Dubinin-Radushkevich Adsorption Models Research Articles

Study of the adsorption process between the phenolic compound catechin and the dietary fiber zymosan A: The influence of pH and concentration

Polyphenolic compounds have shown various beneficial effects on human health as well as certain bioactivities such as interactions with dietary fiber. Factors that can influence their interactions with dietary fibers include the pH value, the polyphenolic compound concentration, and compound stability. The aim of this work was to study the interactions between the polyphenolic compound catechin and the dietary fiber zymosan A from yeast through investigation of the adsorption process. The catechin stability and the influence of concentration and pH value on interactions were investigated. Catechin showed the lowest stability at pH 7.0 with degradation ratio from 6 % to 15 %. The lowest adsorption capacity was at pH 7.0, then higher in water and the highest at pH 1.5. A Dubinin-Radushkevich adsorption model fit to the data and FTIR analysis indicates the presence of physical interactions between catechin and zymosan A. This study can contribute to better understanding of interactions of polyphenols and dietary fiber for possible design of functional food, or to increase bioaccessibility of polyphenols.

Ecological Sorption of Iron and Sulfate Ions onto Starch and Chitosan Biopolymer Blend

Providing safe drinking water free of heavy metal ions like iron and oxyanions like sulfate has become a worldwide issue. Starch, as one of the widely cheapest and available biomaterials, has demonstrated its capability to adsorb heavy metal ions from water in various scientific research, but in low adsorption rates. Therefore, this paper aims to prepare a biopolymer based on a starch–chitosan blend to raise the adsorption efficiency of starch. Two types of chitosan were used to modify potato starch (ps): low molecular chitosan (ch60) and high molecular chitosan (ch4000). Nano potato starch (n.ps) was prepared from potato starch and was also modified with both chitosans. The surface property, the morphology, the particle size, and the structure of the samples were analyzed. Moreover, the investigation of the samples by the zeta potential and charge density were evaluated to determine the charge of the adsorbents’ surface. Furthermore, the pseudo first order (PFO) and pseudo second order (PSO) were employed to examine the adsorption kinetic. The adsorption isotherms of Fe2+/3+ and SO42− were fitted employing Langmuir, Sips, and Dubinin-Radushkevich adsorption models. The maximum achieved sorption capacities from the FeSO4 solution for Fe2+/3+ were as follows: 115 mg/g for n.ps & ch4000, 90 mg/g for ps & ch4000, 80 mg/g for n.ps & ch60, and 61 mg/g for ps & ch60. Similarly, for SO42−, it was 192 mg/g for n.ps & ch4000, 155 mg/g for n.ps & ch60, 137 mg/g for ps & ch4000, and 97 mg/g for ps & ch60.

Adsorption of Nickel(II) Ions by Natural Zeolites Type

The adsorption of nickel (II) ions by natural zeolites of the Sokirnitskoe (Transcar-pathia, Ukraine) and Kholinskoye (Eastern Transbaikalia, Russia) deposits has been studied. According to X-ray phase analysis data, the zeolite-containing sample of the Sokirnitskoe deposit contains at least 75 wt. % clinoptilolite and impurity rock - quartz SiO2. The sample of the Kholinskoye deposit consists of heulandite (not less than 75 wt. %), as well as an impurity rock - potassium spar KAlSi3O8. The assessment of the ad-sorption capacity of zeolites with respect to nickel (II) ions was carried out on the basis of the analysis of adsorption isotherms. The pH of the medium of the studied aqueous solutions was 5.5–5.8. The value of ad-sorption of nickel (II) ions by heulandite is twice that for clinoptilolite and amounts to 0.104 mmol/L. The adsorption of nickel (II) ions was investigated using the Langmuir, Freundlich and Dubinin-Radushkevich models. On the basis of the Dubinin-Radushkevich adsorption model, the values of the free energy of adsorption are determined. That indicates the physical nature of the interaction of the adsorptive and the adsorbent, in the case of the zeolite of the Sokirnitskoe deposit. It is shown that the adsorption of nickel (II) ions by the zeolite of the Kholinskoye deposit proceeds according to the ion-exchange mechanism. This explains the higher adsorption values of nickel (II) ions by this sample.

