Adsorption Isotherms Of Phenol Research Articles

Cellulose-based thermosensitive supramolecular hydrogel for phenol removal from polluted water

Pollution of phenolic effluent from spice and plastics factories has become increasingly serious. Thus, developing a green and highly efficient adsorbent to remove phenolic compounds from wastewater is of urgent need. In this study, cellulose graft copolymer was synthesized through grafting 4-vinylpyridine monomer and polyethylene glycol methacrylate to a molecular skeleton of cellulose by free radical polymerization. The supramolecular hydrogel was successfully synthesized by physical cross-linking of cellulose graft copolymer and α-cyclodextrin. These supramolecular hydrogels were thoroughly characterized and the adsorption performance (adsorption isotherms and adsorption kinetics) of phenol on the supramolecular hydrogel were investigated in batch operation. The supramolecular hydrogel not only exhibited excellent adsorption of phenol, but also demonstrated increased mechanical strength due to the introduction of a modified cellulose base material. The adsorption kinetics of phenol on the supramolecular hydrogel followed a quasi-second-order reaction, with a correlation coefficient of 0.9909. The adsorption isotherm conformed to the Langmuir adsorption isotherm, and the maximum adsorption capacity of phenol can reach 80.71 mg g−1, which was 2–3 times higher than traditional carbon-based materials. The results demonstrate the great promise of the waste-derived supramolecular hydrogel to be used as an efficient adsorbent in wastewater treatment.

Characteristics of ball-milled PET plastic char for the adsorption of different types of aromatic organic pollutants

Ball-milled plastic char (BMPC) was manufactured by ball-milling of native plastic char (PC) that was synthesized via slow pyrolysis of polyethylene terephthalate (PET) water bottle waste, and its adsorption characteristics of aqueous phenanthrene (PHE), phenol, and 2,4,6-trichlorophenol (2,4,6-TCP) and its possible mechanisms were investigated. With the increase of PC pyrolysis temperature, the specific surface area of BMPC increased obviously, forming larger functional groups compared to PC. Boehm titration showed that total acidic groups of BMPC decreased significantly with the increase of pyrolysis temperature. The sorption kinetics of three adsorbates was adequately simulated by pseudo-second-order model (R2 > 0.99). Langmuir model fitted well the adsorption isotherms of PHE and phenol, while Freundlich model simulated the adsorption isotherm of 2,4,6-TCP better. The adsorption amount of PHE, phenol, and 2,4,6-TCP increased significantly as the pyrolysis temperature increased. The maximum BMPC adsorption capacity reached 21.9mg·g-1 (for PHE), 106mg·g-1 (for phenol), and 303mg·g-1 (for 2,4,6-TCP) at 25°C in aqueous solution. FTIR analysis suggested that surface sorption-based π-π interaction was a dominant mechanism of PHE adsorption; meanwhile, H-bonding between O-containing groups on BMPC and hydroxyl groups of adsorbates was responsible for phenol and 2,4,6-TCP removal. This paper shows that BMPC can be used as adsorbent for treating aromatic compounds in aqueous environment and has an economic worth of application.

Influence of force field used in carbon nanostructure reconstruction on simulated phenol adsorption isotherms in aqueous medium

Grand Canonical Monte Carlo (GCMC) simulations have been conducted to investigate the interaction between phenol and a commercial activated carbon cloth KIP1200 in aqueous solution. The nanostructure of KIP1200 has been extracted using Hybrid Reverse Monte Carlo (HRMC) simulations based on experimental measurements of XRD-based structure factor, and shows the presence of pore spaces inaccessible to both phenol and nitrogen. The impact of empirical force fields (EDIP and Erhart-Albe) on the structural parameters and adsorption capacity, as well as pore accessibility is investigated via molecular simulations and materials informatics employing lattice and Voronoi decomposition algorithms. While the Erhart-Albe force field leads to more amorphous structures and inaccessible pores, the EDIP force field creates more lamellar structures with sharp edges and narrow pore width. The molecular state of adsorbed phenol in these structures is markedly different, with the narrower pore spaces of the EDIP-based structure providing stronger interaction between phenol molecules and carbon structure than for water. The calculated X-ray intensities and adsorption isotherms for the simulation-based structure are in good agreement with corresponding experimental results. The simulated solvation state of phenol has been verified by experiments, and demonstrates the existence of inter-layer spaces inaccessible to phenol for both force fields.

