Equilibrium Adsorption Amount Research Articles

Adsorption characteristics of Bisphenol-A on tailored activated carbon in aqueous solutions.

The adsorption behavior of pharmaceuticals and personal care product, Bisphenol-A (BPA), according to four coal-based and four wood-based granular activated carbons modified using outgassing treatment, acidic treatment or alkaline treatment was studied. The adsorption isotherm results indicated that carbon surface acidity played a very important role in the adsorption of BPA. It was found that increasing surface acidity would increase the hydrogen bonding effects and increase adsorption of BPA on activated carbon. The acidic modified sample (F600-A and OLC-A) represented the best adsorption capacity, and the equilibrium adsorption amounts reached 346.42 and 338.55 mg/g, respectively. Further, effects of surface charge and surface basicity were examined. It was found that the adsorbed amount of BPA decreased with the increase of surface charge. Finally, there appeared to be a significant oligomerization phenomenon with BPA molecules onto the surface of activated carbon. OLC and OLC-OG, which have higher micropore percentages, are very effective in hampering the oligomerization of BPA under oxic conditions.

Adsorption of Hg(II) from aqueous solution using thiourea functionalized chelating fiber

A fast and selective adsorbent for Hg(II) from aqueous solutions using thiourea (TU) functionalized polypropylene fiber grafted acrylic acid (PP-g-AA), PP-g-AA-TU fibers, was characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The adsorption behavior of the functionalized chelating fibers for Hg(II) was investigated by static adsorption experiments, and the effects of some essential factors on adsorption of Hg(II) were examined, such as pH, initial concentration, adsorption time, coexisting cations, and temperature. The results showed that the adsorptive equilibrium could be achieved in 10min, and the equilibrium adsorption quantity of PP-g-AA-TU fibers was 20 times that of PP-g-AA fibers. The PP-g-AA-TU fibers showed a very high adsorption rate and a good selectivity for Hg(II) over a wide range of pH. The adsorption isotherm can be well described with Langmuir model, with the maximum adsorption capacity for Hg(II) up to 52.04mg·g−1 and the removal of Hg(II) more than 97%. The kinetic data indicate that the adsorption process is best-fitted into the pseudo-second-order model.

Electrospinning synthesis of porous Al2O3 nanofibers by pluronic P123 triblock copolymer surfactant and properties of uranium (VI)-sorption

Porous Alumina (Al2O3) nanofibers were prepared by electrospinning process using pluronic P123 triblock copolymer surfactant as template. The characterizations of the adsorbent were investigated by X-ray diffraction (XRD) fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption–desorption. The obtained nanofibers were used as adsorbents for the removal of Uranium (VI). The maximum adsorption occurred at pH 5, the equilibrium adsorption amount was about 87 mg/g, and the equilibrium time was 6.0 h. A pseudo-second order model could best describe adsorption kinetics. The adsorption equilibrium data fit Freundlich adsorption isotherm equation well. Thermodynamic parameters such as standard enthalpy (ΔH0), standard entropy (ΔS0), standard free energy (ΔG0) and activation energy (Ea) were calculated. The results predict an endothermic nature of adsorption and a spontaneous process.

Adsorption recovery of Pd(II) from aqueous solutions by persimmon residual based bio-sorbent

A low cost bio-sorbent, named “PPF resin”, was prepared by immobilizing persimmon residual with formaldehyde and it was characterized before and after adsorption of Pd(II). The adsorption behavior of PPF resin towards Pd(II) from aqueous solutions was studied by batch and column adsorption methods. The adsorption equilibrium of Pd(II) on PPF resin was achieved within 840min, and the experimental data were well fitted with the pseudo-second-order rate model. Higher initial concentration and adsorption temperature led to higher equilibrium adsorption amount, and the adsorption isotherms could be well described by Langmuir model. The column studies suggested that the resin was effective for the adsorption of Pd(II) from aqueous solutions, and the loaded Pd(II) could be easily desorbed by acidic thiourea solution. The adsorption process of Pd(II) on PPF resin might be the multiple reactions of electrostatic interaction and reductive adsorption, in which Pd(II) was reduced to Pd(0) as confirmed by the XRD pattern of PPF resin after adsorption of Pd(II). The resin exhibited outstanding selective adsorption towards Pd(II) from actual leach liquor of waste PCBs at a high concentration of HNO3. The results suggested that the PPF resin can be used as an active bio-sorbent for the recovery of Pd(II) from aqueous environment.

