Adsorption Of Catechol Research Articles

Anisotropic emulsion constructed boronate affinity imprinted Janus nanosheets for stir bar sorptive extraction of cis-diol-containing catechol

Molecularly imprinted stir bar sorptive extraction (MI-SBSE) is a powerful method for synchronously achieving rapid mixing and selective enrichment. Herein, boronate affinity imprinted Janus nanosheets for stir bar sorptive extraction of cis-diol-containing catechol is reported. In this work, Janus nanosheets (NS-2) with amino groups on one side and vinyl groups on the other side are firstly prepared by self-organized interfacial sol-gel process from O/W anisotropic emulsion templates. Then, boronate affinity imprinted polymer layer is grafted onto the vinyl groups of NS-2 by initiating a precipitation polymerization (NS-2-MIPs). Finally, NS-2-MIPs are attached to the aldehyde functionalizedglass tube with the magnetic inner core. Finally, MI-SBSE was used for selective enrichment of catechol, which is a typical endocrine disrupting chemical. The effects of solution pH, adsorption kinetics, isotherms, selectivity as well as the regeneration on the catechol adsorption onto the NS-2-MIPs are investigated in detail. NS-2-MIPs show largely enhanced adsorption capacity and good selectivity toward catechol than non-imprinted nanosheets (NS-2-NIPs). The maximum adsorption capacities achieve 286.3 μmol g−1 at 308 K and 263.0 μmol g−1 at 298 K, and the quick adsorption equilibrium reach within 30 min by accomplishing 98% of removal ratio. Moreover, chemical adsorption via boronate affinity mainly dominate the binding process and catechol is homogenously captured onto the binding sites with uniform distribution by a monolayer adsorption. Furthermore, 87.97% of catechol is captured after the effective mixing and selective enrichment by MI-SBSE by accelerating mass transfer. The findings of the present work not only provides insights to develop nanosheet-based stir bar using imprinted Janus nanosheets, but also presents a new method for catechol separation.

Exact matrix treatment of the statistical mechanics of adsorption of large aromatic molecules on graphene.

Experimental studies of adsorption from solution of the large aromatic molecules 1,2-dihydroxybenzene (catechol) and phenyl hydroquinone on graphene nanoplatelets show that at low coverage adsorption is followed by a transition which occurs from adsorbed molecules in flat to more vertically oriented states. Catechol adsorption isotherms exhibit 2 plateaus while phenyl hydroquinone shows 3 plateaus indicating 2 and 3 active conformers respectively participating in the adsorption process. Modelling such adsorption isotherms presents a challenge. Here, an exact matrix treatment of the statistical mechanics of a one-dimensional model of adsorption of catechol and dihydroquinone on graphene nanoplatelets is presented. The theoretical adsorption isotherms successfully reproduce all the features of both the catechol and dihydroquinone experimental adsorption isotherms. As suggested by the experimentalists, our theoretical model demonstrates that adsorbed phenyl hydroquinone molecules adopt a flat orientation at low concentrations and an edge orientation at higher coverage before eventually adopting a vertical configuration. Both catechol and phenyl hydroquinone can be described by our interconvertible monomer-dimer-trimer model. The theoretical adsorption isotherms obtained show several plateaus reflecting the types of conformer on the graphene surface.

Synthesis and Characterization of TiO2-CaO and TiO2-CaO-Fe2O3 Photocatalyst for Removal of Catechol

TiO2-CaO and TiO2-CaO-Fe2O3 photocatalysts have been synthesized through the surfactant-assisted sol-gel method. The catalysts were characterized using XRD, FTIR, SEM-ED Sand BET surface area. XRD pattern showed the formation of anatase TiO2 crystal phase both in TiO2-CaO and TiO2-CaO-Fe2O3. The TiO2-CaO has higher crystallinity than TiO2-CaO-Fe2O3. Based on the peak refinement using Rietveld, there are two peaks identified as Fe2O3 hematite in the sample TiO2-CaO-Fe2O3. BET surface area analysis showed that the average pore size of TiO2-CaO and TiO2-CaO-Fe2O3 catalysts are 8.04 and 8.41 nm respectively, indicating both catalysts are mesoporous.FTIR spectra show that the vibration of Ti-O, Ca-O, and Ca-TiO2 were observed in both catalysts. SEM images confirm that both catalysts are porous material. The catechol removal using TiO2-CaO and TiO2-CaO-Fe2O3 improved with the increase of catalyst concentration. After 360 minutes of UV radiation, the removal of catechol using TiO2-CaO-Fe2O3 reached 46.0%, 48.3%, and 69.2%, while when using TiO2-CaO, it reached 22.1%, 36.8%, and 57.0% for 0.1 g, 0.15 g, and 0.2 g of catalysts, respectively. The photocatalytic activity of TiO2-CaO-Fe2O3 is not so strong compared to TiO2-CaO catalyst but the catechol adsorption property of TiO2-CaO-Fe2O3 is higher than that of TiO2-CaO catalyst.