Kinetic, thermodynamic and mechanism study of the adsorption of phenol on Moroccan clay

Phenol is a toxic pollutant commonly found in industrial wastewaters. Thus, the objective of the present study consisted in removing this organic compound from aqueous solution using a clay from Morocco. Adsorbent characterization was performed using XRF, XRD, SEM, BET and FTIR techniques. Phenol adsorption isotherms and kinetics were experimentally quantified and modeling studies were carried out by statistical physics to explain the phenol adsorption on raw and activated clays. Results showed that: i) the activation of the clay by sulfuric acid increased its adsorption capacity, ii) the phenol adsorption was well fitted by the pseudo-second-order kinetic and Langmuir isotherm models, iii) the adsorption mechanism was dominated by electrostatic interactions and was associated to a multi-docking process. To conclude, the present study illustrates the valorization of this Moroccan clay as a low-cost and effective adsorbent for phenol removal from wastewaters.

Phenol adsorption kinetics and isotherms on coal: effect of particle size

ABSTRACT This work provided the adsorption method to removal phenol by using different coal particles. The characterization of the adsorbents was analyzed by Camsizer XT, FT-IR, X-ray diffusion and Brunauer-Emmett-Teller and Barrett-Joyner-Halenda. The adsorption capacity presents a linear increase as specific surface area increasing. To reveal the process of the adsorption, the adsorption kinetics and isotherms were performed. Pseudo-second-order was found to best represent the kinetics data, which indicated that the process belongs to chemisorption. The equilibrium isotherms data was analyzed by Langmuir model and Freundlich model, which indicated that the Freundlich model was good fitted for the adsorption processes.

Phenol Adsorption from Aqueous Phase onto Prepared Low-cost Carbons from Natural Sources: A Comparative Study

This study demonstrates removal of phenol from aqueous solution using the carbons prepared from the natural sources, i.e. olive-pit, date-pit, and pomegranate-kernel in a batch system. For comparison purpose, the adsorption tests were also carried out on a commercial activated carbon. Influences of effective parameters such as pH, adsorbent dosage, contact time, phenol initial concentration and temperature on the removal of phenol from water were investigated. The optimum conditions for maximum adsorption were determined. In this work, the Langmuir and Freundlich models were chosen to evaluate the adsorption isotherms of phenol. The experimental isotherms showed that Freundlich isotherm fit adequately the experimental data for all adsorbents used. The adsorption data followed closely the pseudo-second-order. In addition, thermodynamic analysis was carried out for phenol adsorption. In this work, the two conventional analysis techniques, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM), were used to investigate the structural and morphological properties of the adsorbents surface.

Efficient removal of phenol from aqueous solutions using hydroxyapatite and substituted hydroxyapatites

Adsorbent materials based on apatites (non-substituted and substituted with Sr and Ba) were used for the adsorption of phenol from aqueous solution at 10, 20 and 30 °C and three pH values (3, 6 and 10.5). Structural studies show the formation of the apatite materials and the replacement of Ca by Sr and Ba. The adsorption isotherms of phenol were determined and modelled with two parameter equations (Langmuir, Freundlich and Temkin) or with three parameter equations (Sips and Dubinin–Radushkevich). Taking into account the Sips isotherm, the maximum amount of phenol uptake was 220 mg g−1 for Ba based adsorbent. Thermodynamic parameters were calculated and indicated that the adsorption of phenol onto prepared apatites was spontaneous and exothermic. The DRIFTS studies detected both phenol and phenolate species adsorbed on the surface. It was also shown that phenol molecules were adsorbed by hydrogen bonding between apatite metal ion or oxygen atom from P–O group and the hydrogen of the phenol functional group. The kinetic data indicate that physical and chemical adsorption, may be involved in the adsorption process.