Facile preparation of highly hydrophilic, recyclable high-performance polyimide adsorbents for the removal of heavy metal ions

To obtain high-performance adsorbents that combine excellent adsorption ability, thermal stability, service life and recycling ability, polyimide (PI)/silica powders were prepared via a facile one-pot coprecipitation process. A benzimidazole unit was introduced into the PI backbone as the adsorption site. The benzimidazole unit induced more hydroxyls onto the silica, which provided hydrophilic sites for access by heavy metal ions. By comprehensively analyzing the effect of hydrophilcity, agglomeration, silica polycondensation, specific surface area and PI crystallinity, 10% was demonstrated to be the most proper feed silica content. The equilibrium adsorption amount (Qe) for Cu2+ of PI/silica adsorbents was 77 times higher than that of pure PI. Hydrogen chloride (HCl) was used as a desorbent for heavy metal ions and could be decomplexed with benzimidazole unit at around 300°C, which was lower than the glass transition temperature of PI. The complexation and decomplexation process of HCl made PI/silica adsorbents recyclable, and the adsorption ability remained steady for more than 50 recycling processes. As PI/silica adsorbents possess excellent thermal stability, chemical resistance and radiation resistance and hydrophilicity, they have potential as superior recyclable adsorbents for collecting heavy metal ions from waste water in extreme environments.

芦丁-槲皮素双模板印迹聚合物的制备、表征及识别

以芦丁（RT）-槲皮素（QT）为混合模板分子制备了芦丁-槲皮素复合模板分子印迹聚合物。优化了制备条件,研究了模板用量比、功能单体及交联剂用量对印迹聚合物吸附性能的影响。用傅里叶红外光谱和扫描电镜对分子印迹聚合物进行结构表征。探讨了分子印迹聚合物的吸附动力学、等温吸附及键合位点特征,考察了其选择识别性能,并以分子印迹聚合物为吸附介质,萃取分离芦丁粗提液中的目标化合物。结果表明,当槲皮素与芦丁的摩尔比为3∶2,且模板总量与功能单体及交联剂用量摩尔比为1∶8∶10时,所得分子印迹聚合物的吸附性能最好,对槲皮素和芦丁的吸附量分别达47.86和60.97 mg/g。吸附可在3.5 h内达到平衡,显示了较快的吸附动力学。Scatchard分析表明,分子印迹聚合物基体中存在四类不同性能的键合位点,分别为芦丁和槲皮素的高亲和键合位点及非选择键合位点。相对分布系数（k=Kd（RT）/Kd（QT）,Kd=qe/ρe,Kd为分布系数,qe为平衡吸附量,ρe为平衡质量浓度）大于1,表明了分子印迹聚合物对芦丁具有更高的选择键合作用,当模拟混合物中芦丁和槲皮素浓度分别为0.07和0.03 mmol/L时,相对分布系数和分离因子（α=qe（RT）/qe（QT））分别达6.669和25.02。另外,以乙腈、甲醇及甲醇-醋酸混合物依次为洗脱剂,通过分子印迹固相萃取可从槐米提取物中分离芦丁和槲皮素两种黄酮类化合物,总回收率分别为96.70%和94.67%。

Surface hydrophilic imprinted particles via a green precipitation polymerization for selective removal of tetracycline from aqueous solution

In this research, hydrophilic molecularly imprinted polymers (HMIPs) were synthesized through a facile one-step green precipitation polymerization in ethanol, which was non-toxic, green and environmentally friendly. HMIPs were tested by FT-IR, SEM, water contact angle studies and water dispersion stability test. HMIPs exhibited a good water-compatibility property. Compared with non-imprinted process, template molecule tetracycline (TC) had a significant influence on morphology of polymer particles. Batch binding experiments were carried out in water to evaluate adsorption equilibrium, kinetics and selectivity. Equilibrium adsorption amount increased with the increase of the temperature, and the data were well described by Freundlich model. Kinetics properties of HMIPs were better fitted to pseudo-second-order rate equations. The thermodynamic analysis indicated that the adsorption process of TC was spontaneous and endothermic. HMIPs exhibited the high affinity and selectivity toward TC over structurally analogous antibiotics than that of non-imprinted polymers. Also, the HMIPs had good reuse ability.

