High Equilibrium Adsorption Capacity Research Articles

Superhydrophobic metal organic framework doped polycarbonate porous monolith for efficient selective removal oil from water

A series of superhydrophobic polycarbonate porous monoliths modified with metal organic framework (Z8/PC) were firstly fabricated through a facile thermally impacted non-solvent induced phase separation method for efficient selective oil/water separation. The performance of the monoliths on oil/water separation was evaluated in terms of selectivity, equilibrium adsorption capacity, corrosion resistance, kinetics, and circulation. The results showed that the use of ZIF-8 significantly compensated for the shortage of pure monolith. Compared with pure PC monolith, the hydrophobic angle of the Z8/PC-2 monolith promoted from 136.18° to 154.25° due to the micro-nano flower surface. Meanwhile, the Z8/PC-2 monolith displayed a more intricate and continuous interconnected 3D hierarchical micro-nano structure, which possessed the monolith a higher specific surface area of 146.84 m2 g−1 and porosity of 89.5%. What’s more, more superior oil/water separation abilities of Z8/PC-2 monolith were manifested by the selective removal of oil or organic solvent from water within 30s, high equilibrium adsorption capacity, and excellent corrosion resistance. In addition, the ten-cycle regeneration of porous monoliths via centrifugation or evaporation displayed additional attractiveness. Therefore, porous Z8/PC monolith will be a promising candidate for the efficient selective oil/water separation of oil spills and organic solvents.

Effective elimination of endocrine disrupting bisphenol A and S from drinking water using phenolic resin-based activated carbon fiber: Adsorption, thermodynamic and kinetic studies

This study investigates the optimization of parametric conditions required for achieving high equilibrium adsorption capacity, and kinetic rate of separation, for the very well-known endocrine-disrupting compounds (EDCs) bisphenols (BPA) and (BPS). A high porous pretreated activated carbon fibers ((ACFs), phenolic resin-based weaved cloth) is used as an adsorbent in controlled aqueous conditions and as well as in real samples. Significant high values of Brunauer–Emmet–Teller surface area (SBET = (2342 m2/g)), total pore volume and pore size distribution (VT = 1.227 cc/g, 78 % microporosity, respectively, favor the separation process. Based on experimental findings, this study found the highest ∼98−99.9 % removal of BPA/BPS in the aqueous phase at optimized conditions (∼pH 7, 15 °C for 2 min). Based on nonlinear model fitting, BPA and BPS data follow pseudo-second-order kinetic and Langmuir adsorption isotherm models. Moreover, in competitiveness environments, like in the presence of ionic salts (NaCl, MgCl2 and CaCl2 ranged from 1−500 mg/L), ACFs is showing maximum adsorption for BPA at 100 mg/L for MgCl2 and 10 mg/L for both NaCl and CaCl2. For BPS, maximum adsorption was 100 mg/L for all the salts. Based on experimental results, ACF has also shown a competent behavior in real sample adsorption.

Fabrication of a porous chitosan/poly-(γ-glutamic acid) hydrogel with a high absorption capacity by electrostatic contacts

A porous chitosan (CS)/poly-(γ-glutamic acid) (γ-PGA) hydrogel was prepared by polymerization by electrostatic contacts of CS with γ-PGA without linker. The porosity of the hydrogel remarkably depends on γ-PGA content, pH regulator, and drying way. The optimization of them had given the hydrogel a high swelling capacity of 1398%, 11-fold higher than that of neat CS hydrogel. The hydrogel was applied to recover bovine serum albumin (BSA) from aqueous solution, and its adsorption capacity was influenced by the initial concentration and pH of BSA solution. Based on the studies of kinetics and isotherm, a high equilibrium adsorption capacity (qe = 948 mg/g) and a correlation coefficient of 0.996 were calculated from pseudo-second order kinetic equation, and a high affinitive constant (kF = 472 mL/mg) and a high saturated absorption capacity (qm = 1818.5 mg/g) were observed from Freundlich isotherm equation, indicating the porous hydrogel will be a good absorbent for protein recovery from sewage.