Study on the preparation of straw activated carbon and its phenol adsorption properties

Using sunflower straw as raw materials to manufacture straw activated carbon-modified by phosphoric acidand adsorption isotherm of phenol on straw activated carbon was studied in a batch reactor. The physical properties of the prepared straw activated carbons were characterized by scanning electron microscopy. The effect of various parameters, adsorbent dose, pH and temperature, were studied on optimum conditions. The results have shown that the absorbent was efficient, the removal ratio of phenol up to 99.36% with an adsorbent dosage of 16 g·L-1, a pH of 6.0-8.0, at 25 °C. The experimental adsorption data fitted reasonably well to the Langmuir isotherm, the maximum adsorption capacity was 109.89 mg/g. The process of adsorption is a exothermic process.

Exceptional Adsorption of Phenol and p-Nitrophenol from Water on Carbon Materials Prepared via Hydrothermal Carbonization of Corncob Residues

Phenol and p-nitrophenol (PNP) are priority pollutants widely present in wastewater. Developing superior or low-cost sorbents for their removal would be of great benefit. Here, corncob residues (CCR) were converted to hydrochars via hydrothermal carbonization (HTC) and further upgraded to carbon materials by thermal activation in an N2 atmosphere. The influence of HTC conditions including the temperature, residence time, and CCR/water weight ratio on the material properties and their performance for removing phenol and PNP from water were investigated and compared with those that were obtained from pyrochar (directly pyrolyzed CCR). Hydrochars showed lower adsorption capacities for phenols than pyrochar. The initial hydrothermal treatment at 220 °C and 2 h resulted in an improved porosity and 4- to 5-fold higher adsorption capacities for phenol and PNP compared with the pyrochar. However, hydrochars prepared at 250 °C or with a prolonged residence time (4 and 6 h) could not be upgraded to high performance carbon materials by thermal activation. The adsorption isotherms of both phenols on the best performance material were well correlated by the Sips model.

Copper(II) and Phenol Adsorption by Cell Surface Treated Candida tropicalis Cells in Aqueous Suspension

An experimental study was performed to determine the feasibility of using physically treated Candida tropicalis cells for sorption of Cu(II) and phenol, the role of competition between phenol molecules and Cu(II). The yeast cells were lyophilized (LC), heat-treated at 65 °C for 24 h (HT1), at 90 °C for 24 h (HT2), and 72 h (HT3), inactivated at 120 °C and 104 kPa for 20 min (PC). The adsorption isotherms were determined in batch system. Experimental equilibrium data were evaluated using Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models by linear and non-linear regression. The adsorbed Cu(II) and phenol amounts by yeast cells were decreased due to the physical treatments of cells. With the increase of biomass dosage from 1 to 10 g L−1, the adsorption efficiency was increased. The Cu(II) adsorption capacity was also determined in the presence of phenol at various initial concentrations, and in these systems, phenol adsorption isotherms were determined. In the presence of phenol, the Cu(II) sorption capacity by lyophilized cells and carbon particles was decreased. The most commonly used sorbent in water treatment is activated carbon with large specific surface; therefore, the results were compared with the experimental data obtained by using activated carbon (AC).