Enhancement of photocatalytic performance of plasmon-assisted metallic ion doped titania

Plasmonic assisted metallic ion doped titania was synthesized successfully by combining the hydrothermal and photoreduction methods. The chromium ion doping resulted to smaller particle size and preferable crystallinity than pure TiO2. Ag@AgI–TiO2–Cr showed the smallest band gap of 1.9 eV, corresponding to the wavelength range until 652 nm. The Ag–AgI plasmonic effect promoted electron transfer and accelerated photocatalytic reaction. Excellent visible light induced MO degradation was effectively realized. The sample Ag@AgI–TiO2–Cr exhibited the best photodegradation activity, which might be related to its smallest band gap, larger specific surface area of 178.3 m2 g−1 and the maximum equilibrium adsorption quantity of 18.0 mg/g.

Kinetics and Thermodynamics of Adsorption of Cr(VI) on Nano Magnetic NiFe Particles in an Aqueous Solution

Magnetic nano materials were known as high adsorption properties Nano-structural Ni2.33Fe alloy was successfully prepared by hydrothermal method and was used to remove CrO42- ions from aqueous solution. The results show that the equilibrium adsorption quantity increased with the increase of initial CrO42- concentration and pseudo-second-order kinetic models were successfully used for fitting the kinetic data. Webb Maurice diffusion model shows adsorption was controlled by external mass transfer followed by internal particle diffusion mass transfer. And the fitting degree of the Langmuir isotherm and the experimental data was quite high. And the Freundlich isotherm also fitted well.

Effect of polycarboxylate superplasticiser adsorption on fluidity of cement–clay system

Clay reduces fluidity and increases fluidity loss of concrete added with polycarboxylate superplasticiser. Sometimes it cuts down concrete durability. Fluidity of clay–cement paste with the addition of polycarboxylate superplasticiser, adsorption amount of polycarboxylate superplasticiser and ζ-potential has been tested to understand the effect of polycarboxylate superplasticiser on cement–clay systems. The results show that cement particles have a smooth surface; there are lots of layered or sheet structure existing on the surface of clay; when the particle size distribution is little different, the specific surface area of clay is 17 times that of cement; it is the reason why polycarboxylate superplasticiser adsorption on clay is much greater than that of cement. Initial adsorption amount and equilibrium adsorption amount of polycarboxylate superplasticiser on clay are 3–4 times that of cement; strong PC adsorption of clay is the main reason why the presence of clay reduces fluidity and increases fluidity loss of cement paste.

Preparation of activated carbon from Xinjiang region coal by microwave activation and its application in naphthalene, phenanthrene, and pyrene adsorption

Coal-based activated carbons (CAC) were prepared from coal in Xinjiang China by microwave-assisted activation. The effects of preparation conditions on adsorption capabilities of CAC for methylene blue (MB) and iodine were investigated. The microwave activation was carried out with coal activator ratio of 1:3 for 12 min at 700 W of power, the adsorption capacities of the prepared CAC achieved the maximal values of 312 and 1048.19 mg/g for MB and iodine. The increasing of CAR, activation time, and microwave power reduced the surface functional groups and improved the pHPZC of CAC. The BET surface area and total pore volume of CAC prepared were identified as 1770.49 m2/g and 0.99 cm3/g, respectively. Hence, the work demonstrates that the use of microwave heating for preparing CAC is more rapid, cheaper and efficient. The adsorption behaviors of typical polycyclic aromatic hydrocarbons (PAHs) in ethanol aqueous solution on CAC were also explored. Equilibrium data were favorably described by the Langmuir and Freundlich isotherms, and adsorption kinetics was fitted to the pseudo-second-order model well. The equilibrium adsorption amounts were 117.17 mg/g for pyrene, 111.39 mg/g for phenanthrene, and 78.18 mg/g for naphthalene. Thus, CAC prepared by microwave activation could have a very effective application in removal of these PAHs.