Eco-Friendly Electroless Template Synthesis of Cu-Based Composite Track-Etched Membranes for Sorption Removal of Lead(II) Ions

This paper reports the synthesis of composite track-etched membranes (TeMs) modified with electrolessly deposited copper microtubules using copper deposition baths based on environmentally friendly and non-toxic reducing agents (ascorbic acid (Asc), glyoxylic acid (Gly), and dimethylamine borane (DMAB)), and comparative testing of their lead(II) ion removal capacity via batch adsorption experiments. The structure and composition of the composites were investigated by X-ray diffraction technique and scanning electron and atomic force microscopies. The optimal conditions for copper electroless plating were determined. The adsorption kinetics followed a pseudo-second-order kinetic model, which indicates that adsorption is controlled by the chemisorption process. A comparative study was conducted on the applicability of the Langmuir, Freundlich, and Dubinin-Radushkevich adsorption models to define the equilibrium isotherms and the isotherm constants for the prepared composite TeMs. Based on the regression coefficients R2, it has been shown that the Freundlich model better describes the experimental data of the composite TeMs on the adsorption of lead(II) ions.

Адсорбционные свойства по отношению к метану функционального пористого материала на основе отходов кофе

A new microporous carbon material (MUM-51) was obtained from waste coffee grounds by carbonization and activation of KOH. MUM-51 has been characterized by various methods, including N2 adsorption-desorption at 77 K, X-ray diffraction analysis, Fourier transform IR spectroscopy, and Raman spectroscopy. Methane adsorption was studied on the resulting adsorbent at pressures up to 10 MPa and temperatures of 298.15, 303.15, 308.15, 313.15, 318.15, and 323.15 K. The specific pore volume of the adsorbent according to DFT is VDFT = 1.604 cm3/g. The BET specific surface is SBET = 3456 m2/g. The maximum value of methane adsorption at a temperature of 298,15 K and a pressure of 10 MPa reaches ~ 19 mmol/g. Experimental data on methane adsorption on MUM-51 were analyzed using the Dubinin–Radushkevich adsorption model in the temperature range 298.15 – 323.15 K and pressures up to 10 MPa. It has been established that the average relative deviations between the experimental results and the results obtained using the Dubinin-Radushkevich model are less than 3%. The initial differential molar heat of methane adsorption on the MUM-51 adsorbent is 28.7 kJ/mol. The results of the work showed that the carbon material obtained from waste coffee grounds, which has a high specific surface area and porosity, can be effectively used as an adsorbent for greenhouse gases, in particular methane.

Сорбционная емкость углеродного материала на основе полимерного сырья по отношению к метану

The carbon material was synthesized from polymer raw materials (MC-032). He MC-032 has been characterized by various methods, including N2 adsorption-desorption at 77 K, X-ray diffraction analysis, Fourier transform IR spectroscopy, and Raman spectroscopy. The resulting adsorbent has a well-developed porous structure (SBET = 2722 m2/g; VDFT = 1.08 cm3/g). The adsorption of methane was studied in a wide range of pressures at temperatures above the critical one. The maximum adsorption value is ~ 14 mmol/g at 298.15 K and 100 bar. Experimental data on methane adsorption on MC-032 were analyzed using the Dubinin–Radushkevich adsorption model in the temperature range 298.15 – 323.13 K and pressures up to 100 bar. It has been established that the average relative deviations between the experimental results and the results obtained using the Dubinin-Radushkevich model are less than 4 %. It is shown that the differential molar heats of methane adsorption decrease from ~ 25 to ~ 10 kJ/mol. The calculated characteristic adsorption energies are in the range of 5.88 – 6.21 kJ/mol, which indicates that the process of methane adsorption on MC-032 belongs to physical adsorption. MC-032 carbon material has strong adsorption capacity for methane and has good prospects for controlling methane emissions and reducing greenhouse gases.