A novel polymeric adsorbent by a self-doped manner: synthesis, characterization, and adsorption performance to phenol from aqueous solution

The organic–inorganic self-doped poly (vinyltrimethoxy silane-ethylene glycol dimethacrylate) (VE resin) was synthesized by solution polymerization, hydrolysis and dehydration condensation. In this method, ethylene glycol dimethacrylate (EGDMA) was used as cross-linked reagent to form a three-dimensional network structure. Then, the system was prepared by radical polymerization in the presence of the hydrolysis of –OCH3 and the dehydration condensation of Si–OH. The maximum adsorption capacity 75.68 mg g−1 was achieved when pH was 6, the contact time 60 min, the adsorbent dose 0.1 g, the initial concentration 3000 mg L−1 and the temperature 293 K. The adsorption kinetics followed the pseudo-second-order kinetic model, and the intra-particle diffusion was but not the only rate-limiting step. Adsorption isotherms of phenol were linearly correlated and found to be well represented by the Freundlich model. Thermodynamic parameters such as changes in the enthalpy (ΔH), free energy (ΔG) and entropy (ΔS) indicated that the adsorption process of phenol on VE resin were physical and exothermic. After four regeneration recycles, the adsorption capacity of VE resin remained at 95.04 % of the initial value, which illustrated that it possessed good regeneration capacity.

Adsorption of Phenol from Aqueous Solutions Using a Hydrophilic Acrylic Ester Resin

Abstract A new hydrophilic acrylic ester resin (MSE-resin) was synthesized by suspension polymerization from methyl methacrylate (MMA), sodium p-styrene sulfonate (SSS), and ethylene glycol dimethacrylate (EGDMA). Batch adsorption studies indicated that the optimum adsorption was achieved when pH was 5, contact time 180 min, adsorbent dose 0.2 g, initial concentration 2,000 mg/L, and temperature 313 K. Experimental data showed a good fit with the pseudosecond-order kinetic model. Intraparticle diffusion analysis indicated that the intraparticle diffusion was involved in the adsorption process, but it was not the only rate-limiting step. Adsorption isotherms of phenol were linearly correlated and found to be well represented by the Freundlich model. Thermodynamic parameters such as changes in the enthalpy (ΔH), free energy (ΔG), and entropy (ΔS) indicated that the process of adsorption phenol on MSE-resin was endothermic and spontaneous.

Preparation of a novel polymeric adsorbent and its adsorption of phenol in aqueous solution

Phenol is one of the most representative pollutants in industrial wastewater, and the designation and development of a novel and valuable polymer adsorbent is one kind of outstanding method to treat phenol aqueous solution. In this study, a new polymeric adsorbent P(MMA-St-NMA) was synthesized and characterized. The affection of solution pH, initial concentration, time, and temperature on adsorption ability of the synthesized polymer adsorbent was then investigated. Based on the analysis of Fourier transform infrared spectra (FT-IR), 1H NMR, 13C NMR, X-ray diffraction, and differential scanning calorimetry, the polymer adsorbent was successfully synthesized. Through the obtained data, the optimum adsorption was achieved when pH was 6, initial concentration 6,000 mg/L, contact time 5 h, and the higher temperature. The adsorption kinetics was found to follow the pseudo-first-order kinetic model. The intra-particle diffusion analysis indicated that particle diffusion was involved in the adsorption process but it was not the only rate-limiting step. Adsorption isotherms of phenol were linearly correlated and found to be well represented by the Freundlich model. Thermodynamic parameters such as changes in the enthalpy (ΔH), free energy (ΔG), and entropy (ΔS) indicated that the adsorption phenol onto P(MMA-St-NMA) was an endothermic and spontaneous process.

