Superior Adsorption Properties Research Articles

Preparation of a 3D multi-branched chelate adsorbent for high selective adsorption of uranium(VI): Acrylic and diaminomaleonitrile functionalized waste hemp fiber

Uranium(VI) is an important strategic resource in the development of nuclear energy with 4.5 billion tons in the seawater. However, because of the low concentration of U(VI) and the presence of multiple competing ions in seawater. It is a significant challenge for extracting U(VI) from seawater. In this study, a series of multi-branched HF-PAA-AOn(n =1,2,3,4,5) adsorption materials were prepared for the extraction of U(VI) from solution, and the adsorption properties of the adsorbents were investigated by batch experiments. The experimental results indicated that the HF-PAA-AO5 material exhibits an excellent removal rate and the maximum adsorption capacity of HF-PAA-AO5 is of 550.28 mg/g. Moreover, the adsorbent still maintains a high adsorption efficiency after five adsorption-desorption recycles. Meanwhile, the adsorbent showed superior selectivity and adsorption properties (removal rate > 89%) in modified artificial seawater. Therefore, the HF-PAA-AO5 composite is considered to be a favorable potential adsorbent for capturing U(VI) from seawater.

Size- and Morphology-Dependent Kinetics and Thermodynamics of Adsorptions of Basic Fuchsin on Nano-TiO2

Nanoparticles have superior adsorption properties compared with corresponding bulk materials, which depends on their particle size and morphology. Herein, by introducing morphology factors, we derived the general relations of adsorption kinetic parameters and thermodynamic properties with an equivalent particle diameter of nanoparticles with different morphologies. Experimentally, we researched the adsorption kinetics and thermodynamics of basic fuchsin on nano-TiO2 with different equivalent particle diameters and morphologies. The results show that the equivalent particle diameter and morphology have significant effects on the adsorption kinetics and the adsorption thermodynamics. Within the range of the experiment, the adsorption rate constant and the equilibrium constant increase, while the activation energy, the pre-exponential factor, the Gibbs free energy, the enthalpy, and the entropy of adsorption decrease with the decrease in the equivalent particle diameter, and the logarithm of rate constant, activation energy, the logarithm of pre-exponential factor, the logarithm of equilibrium constant, molar Gibbs free energy, molar enthalpy, and molar entropy of adsorption are linearly related to the reciprocal of equivalent particle diameter, respectively. For this adsorption system, with the decrease of equivalent particle diameter, the effect of morphology on the adsorption rate constant decreases and the activation energy and the pre-exponential factor approximately remain unchanged, while the logarithm of equilibrium constant, molar Gibbs free energy, molar enthalpy, and molar entropy of adsorption increase. The experimental results are consistent with the theoretical relations. In addition, we are surprised to find a phenomenon that is contrary to the traditional concept of dynamics: compared with the three morphologies, when the adsorption rate constant of nanoparticles is larger, the adsorption activation energy is also larger and when the adsorption rate constant of nanoparticles is smaller, the adsorption activation energy is also smaller, and these can be attributed to the fact that the morphology of nanoparticles has a greater influence on pre-exponential factor than on activation energy. The theory can quantitatively describe the effect of the equivalent particle diameter and morphology on adsorption kinetics and thermodynamics of nanoparticles and better predict the adsorption behaviors of nanoparticles.

Preparation of magnetic resin microspheres M-P(MMA-DVB-GMA) and the adsorption property to heavy metal ions

Magnetic resin microspheres called MPMDG2 were prepared by suspension polymerization combined with basic and acidic hydrolysis. The adsorption property of resin microspheres to heavy metal ions was investigated. Structural and morphological analysis revealed that the resin had high specific surface area and mesoporous structure. The resin contained about 9.2 wt% Fe3O4 and exhibited a high magnetic response. Adsorption experiments showed that the resin can selectively absorb Cr(III) and Pb(II) ions. The adsorption process was well described by a pseudo-second-order kinetic model, and the equilibrium adsorption data fitted the Langmuir isotherm model better than the Freundlich model. Ion exchange along with chemistry chelating was the most probable mechanisms for the adsorption of metal ions on the resin. The superior magnetic response, regeneration and selective adsorption property of the MPMDG2 make it a good candidate as an adsorbent for removing Cr(III), Pb(II) and Cu(II) from wastewater.

