Removal of methylene blue from aqueous solutions by using cold plasma‐ and formaldehyde‐treated onion skins

In this paper, the use of cold plasma‐treated and formaldehyde‐treated onion skins as a biosorbent has been investigated to remove methylene blue dye from aqueous solutions. The surface characteristics of the treated onion skins were investigated using Fourier Transform–infrared spectroscopy. The influence of process variables such as adsorbent dosage, initial dye concentration and pH were studied. Equilibrium isotherms were analysed by Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The results indicated that the data for adsorption of methylene blue onto onion skins fitted well with the Langmuir isotherm model. The sorption capacities for cold plasma‐treated and formaldehyde‐treated onion skins by Langmuir isotherm were found to be 250 and 166.67 mg/g, respectively. The equilibrium time was found to be 150 min for 50 mg/l dye concentrations. The maximum removals for cold plasma‐treated and formaldehyde‐treated onion skins obtained were 90.94 and 95.54% at natural pH 10.0 for adsorbent doses of 0.15 g/200 ml, respectively. The rates of sorption were found to conform to pseudo‐first‐order kinetics. Results indicated that onion skins could be used as a biosorbent to remove methylene blue dye from contaminated waters.     

Removal of Methylene Blue from Aqueous Solutions by using Cold Plasma,Microwave Radiation and Formaldehyde Treated Acorn Shell

In this paper, cold plasma (CPTAS), formaldehyde (FTAS), and microwave radiation treated (MTAS) acorn shell obtained from Quercus petraea tree as biosorbent was characterized and its dye removal ability at different dye concentrations was studied. The isoelectric point, functional groups and morphology of acorn shell was investigated as adsorbent surface characteristics. Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and UV–Vis spectrophotometry were used. Methylene blue (MB) was used as model cationic dye. The Langmuir and Freundlich adsorption isotherm models were applied to describe the equilibrium isotherms. The results indicated that the data for adsorption of MB onto treated acorn shell fitted well with the Langmuir isotherm model. Comparison of adsorption capacities of CPTAS with FTAS has shown a significant increase by as much as about 30 mg/g (33.32%) in MB adsorption.The pseudo-first order, pseudo-second order kinetic models were examined to evaluate the kinetic data, and the rate constants were calculated. Adsorption kinetic of dyes followed pseudo-first order kinetics. Thermodynamic parameters such as free energy, enthalpy, and entropy of dye adsorption were obtained. The results indicated that acorn shell could be used as a natural biosorbent for the removal of cationic dyes.     

Removal of Acid Violet 17 from Aqueous Solutions by Adsorption onto Activated Carbon Prepared from Pistachio Nut Shell

Adsorbents prepared from pistachio nut shell, an agricultural waste biomass, were successfully used to remove Acid Violet 17 from an aqueous solution. The activated carbons PNS1, PNS2, and PNS3 were characterized by scanning electron microscope (SEM), Fourier Transform – Infra Red spectroscopy (FTIR) and (BET). The effect of pH, adsorbent dosage, and temperature on dye removal was studied. Maximum color removal was observed at pH 2. The adsorption increased with the increase in adsorbent dosage. As the adsorption capacity increased with the increase in temperature, the process was concluded to be endothermic. The experimental data were analyzed by the Langmuir and Freundlich isotherm models of adsorption. Equilibrium data fitted well with the Langmuir model. The rates of adsorption confirmed the pseudo-second order kinetics with good correlation values. The results indicated that the activated carbon prepared from pistachio nut shell can be effectively used for the removal of Acid Violet 17 from aqueous solution.     

Synthesis of urethane sodium carboxylate and its dye removal ability from single system

Urethane sodium carboxylate (USC) was synthesized and its dye removal ability was investigated. USC characteristics were studied using FTIR and SEM. Basic Blue 41 (BB41), Basic Red 18 (BR18), and Basic Violet 16 (BV16) were used. The effect of adsorbent dosage, dye concentration and salt on dye removal was evaluated. Adsorption kinetics followed pseudo-second order. The USC adsorption capacity was 474, 538 and 298 mg/g for BB41, BR18 and BV16, respectively. Adsorption isotherm followed with Langmuir isotherm. The results showed that the USC might be a suitable adsorbent to remove dyes from colored wastewater.     