Adsorptive Isotherms and Removal of Microbial Inhibitors in a Bio-Based Hydrolysate for Xylitol Production

Adsorption isotherms and thermodynamics of microbial inhibitors generated by the acid-catalyzed hydrolysis of hemicellulose were investigated using activated carbon as the adsorbent. Parameters of temperature (25–65°C) and pH (1.0–10.0) were employed to study the adsorption isotherms of phenol, acetic acid, and furfural. The results based on the Langmuir model indicated that a higher efficiency of adsorption could be achieved at a lower pH and lower temperature for phenol and acetic acid. Furfural removal from the aqueous solution was only dependent on temperature, with a higher performance at 25°C. Negative values obtained for the heat of adsorption (ΔH), entropy (ΔS), and free energy (ΔG) indicated that the adsorption of all three components is exothermic (physisorption) in nature, with a mechanism based on the affinity of the solute toward the adsorbent and non-spontaneous. The adsorptive removal of the main inhibitors (8.7 g/L phenols and 4.2 g/L acetic acid) from the concentrated hydrolysate of oat hull hemicellulose was dependent on the activated carbon dosage, temperature, and pH. Under operational conditions of pH 1.0 and 25°C with an incremental carbon dosage of 1.25–5% in the hydrolysate, the removal of phenols was 64–95.4% and that of acetic acid was 6–13.2%, respectively. The xylitol fermentation process indicated that oat hull hemicellulosic hydrolysate is low in toxicity to Candida guilliermondii. Meanwhile, a mild adsorptive detoxification using activated carbon resulted in over 10% increase in xylitol yield (≈ 0.8 g/g) and productivity (0.5 g/L/h).

Thermodynamic Study of Adsorption of Phenol, 4-Chlorophenol, and 4-Nitrophenol on Activated Carbon Obtained from Eucalyptus Seed

Activated carbons from shell eucalyptus (Eucalyptus globulus) were prepared by chemical activation through impregnation with solutions of two activators: sulfuric acid and sodium hydroxide, the surface areas for activated carbons with base were 780 and 670 m2 g−1and the solids activated with acid were 150 and 80 m2 g−1. These were applying in adsorption of priority pollutants: phenol, 4-nitrophenol, and 4-chlorophenol from aqueous solution. Activated carbon with the highest adsorption capacity has values of 2.12, 2.57, and 3.89 on phenol, 4-nitrophenol, and 4-chlorophenol, respectively, and was activated with base. In general, all carbons adsorption capacity was given in the following order: 4-chlorophenol > 4-nitrophenol > phenol. Adsorption isotherms of phenols on activated carbons were fitted to the Langmuir, Freundlich, and Dubinin-Radusckevisch-Kanager models, finding great association between them and experimental data. A thermodynamic study was performed, the exothermic nature and spontaneous nature of the adsorption process were confirmed, and the favorability of adsorption on activated carbons with NaOH was confirmed by energy relations and concluded that the adsorption process of phenolic compounds from the activated carbon obtained is physical. The pH of solutions and pH at point of zero charge of the solid play an important role in the adsorption process.

Preparation and adsorption studies ofβ-cyclodextrin grafted onto multi-walled carbon nanotube

BACKGROUND In this study, a novel adsorbent based on multi-walled carbon nanotubes was synthesized by reacting with the modified β-cyclodextrin and was developed for the removal of contaminants from aqueous solutions. RESULTS The characteristic results of Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H NMR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) showed that β-cyclodextrin was grafted onto the surface of multi-walled carbon nanotubes. The adsorption experiments of Cr (VI) and phenol demonstrated that the performance for the removal of phenol and Cr (VI) was enhanced significantly due to the multiple hydroxyl groups and the hydrophobic cavity in β-cyclodextrin forming complexes with metal ions and organic pollutants. The adsorption isotherms of Cr (VI) and phenol onto MWCNTs/β-CD fitted the Langmuir isotherm model and maximum adsorption capacity was 9.74 mg g−1 for Cr (VI) and 100.27 mg g−1 for phenol. CONCLUSIONS These results demonstrated that the novel adsorbent was a suitable material for the preconcentration and separation of inorganic and organic pollutants from aqueous solutions during environmental pollution cleanup. © 2014 Society of Chemical Industry

Phenol photocatalytic degradation over anisotropic TiO2 nanomaterials: Kinetic study, adsorption isotherms and formal mechanisms