Thiol-Ene Click Synthesis of Phenylboronic Acid-Functionalized Covalent Organic Framework for Selective Catechol Removal from Aqueous Medium.

We report a thiol-ene click strategy for the preparation of a novel phenylboronic acid-functionalized covalent organic framework (COF) for selective removal of catechol in aqueous solution. Vinyl-functionalized 2,5-diallyloxyterephthalaldehyde (Da-V) was prepared as a building ligand. Da-V was then condensed with 1,3,5-tris(4-aminophenyl)benzene (Tab) to give a vinyl-functionalized COF DhaTab-V. Subsequently, 4-mercaptophenylboronic acid (4-MPBA) was covalently linked on DhaTab-V via thiol-ene click reaction to give phenylboronic acid-functionalized COF DhaTab-PBA. The adsorption isotherms, energetics and kinetics, and reusability of DhaTab-PBA for the adsorption and removal of catechol from aqueous solution were investigated in detail. This phenylboronic acid-functionalized COF is promising as sorbent for selective removal of catechol from aqueous medium with large adsorption capacity and good reusability.

Adsorption of catechol onto PEDOT films doped with gold nanoparticles: Electrochemical and spectroscopic studies

In this work, the electrochemical processes at the electrode/electrolyte interface of PEDOT:PSS modified electrodes were studied. A detailed investigation using Electrochemical Impedance Spectroscopy (EIS) was done to determine the adsorption and electrochemical effects caused by the interaction of catechol at the conductive substrate. Different parameters such as double-layer capacitance, charge transfer resistance and intercalation charge distribution were analyzed in the presence of different amounts of catechol in the electrolyte. It was found a direct response of the charge transfer resistance (Rct) with catechol concentration, in the same way, the electrocatalytical response of the reversible redox reaction of catechol was observed. The investigation of the incorporation of gold nanoparticles (AuNPs) onto the PEDOT:PSS substrates showed an intrinsic increment in the conductivity, favoring the interaction between catechol and PEDOT, presenting an interesting tool for the construction of impedimetric sensors. The modified electrodes were further characterized by Scanning Electron Microscopy and Raman Spectroscopy.

Non-linear Regression, a Better Approach for the Optimisation of Hydroquinone, Resorcinol and Catechol Adsorption by Chemically Activated Carbon Based on Monkey Kola (Cola lepidota k. schum) Waste

Non-linear Regression, a Better Approach for the Optimisation of Hydroquinone, Resorcinol and Catechol Adsorption by Chemically Activated Carbon Based on Monkey Kola (Cola lepidota k. schum) Waste

Adsorption of Catechol from Aqueous Solutions Using Graphene Oxide

Adsorption of Catechol from Aqueous Solutions Using Graphene Oxide

Removal of catechol from water by modified dolomite: performance, spectroscopy, and mechanism.

Dolomite was treated at 800 °C (D800), characterized, and used in the adsorptive removal of catechol (1,2-dihydroxybenzene) from aqueous solutions. The performances of the D800 sample, named dolomitic solid, were compared with those of the raw material. A bibliographic review shows that the data on the adsorption of phenolic compounds by dolomites are non-existent. Kinetic data, equilibrium isotherms, thermodynamic parameters, and pH influence were reported. Special attention was paid to the spectroscopic study, before and after adsorption. The purpose was to understand the mechanism of catechol uptake on dolomitic materials. Kinetics follows the pseudo-second order model. The Redlich-Peterson isotherm provides the best correlation of our isotherms. Affinity follows the sequence: D800 ≫ raw dolomite. The process is spontaneous at low temperatures and exothermic. After catechol adsorption, the shape of the band in the 3,600-3,000 cm-1 range and its red shift towards 3,429 cm-1 reflect a deep involvement of OH groups both of D800 and catechol, which confirm hydrogen bonding via their respective OH. On this basis, a schematic illustration was proposed. The understanding of the phenolic compound-dolomitic solid interactions constitutes a fundamental approach to developing the application of these materials in wastewater treatment.