Structural and functional relationships of activated char briquettes from pyrolysis of sewage sludge for methylene blue removal

Activated char briquettes from pyrolysis residue of sewage sludge were prepared and characterized for methylene blue removal. The briquettes were prepared with different binder (phenolic resin) content (15–25 wt%), compression pressure (2.5–7.5 MPa) and thickness (3.5–14 mm), followed by CO2 or H2O activation under different temperatures. The effects of these parameters on the compositions, surface properties, apparent densities, mechanical properties, methylene blue adsorption kinetics and isotherms were systematically investigated. The results indicated that all of the prepared briquettes showed a characteristic of hierarchical porous structures, as well as high mechanical performance with impact resistant index much higher than 50. The increase of binder content from 15 to 25 wt% can result in marked increase of surface area (SBET), total pore volume (VT), apparent density and mechanical performance of the briquettes. According to the adsorption kinetics of methylene blue, the highest equilibrium adsorption capacity (qe,exp) for CO2-activated and H2O-activated briquettes were 194.6 and 203.6 mg/g. Both the increase of binder content and activation temperature markedly enhanced qe,exp, due to the increase of SBET and VT. qe,exp was much lowered by increasing the compression pressure or the thickness of briquettes, owing to the increased diffusion resistance and blockage of diffusion pathways inside briquettes. The adsorption kinetics data of the briquettes fit well into a pseudo-first order model system, suggesting physical adsorption of methylene blue onto briquettes surface. The adsorption isotherms of methylene blue indicated that both the CO2-activated and the H2O-activated briquettes followed a Langmuir isotherm model. The leaching tests of briquettes revealed that the leaching concentrations of Cd, Cr, Cu, Pb, Ni and Zn were much lower than the Chinese standard limits.

Microfluidic immobilized metal affinity chromatography based on Ti(IV)-decorated silica microspheres for purification of phosphoproteins

A silica-based immobilized metal affinity chromatography (IMAC) sorbent with the morphological properties suitable for purification of large phosphorylated biomolecules was synthesized. The sorbent was designed in the form of monodisperse-porous silica microspheres, 5.3 μm in size, having bimodal pore size distribution with a large median pore size (40 nm) and high surface area (163 m2/g) decorated with Ti(IV) cations (i.e. Ti(IV)@THSPMP@SiO2 microspheres). The decoration of silica microspheres with Ti(IV) cations was made by using 3-(trihydroxysilyl)propyl methylphosphonate (THSPMP) as a bifunctiontional linker, by preserving their bimodal pore size distribution. The mesopores provided a large surface area for parking of adsorbed phosphoproteins as large phosphorylated biomolecules while the intraparticular transport of phosphoproteins was facilitated by the macropores providing a large median pore size. High equilibrium adsorption capacity and high desorption yield in the purification of phosphoproteins were obtained using Ti(IV)@THSPMP@SiO2 microspheres as the sorbent in batch- and microfluidic-IMAC systems. The phosphoproteins, α-casein and β-casein were isolated from milk and human serum with almost quantitative yields and high purity in the batch IMAC system. The appropriate microcolumn permeability (3.66 × 10−14 m2) originating from its appropriate average diameter (5.3 μm), high porosity (0.948 cm3/g) and high surface area (163 m2/g) of Ti(IV)@THSPMP@SiO2 microspheres makes the synthesized sorbent a promising stationary phase for dynamic chromatography. Hence, a new phosphoprotein enrichment format, a microfluidic IMAC system was constructed and successfully operated for highly selective purification of phosphoproteins from non-fat milk as a complex sample. The microfluidic-IMAC system is a promising tool particularly for phosphoproteomic applications performed using samples in microliter or nanoliter scale, also involving an on-line connection of purification unit to LC-MS for the identification of large phosphorylated biomolecules enriched.

