The cellulose matrix was characterized by FTIR, 13C NMR, XRD, TG, SEM and applied in the removal of the reactive red RB dye in an aqueous medium, with a capacity of adsorption at a pH of 2.0, and an adsorption equilibrium time which was reached at around 200 mins. The kinetic study for the system followed the Elovich model. The adsorption isotherms for the system at temperatures of 35°C, 45°C, and 55°C were adjusted to the Langmuir, Freundlich, Sips, and Redlich-Peterson non-linear models, with a capacity of adsorption for adsorbent of 5.97 mg g-1, 5.64 mg g-1, and 4.62 mg g-1, respectively. The adsorption occurred by electrostatic interactions and it was favorable and spontaneous, with the influence of temperature.
This work is a systematic review of the literature over the past decade of the application of activated carbon (microporous or mesoporous) as adsorbents for the removal of heavy metals, focusing especially on lead (Pb) and arsenic (As) ions from the aqueous phase. Classical examples from our lab are also given. Activated carbon is known to provide a high surface area for adsorption. Generally, surface modification is typically required, such as oxidation, treatment with ammonia or even impregnation with ferric ion, etc. and the adsorbent material may originate from various sources. The pristine materials, after modification and those after batch-wise adsorption, were characterized by available techniques (BET analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, thermal analyses, X-ray photoelectron spectroscopy). Adsorption isotherms, thermodynamics and kinetics of the process are also discussed. Selected studies from the literature are examined in comparison with other adsorbents. The role of chemistry in the metals adsorption/removal was investigated.
In this study, we evaluated the effectiveness of cadmium and zinc adsorption and desorption from solutions containing single metals and a mixture of metals in the ratio of 1:2 by activated sludge immobilized onto chitosan (ASC). The optimal pH value determined for metals adsorption ranged from pH 5 to pH 6, whereas that established for desorption reached pH 2. In the case of individual metals, the state of adsorption equilibrium in the solution was achieved after 180 min, whereas in the case of a metal mixture – after 270 min. In the case of desorption, the state of equilibrium was achieved after 45 min. It was stated that both adsorption and desorption proceeded according to the pseudo-second order reaction. The study enabled determining the maximum adsorption capacity based on Langmuir, Freundlich and Sips models. The Sips model was found suitable for the description of adsorption of single metals onto ASC, whereas both Sips and Freundlich models – for description of the adsorption of a metal mixture, which was indicated by the determined values of R2 coefficient. The adsorption capacity of ASC determined from Sips model for individual solutions of cadmium and zinc reached 216 and 188.3 mg/g d.m., respectively, whereas that determined for their mixture reached 106 mg/g d.m. for both metals.
In this study, we investigated the effectiveness of Reactive Black 5 dye adsorption onto chitin and chitosan flakes. Adsorption capacity of chitin and chitosan, optimal pH of the adsorption process and reaction equilibrium time were determined. Results achieved were described with Freundlich, Langmuir and double Langmuir models. The pH value ensuring the highest dye adsorption effectiveness onto chitosan was pH 4. In turn, the highest dye adsorption effectiveness onto chitin was determined at pH 2, however considering that the pH value of industrial wastewater containing reactive dyes ranges from pH 3 to pH 4, further analyses with chitin were continued at pH 3. The time needed to reach the equilibrium concentration of dye was 360 min for chitin and 72 hours for chitosan. The study demonstrated that chitosan is the most effective sorbent of RB5. Its maximum adsorption capacity of the reactive dye accounted for 696.99 mg/g d.m., compared to 131.56 mg/g d.m. determined for chitin. Higher effectiveness of RB5 removal by chitosan is result of more number of amine groups in the chemical structure of this polymer, compared to chitin.