Sulfurized biochar prepared by simplified technic with superior adsorption property towards aqueous Hg(II) and adsorption mechanisms

The biomass-based sulfurized biochar (CSS) that was prepared by co-heating sublimed sulfur and raw corn stalk in relatively low temperature (450 °C) and heating duration (15 min) showed an excellent adsorption property towards aqueous Hg(II) and was evaluated for its Hg(II) adsorption behavior and mechanism. Meanwhile, biochar-based sulfurized biochar (BCS) produced by co-heating sublimed sulfur and corn stalk biochar would be used for comparison. The results showed that the sulfur content of CSS and BCS was 7.4 and 2.2 wt% and the maximum Hg(II) adsorption capacity of CSS and BCS were 268.5 and 117.7 mg g−1. The Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy data suggested that the species of functional groups for Hg(II) adsorption on sulfurized biochar might be hydroxy, C=S and sulfoxide groups, etc. The X-ray photoelectron spectroscopy (XPS) results showed that the dominant existing forms of sulfur on sulfurized biochar were alkyl sulphides and sulphone groups along with thiophene and inorganic sulfur. The XPS data also verified the complexation between Hg(II) and CSS by forming irreversible Hg–S and Hg–O bond. Our research suggested that CSS processed more sulfur-containing groups with greater affinity to Hg(II) than BCS, and Hg(II) was stable adsorbed via complexation with hydroxy, C=S and sulfoxide groups in CSS by forming Hg–S and Hg–O bond.

Cu–Co‐codoped titanate/TiO2nanocomposite thin films for enhanced visible light absorption

Titanate nanotube thin (TNT) films were synthesised by alkaline hydrothermal method using titanium (Ti) plates as precursors. Copper–cobalt (Cu–Co)-codoped titanate/Ti dioxide (TiO2) nanocomposite thin films were prepared by doping Cu and Co to TNT films through ion exchange method and annealed at 500°C for 120 min. The as-prepared nanocomposite films were characterised by scanning electron microscopy, transmission electron microscopy, X-ray diffractometer, and ultraviolet–visible absorption spectra. The results show that anatase TiO2 particles were grown on the surface of titanate nanomaterial films. The composite materials mainly consisted of anatase TiO2 particles and titanate nanotubes/nanosheets. Cu–Co-codoped titanate/TiO2 nanocomposite thin films exhibited superior visible height adsorption property due to the reduced energy bandgap of composites introduced by additional Cu and Co 3d orbitals.

Facile synthesis of MnOx‐loaded biochar for the removal of doxycycline hydrochloride: effects of ambient conditions and co‐existing heavy metals

AbstractBACKGROUNDIn this study, manganese oxide (MnOx) nanoparticle loaded biochar (BC) was applied for doxycycline hydrochloride (DOX) removal from water. Biochar composites were synthesized by either pre‐treating biomass using MnCl2/KMnO4/NaOH (PMBC) or inserting MnOx ultrafine particles after pyrolysis of biomass (AMBC). In complex water environments, the presence of heavy metals may affect the removal of antibiotics. Cu(II) and Cr(VI) were used to study their effect on DOX removal.RESULTSThe BC loaded with MnOx exhibited superior adsorption properties for DOX. The adsorption capacity of AMBC and PMBC was ≈93 mg/g and 104 mg g−1, respectively, which was about nine‐ and ten‐fold higher than that of raw BC (11.48 mg g−1). The characterization indicated that AMBC and PMBC had better surface structure and more surface functional groups than raw BC. The main mechanisms for DOX adsorption onto PMBC were surface complexation, H‐bond, π–π interaction and electrostatic interaction. DOX removal by PMBC also involved its degradation effect on DOX. Adsorption experiments were carried out with the influence of pH, ionic strength and background electrolyte. The presence of Cu(II) obviously enhanced the DOX adsorption capability through Cu(II) bridging effect, whereas the presence of Cr(VI) significantly inhibited DOX adsorption through competitive adsorption and electrostatic repulsion.CONCLUSIONSThe results suggested that PMBC could be implemented as a cost‐effective and environmentally friendly adsorbent for DOX removal from water. Heavy metal ions can obviously enhance or weaken the adsorption ability of PMBC for DOX. © 2019 Society of Chemical Industry