Monolithic Covalent Organic Framework Aerogels through Framework Crystallization Induced Self-assembly: Heading towards Framework Materials Synthesis over All Length Scales

Here, through the synergism between kinetic dynamic imine-exchange control and thermodynamic control, rarely observed compressible, porous, crystalline covalent organic framework (COF) aerogels were synthesized, the mechanism behind which is a framework crystallization induced self-assembly (FCISA) process. The prepared COF aerogel possessed extremely high BET surface over 2000 m2·g−1 and high maximum equilibrium adsorption capacity toward bisphenol-A of 699 mg·g−1 in aqueous solution.

Feasibility Assessment of Chromium Removal from Groundwater for Drinking Purposes by Sorption on Granular Activated Carbon and Strong Base Anion Exchange

The goal of this study was to compare the performances of strong base anion (SBA) exchange and activated carbon adsorption in the removal of hexavalent chromium, Cr(VI), from a real groundwater matrix exploited for drinking purposes. Two SBA resins and three granular activated carbons (GAC) were tested by batch experiments for kinetics and equilibrium isotherm determination. SBA resins showed higher affinity toward Cr(VI) (present in raw water at about 20 μg L−1) with respect to the GACs, with faster kinetics and higher equilibrium adsorption capacities. Among GACs, vegetal-based carbons showed higher Cr(VI) removal efficiencies than the mineral-based carbon, which can be related to the more developed textural properties. SBA resins also displayed relevant removal capacities towards nitrate and sulfate (present at mg L−1 concentration levels), while boron (present at about 60 μg L−1) was effectively removed by GACs. Batch experiment results were elaborated to estimate the chromium throughputs for the studied materials, to preliminary compare their performances in a real-scale application. The monitoring of a real-scale GAC adsorption stage permitted to validate throughputs estimation and confirmed that, despite being effective toward synthetic organics, GAC adsorption is a not feasible solution for Cr(VI) removal, with extremely early breakthrough. SBA exchange process resulted to be the most suitable solution, providing the best sorbent usage rates. However, SBA resin usage rates can strongly increase when considering the removal of nitrate and sulfate ions, requiring much shorter cycle times.

Yolk-shell structured composite for fast and selective lithium ion sieving

Yolk-shell structured C@Li4Ti5O12 microspheres composed of carbon core (ca. 500 nm) and sea urchin-like Li4Ti5O12 shell (ca. 400–500 nm) are formed by hydrothermally treating the core–shell structured C@TiO2 in the EtOH/H2O solution of LiOH and calcining it in N2 atmosphere. Yolk-shell structured TiO2-type lithium ion sieve is further transformed from C@Li4Ti5O12 through the acid treatment, which have a high specific surface area of 201.74 m2/g. The composite shows adsorption capacity towards Li+ proportional to the pH value in the range of 7–13. The adsorption reaches equilibrium within 2 h with a high equilibrium adsorption capacity of 28.46 mg/g under alkaline conditions, which is ca. 8 times the value of ordinary TiO2 lithium ion sieve with comparable size and surface area, demonstrating the enhanced adsorption is attributed to the generation of more accessible surficial voids by replacing internal part with light carbon core. The adsorption follows Freundlich and pseudo-second-order kinetic models with a high rate constant of 0.015 g/(mg·min). The selective adsorption to Li+ is verified in the presence of K+, Na+, Ca2+ and Mg2+.

Enhanced adsorption behavior of 17β‐estradiol by anaerobic granular sludge combined with zero‐valent iron

AbstractBACKGROUNDThe release of natural estrogen 17 β‐estradiol (E2) to the aquatic environment is a matter of concern. Batch experiments were conducted to study the adsorption of E2 by anaerobic granular sludge (AnGS) combined with zero‐valent iron (ZVI). The enhancement mechanism of ZVI for E2 adsorption by AnGS was also analyzed.RESULTSThe E2 adsorption efficiency of AnGs with ZVI was 48% higher than that without ZVI. The optimal conditions for high E2 adsorption efficiency (92.21%) and high equilibrium adsorption capacity (4.92 µg g‐1 VSS) were rZVI/AnGS 1.33, pH 6, and temperature 25°C. E2 adsorption by ZVI/AnGS was a spontaneous and exothermic process, well described by the Freundlich isotherm.CONCLUSIONThe addition of a suitable amount of ZVI enhanced E2 adsorption by AnGS. © 2017 Society of Chemical Industry