Fabrication of α-MnO2/Fe-Mn binary oxide nanocomposite as an efficient adsorbent for the removal of methylene blue from wastewater

The development of the safe and cost-effective technologies for treating the dye-polluted wastewater has been a significant focus of researchers. In the light of this, α-MnO2/Fe-Mn binary oxide (α-MnO2/Fe-Mn BO) nanocomposite has been synthesized by a co-precipitation method. It was characterized by the FT-IR, XRD, BET, SEM, EDX, and TEM. The results indicated that the nanocomposite has a spheroid-like surface, a surface area of 92.954 m2/g and an average pore diameter of 2.39 nm. It was used as an adsorbent for the removal of methylene blue (MB) dye from an aqueous medium. The batch experiment revealed that 0.013 g of the nanocomposite can remove 98 % of MB (12.71 mg/L) in 30 min. The pH of the medium was the dominant factor in MB adsorption, where the highest removal efficiency was obtained at pH 4. Incorporation of sodium dodecyl sulfate (SDS) and NaCl decreased the MB adsorption. The adsorption process followed the pseudo-second-order and Elovich kinetic models. The results also fitted well with the Langmuir and Dubinin-Radushkevich (D-R) adsorption models. The maximum adsorption capacity was 89.63 mg/g at 30 °C and the nanocomposite showed good separation and regeneration properties. The removal efficiency decreased by about 20 % through five cycles. The α-MnO2/Fe-Mn BO is therefore considered a promising adsorbent for dyes owing to its high adsorption capacity, high chemical stability, good reusability, and simple synthesis procedure.

"EVALUATION OF OPUNTIA FICUS INDICA AS AN ECONOMIC ADSORBENT FOR ANIONIC RED BEMACID DYE FROM AQUEOUS SOLUTION "

Opuntia ficus indica cladodes (OFIC) were used as an adsorbent for the removal of anionic Bemacid Red (RB) dye from an aqueous solution. The study was performed in a batch reactor under different experimental conditions. The adsorption process was very fast during the first 60 min of phases’ contact at 25 °C, the adsorbent being characterized by an adsorption capacity of 16.721 mg/g at pH 2. The experimental data fitted very well with the pseudo-second-order kinetic model (R2 = 0.994), and the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich adsorption models were applied to describe the adsorption equilibrium isotherms. The thermodynamic parameters: enthalpy (-20.739 kJ/mol), entropy (-0.226 kJ/K.mol) and the Gibbs free energy (-14 to -13.557 kJ/mol) were determined over the selected temperature range (25 to 45 °C). The adsorption using the studied system (OFI cladodes/RB) proved to be an exothermic and spontaneous process.

Exploring a novel family of poly(amide-imide)s as promising cationic sorbents for water remediation

A new monomer 5-(5-(chlorocarbonyl)-1,3-dioxoisoindolin-2-yl) isophthaloyl chloride was synthesized and subsequently condensed with a variety of diamines yielding a novel family of poly(amide-imide)s (PAIs), which were exploited as potential cationic sorbents for water treatment. The synthesized monomer and all PAIs were characterized using Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopic analyses. High thermal stability and molar masses of the whole PAIs family were determined using thermogravimetric analysis (TGA) and gel permeation chromatography (GPC). Decomposition temperatures and char yields were found to be in the range 422-600 °C and 2–57% respectively. X-ray diffraction (XRD) patterns revealed the crystalline nature of PAIs family with few exceptions. PAI-2 was found to be the best contender with 99% optimum adsorption capacity for both Cd(II) and Pb(II) cations at optimal conditions. Adsorption capacities have been improved till 700 and 800 mg/g for Cd and Pb respectively for 100 ppm feed concentration, which depicted the efficiency of adsorbent. Adsorption data of all PAIs fitted well to Langmuir as compared to Freundlich, Temkin and Dubinin-Radushkevich adsorption models and exhibited favorable monolayer adsorption mechanism. The relative uptake of cations by PAIs followed the preferential trend Fe(II) > Pb(II) > Cd(II) > Cu(II) in a mixture of metal ions.