In clinical practice for the treatment of obesity, several natural macromolecular compounds are used, whose operation is based on supporting weight loss. During the use of dietary supplements containing chitosan, disease sometimes occurs and treatment for this often comprises different therapeutic agents and antibiotics. The aim of our study was to determine the binding capacity of simvastatin to chitosan, which is found in dietary supplements promoting weight loss, depending on variable physicochemical factors in the gastrointestinal tract model. The phenomenon of adsorption of simvastatin was investigated by a static and dynamic pharmaceutical model (according to the Modified method of Polish Pharmacopoeia IX) simulating the conditions in vitro. The amount of bound drug is used to calculate the average percentage of the adsorbed dose. The obtained results showed that simvastatin is adsorbed by chitosan in the used pH ranges, and the binding capacity is dependent on the environmental pH, viscosity, the concentration of the drug, the type of chitosan and additional substances present in the gastrointestinal tract. The average adsorption of simvastatin in the system of chitosan-nutrients, depending on the pH of the medium, was in the range of 27 to 95%. The highest amount of adsorption was noted above pH 7 (chitosan precipitated polymer forming the emulsion-gel system), when the bioavailability of dietary supplement using chitosan was almost zero.
Multilayer clustering based adsorption model (uniBET) is aimed at adsorption phenomena modeling with having regard to surface geometrical and energetical heterogeneities. Facilitation of the uniBET model formulas leads to the LBET class models. A review on uniBET model and the analysis of the multilayer heterogeneous adsorption models for characterization of porous materials of carbonaceous origin are presented.
The components of fresh vegetable oils are mainly non-polar. During frying of food, complex and multistage reactions occur in the oil, which produce various polar compounds. Active carbons are characterized by small contents of polar functional groups, which are responsible for adsorbing such polar compounds. Effective purification of the used frying oils must involve the removal of the polar substances. To improve the quality of the used palm oil, an active carbon oxidized by a hydrogen peroxide treatment was used. Such a carbonaceous adsorbent improves the quality of the oil used for frying food by purifying it from colour substances, lipid hydrolysis products, oxidation products and total polar compounds.
Searching for new refrigerants is one of the most significant scientific problems in refrigeration. There are ecological refrigerants commonly known: H2O and CO2. H2O and CO2 known as natural refrigerants, but they have problems:a high freezing point of H2O and a low triple point of CO2. These problems can be solved by the application of a hybrid sorption-compression refrigeration cycle. The cycle combines the application possibility of H2O in the high temperature sorption stage and the low temperature application of CO2 in the compression stage. This solution gives significant energy savings in comparison with the two-stage compressor cycle and with the one-stage transcritical CO2 cycle. Besides, the sorption cycle may be powered by low temperature waste heat or renewable heat. This is an original idea of the authors. In the paper an analysis of the possible extension of this solution for high capacity industrial refrigeration is presented. The estimated energy savings as well as TEWI (Total Equivalent Warming Impact) index for ecological gains are calculated.
In clinical practice, in the treatment of obesity, a plurality of natural high-molecular compounds are used, the activity of which supports weight loss. During the use of dietary supplements containing chitosan, illness sometimes develops and other therapeutic agents are applied as antibiotics The aim of our study was to determine the binding capacity of the antibiotic erythromycin depending on variable physicochemical factors, in the model of the gastrointestinal tract, by chitosans found in slimming dietary supplements Erythromycin adsorption phenomenon was studied by static and dynamic pharmaceutical model (according to the modified method of the Polish Pharmacopoeia) simulating in vitro conditions. The amount of bound drug was used to calculate the average percentage of the adsorbed dose. The results obtained show that erythromycin is adsorbed by chitosans at various pH ranges, and the binding capacity of the environment depends on the pH, viscosity and concentration of the antibiotic, as well as the chitosan and type and additional substances present in the gastrointestinal tract. The average level of the adsorption of erythromycin in the chitosan-nutrients system depends on the pH of the medium. The highest amount of adsorption was noted above pH 7 (chitosan precipitated polymer forming the emulsion-gel system).