Photo-fenton refreshable Fe3O4@HCS adsorbent for the elimination of tetracycline hydrochloride

A yolk–shell-structured sphere composed of a superparamagnetic Fe3O4 core and a carbon shell (Fe3O4@HCS) was etched from Fe3O4@SiO2@carbon by NaOH, which was synthesized through the layer-by-layer coating of Fe3O4. This yolk–shell composite has a shell thickness of ca. 27 nm and a high specific surface area of 213.2 m2 g−1. Its performance for the magnetic removal of tetracycline hydrochloride from water was systematically examined. A high equilibrium adsorption capacity of ca. 49.0 mg g−1 was determined. Moreover, the adsorbent can be regenerated within 10 min through a photo-Fenton reaction. A stable adsorption capacity of 44.3 mg g−1 with a fluctuation <10% is preserved after 5 consecutive adsorption–degradation cycles, demonstrating its promising application potential in the decontamination of sewage water polluted by antibiotics.

Capturing of Nano-TiO2 from Complex Mixtures by Bisphosphonate-Functionalized Fe3O4 Nanoparticles

Selectively capturing nanosized titanium dioxide (nano-TiO2) from complex mixtures is a very significant but very formidable task both for enriching the analytical methodology and removing/recycling of nano-TiO2. We presented a novel sustainable strategy for such a task by using the bisphosphonate-functionalized Fe3O4 (BP-Fe3O4) nanoparticles as the highly selective adsorbents toward nano-TiO2. The BP-Fe3O4 exhibited high equilibrium adsorption capacity (Qe) toward nano-TiO2 (2.45 g g–1 for 60 nm anatase TiO2) but negligible Qe toward nano-SiO2 (0.01 g g–1 for 15 nm SiO2). The BP-Fe3O4 also had good adsorption capability toward nano-TiO2 in complex liquid media, or in the solid mixtures containing 10−500 times of coexisting nano-SiO2. This capturing strategy enables the green pretreatment for quantitative analysis of nano-TiO2 in complex real samples with the spike recoveries of 69.9–99.0% and low detection limit of 0.02 ppm. Furthermore, this strategy offers great convenience for identification of the crystal forms and even the morphology of nano-TiO2 existing in complex real samples. Besides, this capturing strategy holds great potential for separating or removing nano-TiO2 from the environment and the sustainable recycling of nano-TiO2.

Comparative study of adsorbents performance in ethylene/ethane separation

Some potential adsorbents for ethylene/ethane separation are ethylene selective while the others are ethane selective. Among different adsorbents, i.e., zeolites and metal organic frameworks (MOFs), a comparative study is critical to find the more suitable adsorbent for the separation. In this paper, binary ethylene/ethane adsorption performances of zeolites and MOFs, i.e., equilibrium selectivities and adsorption capacities are investigated utilizing ideal adsorbed solution theory (IAST). IAST model is applied at different gas compositions (0.1–0.9 ethylene mole fractions) and pressures up to 100 kPa. The results revealed that the most selective adsorbent toward ethylene is 5A zeolite while MOFs have higher equilibrium adsorption capacities. Among zeolites and MOFs, 5A and Fe2(dobdc) have the highest selectivity (27.4 and 13.6) and capacity (≈2.8 and 5.8 mmol ethylene/g) at 100 kPa and 298 K for a 50/50 mixture. Among ethane selective adsorbents, Silicalite-1 zeolite and UTSA-33a (MOF) have the highest selectivity and capacity (≈2.9 and ≈1.5 mmol ethane/g) at 100 kPa and 298 K for a 50/50 mixture, respectively. Investigation showed that adsorption capacity of ethylene selective adsorbents is higher than that of ethane selective ones.