Comparative study of Cadmium adsorption on three contrasting soils from a highly industrialized region

Evaluation of natural soils potentiality to effectively immobilize heavy metals is a fundamental tool for a sustainable management of an industrialized region. Three soil textures from Bahía Blanca Citýs industrial zone (Argentina) were analyzed to quantify Cd adsorption and assess its applicability for industrial land use. Soils textural classes corresponded to sandy loam (M1), sand (M2) and silt loam (M3). Batch adsorption kinetics and isotherms were carried out with a 1:10 soil:solution ratio. Adsorption kinetics was conducted for 240 min at constant initial Cd concentration (250 mg l−1) and varying pH (4–8 range). Adsorption isotherm was done for twenty Cd concentrations (range 0.5 mg l−1 to 460 mg l−1) and contact time of 24 h. Kinetics showed a fast instantaneous initially adsorption. Soil-water partitioning coefficient (Kd) was calculated for each concentration supplied to soils, showing a direct relationship between pH and Kd. Adsorption isotherms plots showed a nonlinear shape for M1 and M2 and a linear shape for M3. The affinity of Cd for soils is in the order: M3 > M1 > M2. Metal retention in M3 was upper than 97.8%. Langmuir, Freundlich and Dubinin-Radushkevich (DRK) adsorption models correctly reproduced experimental data. However, M1 (R2 = 0.992) and M3 (R2 = 0.985) fitted better to Freundlich model. Otherwise, M2 (R2 = 0.981) fitted better to Langmuir adsorption model. M3 presented the highest buffer and Cd retention capacity, possibly related to its clay content. Based on desorption studies, M3 presented the strongest binding site as 95% of metal removal was attributed to specific sorption. Silt loam is the most suitable soil coverage for industrial land of all analyzed soils.

Potential of natural ferruginous manganese (NFM) ore as a natural adsorbent for As(III) removal at low concentration

ABSTRACT The findings of the current work pertain to the assessment of potential of natural ferruginous manganese (NFM) as a green, effective and economic adsorbent for decontamination of As(III) from aqueous media. Several techniques such as SEM coupled with EDX, BET, FTIR and XRD were used to characterise the NFM adsorbent. The adsorption parameters such as pH, contact time, temperature and NFM dose were considered and investigated in detail for the As(III) removal. The adsorption of As(III) was observed to increase with increasing temperature, concentration, adsorbent dosage and contact time of the system. The maximum As(III) adsorption of 1.9 mg g−1 over NFM revealed it to be an effective adsorbent for removing As(III) in the range of 0.45–2.5 mg/L. Langmuir, Freundlich and Dubinin Radushkevich (D-R) adsorption models were used to analyse the adsorption data and the Langmuir model provided the best fit with high regression coefficient (R 2). The time profile studies demonstrated that As(III) uptake followed a pseudo-second-order kinetics while the maximum As(III) removal of 96% was obtained within the first 50 min of contact time within a pH range of 4–6. Thermodynamics results showed that As(III) adsorption by NFM was spontaneous and endothermic in nature. Based on the results, it is claimed that natural NFM can effectively serve as green, economic and potential natural adsorbent for As(III) removal and likewise from the aqueous solutions.

Adsorption of caffeic acid on chitosan powder

Adsorption of caffeic acid (CA) on chitosan (CH) powder from aqueous solution has been investigated to obtain insoluble CA–CH complex powders having different amount of CA. The pseudo-second kinetic model and the Langmuir, Freundlich and Dubinin–Radushkevich adsorption models were used to describe the kinetic and equilibrium adsorption of CA on CH. With the increase of adsorption temperature, the rate of adsorption increased while the amount of adsorbed CA decreased. The Langmuir adsorption model predicted that adsorption of CA takes place on the ionized amino groups of CH. However, with the increase of adsorption temperature the ion-exchange between carboxylic groups of CA and amino groups of CH became moderately difficult. The thermodynamic characteristics of adsorption have been evaluated. CA–CH complex formation was confirmed by FT-IR spectroscopy. With increasing amount of adsorbed CA the CA–CH powder was becoming more hydrophobic. 2,2′-Azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) assay confirmed that CA retained the antioxidant activity when immobilized on chitosan power.