Isotherm,Kinetic, and Thermodynamic of Cationic Dye Removal from Binary System by Feldspar

In this paper, the isotherm, kinetic, and thermodynamic of cationic dye removal onto inorganic adsorbent (Feldspar) were investigated in single and binary systems. Basic Red 18 (BR18) and Basic Blue 41 (BB41) were used as cationic dyes. The characterization of the Feldspar was carried out using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) techniques. The effect of operational parameters such as adsorbent dosage, initial dye concentration, pH, ionic strength, and temperature on dye removal was studied. It was found that the adsorption of BR18 and BB41 onto Feldspar followed with Langmuir and extended Langmuir isotherms in single and binary systems, respectively. Adsorption kinetic of dyes was found to conform to pseudo-second order kinetic in single and binary system. The thermodynamic data showed that dye adsorption onto Feldspar was spontaneous, endothermic, and physisorption reaction. Based on the data of the present investigation, one could conclude that the Feldspar as an eco-friendly and low-cost adsorbent might be a suitable alternative to remove dyes from colored aqueous solutions containing cationic dyes.     

Radiation synthesis and characterization of styrene/acrylic acid/organophilic montmorillonite hybrid nanocomposite for sorption of dyes from aqueous solutions

Organophilic montmorillonite (OMMT) was synthesized by cationic exchange reaction of Na⁺‐MMT and vinyl benzyl triethyl ammonium chloride (VBTAC) as a reactive organic modifier in an aqueous solution. A series of styrene (St)/acrylic acid (AA)/OMMT nanocomposite hydrogel containing different wt% of OMMT was synthesized through in situ polymerization using γ‐ray. The samples were characterized using Fourier transform infrared (FTIR), X‐ray powder diffraction (XRD), and transmission electron microscope (TEM), whereas thermal stability was examined by thermogravimetric analysis (TGA). The adsorption capacity and rate for both Acid Green B (anionic) and Maxilon C.I. Basic (cationic) dye including adsorption kinetics and isotherm were investigated at 30°C. TEM measurements showed spherical nanosized particles of average diameter 30–40 nm and XRD suggested the formation of exfoliated nanocomposite. TGA measurements showed that the addition of OMMT did not enhance the thermal stability where the onset temperature of the degradation for all samples was around 125°C. The effect of some important parameters on dye adsorption such as solution pH, initial dye concentration, and contact time was investigated. The equilibrium data obtained in batch experiments were correlated to Langmuir and Freundlich isotherm equations. Results showed that the adsorption of Acid Green B fitted well to the Langmuir model while the adsorption pattern of Maxilon C.I. Basic followed the Freundlich isotherm, which suggests heterogeneity of the adsorption sites on the nanocomposite. POLYM. COMPOS., 35:2353–2364, 2014. © 2014 Society of Plastics Engineers     

Adsorption of cationic dyes on Jalshakti®, super absorbent polymer and photocatalytic regeneration of the adsorbent

This paper presents a study on the batch adsorption kinetics of seven cationic dyes, namely, Methylene Blue, Safranine T, Rhodamine B, Crystal Violet, Malachite Green, Brilliant Green, and Basic Fuchsine onto Jalshakti^® (JS), a super absorbent polymer, from aqueous solution. The adsorption of dyes reaches equilibrium in 60–90 min. Equilibrium isotherms and intraparticle diffusion rate constants were measured for single component systems. It is found that uptake of dyes on JS follows the Langmuir and Freundlich isotherm models. The particle diffusion study showed that the initial boundary layer diffusion is followed by intraparticle diffusion effects. The flat and planar dye molecules are readily adsorbed as compared with the propeller shaped triphenylmethane dyes. Photocatalytic regeneration of spent JS using UV/TiO₂ is more effective compared to conventional methods. Further, the regenerated JS exhibits 90% efficiency for subsequent adsorption cycle with Methylene Blue and Safranine T aqueous solutions.     

Adsorption of Crystal Violet From Aqueous Solution by Citric Acid Modified Rice Straw: Equilibrium,Kinetics, and Thermodynamics

Rice straw, an abundant, lignocellulosic agricultural residue was thermochemically modified with citric acid to develop a biodegradable cationic adsorbent. The application potential of the prepared adsorbent to remove hazardous Crystal Violet dye from its aqueous solution was investigated. The morphological and chemical characteristics of the adsorbent were established by scanning electron microscopy (SEM), surface area, and porosity analysis by the BET (Brunauer, Emmett, and Teller) nitrogen adsorption method and Fourier transform infrared (FTIR) spectroscopy. Batch adsorption studies were carried out as a function of solution pH, adsorbent dose, initial dye concentration, and temperature, in order to get insights into the effect of these independent parameters on the adsorption process. The Langmuir, Freundlich, and Dubinin–Radushkevich models were used to describe the equilibrium adsorption data. The sorption mechanism was also evaluated in terms of kinetics and thermodynamics. The adsorption equilibrium data was well described by the Langmuir isotherm model. The adsorption process followed the pseudo-second-order rate kinetics. Thermodynamic study showed spontaneous and exothermic nature of the adsorption process.     