Anisotropic TiO2 nanomaterials (nanotubes, nanorods, nanoplates, nanospheres, and nanoparticles) with controlled structural and textural properties have been evaluated in the photocatalytic degradation of phenol under UV conditions. The kinetic study of phenol adsorption fits well to a quasi-second-order model whereas the adsorption isotherms of phenol over the different TiO2 nanomaterials follow the Langmuir model and the degradation kinetics the Langmuir–Hinshelwood (L–H) model. TiO2 nanomaterials exposing (001) or (101) anatase facets are less active than TiO2 P25 for the phenol degradation. This is related to their tendency to degrade faster intermediates products (organic acids) rather than phenol itself. A good compromise between anatase crystallinity, crystallites sizes, and specific surface area can however improve the photocatalytic activity of the TiO2 nanomaterials. Results also showed that the degradation mechanism follows pseudo-first order kinetics. Pseudo-rate constants were therefore determined and formal mechanism schemes proposed.

Removal of phenol from aqueous solutions by adsorption onto Mn–Ce–K solids

Mn–Ce solids were used for the adsorption of phenol from aqueous solution at 25 and 50 °C. The samples were prepared with a Mn–Ce molar ratio between 0 and 100 % by the alkaline co-precipitation method (KOH). Structural studies showed the formation of cryptomelane, Mn2O3, Mn5O8, Mn3O4 and CeO2. The formation of different phases is a function of the Ce concentration. The adsorption isotherms of phenol were determined and modelled with Langmuir and Freundlich equations. Sample 7/3 had a high adsorption capacity. Thermodynamic parameters, in flat and vertical position of phenol, were calculated. These parameters indicated that the adsorption of phenol onto Mn–Ce was spontaneous and exothermic. The DRIFTS study detected of both phenol and phenolate species adsorbed on the surface and the aromatic ring of phenol is parallel to the surface. The interaction between Mn and Ce enhanced the reducibility of the oxides and activated oxygen, which is favorable for the adsorption process.

Regeneration of a silica monolithic rod column using harsh methods followed by firm thermodynamic and kinetic validation

In this study, a numerical tool is introduced--based on thermodynamic and kinetic separation theory--for validating the regeneration of monolithic rod columns after cutting their inlet sections. A long-used RP-18e monolithic column was deemed to be unfit for further coffee analysis because of poor separation performance. The columns brownish inlet section was physically removed with a lathe, leaving a clean white inlet section. The original and regenerated columns were extensively analyzed and compared using numerical tools for processing adsorption data. The perturbation peak method was used to measure the adsorption isotherm of phenol on the original and regenerated monolith and the adsorption energy distributions were calculated for identifying any change in the degree of heterogeneity. Although peak shapes improved considerably after regeneration, no significant differences were found in the detailed characterization of the processed adsorption data between the original column and the regenerated one. This indicates that the removal of a section of the monolithic bed can be undertaken without damaging the column and columns in which their inlet head sections are contaminated may still function with normal adsorption behavior. In addition, the combined thermodynamic and kinetic methodology could accurately be used to evaluate any regeneration method of columns.

Study of adsorptive removal of phenol by MOF-5

Phenol adsorption experiments were conducted at constant temperature under oscillation conditions. The effects of the initial concentration of the aqueous phenol solution, temperature, adsorbent dosage, and initial pH of the solution on the removal rate were investigated. For an initial concentration of the aqueous phenol solution in the range 25–200 mg/L, a temperature of 40°C, a neutral solution, and a ratio of adsorbent/phenol in the range 40:1 to 2.5:1, the removal rate of phenol was 97% or more. The adsorption isotherm of phenol with MOF-5 followed the Langmuir and Freundlich models, with relative coefficients of 0.9855 and 0.9960, respectively. The adsorbent was recycled by soaking and washing with ethanol, and the recycled adsorbent gave good results after being reused six times.