Comparative and Competitive Study of LDH/Diatomite and Chitosan/Diatomite for Adsorptive Removal of Chloride Ion from Aqueous Solution

In this work, two clay-based composites are prepared for the adsorptive removal of the chloride ions from aqueous solutions. These composites are characterized through Fourier transform-infrared spectroscopy, scanning electron microscopy, X-ray fluorescence spectroscopy, and X-ray diffraction analysis. The effects of different parameters such as the contact time, amount of adsorbent, chloride concentration, temperature, and pH are studied by batch experiments. Also the isotherm, kinetic, and thermodynamic of the adsorptive removal of the chloride ions from these two composites are investigated. According to the results obtained, the adsorptive removal of chloride ions is initially rapid, and the equilibrium time is reached after 30 min. The optimal pH value is 7.0 for a better adsorption, and the maximum capacity can be achieved, which is 60.2 mg/g with 1000 mg/L of the initial chloride concentration. The Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich adsorption models are applied to describe the equilibrium isotherms at different chloride concentrations. According to the equilibrium isotherms and the correlation coefficients (R2CDC: 0.9424, R2LDC: 0.996), the process can be described by the Langmuir model, and exhibits the highest removal rate of 97.24% (24.31 mg/g) with 250 mg/L of the initial chloride concentration. The pseudo-first-order and pseudo-second-order, intra-particle diffusion, and mass transfer kinetics models are used to identify the mechanism of the adsorptive removal of the chloride ions. The pseudo-second order model due the correlation coefficients (R2CDC: 0.9217-0.9852, R2LDC: 0.9227-0.9926) can be fitted to the kinetic calculations, and it is applicable for the adsorptive removal of chloride ions by the adsorbents. The thermodynamic calculations show that in a low chloride concentration, the sorption is spontaneous, associative, and endothermic; and in a high concentration, it is unspontaneous, dissociative, and endothermic. The calculated value of free energy (E) for adsorption onto the adsorbents suggests that the reaction rate controls the adsorptive removal of the chloride process rather than diffusion. It can be concluded that these two composites can be used as effective and applicable adsorbents for the adsorptive removal of chloride ions.

Synthesis, morphology, crystallite size and adsorption properties of nanostructured Mg–Zn ferrites with enhanced porous structure

Mg–Zn ferrites with porous cavity structure were produced by sol-gel auto-combustion method utilizing a new mixture of dl-alanine and urea as an organic fuel-reductant. The influence of non-magnetic Zn ions content on the structural, morphological and adsorption characteristics of Mg–Zn NPs has been investigated. It was found that Zn effects the porosity of Mg–Zn ferrospinels. X-ray diffraction analysis confirmed the formation of cubic spinel phase and the crystallite size was calculated by the SSP method, W-H method and modified Scherrer formula. SEM observations revealed mesh-like microstructure with the presence of 1–2 μm macropores and agglomerated nanoparticles. The EDS spectra confirmed the desired chemical composition of ferrites powders. Mössbauer spectroscopy confirmed the valence state of cations and their distribution over the spinel sublattices. The adsorption characteristics of spinel compounds were studied on Congo Red dye removal. The appropriateness of Langmuir, Freundlich, and Dubinin-Radushkevich adsorption models were investigated and the parameters of all models were determined. The observed data fitted well by Langmuir model, indicating that the Congo Red adsorption occurred on a homogeneous surface and that the active surface centers possessed similar energy values. The Dubinin-Radushkevich isotherm model was utilized to calculate the free energy of Congo Red adsorption, i.e. setting in the range 7.81–22.4 kJ/mol and indicating that the Zn content affects the mechanism of Congo Red adsorption onto ferrite surfaces and the removal efficiency is enhanced with the rise in Zn content.