Dye removal from colored textile wastewater using chitosan in binary systems

In this paper, the removal of two anionic dyes from textile effluent in single and binary systems was investigated. Direct Red 23 and Acid Green 25 were used as anionic dyes. The surface characteristics of chitosan were investigated using Fourier transform infrared. The effects of operational parameters such as chitosan dosage, initial dye concentration, salt and pH on dye removal were studied. The isotherms of dye adsorption were investigated. It was found that the isotherm data of Direct Red 23 and Acid Green 25 in single and binary systems followed Tempkin isotherm. In addition adsorption kinetics of dyes was studied in single and binary systems and rate sorption was found to conform to pseudo-second order kinetics with a good correlation. Results indicated that chitosan could be used as a biosorbent to remove the anionic dyes from contaminated watercourses in both single and binary systems of pollutants.     

Preparation of an ecofriendly chitosan–ZnO composite for chromium complex dye adsorption

Three chitosan‐ZnO composites were prepared by the chitin deacetylation process using zinc chloride as source material and sodium hydroxide as precipitant. The physical characteristics of chitosan‐ZnO composites were studied using Fourier Transform infrared spectroscopy and scanning electron microscopy. The adsorption of a chromium complex dye onto commercial chitosan, prepared chitosan and chitosan‐ZnO composites was investigated in aqueous dye solution. Dye calibration was carried out by UV‐vis spectroscopy. The calculated dye adsorption values for commercial chitosan, prepared chitosan, and chitosan‐ZnO composite samples are 0.0086, 0.0137, and 0.0214 mg/g respectively, indicating that the chitosan‐ZnO composites have better dye adsorption capacity than commercial chitosan and prepared chitosan. The experimental isotherm data for the composites fitted the Langmuir isotherm model well. Thus, the chitosan‐ZnO composites can be used as an effective biosorbent for the removal of anionic dyes.     

The use of Jatobá bark for removal of cationic dyes

In this work, the application of Jatobá bark (the waste product of medicinal plant processing) in removal of the cationic dyes Methylene Blue, Crystal Violet and Rhodamine B from aqueous solution was studied in a batch system. The effect of contact time, pH and temperature on dye removal was investigated. An increase in pH from 2 to 10 was accompanied by an increase in the amount of dye adsorbed. The equilibrium sorption data fitted to the Langmuir, Freundlich and Langmuir–Freundlich equations were investigated. The Langmuir–Freundlich isotherm exhibited the best fit with the experimental data and the maximum adsorption capacities at room temperature being 211.5, 89.5 and 69.4 for Rhodamine B, Methylene Blue and Crystal Violet, respectively. The kinetic sorption was evaluated by the pseudo‐first‐order, pseudo‐second‐order and intraparticle diffusion models. It was observed that sorption follows the pseudo‐second‐order kinetic model. The thermodynamic parameters for the sorption process were also determined. The spontaneous and endothermic nature of adsorption was obtained based on the negative value of free energy (ΔG) and the positive value of enthalpy (ΔH). The results indicate that Jatobá bark could be used as a low‐cost material for the removal of cationic dyes from wastewater.     

Prediction of binary component isotherms for adsorption on heterogeneous surfaces

The adsorption of three basic dyes onto peat has been studied as single and bisolute equilibrium isotherms. The Freundlich equilibrium isotherm, suitable for heterogeneous adsorption systems has been selected to describe the single component data. Furthermore, the extended Freundlich formula for binary systems has been used to describe binary system equilibrium. A very good agreement is obtained between experiment and theory. The dyes under investigation are: Basic Blue 3, Basic Red 22 and Basic Yellow 21 in their single phases and binary solutions, respectively, all onto peat.     

Preparation of betaine‐modified cationic cellulose and its application in the treatment of reactive dye wastewater

Betaine‐modified cationic cellulose was prepared through the reaction of cellulose with betaine hydrochloride by an efficient one‐step dry method. Dicyandiamide was used as a dehydrating agent to promote the formation of ester bonds between the reactants. Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy were used to characterize the cellulose betainate. Experiments showed that at a molar ratio of the cellulose glucose unit, betaine hydrochloride to dicyandiamide, of 1:1:0.5 at 150°C for 3 h, the degree of substitution of the cationic group reached 0.80. The adsorption of simulated C. I. Reactive Red 24 and C. I. Reactive Red 195 wastewater on the cationic cellulose was carried out, and the effects of the adsorbent dose, initial dye concentration, and salt concentration on the dye removal efficiency were investigated. The equilibrium adsorption isotherm data of the cationic cellulose exhibited a better fit to the Langmuir isotherm model than the Freundlich one. The experimental results suggest that the prepared cationic cellulose materials show potential application for reactive dye wastewater treatment. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40522.     

In-Situ UV-Visible Spectroscopic Study on the Adsorption of some Dyes onto Activated Carbon Cloth

Abstract

Adsorptive removal of the dyes C.I. Basic Blue 9, C.I. Basic Red 2, and C.I. Acid Blue 74 from aqueous solution onto the activated carbon cloth (ACC) has been investigated. The removal of each dye has been followed by in-situ UV-visible spectroscopic method using the so-called scanning kinetics technique. Kinetic data obtained in this way were tested according to pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion models. Pseudo-second order model was found to be the best in representing the experimental kinetic data. Adsorption isotherms at 30°C were derived for each dye. Isotherm data were found to fit best to Freundlich isotherm model among the three isotherm models tested; Langmuir, Freundlich, and Redlich-Peterson. High specific surface area of the ACC allowed almost complete removal of each dye under the experimental conditions applied. Adsorption capacity of the ACC for the three dyes was correlated with the dimensions of dye molecules and pore sizes of the ACC.     

Kinetics,Thermodynamics, and Isothermic Evaluation in Sorption Study of Hazardous Dye Using Sodium Dodecylsulfate Physically Impregnated in Polyester‐Type Polyurethane Foam

Use of polyester‐type polyurethane foam (PUF) is an effective adsorbent for the removal of hazardous dye: crystal violet (CV) from an aqueous solution. In this adsorption study, the formation of hydrophobic ion pair (opposite charge attraction) between the charged species, i.e., cationic (basic) dye CV and anionic surfactant sodium dodecylsulfate (SDS) sorbed onto PUF. Chemical calculations were performed using quantum simulation to understand ion‐pair formation for CV–SDS at the semiempirical PM6 level. Adsorption studies were performed using 200 mg cylindrical PUF with an overhead stirrer in solutions containing varying compositions of the dye–surfactant mixture. The equilibrium thermodynamics and kinetics of the adsorption process were studies by measuring CV dye removal as a function of time and temperature. Results show that the formation of the dye–surfactant ion pair is necessary for effective adsorption onto PUF. Various adsorption isotherms, viz., Langmuir, Freundlich, Temkin, Dubinin–Radushkevich (DRK), Harkin‐Jura, and several kinetic models, viz., pseudo‐first order, pseudo‐second order, Elovich, and Intraparticle diffusion were used to fit the spectrophotometric result. The equilibrium adsorption data fit to the Langmuir isotherm gives the maximum adsorption of PUF as 33.39 mg g^?1 from 200 mL 5.0 × 10^?5 mol L^?1 CV solution at 298.15 K. The kinetics study showed that the overall adsorption process follows pseudo‐second‐order kinetics. The Morris–Weber model suggests that an intraparticle diffusion process is active in controlling the adsorption rate. The Freundlich, Temkin, DRK adsorption isotherms showed that solute dye transfers from solution to the PUF adsorbent surface through physical adsorption. The Langmuir and Harkin‐Jura adsorption isotherms suggest that the adsorbent surface is homogeneous in nature. The thermodynamic data showed that the adsorption process is spontaneous and endothermic with a positive enthalpy change and a negative change in Gibb's energy.     

Dye adsorption and desorption properties of Mentha pulegium in single and binary systems

This article deals with the dye adsorption and desorption properties of Mentha pulegium (MP) from single and binary (mixture of dyes) systems. Direct Red 80 (DR80) and Acid Black 26 (AB26) were used as model dyes. The Fourier transform infrared (FTIR) was used to investigate the biosorbent characteristics. The effects of biosorbent dosage, contact time, dye concentration, salt, and pH on dye removal were studied. The biosorption isotherms, kinetics, and thermodynamic were studied. In addition, dye desorption was carried out to study adsorbent recovery. The results showed that the isotherm data of single and binary systems of dyes followed the Langmuir isotherm. The adsorption kinetic of the dyes was found to conform to a pseudosecond order kinetic model. Desorption tests showed maximum dye releasing of 97% for DR80 and 95% for AB26 in single system and 92% for DR80 and 94% for AB26 in binary system of dyes at pH 12. The thermodynamic data showed that the biosorption process is spontaneous, endothermic, and a physisorption reaction. It can be concluded that MP is an ecofriendly biosorbent to remove dyes from single and binary systems. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Removal of Basic Dye from Aqueous Solution using Cinnamomum camphora Sawdust: Kinetics,Isotherms, Thermodynamics,and Mass-Transfer Processes

Cinnamomum camphora sawdust (CCS) was employed as a cheap and effective biosorbent to remove basic dye from aqueous solutions. The biosorbent was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Adsorption experiments were carried out in a batch system as a function of initial pH, adsorbent dose and particle size, ionic strength, initial dye concentration, and reaction temperature. The selected basic dye (malachite green) adsorption onto CCS significantly depended on these factors. By comparative kinetic analysis, the rate of sorption was conformed with good correlation to pseudo-second-order kinetics. Equilibrium data were fitted well by Langmuir isotherm with the maximum adsorption capacity of 155.0 mg/g at the temperature of 318 K and pH 7.0 ± 0.1. Thermodynamic parameters proved that malachite green dye biosorption process was spontaneous and endothermic within the investigated temperature range. The mechanism of adsorption was also studied. It was found that the adsorption of malachite green onto CCS was mainly governed by film diffusion. The electrostatic attractions and ionic interactions between malachite green dye and CCS might be responsible for the adsorption process. The comparative investigation suggested that the sawdust could be considered as a potential adsorbent for malachite green dye removal from wastewater.     

Synthesis and characterization of glutaraldehyde‐crosslinked calcium alginate for fluoride removal from aqueous solutions

A novel biosorbent was developed by the crosslinking of an anionic biopolymer, calcium alginate, with glutaraldehyde. The glutaraldehyde‐crosslinked calcium alginate (GCA) was characterized by Fourier transform infrared spectroscopy and porosity and surface area analysis. The batch equilibrium and column flow adsorption characteristics of fluoride onto the biosorbent were studied. The effects of the pH, agitation time, concentration of adsorbate, and amount of adsorbent on the extent of adsorption were investigated. The experimental data were fitted to the Langmuir and Freundlich adsorption isotherms. The data were analyzed on the basis of the Lagergren pseudo‐first‐order, pseudo‐second‐order, and Weber–Morris intraparticle diffusion models. The maximum monolayer adsorption capacity of the GCA sorbent as obtained from the Langmuir adsorption isotherm was found to be 73.5 mg/g for fluoride. The χ² and sum of squares of the error analysis were used to correlate the equilibrium isotherm models and kinetics. In addition, breakthrough curves were obtained from column flow experiments. The experimental results demonstrate that the GCA beads could be used for the defluoridation of drinking water through adsorption. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

ADSORPTION KINETICS AND EQUILIBRIA OF BASIC DYES ONTO ZEOLITE IN SINGLE AND BINARY COMPONENT SYSTEMS

Adsorptive removal of Basic Blue 3 (BB 3) and Basic Red 18 (BR 18) by a clinoptilolite-type natural zeolite from their single-component solutions has been studied in the temperature range of 298–328 K. Experimental equilibrium results are well described by the Freundlich and the Langmuir isotherm models. The model parameters obtained for single-solute systems at 298 K have been used for the prediction of adsorption isotherms in binary dye solutions using multicomponent isotherm models. Competitive adsorption results between BB 3 and BR 18 in binary solutions satisfactorily fit the extended Freundlich, extended Langmuir, and modified Langmuir models. A site distribution function that gives information about affinity of adsorption sites for competing species in binary systems has been mathematically calculated using the Freundlich parameters. Time-dependent results for single and binary dye solutions have been analyzed according to a pseudo-second-order kinetic model based on chemisorption and a McKay model assuming two resistance diffusion processes, respectively. The diffuse reflectance FT-IR spectra indicate that the dyes are adsorbed via electrostatic interactions in external rings of clinoptilolite by replacing the zeolitic water in a single system, and they diffuse through the liquid associated with zeolitic water in TO₄ tetrahedra (T: Al, Si) in a mixed solution.