Oxidative decomposition of volatile organic compound on hydroxyapatite with oriented crystal structures

Hydroxyapatite (HAp) exhibits superior biocompatibility, ion-exchange ability and high adsorption property has attracted much attention as one of the most well-known ceramic functional materials. We have previously reported the efficient oxidative decomposition of volatile organic compounds (VOC) on commercial HAp powders, which makes HAp a promising alternative material of precious metal nanoparticle catalyst for environmental purification. In this work, HAp with oriented crystal growth of a-plane and c-plane were synthesized via air-liquid interface precipitation in solution, and the influence of crystal orientation on VOC decomposition performance was systemically investigated. As a result, HAp with preferential growth of c-plane performs higher catalytic VOC decomposition activity, which can be attributed to the large number of active radicals generated on surface despites the relative smaller sufficient surface area. The results in this study highlight the important relation between crystal structure of HAp and the decomposition activity of VOC, which also provide useful information for the structure design of ceramic functional materials.

Effect of Formaldehyde to Phenol Ratio in Phenolic Beads on Pore Structure, Adsorption and Mechanical Properties of Activated Carbon Spheres


 
 
 Phenolic beads (PBs) prepared from different formaldehyde to phenol (F/P) molar ratios were used as polymeric precursor for activated carbon. Activated carbon spheres (ACSs) have been produced from PBs via the physical activation process using carbon dioxide (CO2) as activating agent at 950 °C for different burn-off. The prepared ACSs were investigated for nitrogen adsorption, surface morphology and compressive strength by means of BET surface area analyser, scanning electron microscopy (SEM) and carbon and sphere tester techniques. The results indicated that the effects of F/P ratio observed, especially variation in the adsorption and mechanical properties. It was found that ACSs obtained from F/P ratio one showed the superior adsorption properties, possessed a high BET surface area in a range of 836 m2 g-1 to 3694 m2 g-1 with high pore volume (0.47 cm3 g-1 - 2.47 cm3 g-1) and 73-97 per cent microporosity. The BET surface area and pore volume increased, while the microporosity gradually decreased, with increasing the extent of burn-off. Compressive strength decreased with increasing F/P ratio as well as the extent of burn-off. ACSs upheld improved compressive strength (from 160 N mm-2 to 9 N mm-2) than those obtained from F/P ratio 2 and 3 in PBs. SEM studies of ACSs demonstrated well developed pore structure.
 
 

Highly biocompatible Co@Silica@meso-Silica magnetic nanocarriers

Core-shell structured Co@Silica@meso-Silica nanoparticles have been synthesized via a layer-by-layer approach. The magnetic cobalt core makes the nanoparticles easy to separate with an external magnetic field. The inner dense silica layer prevents the Co from oxidation and leaching. The outer mesoporous silica presents high surface area and pore volume, endowing the material with superior adsorption properties of organic molecules. The core-shell structure prevents the direct contact of cobalt with living cells, thus enhancing the biocompatibility remarkably. This dual encapsulation provides a golden opportunity to the nanocarrier design with easy magnetic separation, high drug loading, and high biocompatibility.

A solid-state chemical method for synthesizing MgO nanoparticles with superior adsorption properties.

As a traditional and effective adsorbent, MgO is a low-cost, eco-friendly, nontoxic, and economical material for wastewater treatment. However, multistep processing and the use of organic agents result in high costs and lead to environmental pollution, strongly inhibiting the practical application of MgO. Herein, a simple solid-state chemical route has been used to prepare small-sized MgO nanoparticles with a large specific surface area of 213 m2 g−1 without using liquid solvents, template agents, or surfactants. This facile method is a green strategy that is suitable for large-scale production, avoiding complex preparation processes and serious environmental pollution. The obtained small-sized MgO nanoparticles showed a superior adsorption capacity of 2375 mg g−1 towards Congo red, originating from the large specific surface area and surface features (hydrogen bonds and electrostatic interactions). The adsorption behavior obeyed a pseudo-second-order rate equation and the Langmuir isotherm adsorption model. This study provides a route for the synthesis of oxides with large specific surface areas and obtained an adsorbent with superior adsorption capacity.