Sodium Salt of the Maleic Acid-Decene-1-Styrene Terpolymer as a Sorbent for Removal of Copper Ions from Water Solution

The study is aimed at investigating the efficiency of the sodium salt of maleic acid-decene-1-styrene terpolymer as a sorbent for the removal of copper ions from aqueous solution. The removal of copper ions on synthesized polymer-sorbent was carried out using a batch experiment method. Sorption of copper ions was studied at different values of the contact time, sorbent dosage, pH and initial concentrations of copper ions. The obtained results have been analyzed in Langmuir, Freundlich, and Dubinin—Radushkevich adsorption models. The equilibrium experimentally measured sorption capacity of the sorbent is 0.512 g·g−1. The calculated value of the maximum experimental sorption capacity from the Langmuir and Freundlich equations is equal to 0.754 and 0.725 g·g−1, respectively. The value of (1/n) in Freundlich equation is between 0 and 1, which indicates that the sorption process is governed by chemisorption. The value of the mean sorption energy calculated from Dubinin—Radushkevich equation also confirms that the sorption of copper ions by synthesized polymer salt has chemical character.

Immobilization of Copper from Aqueous Solution and Contaminated Sediment Using Modified Clinoptilolite

The efficiency and mechanism of modified clinoptilolites immobilizing Cu from aqueous solutions and contaminated sediments were investigated. The results showed that the clinoptilolite modified by lanthanum chloride (LaCl3) at a particle size of 0.5–1.0 mm could remove 65% of Cu2+ from 100 mg L−1 of Cu2+ solutions at the sorbent:solution mass ratio of 1:100. The equilibrium data fitted well to the Langmuir isotherm model with a maximum adsorption capacity of 21.09 mg Cu2+ g−1 at 25 °C. The Dubinin–Radushkevich adsorption model indicated that the adsorption of Cu2+ by modified clinoptilolite can be identified as chemisorption. The pseudo-second-order model could well represent the kinetics of the adsorption. The results of toxicity characteristic leaching procedure (TCLP) and Community Bureau of Reference (BCR) sequential extraction procedure showed that the modified clinoptilolite could reduce the leaching of Cu in the sediment and effectively transform Cu from the acid extractable or reducible fractions to the oxidizable or residual fractions. The presented work showed that the modified clinoptilolite holds great potential to remove Cu2+ from water, and to stabilize Cu-contaminated sediment.

Comparative analysis of removal of crude oil and some refined petroleum products from the environment using rice husk: Adsorption isotherm and kinetic studies

Rice husk a low cost agricultural waste was assessed for its efficiency as an oil spill sorbent by comparing its oil (crude oil, diesel and kerosine) uptake with that of a standard; conventional synthetic sorbent mat used in oil spill clean-up. The experiment was performed under the same experimental condition and procedure. The sorption process of crude oil, diesel and kerosine onto rice husk and the standard was studied using Langmuir, Freundlich, Elovich, Temkin and Dubinin – Radushkevich adsorption models while the sorption kinetics was studied using Lagergren pseudo-first-order, pseudo-second-order, intraparticle diffusion and liquid film diffusion models. Suitable environmental applicability of both sorbents was also studied.. The result of the study shows that rice husk sorbed 3.30g of crude oil, 2.50g of diesel and 1.95g of kerosine per unit mass while the standard sorbed 11.50g of crude oil, 10.34g of diesel and 8.20g of kerosine per uint mass. About 2.46g of crude oil, 1.60g of diesel and 1.57g of kerosine were recovered from a unit mass of rice husk, while, 9.67g of crude oil, 8.40g of diesel and 6.50g of kerosine were recovered from a unit mass of synthetic sorbent mat. The amount of oils retained by a unit mass of rice husk is about 0.84g of crude oil (25 % of absorbed crude oil), 0.90g of diesel (36 % of absorbed diesel), and 0.38g of kerosine (20 % of absorbed kerosine), while, 1.83g of crude oil (15 % of absorbed crude oil), 1.94g of diesel (19 % of absorbed diesel) and 1.70g of kerosine (20 % of absorbed kerosine) were retained by a unit mass of synthetic sorbent mat. The result of the study indicates that the standard is a better sorbent for oil removal than rice husk. Rice husk has the ability to retain sorbed oil which makes it a good sorbent when oil recovery is not required. The sorption process for both sorbents follows the Langmuir isotherm. intraparticle diffusion contributed more than liquid film diffusion in the sorption mechanism for the standard, while the reverse is the case for rice husk. The standard and rice husk can be applied on oil spill clean-up on land and surface waters. Rice husk is not a very efficient sorbent for oil spill mop.