In clinical practice a lot of natural macromolecular compounds which operation is based on assisting weight loss are used in the obesity treatment. These measures swell in the digestive tract and form the polymer gel system, which has the ability to adsorb up to 5 times more lipids relative to its own weight. When using dietary supplements containing chitosan, sometimes it comes to illness and in the therapy other agents such as chemotherapeutics are used. The aim of our study was to determine the binding capacity of chemotherapeutic norfloxacin present in the digestive tract model by chitosans found in slimming medicines, depending on variable physico-chemical factors. Phenomenon of norrfloxacin adsorption was studied by a dynamic pharmaceutical model simulating in vitro conditions. The amount of adsorbed chemotherapeutic agent by chitosan was calculated by the difference in concentrations of study drug before and after sorption. The results of measurements of quantities bounded norfloxacin were used to calculate the average percentage of adsorbed dose. The results show that norfloxacin is adsorbed by the chitosans in the applicable pH ranges, and the binding capacity depends on the pH, viscosity and concentration of chemotherapeutics, as well as the type of chitosan and additional substances in the gastrointestinal tract. The average amount of chemotherapeutic adsorption in the system chitosan-nutrients, depending on the pH ranged from 80 to 98%. The highest number of adsorption points above pH 7. In conclusion, the addition of dietary supplement such as chitosan reduces the amount of administered uniformly chemotherapeutic and simultaneously has a large impact on the bioavailability. The observed dependence may require changes in therapeutic process.
Potential theory of adsorption was used for description of adsorption isotherms of n-butane on microporous active carbon. It was shown that characteristic curve of adsorption can be treated as specific form of thermal equation of adsorption giving the possibility to calculate and predict both equilibrium and thermodynamic characteristics of adsorption in wide range of temperature and relative pressure. The results can be used for the design of adsorption systems and for predicting adsorption equilibrium behavior of binary and/or multicomponent gaseous mixtures on active carbon under wide range of conditions, without time consuming and expensive experimental determination.
The removal of Ni2+ from aqueous solution by magnetic multiwalled carbon nanotube nanocomposite (MMWCNTs-C) was investigated. MMWCNTs-C was characterized by X-ray Diffraction method (XRD), High-Resolution Transmission Electron Microscopy (HRTEM), surface area (BET), and Fourier Transform-Infrared Spectroscopy (FTIR). The effects of initial concentration, contact time, solution pH, and temperature on the Ni2+ adsorption onto MMWCNTs-C were studied. The Langmuir and Freundlich isotherm models were applied to fit the adsorption data. The results showed that the adsorption isotherm data were fitted well to the Langmuir isotherm model with the maximum monolayer adsorption capacity of 2.11 mg g–1. The adsorption kinetics was best described by the pseudo-second-order model. The thermodynamic parameters, such as ΔHo, ΔGo and ΔSo, were also determined and evaluated. The adsorption of Ni2+ is generally spontaneous and thermodynamically favorable. The values of ΔHo and ΔGo indicate that the adsorption of Ni2+ onto MMWCNTs-C was a physisorption process.
In this study, we tried to characterize a kind of low crystallinity carbon materials. The structure of polyparaphenylene(PPP)-based carbon was analyzed by means of high energy X-ray diffraction using the apparatus of SPring-8. The experimental results revealed the existence of basic structural units (BSU) in the highly disordered materials like PPP-based carbon. It is thought that the PPP-based carbons consist of small turbostratic particles, which have a few piled up poly-aromatic layers. The structure of the PPP-based carbon which seemed to be amorphous was estimated to have hexagonal carbon layers with the size of up to 1 nm. The pores in the PPP-based carbon seem to be clearances formed among the BSUs and amorphous carbon. The pore size of PPP-based carbon was estimated from the result of N2 absorption measurement. The experimental results suggested that the lithium ion charge mechanism in the PPP-based carbon differs from that in graphite.