Novel bile acid sequestrant: A biodegradable hydrogel based on amphiphilic allylamine copolymer

Amphiphilic copolymer P(AH-co-AHH) was synthesized by aqueous solution copolymerization of allylamine hydrochloride (AH) with allylhexylamine hydrochloride (AHH). The double Schiff-base cross-linked hydrogel, which could be used as a biodegradable bile acid sequestrant was prepared using P(AH-co-AHH) and the double aldehyde cross-linker (OG) obtained by the oxidation of methyl α-d-glucopyranoside by sodium periodate. The properties of the P(AH-co-AHH)/OG hydrogel material including the gelation mechanism, rheological research, SEM observations, swelling characteristics, and the in vitro biodegradability were systematically studied. The binding mechanism between sodium glycocholate (NaGC) and the P(AH-co-AHH) precursor was confirmed as an synergetic effect of electrostatic interactions and hydrophobic associations, which were investigated by isothermal titration calorimetry (ITC). Moreover, the hydrogel showed high equilibrium adsorption capacity towards NaGC within only 2h and the adsorption kinetics and isotherms fit the pseudo-second-order model and Langmuir model, respectively. According to our experimental results, the hydrogel materials showed great potential to break the enterohepatic circulation of bile acid salts and could be further used for treating hypercholesterolemia.

Adsorption and regeneration study of polyethylenimine-impregnated millimeter-sized mesoporous carbon spheres for post-combustion CO2 capture

The feasibility of polyethylenimine (PEI)-impregnated millimeter-sized mesoporous carbon spheres (MCSs) for post-combustion CO2 capture is systematically studied over a wide range of adsorption and regeneration conditions. MCSs with developed mesoporous structure and good electrical conductivity are used as supports, while high-molecular-weight PEI (Mn∼10,000) is screened to be the optimal amine due to its thermal stability. At the optimal polyethylene glycol (PEG) loading of 20wt.%, the mass/volume-based adsorption capacity is efficiently improved by 25.7% and 109.5%, respectively. The optimized adsorbent exhibits high equilibrium adsorption capacity of 163.4mg/g for 15% CO2 at 75°C under dry condition, and it could be further enhanced to 187.5mg/g at the relative humidity of 60%. The presence of O2, SO2, NO and NO2 would lead to the decreased adsorption capacity after consecutive adsorption–desorption cycles, due to the irreversible chemical reaction. Moisture could inhibit the negative effect of O2 but deteriorate the detrimental effects of SO2, NO and NO2. Depending on the good sphericity, uniform particle size, excellent thermal/electrical conductivity and good mechanical properties of MCS, PEI-impregnated MCS adsorbents could be directly used in fixed bed system and be applicable for thermal swing adsorption (TSA), vacuum swing adsorption (VSA) and novel electric swing adsorption (ESA) processes. The adsorbents could maintain fairly stable cyclic performance during the rapid VSA process, making rapid VSA of great potential for technical–economical post-combustion CO2 capture.

Effect of pore structure on adsorption behavior of ibuprofen by magnetic anion exchange resins

A series of magnetic anion exchange resins (ND-1, ND-2 and ND-3) with different pore structure were prepared for ibuprofen (IBU) adsorption by using different amount of cyclohexanol as porogen in this work. For adsorption kinetics, resins with larger pore structure showed faster adsorption rates and higher equilibrium adsorption capacities because the internal diffusion process was facilitated by the increase of pore diameter and pore volume. As for adsorption isotherms, the experimental data was better fitted by Freundlich model especially for the resins with broader pores, suggesting that heterogeneous interactions took place in pores. The counter ion released by resin was measured, and ratios of equilibrium adsorption capacity to the counter ion were between 1.22 and 1.56, which confirmed that adsorption process was predominantly attributed to ion exchange while other interactions also existed. Hence, the co-existent anion reduced the adsorption amount of IBU onto resin by competing adsorption in ion exchange process, and the optimal pH ranged from 6 to 8. Resins with more open structure showed better regeneration abilities, of which the adsorption amounts witnessed no significant decrease during 7 circles of use, indicating the advantages of larger pore canal in the adsorption and regeneration behavior.

Preparation of novel chelating sponge as an adsorbent for the removal of Cu2+ from water

Abstract The novel chelating sponge modified with hydroxamic acid groups was prepared by a grafting polymerization followed by a nucleophilic substitution reaction. Elementary analysis, SEM, FT-IR spectroscopy and XPS were used to characterize the spongy adsorbent (PVA-MA-HH). Adsorption isotherm study indicated that PVA-MA-HH had high equilibrium adsorption capacity for Cu 2+ .

Preparation of new spongy adsorbent for removal of EDTA–Cu(II) and EDTA–Ni(II) from water

Abstract A new spongy adsorbent (PU-DTC) was prepared with a polyurethane (PU) adsorbent for removal of EDTA–Cu(II) and EDTA-Ni(II) from water. This new spongy adsorbent was characterized by using SEM and 13 C NMR and FT-IR spectroscopy. Adsorption kinetic curve indicated that this new spongy adsorbent could quickly remove EDTA–Cu(II) and EDTA–Ni(II) from water, and adsorption isotherm also indicated that PU-DTC had high equilibrium adsorption capacity for EDTA–Cu(II) and EDTA–Ni(II).

Adsorption Kinetics Studies of Polymeric Nanocomposite Coagulants

The aim of this study is to investigate the adsorption characteristics of dicyandiamide-formaldehyde resin (DCD-F) nanocomposites. For this purpose, 2%, 4%, and 8% unmodified layered silicate clay (Na-Montmorillonite) containing DCD-F nanocomposites (DCD-F- MMT) were prepared. The synthesized samples were structurally defined by XRD, SEM-EDX, and TGA characterizations. The adsorption performance of nanocomposites was tested by using two anionic dyes. Adsorption capacities of pure resin and three nanocomposites were followed against time and the nanocomposite containing 8% Na-MMT (DCD-F-MMT8%) was found to have the highest equilibrium adsorption capacity (qe). Therefore, the effects of dye concentration, pH, and temperature on qe were investigated using DCD-F-MMT8%. The kinetic and thermodynamic parameters of adsorption were obtained based on the experimental data.

Preparation of new base-aluminum-chloride-loaded fiber as adsorbent for fast removal of arsenic(V) from water

Abstract A new base-aluminum-chloride-loaded fiber [PET-AA-NN-Al2(OH)nCl6−n] was prepared with polyethylene glycol terephthalate (PET) as adsorbent for fast removal of arsenic (V) from water. This new fibrous adsorbent was characterized by using SEM and C NMR spectroscopy. Adsorption kinetic curve indicated that this new fibrous adsorbent could fast remove arsenic (V) from water, and adsorption isotherm also indicated that PET-AA-NN-Al2(OH)nCl6−n had high equilibrium adsorption capacity for arsenic (V).

Preparation of High Surface Area Mesoporous Activated Carbon: Kinetics and Equilibrium Isotherm

Activated carbon prepared from palm shell by phosphoric acid impregnation, at significantly favorable experimental conditions is characterized for the porous nature and adsorption of methylene blue dye molecules. The activation is carried out using a 2-stage activation process with the activation in a self-generated atmosphere. An activation temperature of 500°C, with an activation time of 75 minutes using a phosphoric acid impregnation ratio of 3 has yielded an activated carbon having unique characteristics. An activated carbon with a yield of 48%, total pore volume of 1.9 cm3/g, surface area of 1956 m2/g, an average pore diameter of 3.8 nm, with the ratio of the mesopore to the total surface area in excess of 75% has been prepared. The activated carbon exhibits a high methylene blue equilibrium adsorption capacity of 438 mg/g with the adsorption isotherm increasing with an increase in the adsorption temperature. Among the various adsorption isotherm models, the Langmuir model is able to explain the adsorption process well, evidenced by the proximity of the model with the experimental data. Among the different kinetic models tested with the experimental kinetic data, a pseudo-second-order model is found to fit the experimental data with close proximity.