Sorption properties of a copolymer based on divinyl sulphide and 4-vinylpyridine

Organic polymers with N, S-functional groups are widely used as effective materials for the adsorption of transition metal ions. The adsorption of noble metals by copolymer of divinyl sulphide with 4-vinylpyridine has been studied in solutions of mineral acids. The copolymer under study has displayed high values of static sorption capacities, amounting to 1200, 340, 1040, 520 mg/g in Au (III), Ag (I), Pt (IV) and Pd (II), respectively. A comparative study of the Langmuir, Freundlich and Dubinin-Radushkevich adsorption models has been carried out to describe the experimental adsorption isotherms of noble metal ions on the surface of the copolymer under investigation. Constants and parameters of the considered adsorption models have been identified. Analysis of the values of the coefficients of determination R 2 indicates that the adsorption of noble metal ions from sulphuric acid solutions and Ag from nitric acid solutions is most adequately described within the Langmuir model. The obtained results demonstrate that the adsorption of noble metal ions occurs on an energetically heterogeneous surface and represents a monomolecular process.

Sorption capacities of chitosan/polyethylene oxide (PEO) electrospun nanofibers used to remove ibuprofen in water

Abstract Pharmaceutical residues coming from urban wastewater were recognized as a major source of pollution for the aquatic environment. Their occurrence in most municipal effluent seems to indicate that conventional wastewater treatments have only a limited ability to remove such substances from sewage. Therefore, the undesired effects caused by these emergent contaminants on the environment force the authorities to consider new measures to treat and recycle contaminated water. In this study, electrospun nanofibers made of chitosan and poly(ethylene oxide) (PEO) were used to remove the anti-inflammatory drug ibuprofen in solution. The electrospinning parameters such as the mixture solution concentration, applied voltage, distance needle-collector, and flow rate were optimized to get the best nanofiber morphology characterized by scanning electron microscopy (SEM). With the use of a high-performance liquid chromatography with ultraviolet diode array detection (HPLC-UV DAD) system, sorption tests were performed by modifying experimental conditions, e.g. pH, concentration of ibuprofen, and temperature of the tested solutions. Langmuir, Freundlich, and Dubinin-Radushkevich (DR) adsorption models were compared for the mathematical description of adsorption equilibria. Kinetic assays showed that the adsorption of chitosan nanofiber followed a pseudo-second-order model. After 20 min of exposure, 25 mg of nanofiber had removed 70% of the initial ibuprofen concentration.

Functionalization of activated carbons with magnetic Iron oxide nanoparticles for removal of copper ions from aqueous solution

Magnetic activated carbon particles (MACP) were fabricated using a facile co-precipitation method and employed as an adsorbent for the removal of Cu ions from aqueous solutions. The application of magnetic Fe3O4 nanoparticles significantly enhanced the adsorption capacity and regeneration efficiency of the MACP adsorbents. The Fe3O4 magnetite loading onto the carbon matrix is a crucial factor for an efficient removal of copper ions. The Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) adsorption models were used to validate the adsorption isotherms. Both the equilibrium rate constant (Langmuir model) and the adsorption energy (D-R model) show an increase in the deposition of magnetite nanoparticles. The presence of magnetic Fe3O4 nanoparticles further facilitates the regeneration efficiency of Cu-adsorbed intermediates from the MACP adsorbents. Superior magnetic property enabled via the utilization of Fe3O4 nanoparticles significantly enhanced the separation efficiency and regeneration of spent MACP adsorbents. Therefore, the design procedure explained in this work for preparing the MACP adsorbents can be adopted for various environmental applications dealing with separation processes.