Modelling of Binary Isotherm Behaviour for the Adsorption of Catechol with Phenol and Resorcinol onto Rice Husk Ash

The present paper assesses the adsorption capability of rice husk ash (RHA) to adsorb catechol (C) along with phenol (P) and resorcinol (R) individually and simultaneously from aqueous solution in both single and binary solutions using batch experiments. Equilibrium isotherm data were collected at 30°C by carrying out experimental runs for 24 h contact time with pre-optimized RHA dosage of 20 mg/L and initial concentration variation of individual components in the range of 50–500 mg/L. The equilibrium adsorption data for single component were fitted in three adsorption isotherm models, namely the Langmuir, the Freundlich and the Redlich–Peterson. Equilibrium adsorption data of binary aqueous solution of catechol–phenol, catechol–resorcinol and the parameter evaluated from single adsorption isotherm were fitted in various multi-component adsorption isotherm models. Extended Langmuir model which assumes overlapping of sites for different adsorbates better represented the binary isotherm data for both catechol–phenol and catechol–resorcinol systems.

Catechol adsorption on graphene nanoplatelets: isotherm, flat to vertical phase transition and desorption kinetics.

The adsorption of catechol (1,2-dihydroxybenzene) on graphene nanoplatelets (GNPs) is investigated electrochemically and spectroscopically. The reversible adsorption of catechol on GNPs is Langmuirian with an adsorption constant of (0.2 ± 0.002) mM-1 at low adsorbate concentrations (≤100 mM). At higher concentrations (>100 mM) the adsorption of catechol on GNPs is shown to undergo a flat to vertical concentration driven phase transition. The kinetics of desorption are measured with a single particle electrochemical technique. The study of individual impacts allows the determination of the rate of catechol desorption from GNPs to be k = 0.08 ± 0.01 s-1 with first order kinetics. The method provides a powerful and efficient generic approach to study adsorption and, importantly, desorption of molecules on nanomaterials, as well as giving insight into the modification process.

Electrochemical estimation of the active site density on metal-free nitrogen-doped carbon using catechol as an adsorbate.

Carbon is heat-treated with a nitrogen-containing precursor (ammonia) to obtain nitrogen-doped carbon and the composition is estimated using CHN and XPS analysis. The active site density of the carbon and nitrogen-doped carbon is quantified using 1,2-dihydroxybenzene (catechol) molecules as an adsorbate in phosphate buffer (pH 7) solution. The features of the voltammograms of the catechol-adsorbed high surface area carbon and nitrogen-doped carbon are similar to that of the polished nitrogen-grafted glassy carbon electrode (GCE) reported in the literature. At the same time, the polished GCE does not show any well-defined catechol adsorption features. It is found that the adsorption charge (obtained by integrating the peak area, after subtracting the background) is in the order of N/C 900 > N/C 1000 > N/C 800 > N/C 700 > C. A similar trend is observed in their oxygen reduction reaction (ORR) activity in 0.1 M KOH. Moreover, the turnover frequency (ToF) of the catalysts is calculated and it is comparable to that reported in the literature using other methods for non-precious catalysts. Therefore, the adsorption charge can be correlated with the active site density of the carbon and nitrogen-doped carbon samples.