Crystal Engineering of Metal–Organic Framework Thin Films for Gas Separations

Metal–organic frameworks or MOFs have witnessed a phenomenal rise owing to a highly tunable synthetic chemistry allowing flexibility in the selection of its constituents, namely metal nodes and linkers. Combined with their superior adsorption and diffusion properties, MOFs have become one of the most promising nanoporous materials for the fabrication of high-performance membranes. Polycrystalline MOF membranes have yielded one of the best gas separation performances, and are expected to replace or partially substitute thermally driven separation processes. In this respect, we present our perspective on the crystal engineering of MOF films that offers control over nucleation and growth of MOFs, film morphology, lattice defects, and therefore the separation performance of the resulting MOF films.

Hydroxyl-Based Hyper-Cross-Linked Microporous Polymers and Their Excellent Performance for CO2 Capture

A series of benzyl alcohol (BA)-based hyper-cross-linked microporous polymers (HCPs) were designed and synthesized via facile Friedel–Crafts alkylation using formaldehyde dimethyl acetal (FDA) as external cross-linker promoted by anhydrous ferric chloride (FeCl3). Results demonstrated that Brunauer–Emmett–Teller (BET) specific surface area and pore volume for the HCPs could be controlled by adjusting the amount of FDA and FeCl3. The HCPs obtained under optimal conditions showed a BET specific surface area up to 1101 m2/g, whose capacity of CO2 uptake could be as high as 3.03 mmol/g at 273 K/1.0 bar. The isosteric heats of CO2 sorption for the BA-based HCPs exceed 27 kJ/mol at the low coverage. In addition, the polymer networks possessed high CO2/N2 selectivity of 42. Compared with those BA-based HCPs which is without FDA, the prepared material has higher BET specific surface area and superior CO2 adsorption properties. These results demonstrated that these prepared HCPs are promising for CO2 capture and s...

Bamboo-like Co3O4 nanofiber as host materials for enhanced lithium-sulfur battery performance

To inhibit the shuttle effect of Li-S batteries, many polar materials were applied to absorb the polysulfide due to their superior adsorption properties. Herein, bamboo-like polar Co3O4 nanofiber was prepared by hydrothermal method and used as sulfur host material. The as-prepared Co3O4-S composite electrode displayed excellent cycle stability because of its strong absorption of polysulfide. The Co3O4-S composite electrode exhibited high initial specific capacity of 1110 mAh g−1 at 0.1C. Even when the current density improved to 1 C, the capacity of Co3O4-S composite electrode still remained 796 mAh g−1 after 300 cycles.

A multifunctional gelatin-based aerogel with superior pollutants adsorption, oil/water separation and photocatalytic properties

Designing multifunctional adsorbents that can satisfy sophisticated requirements in complex water treatment fields remains challenging these days. In this work, an original and environment-friendly gelatin-based organic-inorganic composite aerogel equipped with integrative functions was fabricated through facile methods. The uniform dispersion of TiO2 nanoparticles was successfully achieved in the three-dimensional structure of the composite aerogel, and the branched polyethyleneimine (PEI) was cross-linked onto it through the effect of glutaraldehyde. The gelatin/TiO2/PEI (GTP) aerogel had a hierarchical porous structure and a superamphiphilic surface, which endowed it with excellent oil/water separation properties, for both oil/water free mixtures and oil-water emulsions. Both cationic (methylene blue and crystal violet) and anionic (congo red and methyl orange) organic dyes could be adsorbed by the GTP aerogel with good adsorption capacity. It was noteworthy that the GTP aerogel was capable of realizing dye degradation because of its photocatalytic performance. Furthermore, this composite aerogel was able to remove copper ions from aqueous solutions with high capacity and good reusability. The regeneration of the GTP aerogel was realized by methanol and EDTA for dyes and copper ions respectively. Combined with comprehensive functions including oil/water separation, organic dyes adsorption, copper ions removal and photocatalytic property, the bio-based organic-inorganic composite GTP aerogel holds great promise for practical usage in water remediation, especially in the treatment of polluted water with complex components.

Hybrid Metal–Organic-Framework/Inorganic Nanocatalyst toward Highly Efficient Discoloration of Organic Dyes in Aqueous Medium

Nanoscale metal-organic frameworks (NMOFs) represent a unique class of solids with superior adsorption, mass transport, and catalytic properties. In this study, a facile and novel approach was developed for the generation of hybrid Cu-NMOF/Ce-doped-Mg-Al-LDH nanocatalyst through in situ self-assembly and solvothermal synthesis of a 2D Cu-NMOF, [Cu2(μ-OH)(μ4-btc)(phen)2] n·5 nH2O {H3btc, trimesic acid; phen, 1,10-phenanthroline}, on a cerium-doped Mg-Al layered double hydroxide (Ce-doped-Mg-Al-LDH) matrix. Self-assembly between Cu-NMOF nanocrystals and exfoliated LDH led to their nanoscale mixing and prevented the formation of aggregated Cu-NMOF nanoparticles. In the resulting hybrid nanostructure, Cu-NMOF nanocrystals (∼10-20 nm particle size) are anchored uniformly on a Ce-doped-Mg-Al-LDH's surface, possessing a dimension of several hundred nanometers. Catalytic activity of Cu-NMOF/Ce-doped-Mg-Al-LDH and Cu-NMOF was evaluated under ambient conditions in the reductive degradation (discoloration) of aqueous solutions of 4-nitrophenol (4-NP, model substrate) and a series of commercial organic dyes by applying sodium borohydride as a reducing agent. The Cu-NMOF/Ce-doped-Mg-Al-LDH nanocatalyst exhibited an outstanding catalytic activity toward degradation of 4-NP, with kapp (rate constant) of 0.03 and a catalyst TOF (turnover frequency) up to 7.1 × 103 h-1. Full and very quick discoloration of organic dyes {rhodamine B (RhB), methylene blue (MB), Congo red (CR), methyl orange (MO), and rhodamine 6G (R6G)} was also achieved with TOF values of up to 1.4 × 105/h. A superior activity of the hybrid nanocatalyst over Cu-NMOF can be regarded as a synergic effect among Cu-NMOF and Ce-doped-Mg-Al-LDH components, while the Ce-doped-Mg-Al-LDH carrier acts as a cocatalyst. The hybrid nanocatalyst can easily be recovered and reused successfully for the five consecutive reaction runs with the same catalytic performance. This study also shows that NMOFs can be easily incorporated onto conventional catalyst supports, resulting in hybrid nanocatalysts with a highly uniform structural architecture, controlled chemical composition, and excellent catalytic function.

A vacuum calcination route to high-surface-area MgO nanoplates for superior arsenate adsorption and catalytic properties

Porous MgO nanoplates with high surface area has been synthesized by a vacuum calcination route using industrially available Mg(OH)2 as the precursor. The vacuum calcination not only promoted the phase transformation of Mg(OH)2 to MgO at a low temperature (300 °C), but also inhibited the thermally-induced particle growth and pore coalescence, leading to the formation of MgO nanoplates with fine grain sizes (5.5 nm), ultrasmall pores (2–4 nm) and high surface area (390 m2 g−1). The as prepared MgO nanoplates exhibited superior arsenic adsorption properties with a maximum adsorption capacity of 481.0 mg g−1, as well as excellent catalytic activity for the Claisen-Schmidt condensation reaction.

Integrating Superwettability within Covalent Organic Frameworks for Functional Coating

Summary Despite the availability of a variety of skeletons for covalent organic frameworks (COFs), control of pore-surface wettability remains undeveloped, which could immensely expand their overall versatility. Herein, we contribute an effective strategy for imparting superwettability on COFs by chemically coating the pore surface with perfluoroalkyl groups to confer them with superhydrophobicity. Taking advantage of controllable modification, the resultant COFs retain the porosity and crystallinity of the pristine COFs. Benefiting from the bulk superhydrophobicity of the COF crystals and the feasibility of COF synthesis, they can be used as a coat or in situ integrated within various substrates; once applied, this renders them superhydrophobic. Given the modular nature, this protocol is compatible with the development of various specific wettabilities in COFs, which thereby constitutes a step for expanding the scope of COF applications and provides many opportunities for the processing of advanced materials and devices.

