Adsorption Characteristics of Congo Red from Aqueous Solution onto Tea Waste

The feasibility of using tea waste (TW) as a low-cost adsorbent for the adsorption of an anionic dye (Congo red) from aqueous solution has been investigated. Adsorption in a batch process was conducted to study the effect of adsorbent dosage, initial dye concentration, contact time, pH, and temperature. The experimental data were analyzed by the Langmuir, Freundlich, and Temkin models. The adsorption system was best described by the Langmuir isotherm (R ² > 0.99). Adsorption kinetics followed a pseudo-second-order model (R ² > 0.99). The effect of mechanical treatment (vibratory mill) was also studied. The experimental results showed that using this physical treatment leads to an increase in the adsorption capacity of TW from 32.26 to 43.48 mg/g. Thermodynamic analyses revealed that the adsorption of Congo red on TW was endothermic and spontaneous in nature. The results indicated that TW can be employed as a potential low-cost adsorbent for the removal of Congo red from aqueous solution.     

A new application of Hydroxyapatite extracted from dromedary bone: Adsorptive removal of Congo red from aqueous solution

The aim of this paper is to evaluate the efficiency of the natural hydroxyapatite powder for anionic dye (Congo red) elimination from water and optimization of adsorption process parameters that are contact time (0-360 min), solution pH (4-9), initial dye concentration (400-2400 mg/l), and adsorbent dosage (0.4-20 g/l). Natural hydroxyapatite with high surface area was prepared from animal agriculture waste dromedary bone. X-ray diffraction, transmission electron microscopy, transform infrared spectroscopy, and elemental analysis characterizations of the powder prepared show a hexagonal structure, the irregular form of hydroxyapatite and presence of other elements as trace element. The results of adsorption tests demonstrated the high efficiency of natural hydroxyapatite for removal of Congo red from water solution whose maximum experimental capacity adsorption of Congo red by natural hydroxyapatite is 900 mg/g at pH 4.5, equilibrium time 240 min and adsorbent dosage 2 g/l. According to the correlation coefficient value, the pseudo-second order kinetic model identified the sorption mechanism of pollutant used on natural hydroxyapatite. The Freundlich isotherm is the best representative theoretical model of the dye molecules’ adsorption on the natural hydroxyapatite support.     

Fe2+-modified Vermiculite for the Removal of Chromium (VI) from Aqueous Solution

A novel adsorbent: Fe²⁺-modified vermiculite was prepared in a two-step reaction. Adsorption experiments were carried out as a function of pH, contact time, and concentration of Cr(VI). It was found that Fe²⁺-modified vermiculite was particularly effective for the removal of Cr(VI) at pH 1.0. The adsorption of Cr(VI) reached equilibrium within 60 min, and the pseudo-second-order kinetic model best described the adsorption kinetics. The adsorption data follow the Langmuir model more than the Freundlich model. At pH 1.0, the maximum Cr(VI) sorption capacity (Q _max ) was 87.72 mg · g^?1. Desorption of Cr(VI) from Fe²⁺-modified vermiculite using NaOH treatment exhibited a higher desorption efficiency by more than 80%. The sorption mechanisms including electrostatic interaction and reduction were involved in the Cr (VI) removal. The results showed that Fe²⁺-modified vermiculite can be used as a new adsorbent for Cr(VI) removal which has a higher adsorption capacity and a faster adsorption rate.     

Efficient removal of Congo red by magnetically separable mesoporous TiO2 modified with γ-Fe2O3

Magnetically separable mesoporous TiO₂ modified with γ-Fe₂O₃ was prepared and characterized by X–ray diffraction, N₂ adsorption–desorption measurements, scanning electron microscopy, UV–vis absorption and magnetic measurements. The adsorptive removal of Congo red using the binary system was performed under various experimental conditions to examine the effects of contact time, solution pH, and initial concentration of Congo red. The results show that the removal abilities and separability of mesoporous TiO₂ adsorbent for Congo red can be significantly improved by modification with γ-Fe₂O₃. The adsorption of Congo red on the γ-Fe₂O₃–TiO₂ reaches the maximum percentage removal of ca. 97 % within 60 min, showing that most of Congo red can be removed in a short time. When the pH of solution is varied from 3.4 to 10.3, the percentage removal of Congo red decreases from ca. 97 to ca. 15 %, showing that the adsorption is strongly dependent on solution pH. The adsorption kinetics of Congo red fit well with pseudo-second-order kinetic model, and the equilibrium data is best described by Langmuir adsorption model. The maximum adsorption capacity of the γ-Fe₂O₃–TiO₂ for Congo red is estimated to be 125.0 mg/g.     

Adsorption of Cu2+ Cations from Aqueous Solution by S-doped TiO2

S-doped TiO₂ as a novel adsorbent for Cu²⁺ cations removal from aqueous solutions was synthesized by simple sol-gel process. Removal of Cu²⁺ cations from aqueous solutions was investigated with particular reference to the effects of initial Cu²⁺ cations concentration, pH-value, adsorbent dosage, and temperature on adsorption. It was found that the maximum adsorption capacity was 96.35 mg g^?1 at 328 K. The adsorption equilibrium isotherms and the kinetic data were well described by the Langmuir and pseudo-second-order kinetic models, respectively. The high uptake capability of S-doped TiO₂ makes it a potentially attractive adsorbent for the removal of heavy metal pollutants from aqueous solution.     

Batch Removal of Crystal Violet from Aqueous Solution by H2SO4 Modified Sugarcane Bagasse: Equilibrium,Kinetic, and Thermodynamic Profile

Batch adsorption studies were carried out using H₂SO₄ modified sugarcane bagasse (HMSB) for the removal of hazardous Crystal Violet (CV) dye from aqueous solutions. The effects of initial solution pH, adsorbent dose, and temperature on the adsorption process were investigated. The Langmuir isotherm model well described the equilibrium dye uptake while the pseudo-second-order kinetic model showed good agreement with the experimental kinetic data. Gibb's free energy change (ΔG⁰) was spontaneous for all interactions, and the adsorption process exhibited endothermic enthalpy values. Results suggest that HMSB is an effective adsorbent for the removal of CV from wastewater.     

Synthesis and adsorption properties of nanocrystalline ferrites for kinetic modeling development

Nanocrystalline ferrites are known to be used in different applications, including industrial wastewater management. For environmental water issues, one of the most widely applied techniques is the adsorption of pollutants. The adsorption capacity of Congo red (CR) dye on different MFe₂O₄ (M = Co²⁺, Mg²⁺, Mn²⁺, Ni²⁺, and Zn²⁺) ferrites, synthesized by coprecipitation method, was determined. Specific isotherms and kinetic models were used to characterize the adsorption process. Interesting results were obtained for MgFe₂O₄ with adsorption capacity ranging from 39% up to 70% dependent on the initial dye concentration. Furthermore, an artificial intelligence model based on neural network was developed in order to model the adsorption rates followed by the generation of 3D adsorption rate models for each type of synthesized ferrite. These models were obtained in order to provide information about the particle-dye system`s kinetics at various initial CR concentration. