Dubinin-Redushkevich Research Articles

High storage capacity of curcumin loaded onto hollow mesoporous silica nanoparticles prepared via improved hard-templating method optimized by Taguchi DoE

The ability of drug carriers, such as silica nanoparticles, to store high-concentrated bioactive compounds like curcumin within their mesoporous structure is technologically and economically advantageous to suppress their amount administered to the human body as little as possible. In this study, we succeeded in synthesizing and formulating a high storage capacity of curcumin loaded onto hollow mesoporous silica (HMS) nanoparticles via an improved hard-templating method which was in tandem with Taguchi design of optimization. The amount of silica precursor (TEOS), ethanol to water ratio, and pH condition are three critical variables used to optimally design nine HMS nanoparticles following the Taguchi approach. The textural properties, including surface area, pore-volume, pore size, hydrodynamic particle size, zeta-potential, and morphology, of the HMS nanoparticles, were discussed in this report. The curcumin adsorption study calculated following Langmuir and Dubinin Redushkevich isotherm models reveals the robustness of Taguchi DoE in providing a contribution of each variable toward adsorption capacity value, in which the amount of silica precursor has the highest contribution value. Moreover, the signal-to-noise (SN) ratio analysis, a feature of Taguchi DoE, indicates that the level 1 of TEOS, level 1 of ethanol to water ratio, and level 3 of pH are the optimal composition to construct HMS nanoparticles with high storage capacity reaching 183.08 mg g−1. The involvement of Taguchi DoE in the synthesis of HMS nanoparticles is not only able to provide the optimal number of procedures but also afford a better explanation of the contribution of each synthesis variable. Moreover, our study is capable to explain the relation of each variable on determining the properties of HMS nanoparticles which are beneficial in designing of effective properties of materials.

Kinetic, isotherm and thermodynamic study of methyl orange adsorption on raw clay from north of Morocco

Clay and clays minerals have highly reactive surface and interesting texture properties that can easily remove organic and inorganic contaminants from wastewaters. In this perspective, this work reports the study of clay-pollutant interactions by using Moroccan clay as absorbents and methyl orange as anionic model of dyes textile. The clay was sampled in the region of Tetouan. Structural and physicochemical properties of the sample were determined by different characterization techniques (XRD, IR, FTIR, SEM, ATG/ADT, BET, and CEC). The results reveal that the raw clay is mainly composed of kaolinite and smectite as clay minerals. The SiO2 / Al2O3 ratio is about 2.4. Its CEC is about 25.34 meq/100g. The specific surface area is about 51.28 m2/g. The adsorption isotherms were carried out using batch conditions. The kinetics adsorption of MO on the clay revealed that equilibrium is rapidly reached. The data were adjusted by four kinetic models: pseudo-first-order, pseudo-second-order, intra-particle diffusion model and Elovich model. The pseudo second-order model was the most adequate to describe the adsorption kinetics of the MO dye. The experimental results were modeled by four models, namely Langmuir, Freundlich, Dubinin Redushkevich (D-R) and Elovich. The adsorption isotherm shows that the Langmuir model perfectly represents the adsorption of methyl orange on the studied clay. The adsorption capacity is high and reach 113 mg/g. The thermodynamic parameters obtained indicate that the adsorption of methyl orange is feasible and spontaneous. The obtained results showed clearly the selected clay could be used as adsorbent of anionic dyes.

Removal of aniline from aqueous solution by activated kaolinite: Kinetic, equilibrium and thermodynamic studies

In this study, the adsorption kinetics, equilibrium and thermodynamics of aniline on native (NK) and acid activated (AK) kaolinites were examined. It was shown that modification of kaolinite with acid not only increases the adsorption capacity of the adsorbent from 109.89 to 256.41 mgg−1for aniline but also its initial sorption rate for aniline, suggesting the activated kaolinite with higher adsorption capacity have great potential application in removal of aniline from water and wastewater. Adsorption efficiency for AK reached at about 91% while it was at about 75% for NK. The kinetics of adsorption of aniline was discussed using three kinetic models, the pseudo-first-order, the pseudo-second-order and the intra-particle diffusion model. The experimental data fitted very well the pseudo-second-order kinetic model due to the higher correlation coefficient and lower sum of squared errors (SSE,%) values, and a good agreement between the experimental and the calculated qe values. Experimental results were also analysed by the Langmuir, Freundlich and Dubinin–Redushkevich (D–R) isotherm models. RL separation factor for Langmuir and the n value for Freundlich isotherm show that aniline are favourably adsorbed by NK and AK. The negative value of ΔG and positive value of ΔS showed that the adsorption of aniline onto NK and AK was feasible and spontaneous. The positive value of ΔH confirmed the endothermic nature of adsorption.

Utilization of paper mill sludge for removal of cationic textile dyes from aqueous solutions

ABSTRACTThe present study is concerned usage of paper mill sludge (PMS) as an effective adsorbent to remove the two cationic character dyes (Basic Blue 3 [BB3] and Basic Yellow 28 [BY28]) from aqueous solutions. The surface morphology and some characteristics of PMS were determined by Fouirer Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Brunauer Emmett Teller (BET). The parameters affecting the process – temperature (10–55°C), adsorbent dose (0.5–10 g/l), initial pH (2–10 pH), initial concentration (50–250 mg/l) and contact time (0–24 h) – were examined in the batch adsorption experiments. Maximum adsorption capacities (qmax) of two dyes at 1 g/l dose and pH value of 7 were also calculated as 89.35 and 79.81, respectively. Adsorption phenomena of BB3 and BY28 cationic dyes onto PMS is controlled by pseudo-second-order model. Thereafter, equilibrium experimental data were applied to Langmuir, Freundlich and Dubinin–Redushkevich (D-R) isotherms, and Langmuir isotherm is the best represent the equilibrium adsorption process for both dyes. The processes occurred by physical adsorption because of calculated activation values (Ea) of BB3 and BY28 dyes were 19.43 and 9.35 kJ/mol, respectively. In addition, based on thermodynamic calculations such as free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°), the results clearly demonstrated that the adsorption process were of exothermic and spontaneous nature for both dyes. At the light of obtained findings, it can be stated that PMS can be used effectively in removal of cationic dyes from textile wastewaters and is an alternative to commercial adsorbents due to its low-cost and abundance in the paper industries.

Thermodynamics and sorption characteristics of Zn(II) onto natural and chemically modified zeolites for agricultural and environmental using

Zeolites with high porous and cation exchange capacity have been widely used for agricultural and environmental purposes. This study was conducted to assess the thermodynamics and sorption characteristics of chemically modified zeolite (CMZ) from obtained natural zeolite (NZ), and to compare its properties. At first step of the sorption experiment, effects of pH, slurry concentration, stirring time, and heat on Zn removal were determined. Linear Langmuir isotherm was well fitted to data, and maximum sorption capacities (q max) were calculated as 20.87 and 33.44 mg/g for NZ and CMZ, respectively. Dubinin-Redushkevich (D-R) isotherm showed that the adsorption process was probably controlled by chemical ion-exchange mechanism. The solubility of zinc DTPA should be so directly related to the model of D-R model. Therefore, zeolites can be used as carrier Zn in soils with insufficient zinc arid and semiarid regions. Enthalpy (ΔH°) and entropy (ΔS°) values were positive. The change values of Gibbs free energy (ΔG°) illustrated that the sorption of Zn ions onto zeolites was feasible and spontaneous. From the obtained results, it could be concluded that chemical modification increased q max value of NZ, and the findings indicate clearly the possibility of using NZ and CMZ as Zn carrier in agricultural and also environmental treatments.

Application of novel metal organic framework, MIL-53(Fe) and its magnetic hybrid: For removal of pharmaceutical pollutant, doxycycline from aqueous solutions

As a pharmaceutical pollutant, doxycycline causes contamination when enters into the environment. In this research MIL-53(Fe), and its magnetic hybrid MIL-53(Fe)/Fe3O4 were synthesized and employed for removal of doxycycline from aqueous solutions. The adsorbents were characterized by XRD, SEM, BET, FTIR, EDAX, VSM and TG-DTG technique. The effect of different variables such as DOC concentration, pH, contacting time, and adsorbent dose on the removal efficiency was studied and under optimized conditions the adsorption capacity of 322mgg−1 was obtained. The adsorption process was kinetically fast and the equilibration was attained within 30min. The used adsorbent was easily separated from the solution by applying external magnetic field. The regenerated adsorbent retained most of its initial capacity after six regeneration steps. The effect of ionic strength was studied and it was indicated that removal of doxycycline from salt-containing water with moderate ionic strengths was quite feasible. Langmuir, Freundlich, Tempkin and Dubinin–Redushkevich isotherms were employed to describe the nature of adsorption process. The sorption data was well interpreted by the Longmuir model.

Impact of contact time, pH, ionic strength, soil humic substances, and temperature on the uptake of Pb(II) onto graphene oxide

ABSTRACTThe uptake of Pb(II) from wastewaters onto graphene oxide was studied as a function of various water quality parameters. The results indicated that uptake was fast and kinetic uptake could be well fitted by a pseudo-second-order model. The uptake was strongly dependent on pH and independent of ionic strength. Namely, inner-sphere surface complexation was the main uptake mechanism. The presence of humic acid or fulvic acid enhanced the uptake at low pH values, while reduced at high pH. The Langmuir, Freundlich, and Dubinin–Redushkevich (D-R) isotherm models were used to simulate the uptake. Thermodynamics indicated that the uptake was endothermic and spontaneous.

Study to observe the applicability of the adsorption isotherms used for the adsorption of medicine organics onto activated carbon

ABSTRACTIn the present study, the activated carbon was prepared by chemically activating polymer waste under the influence of potassium hydroxide (KOH). The pore properties including the Brunauer–Emmett–Teller (BET) surface area, the volume of the pore, its size distribution, and average diameter were also characterized herein. The present study also evaluated the ability of the activated carbon to remove naproxen sodium, tannic acid, and caffeine from aqueous solutions through a process of adsorption. The equilibrium isotherms employed for the adsorption of drug organics onto the activated carbon were measured experimentally. The obtained results were analyzed by employing the Redlich–Peterson, Dubinin–Redushkevich, Temkin, Frumkin, Halsey, and Henderson equations by using a linearized correlation coefficient and statistically at varied temperatures. The models and the isotherm constants were evaluated based on the changes in the temperature. Among all, the Redlich–Peterson equation was determined to best represent the equilibrium data for the adsorption of naproxen sodium, and caffeine onto the activated carbon.

β-carotene rejection mechanism from organic medium by using activated carbon produced from waste biomass apricot

ABSTRACTThe present paper deals with the study of adsorption of β-carotene in tetrahydrofuran solution on activated carbon. Activated carbon was prepared from apricot waste, which is a by-product of apricot processing by means of chemical activation with ZnCl2. BET surface area of activated carbon was measured to be 1060 m2 g−1. The effect of adsorption time, percentage of activated carbon in β-carotene solution, and β-carotene concentration on adsorption efficiency was also determined. Results were analyzed by the Langmiur, Freundlich, Dubinin−Redushkevich (D-R), Temkin, Frumkin, Harkins−Jura, Halse, Henderson, and Henry isotherms with linearized correlation coefficient. The characteristic parameters for each isotherm have also been determined. The kinetics of β-carotene adsorption has been discussed by the pseudo-first-order model, the pseudo-second-order model, the Elovich equation, the intraparticle diffusion model, the Bangham equation, and the modified Freundlich equation. Three error analysis methods of residual mean square error (RMSE), chi-square statistic (χ2), and the average percentage error (% APE) have been used.

Functionalized nanocrystalline cellulose: Smart biosorbent for decontamination of arsenic

This study explored the adsorption capacity of diethylene triamine grafted dialdehyde nanocrystalline cellulose (DETA-g-DA-NCC) for As (III and V) removal from aqueous solution. Nanocrystalline cellulose (NCC) was selectively oxidized using sodium periodate followed by grafting of diethylene triamine (DETA) to obtain their amine derivatives in 80–85% yield. A corresponding increase in carbonyl content of the dialdehyde nanocrystalline cellulose (DA-NCC) with the increase in oxidant concentration was measured by titrimetric analysis and was evidenced by FT-IR spectroscopy. Morphological integrity and crystallinity of the NCC were maintained after the functionalization as studied by AFM, SEM and XRD, respectively. The effect of various operational parameters such as arsenic ion concentration, pH, biosorbent dosage and time was investigated using batch experiments and found that DETA-g-DA-NCC can be used as a cost effective biosorbent for decontamination of arsenic. The experimental data were analyzed by Langmuir, Freundlich, Temkin and Dubinin–Redushkevich (D–R) models of sorption. The sorption isotherm data were fitted well to Langmuir isotherm. The kinetic data were fitted very well in the pseudo-second-order kinetic model and suggested that the chemisorptions were the rate-limiting step. The results indicate that there is significant potential for DETA-g-DA-NCC as a biosorbent for arsenic removal [As(III) 92.84% and As(V) 97.86%] from aqueous solutions.

Multimetal biosorption modeling of Zn2+, Cu2+ and Ni2+ by Sargassum ilicifolium

The biosorption process of Zn2+, Cu2+ and Ni2+ by Sargassum ilicifolium was studied in single and ternary systems. Experimental parameters such as biosorbent dose, pH and time were analyzed using response surface methodology (RSM). The overall biosorption data were best described by the pseudo second-order kinetic model. The biosorption process was slightly slower in the ternary system comparing with single system which was related to competition phenomena between metal cations in solution. In single and ternary systems, the Dubinin–Redushkevich (D–R) isotherm showed a better fit with the following sorption order: Zn2+>Ni2+>Cu2+. FT-IR analysis revealed that carboxylic function group would be the active binding site. In addition, the effectiveness of the biomass was investigated in several sorptions–desorption cycles using HCl.

Removal of hexavalent chromium from aqueous solution by barium ion cross-linked alginate beads

Barium ion cross-linked alginate beads have shown great affinity to toxic hexavalent chromium ions in aqueous solution, in contrast to the traditionally used calcium alginate beads. Our adsorption experiments were carried out by the batch contact method. The optimal pH for removal was found to be pH 4. The equilibrium was established in 4 h, and the removal efficiency of chromium(VI) was found to be 95 %. The adsorption data were applied to Langmuir, Freundlich, Dubinin–Redushkevich (D–R), and Temkin isotherm equations. Both Langmuir and Freundlich isotherm constants indicated a favorable adsorption. The value of mean sorption energy calculated from D–R isoterm indicates that the adsorption is essentially physical. The high maximum chromium(VI) adsorption capacity was determined from the Langmuir isotherm as 36.5 mg/g dry alginate beads. The chromium(VI) adsorption data were analyzed using several kinetic models such as the pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models, and the rate constants were quantified. Our study suggests that barium alginate beads can be used as cost-effective and efficient adsorbents for the removal of chromium(VI) from contaminated waters.

Preconcentration and Determination of Toxic Metals by A New Calix[4]arene Bonded HPLC Column

The present study deals with the preconcentration and determination of toxic metal ions using p-tetranitrocalix[4]arene (3) appended silica-based new HPLC column. The synthesized material was characterized using Fourier transform infrared and scanning electron microscopy techniques. The sorption characteristics of the HPLC column were investigated for three toxic metals (Cd2+, Hg2+ and Pb2+) in column agreement. The experiments were performed in five steps that were monitored using a UV–visible diode-array detector. However, all the HPLC experimental results were reconfirmed by using atomic absorption spectrophotometer. The effect of concentration on the sorption efficiency of the column was evaluated for all the three metals and the data obtained were investigated using Langmuir, Freundlich and Dubinin–Redushkevich (D–R) sorption isotherms. The value of coefficient of determination (R2), i.e. 0.99, suggested that the Freundlich sorption isotherm was found to be the best-fit model for all the three toxic metal ions, whereas, mean free energy was calculated from the D–R isotherm as 5.3, 5.7, and 5.8 kJ/mol for Pb2+, Cd2+, and Hg2+, respectively; suggesting that physical electrostatic force is involved in the sorption process. The developed method was validated for system efficiency, accuracy, and precision.

Synthesis and characterization of modified UZM-5 as adsorbent for nitrate removal from aqueous solution

This article introduces synthesis and characterization of UZM-5 and its surfactant modification by using solutions of hexadecyltrimethylammonium bromide (CH3(CH2)15N(Br)(CH3)3, HDTMABr). Potential application of produced surfactant modified UZM-5 (SMU) as adsorbent for nitrate removal from aqueous solution were investigated. The effect of HDTMABr concentration on its adsorption on UZM-5 was studied by FTIR, TGA, N2 adsorption–desorption, and XRD techniques. Intense reduction in surface area, total pore volume of the UZM-5 sample upon alkyl chain attachment was observed by the BET method. From the TGA results, the electrostatic interactions were proved to be the main mechanisms that govern the adsorption of HDTMA cation on UZM-5. Adsorption isotherms of nitrate on SMU were measured at aqueous concentration range of 30–100mgL−1. The adsorption data was fitted by the Langmuir, Freundlich and Dubinin–Redushkevich (D–R) isotherms. The maximum monolayer sorption capacity of SMU for nitrate removal was found to be 18.62mgg−1 at 298K. Thermodynamic study of nitrate sorption on SMU was performed based on ΔHo, ΔGo and ΔSo. The results showed that nitrate sorption on SMU were strongly affected by pH, initial ion content and rival anions.

Removal of hexavalent chromium from aqueous solution by barium ion cross-linked alginate beads

Barium ion cross-linked alginate beads have shown great affinity to toxic hexavalent chromium ions in aqueous solution, in contrast to the traditionally used cal- cium alginate beads. Our adsorption experiments were carried out by the batch contact method. The optimal pH for removal was found to be pH 4. The equilibrium was established in 4 h, and the removal efficiency of chro- mium(VI) was found to be 95 %. The adsorption data were applied to Langmuir, Freundlich, Dubinin-Redushkevich (D-R), and Temkin isotherm equations. Both Langmuir and Freundlich isotherm constants indicated a favorable adsorption. The value of mean sorption energy calculated from D-R isoterm indicates that the adsorption is essen- tially physical. The high maximum chromium(VI) adsorption capacity was determined from the Langmuir isotherm as 36.5 mg/g dry alginate beads. The chro- mium(VI) adsorption data were analyzed using several kinetic models such as the pseudo-first-order, pseudo-sec- ond-order, intraparticle diffusion, and Elovich models, and the rate constants were quantified. Our study suggests that barium alginate beads can be used as cost-effective and efficient adsorbents for the removal of chromium(VI) from contaminated waters.

Equilibrium adsorption studies on removal of diclofenac sodium from aqueous solution using sawdust–polyaniline (SD–PAn) composites

AbstractIn this work, equilibrium adsorption studies were carried out for the removal of antiinflamatory drug diclofenac sodium (DS) from aqueous solutions using sawdust–polyaniline(SD‐PAn) composite as a potential sorbent at 20, 30, and 40°C. The composite sorbent was characterized by FTIR and SEM analysis. The particles exhibited porous and rough surface. The equilibrium uptake data was interpreted by the Langmuir, the Freundlic, the Temkin, and the Dubinin–Redushkevich (D‐R) isotherm models. The maximum adsorption capacity was found to decrease with increase in temperature, thus indicating exothermic nature of the adsorption process. The thermodynamic parameters were evaluated using Langmuir, Flory–Huggins, Frumkin, and modified‐Frumkin models. The negative values of ΔGads0 and ΔH0 indicated spontaneous and exothermic nature of the adsorption process, respectively. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125:1382–1390, 2012

Elimination of mercury by adsorption onto activated carbon prepared from the biomass material

Following the previous work (Kaghazchi et al., 2010 [11]), dealing with applying a combination of two kinds of agricultural wastes to produce a new adsorbent, this study is dedicated to investigate the details of mercury adsorption process from aquatic medium by this adsorbent. So the Mix-ZC activated carbon (the sample prepared by chemical activation of a mixture of pistachio-nut shells and licorice residues impregnated with zinc chloride) was selected for doing a series of batch adsorption experiments on it. Equilibrium isotherms, such as Freundlich, Langmuir, Dubinin–Redushkevich and Temkin have been tested. Kinetic studies based on Lagergren first-order, pseudo-second-order rate expressions and intra-particle diffusion studies have been done. The mechanisms of mercury adsorption onto this adsorbent under the operating conditions were also studied.

Analysis of the Textural Characteristics and Pore Size Distribution of a Commercial Zeolite using Various Adsorption Models

Analysis of the textural characteristics and pore size distribution of a commercial zeolite (Sigma Aldrich, product No. 96096) have been conducted experimentally using a surface analyzer by measuring the N2 adsorption isotherm at 77 K. The resulting data were fitted to several well-known adsorption models, i.e., the Brunauer-Emmett-Teller (BET) model, the de Boer model, the Dubinin-Redushkevich (DR) model, the Barret, -Joyner-Halenda (BJH) model, the Horvath-Kawazoe (HK) model and the Density Functional Theory (DFT) model. The zeolite was found to be highly microporous with a BET surface area of 609 m2 g-1. The HK model is rather limited in terms of pore volume distribution analysis and not appropriate for analysis of nanoporous materials that exhibit a wide porosity range compared to BJH and DFT model that cover much wider range (micropore, mesopore and macropore) than HK model that cover until micropore range.

Use of Orange Peel Waste for Arsenic Remediation of Drinking Water

Arsenic is a toxic element and is found in natural waters throughout the globe. The purpose of present study is to demonstrate the As (V) uptake by orange peel from real ground water samples through adsorption. Different parameters such as pH, shaking speed, contact time, adsorbent dosage, concentration, volume and temperature etc, were optimized. The maximum uptake capacity was observed at pH-7. The sorption was found to be time dependent and the kinetics followed well by the Morris-weber, Pseudo second order and Elovich equations. The Freundlich, Langmuir, Dubinin Redushkevich and Flory–Huggins isotherm were used to model the adsorption behavior of arsenic retention. Thermodynamic parameters calculated from these isotherms show that the adsorption was spontaneous and endothermic in nature. Orange peel was found to be effective (~85%) for arsenic removal from real water systems containing concomitant ions.

Optimization and Characterization of Tl(I) Adsorption onto Modified Ulmus carpinifolia Tree Leaves

AbstractUlmus carpinifolia tree leaves were successfully used to remove Tl(I) from aqueous solution in a batch system. In order to improve the uptake capacity of sorbent, it was modified by various chemical agents such as NaOH, HNO3, NH3, NaCl, NaHCO3, and CaCl2. Among the modifiers, NaCl was the best. Equilibrium behavior of sorbent with Tl(I) was examined by the several isotherms. Considering modified U. carpinifolia equilibrium data fitted well to the Langmuir model with maximum capacity of 54.6 mg/g. The other isotherms such as: Freundlich and Dubinin‐Redushkevich (D‐R) models were also examined. The central composite design (CCD) was successfully employed for optimization of biosorption process. An empirical model was given through using response surface methodology. Also its validation was recognized by using relevant statistical tests such as ANOVA. The optimum conditions of biosorption: pH, m (amount of sorbent) and C (initial concentration) were found to be 7.9, 11.4 g/L, and 8.8 mg/L, respectively. On the other hand thermodynamic parameters: ΔG, ΔH, and ΔS were evaluated: the obtained results show that biosorption process was spontaneous and exothermic. Eventually, FT‐IR analysis confirmed that the main functional groups of sorbent have been involved through the biosorption process.