Photocatalytic selective oxidation of phenol to produce dihydroxybenzenes in a TiO2/UV system: Hydroxyl radical versus hole

Photocatalytic oxidation plays an important role in organic synthesis. This research systematically studied the effect of reactive oxidation species (ROSs) such as surface-bounded hydroxyl radicals (OHb), free hydroxyl radicals (OHf), and hole (h+) on the photocatalytic selective oxidation of phenol in the TiO2/UV system and its corresponding important chemical intermediates, dihydroxybenzenes. Experimental results showed that (1) the oxidation of phenol by hydroxyl radicals, whether in free (OHf) or bounded states (OHb), led mainly to the ortho- (catechol) and para-oriented hydroxy derivatives (hydroquinone), whereas the meta-oriented hydroxy derivative (resorcinol) became the main product when holes were used as the active species; (2) in naked TiO2 suspensions, where OHb was the main ROSs, the selectivity of the catechol detected in the solution was much lower than that on the surface of the fluorinated TiO2 system (TiO2-F), where OHf served as the main ROSs. This finding can be attributed to the very strong catechol adsorption on the surface of naked TiO2. However, this adsorption was severely inhibited in the presence of fluorine because of the competitive adsorption between catechol and fluoride ions over TiO2 photocatalyst; and (3) the hole oxidation of phenol provided a slower oxidation rate but a higher yield of dihydroxybenzenes compared with hydroxyl radical-mediated oxidation.

Effects of Thermal Fluctuations on the Structure, Level Alignment, and Absorption Spectrum of Dye-Sensitized TiO2: A Comparative Study of Catechol and Isonicotinic Acid on the Anatase (101) and Rutile (110) Surfaces

The adsorption of catechol and isonicotinic acid on the TiO2 anatase (101) and rutile (110) surfaces has been studied by means of first-principles molecular dynamics simulations and time-dependent density functional calculations. Our results show that thermal fluctuations induce changes in the position of the molecular levels around the TiO2 valence band edge. For the anatase (101) surface, the alignment of the molecular levels with the TiO2 valence band edge has a significant effect on the absorption spectrum. For rutile (110), instead, the adsorption of catechol and isonicotinic acid induces only a minor sensitization. The sensitization of anatase (101) by catechol and isonicotinic acid can be enhanced by increasing the hybridization between the adsorbed dye and TiO2 states.

Effect of phosphate on heterogeneous Fenton oxidation of catechol by nano-Fe3O4: Inhibitor or stabilizer?

The effect of phosphate on adsorption and oxidation of catechol, 1,2-dihydroxybenzene, in a heterogeneous Fenton system was investigated. In situ attenuated total reflectance infrared spectroscopy (ATR-FTIR) was used to monitor the surface speciation at the nano-Fe3O4 catalyst surface. The presence of phosphate decreased the removal rate of catechol and the abatement of dissolved organic compounds, as well as the decomposition of H2O2. This effect of phosphate was mainly due to its strong reaction with surface sites on the iron oxide catalyst. At neutral and acid pH, phosphate could displace the adsorbed catechol from the surface of catalyst and also could compete for surface sites with H2O2. In situ IR spectra indicated the formation of iron phosphate precipitation at the catalyst surface. The iron phosphate surface species may affect the amount of iron atoms taking part in the catalytic decomposition of H2O2 and formation of hydroxyl radicals, and inhibit the catalytic ability of Fe3O4 catalyst. Therefore, phosphate ions worked as stabilizer and inhibitor in a heterogeneous Fenton reaction at the same time, in effect leading to an increase in oxidation efficiency in this study. However, before use of phosphate as pH buffer or H2O2 stabilizer in a heterogeneous Fenton system, the possible inhibitory effect of phosphate on the actual removal of organic pollutants should be fully considered.

Quantifying Adsorption on Single Alumina Particles via Impact Voltammetry and Current Transient Analysis

Particle impacts are used to quantify the adsorption of catechol on single alumina particles. In these experiments, particles suspended in solution impact a microelectrode held at a suitable potential for the oxidation or reduction of the adsorbed species and the resulting current/time transient “spikes” associated with individual impacts measured. Using theory for charge diffusion over the surface of a sphere, the individual impact spikes arising from the electro-oxidation of adsorbed catechol can be modeled to derive the diffusion coefficient of charge transfer over the surface of alumina as (2.5 ± 0.5) × 10–6 cm2 s–1. The coverage of catechol on the surface of alumina is found to be (5.9 ± 1.9) × 10–10 mol cm–2.