Hierarchical hybrid carbon nano-structures as robust and reusable adsorbents: Kinetic studies with model dye compound

This study demonstrates the potential of using multi-scale hierarchical carbon structures as robust, reusable solids suitable for removal of aqueous pollutants such as dye molecules from wastewater. Carpet-like vertical arrays of carbon nanotubes (CNT) were attached on surfaces of porous carbon foams by pre-coating with silica buffer layer followed by chemical vapor deposition (CVD). The surface morphology and specific surface areas were varied by controlling the buffer layer thickness and CVD deposition times. Surface characteristics have been correlated with adsorption thermodynamics and kinetics by investigating the removal rates of methylene blue (MB) dye in simulated water. The results show that MB adsorption capacity correlates well with total CNT surface area in the carpet, indicating full utilization of the nanotube surfaces. Adsorption rates fit well with pseudo second order kinetics model. Maximum MB adsorption capacity of the CNT surfaces in this structure was estimated by extrapolating equilibrium adsorption amounts at different dye concentrations using the Langmuir isotherm. This was found to be about 43.5mg/g, which compares favorably with adsorption capacity of isolated nanotubes. It must be noted that whereas isolated nanotubes can disperse in the liquid and pose environmental threats, the hierarchical solids as demonstrated in this study can be repeatedly agitated in water without the loss of CNT or performance deterioration. These results indicate promising application potential for these types of hybrid materials in environmental purification applications.

Fabrication and evaluation of molecularly imprinted multi-hollow microspheres adsorbents with tunable inner pore structures derived from templating Pickering double emulsions

In this work, lignin was simply tailored by chemical modification with oleic acid, and then surfactant-free water-in-oil-in-water (W1/O/W2) Pickering double emulsions were formed by stabilizing two types of lignins (original and modified) at both interfaces. Based on as-prepared W1/O/W2 emulsions, three kinds of molecularly imprinted multi-hollow microspheres (denoted as MIMMs1, MIMMs2 and MIMMs3) were fabricated and evaluated as adsorbents to selective removal of lambda-cyhalothrin (LC). MIMMs exhibited tunable pore structures (size and number of inner pores) by adjusting the volume ratio of internal water phase to the medium oil phase (W1O), and MIMMs2 showed the larger adsorption capacity than those of MIMMs2 and MIMMs3, resulting from the common action mechanism of more and larger inner pores. Static adsorption experiments showed that equilibrium time was about 3.0h, and the equilibrium adsorption amount was 24.79mgg−1 for MIMMs2. The selective recognition experiments exhibited the obviously selective adsorption effect of the MIMMs2 for target LC, and MIMMs2 could be effectively regenerated and recycled at less seven times without significant loss of adsorption capacity. Overall, batch mode data suggested that MIMMs2 may be useful for the selective removal of LC from aqueous media.

Molecular dynamics simulation of carbon molecular sieve preparation for air separation

Carbon deposition process on activated carbon (AC) in order to produce carbon molecular sieve (CMS) was simulated using molecular dynamics simulation. The proposed activated carbon for simulation includes micropores with different characteristic diameters and lengths. Three different temperatures of 773 K, 973 K, and 1,273 K were selected to investigate the optimum deposition temperature. Simulation results show that the carbon deposition process at 973 K creates the best adsorbent structure. While at lower temperature some micropore openings are blocked with carbon atoms, at higher temperature the number of deposited carbons on the micropores does not change significantly. Also, carbon deposition process confirms the pseudo-second-order kinetic model with an endothermic behavior. To evaluate the sieving property of adsorbent products, nitrogen and oxygen adsorption on the initial and final adsorbent products are examined. Results show that there is not any considerable difference between the equilibrium adsorption amounts of nitrogen and oxygen on the initial and final adsorbents especially at low pressure (P<10 atm). Although, adsorption kinetics curves of these gases change significantly after the carbon deposition process in comparison with the initial sample. These observations indicate that the final adsorbent has high selectivity towards oxygen compared with the nitrogen, so it can be called a carbon molecular sieve. All simulated results are in good agreement with experiments.

