clinoptilolite samples, such as cation type, structure of the zeolite framework and ECEC value, determined the mechanism of oleylamine adsorption, and consequently anion adsorption on the external clinoptilolite surface. According to the strength of the anion adsorption, two groups of SMCs could be distinguished: strong and weak anion adsorbents. Strong anion adsorbents were obtained by oleylamine adsorption on H⁺-clinoptilolites by protonation of the –NH₂ groups. This mechanism of oleylamine adsorption resulted in the surface precipitation mechanism of anion adsorption being the dominant mechanism. The oleylamine derivatives of Ca- and Na-clinoptilolite were weak anion adsorbents. Oleylamine is adsorbed on Ca- and Na-clinoptilolite by hydrogen bonding, thus yielding insufficient adsorption sites for anions. Hydrogenchromate and dihydrogenphosphate anions were nevertheless adsorbed on these SMCs by interaction with oleylamine. The experiments of anion adsorption on various oleylamine loaded SMCs confirmed the existence of two types of anion adsorption sites and showed that excess oleylamine did not significantly influence the anion adsorption in the investigated concentration range. The kinetic results showed that SO₄²⁻ and H₂PO₄⁻ adsorptions were slow processes while HCrO₄⁻ adsorption was completed in a few minutes.     

Application of heterogeneous adsorbents in removal of dimethyl phthalate: Equilibrium and heat

Aminated resin (NDA‐101) and oxidized resin (NDA‐702) were synthesized to remove Dimethyl phthalate (DMP) from the contaminated water. The equilibrium and heat properties in the course of adsorption process were examined and compared with two commercial heterogeneous adsorbents, namely an acrylic ester resin (Amberlite XAD‐7) and a coal‐based granular activated carbon (AC‐750). The associated equilibrium isotherms can be well fitted by Freundlich equation and the adsorption capacities for DMP followed the order: NDA‐702 > NDA‐101 > AC‐750 > XAD‐7. The surface of XAD‐7 was demonstrated to be relatively homogeneous through surface energy heterogeneity analysis, offering the sole hydrogen bonding interaction. Contrarily, heterogeneous surface of oxidized resins NDA‐702 and the aminated resins NDA‐101 exhibited a promising adsorption capacity and affinity toward DMP probably derived by multiple hydrogen bonding, π–π stacking, and micropore filling interactions. © 2010 American Institute of Chemical Engineers AIChE J, 2010