Multi-carboxylic magnetic gel from hyperbranched polyglycerol formed by thiol-ene photopolymerization for efficient and selective adsorption of methylene blue and methyl violet dyes

Synthesis of adsorbents that simultaneously possess high adsorption performance and convenient separation characteristic remains a big challenge. Herein, we report a viable strategy to prepare hyperbranched polyglycerol (HPG)-based multi-carboxylic magnetic gel (MMG) based on the thiol-ene click chemistry. The obtained HPG-based MMG adsorbent with porous structure and multiple carboxylic groups not only exhibited fast adsorption rate, superior adsorption capacity, and favorable adsorption selectivity towards cationic dyes (e.g., methylene blue (MB) and methyl violet (MV)) but also presented convenient magnetic separation characteristic. The adsorption data showed nice correlation with pseudo-second-order kinetic model and Langmuir isotherm. The optimal adsorption capacity of HPG-based MMG for MB and MV can reach as high as 458.7 and 400.0 mg g−1, respectively. Moreover, the dye-adsorbed HPG-based MMG could be regenerated in ethanol for reuse without obvious decline of removal efficiency. On the basis of the superior adsorption property of HPG-based MMG, this work offers an effective strategy to prepare advanced adsorbent for dye removal from wastewater.

In situ formation of La(OH)3-poly(vinylidene fluoride) composite filtration membrane with superior phosphate removal properties

It is of great practical interest to combine membrane filtration with the removal of phosphate, which is the key nutrient in waters causing the eutrophication. In this study, we report the first example of in situ formation of La(OH)3 nanorods in poly(vinylidene fluoride) (PVDF) membrane by adding LaCl3·7H2O precursor in the membrane casting solution, after a non-solvent induced phase separation process in alkaline solution. The structures, morphologies, and surface properties of the La(OH)3-PVDF composite membranes were characterized by SEM, TEM, XRD, FT-IR, XPS, and water contact angle measurements. The adsorption and filtration experiments demonstrated that the La(OH)3-PVDF composite membrane exhibited a molecular weight cut-off of 16 kDa and superior adsorption and filtration properties, i.e. high adsorption capacity (256.6 mg P/g (La)), fast adsorption kinetics, excellent regenerability, negligible lanthanum leakage, efficient phosphate removal under high filtration permeability and simultaneous removal of organic pollutants and phosphate. We hope that our work has presented a new direction for the design of filtration membrane with superior adsorption properties.

Starch Particles, Energy Harvesting, and the "Goldilocks Effect".

This study reports on the unique water vapor adsorption properties of biomass-derived starch particles (SPs). SPs offer an alternative desiccant for air-to-air energy exchangers in heating, ventilation, and air conditioning systems because of their remarkable adsorption–desorption performance. SP15 has a particle diameter (dp) of 15 μm with a surface area (SA) of 2.89 m2/g and a pore width (Pw) of 80 Å. Microporous starch particles (SP15) were compared with high amylose starch (HAS15; SA = 0.56 m2/g, dp = 15 μm, Pw = 46 Å) and silica gel (SG13; SA = 478 m2/g, dp = 13 μm, Pw = 62 Å). Transient water vapor tests were performed using a customized small-scale energy exchanger coated with SP15, HAS15, and SG13. The water swelling (%) for SP15 was ca. 2 orders of magnitude greater with markedly higher (ca. three- and six-fold) water vapor uptake compared to HAS15 and SG13, respectively. At similar desiccant coating levels on the energy exchanger, the latent effectiveness of the SP15 system was much improved (4–31%) over the HAS15 and SG13 systems at controlled operating conditions. SP15 is a unique desiccant material with high affinity for water vapor and superior adsorption properties where ca. 98% regeneration was achieved under mild conditions. Therefore, SPs display unique adsorption–desorption properties, herein referred to as the “Goldilocks effect”. This contribution reports on the utility of SPs as promising desiccant coatings in air-to-air energy exchangers for ventilation systems or as advanced materials for potential water/energy harvesting applications.