Experimental investigation on the ammonia adsorption and heat transfer characteristics of the packed multi-walled carbon nanotubes

Carbon nanotube (CNT) is considered as a kind of potential adsorbent because of its large surface area, uniform micropores and unique physicochemical properties. The adsorption performance of ammonia on the packed multi-walled carbon nanotubes (MWCNTs) were studied in this paper. Firstly, the packed MWCNTs were characterized by the scanning electron microscope (SEM) and transmission electron microscopy (TEM). Secondly, the effect of working pressure and adsorbent temperature on the adsorption capacity of ammonia by the packed MWCNTs was investigated. Thirdly, Langmuir and Freundlich models were used to analyze the equilibrium adsorption data and the adsorption kinetics was also discussed using a classical gas diffusion model. The Freundlich isotherm model could elucidate well the adsorption of ammonia on the MWCNTs when compared to the Langmuir equation. The research results showed that the equilibrium adsorption amount of ammonia by the MWCNTs varied between 22.69 and 90.05 mg/gCNT at the adsorbent temperature of 25–35 °C and working pressure of 0.368–0.744 MPa. It seems that the pure MWCNT is not appropriate to act as the adsorbent for the solid–gas adsorption refrigeration due to its low adsorption capacity. However, our research indicates that the MWCNTs can be used as additive to some other chemical adsorbents to improve their heat transfer characteristics.

Adsorption behavior of reactive orange 5 and reactive red 2 on ramie fabric and their quantum chemical calculations

The adsorption behavior of Reactive Orange 5 and Reactive Red 2 on ramie fabric is studied, and their structures are investigated by using density function theory (DFT) and time-dependent DFT (TD-DFT) calculations. The results indicate that Reactive Red 2 reaches a saturation adsorption state more quickly than Reactive Orange 5. With the increase of temperature from 30 to 50 °C, the equilibrium adsorption amount of Reactive Red 2 and Reactive Orange 5 increases correspondingly, and at the same temperature the former presents a larger adsorption amount than the latter. In addition, the chlorine atom and the conjoint carbon atom of Reactive Red 2 produces a weaker binding force than those of Reactive Orange 5, which implies the nucleophilic attack of hydroxyl groups of ramie fabric to the corresponding carbon atoms occurs more easily in Reactive Red 2 than in Reactive Orange 5. The energy band gap (translation from HOMO to LUMO) of Reactive Red 2 is lower than that of Reactive Orange 5, and this indicates Reactive Red 2 has a higher chemical activity. The LUMO of Reactive Red 2 (−3.05 eV) is lower than that of Reactive Orange 5 (−2.93 eV), which indicates that Reactive Red 2 presents a stronger ability to accept electrons than Reactive Orange 5. The conclusion that Reactive Red 2 has stronger adsorption activity than Reactive Orange 5 is supported and explained by the results of these quantum chemical calculations.

Adsorption equilibrium and kinetics of cesium onto insoluble Prussian blue synthesized by an immediate precipitation reaction between Fe3+ and [Fe(CN)6]4−

The adsorption equilibrium and kinetics of cesium ion (Cs+) onto insoluble Prussian blue (PB) prepared by an immediate precipitation reaction between Fe3+ and [Fe(CN)6]4− was investigated under initial Cs+ concentration of under 0.15 mmol/L. Synthesis conditions in this method were almost insensitive to the adsorption ability of insoluble PB, and this method provided one of the smallest PB crystallites among synthesis methods. Even when molar concentration of H3O+ was more than 200 times higher or molar concentration of K+ was more than 50,000 times higher than that of Cs+ in the aqueous solution, the equilibrium adsorption amount was reduced by only approximately one-half to two-third of that in the pure system; that is, the insoluble PB synthesized possessed a considerably high adsorption selectivity for Cs+. In contrast to the excellent adsorption ability under adsorption equilibrium, adsorption rate was quite slow. It took at least 2 weeks at 25 °C to completely attain the adsorption equilibrium, even though the primary particle size (crystallite size) and secondary particle size (aggregate size of the crystallites) were sufficiently small at approximately 14 nm and 53–106 μm, respectively. This slow adsorption is primarily due to the large resistance of intracrystalline diffusion; the intracrystalline diffusion coefficient was extremely small at less than 3.3 × 10−22 m2/s. We also found that increase in temperature could significantly decrease this diffusion resistance, resulting in much quicker elimination of Cs+ from the aqueous solution.