The ability of simple molecular building blocks to form extended ordered patterns by adsorption and self-assembly on solid substrates is an advantageous property that has been widely used to create nanostructured surfaces. In this contribution we demonstrate how the lattice Monte Carlo simulation method can be used to predict morphology of adsorbed overlayers comprising simple functional cross-shaped molecules resembling phthalocyanines and porphyrins. In particular, we focus on the influence of the distribution of active interaction centers within a model crossshaped molecule on the structure of the resulting molecular networks. Additionally, we investigate how using racemic mixtures of input prochiral molecules affects the chirality and porosity of the corresponding ordered patters. The obtained results show that suitable manipulation of the chemistry of cross-shaped building block allows for the controlled creation of largely diversified molecular porous networks.
This paper presents the feasibility for the removal of methyl orange (MO) dye from aqueous solution using an activated carbon prepared from Prosopis juliflora bark. Batch adsorption experiments were carried out as a function of pH, contact time, adsorbate concentration, adsorbent dosage and temperature. The commonly applicable isotherms namely Freundlich and Langmuir equations are used for the prediction of isotherm parameters. A comparison of linear least-square method and a trial-and-error non-linear method are examined in Freundlich and Langmuir (Four forms) isotherms. The nature of adsorption isotherm feasibility was evaluated with dimensionless separation factors (RL). The dynamics of adsorption process was analyzed with Lagergren’s Pseudo-first order and Pseudo-second order kinetic equations. Thermodynamic parameters like the change in enthalpy (ΔHo), change in entropy (ΔSo) and change in Gibbs free energy (ΔGo) were evaluated and ΔGo shows a negative value whereas ΔHo shows the positive value indicating that the adsorption process was spontaneous and endothermic in nature. The functional group characterization of the adsorbent was done using Fourier transform infrared spectroscopy (FTIR). The thermal stability of activated carbon was analyzed using Thermo gravimetric analysis (TGA) and Differential thermal analysis (DTA).
This paper presents the adsorption of dyes – the anionic Reactive Black 5 (RB5) and cationic Basic Violet 10 (BV10) dyes – on activated carbon (AC) immobilised on chitosan (CHs). The results were compared with the removal efficiency of RB5 and BV10 on the individual sorbents: chitosan beads and activated carbon. In this study, the sorption capacities of the sorbents, sorption pH and the point of zero charge (pHZPC) were determined. For the description of the obtained results, the Freundlich, Langmuir and double Langmuir models were used. The results show that the developed sorbent (CHs-AC) is effective for both types of dye (RB5 or BV10) over a broad pH range 4–10, which makes it a universal sorbent. The maximum sorption capacity of CHs-AC with RB5 was 639.8 mg/g, while for BV10 it was 50.7 mg/g.
The article presents the effectiveness of phosphate adsorption on the flakes of chitin and chitosan. Studies performed determined adsorption capacity of chitin and chitosan, best among the tested adsorption pH and the equilibrium time. Langmuir model was used to describe the results. The highest removal efficiency of phosphorus compounds using chitin was obtained at pH 3 and with chitosan at pH 4. The study of phosphate equilibrium concentration time obtained for both sorbents was carried out at three concentrations of 1, 5 and 10 mg/dm3. The highest sorption efficiency of the phosphate using chitin was achieved after 20 minutes of the process and at the chitosan after 40 minutes. In the case of chitosan after the equilibrium time the effect of partial P-PO4 release was observed, which could be related to the change in pH of the solution by the sorbent. Studies have shown that chitosan is a more effective absorbent for phosphorus compounds. The maximum adsorption capacity of chitosan with phosphate was 6.65 mg/g, and chitin - 2.09 mg/g.
We study a model for a monolayer single adsorbate system used to describe pattern formation on adsorbates with lateral interactions, when it is submitted to pressure oscillations. Through numerical and analytical (based on a two-state approximation) methods to analyze the existence of stochastic resonance in such a bistable system. This is a first step toward the study of resonant phenomena in adsorbate systems with moving fronts and/or with presence of micro-reactors or spots.
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