Surface charge-transfer complex formation of catechol on titanium(IV) oxide and the application to bio-sensing

Adsorption properties of 2-hydroxyphenol (catechol) on TiO2 particles has been studied at 298K. The adsorption proceeds from the aqueous solution with the Langmuir type behavior. Diffuse reflectance infrared spectra of the catechol-adsorbed TiO2 suggested that catechol is adsorbed on TiO2 solution via the chelation to the surface Ti ions. The adsorption induces a strong absorption in the whole visible region, of which intensity increases with an increase in the adsorption amount. Photoelectrochemical experiments and molecular orbital calculations indicate that the absorption stems from the charge-transfer (CT) transition from the HOMO of catechol to the conduction band of TiO2. Time courses for the adsorption of catechol on mesoporous TiO2 nanocrystalline film-coated glass was traced by measuring the change in the absorbance of the CT band, and analyzed on the basis of the Langmuir model. This study would present a new simple technique for sensing of important biomolecules bearing the catechol moiety.

Catechol and HCl Adsorption on TiO2(110) in Vacuum and at the Water-TiO2 Interface.

Coadsorbed water is often unavoidable in electrochemistry and low-temperature catalysis. In addition, water influences the adsorption of biomolecules on surfaces. We use ab initio DFT molecular dynamics and ground-state calculations to study the adsorption of HCl and catechol on the rutile TiO2(110) surface and at a water-rutile interface. We find that a coadsorbed water film reduces the adsorption energy of both catechol and HCl significantly because water molecules must be displaced from the surface before catechol or HCl can adsorb. The adsorption energy of catechol (or HCl) at the water-rutile interface can be estimated as the adsorption energy in vacuum minus the energy to remove two water molecules (respectively, one water molecule) from the rutile surface in vacuum and place them in liquid water. This estimate predicts the effect of a surface water film on adsorption without the need of molecular dynamics.

Molecular Dynamics Simulations of Adsorption of Catechol and Related Phenolic Compounds to Alumina Surfaces

We performed atomistically detailed molecular dynamics simulations to study adsorption behaviors of catechol, which is a key functional group in marine bioadhesives, to two different alumina surfaces in both anhydrous and aqueous conditions. In anhydrous conditions, without competing interactions from water molecules, catechol adsorbed to both hydroxylated and nonhydroxylated alumina surfaces. In aqueous conditions, catechol and several analogous phenolic compounds displaced water molecules and were strongly attracted to the nonhydroxylated alumina surface, which is more hydrophobic. When comparing the phenolic moieties near the hydroxylated alumina surface in aqueous conditions, the catechol molecules displayed the strongest adsorptions mainly through cooperative hydrogen bonding interactions of two neighboring hydroxyl groups with the surface hydroxyl groups of alumina as evidenced by the longer hydrogen bonding lifetimes and the larger number of adsorbed molecules near the surface. Insights gained from...

A fundamental understanding of catechol and water adsorption on a hydrophilic silica surface: exploring the underwater adhesion mechanism of mussels on an atomic scale.

Mussels have a remarkable ability to bond to solid surfaces under water. From a microscopic perspective, the first step of this process is the adsorption of dopa molecules to the solid surface. In fact, it is the catechol part of the dopa molecule that is interacting with the surface. These molecules are able to make reversible bonds to a wide range of materials, even underwater. Previous experimental and theoretical efforts have produced only a limited understanding of the mechanism and quantitative details of the competitive adsorption of catechol and water on hydrophilic silica surfaces. In this work, we uncover the nature of this competitive absorption by atomic scale modeling of water and catechol adsorbed at the geminal (001) silica surface using density functional theory calculations. We find that catechol molecules displace preadsorbed water molecules and bond directly on the silica surface. Using molecular dynamics simulations, we observe this process in detail. We also calculate the interaction force as a function of distance, and observe a maximum of 0.5 nN of attraction. The catechol has a binding energy of 23 kcal/mol onto the silica surface with adsorbed water molecules.

A Study about the Influence of Microorganisms on the Properties of D301 Resin Adsorption Catechol

With the development of industry, the phenolic wastewater pollution has become increasingly serious, This paper studies the effects of microbial life activities on D301 resin adsorption and catechol were discussed, Study found that the resin of the ability after the microbial treatment on the adsorption of catechol contribute. The optimum concentration of D301 for 0.8g/L adsorption of catechol; blank treatment was the highest adsorption capacity is 126mg/g, and the maximum adsorption capacity through the resin after the microbial treatment can reach 155mg/g, but its mechanism needs further study.