Molecularly imprinted polymers derived from lignin-based Pickering emulsions and their selectively adsorption of lambda-cyhalothrin

Lignin particles were used as stabilizers to establish a stable Pickering oil–water emulsion, and then the molecularly imprinted polymers (MIPs) were fabricated by radical polymerization in the presence of functional and cross-linked monomers in the oil phase. As-prepared MIPs were observed with a diameter from 10 μm to 65 μm when oil/water ratio increased from 0.11 to 0.68, and exhibited thermal stability and hydrophobic surface. A series of static adsorption experiments were conducted to analyze their adsorption performance for lambda-cyhalothrin (LC). The preliminary results showed that MIPs possessed good recognition toward LC, that is, the adsorption equilibrium time was about 3.0 h and the equilibrium adsorption amount was 72.25 μmol g−1 for MIPs and 43.10 μmol g−1 for nonimprinted Polymers (NIPs), respectively, indicating the enhanced selectively adsorption of LC. The adsorption process followed pseudo-second-order model by the kinetic analysis and Freundlich equation by the isothermal analysis, respectively. The selective recognition experiments displayed the outstanding selective adsorption effect of the MIPs for target LC. Moreover, the obtained MIPs could be effectively regenerated and recycled at less three times without significant loss of adsorption capacity.

Adsorption Research of Polymer on Oil Sands in Qidongyi Block of Xinjiang Conglomerate Reservoir

In the process of polymer flooding in porous media, polymer was detained due to interactions between surface adsorption and polymer molecules, and this could lead to negative effects on oil displacement. For polymer adsorption in Xinjiang conglomerate reservoir, HPLC analysis was adopted to study the static and dynamic laws. Results have showed that the adsorption process could be divided into 3 stages: rapid growth, slow growth and stable state. With the loss of polymer molecular weight, equilibrium adsorption quantity reduces gradually. The adsorption amount is different for the same polymer on four types of oil sands. For equilibrium adsorption, the maximum value is argillaceous sandstone, followed by conglomeratic sandstone.The third is argillaceous gravel, and the minimum is sand gravel. For polymer flooding in conglomerate cores, the dynamic retention amount of seriate conglomerate is much greater than that of fine particle conglomerate. These data have provided reference for project design of polymer flooding in conglomerate reservoir.

Adsorption thermodynamics and kinetics of N,N′-diisopropoxypropyl-N″,N‴-oxydiethylenedicarbonyl bis (thiourea) on chalcopyrite surfaces

In this paper, a novel surfactant, N,N′-diisopropoxypropyl-N″,N‴-oxydiethylenedicarbonyl bis (thiourea) (DiPOPECTU) was first introduced, and its adsorption thermodynamics and kinetics on chalcopyrite surfaces were investigated. DiPOPECTU exhibited superior hydrometallurgical performances for flotation recovery of chalcopyrite, and preferred attaching onto chalcopyrite surfaces at pH 5–10. The thermodynamic results demonstrated that the adsorption agreed well with Langmuir isotherm and its thermodynamic parameters were ΔG (298K)=−23.48kJmol−1, ΔS=−5.95Jmol−1K−1 and ΔH=−25.28kJmol−1, respectively. This inferred DiPOPECTU adsorption onto chalcopyrite was a spontaneously exothermic chemisorption process. The kinetic results showed that the adsorption process was well fitted by the pseudo-second-order equation. The adsorption rate constant was 0.14×105m2mol−1h−1 and the calculated equilibrium adsorption amount Qe (5.71×10−5molm−2) was close to the experimental value Qe (5.41×10−5molm−2). The results of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy further indicated that DiPOPECTU might chemisorbed on chalcopyrite surfaces by formation of DiPOPECTU-copper complexes. The uniquely double chelate ring structures and steric orientation of DiPOPECTU on chalcopyrite surfaces would improve the hydrophobicity of chalcopyrite particles along with superior flotation recovery.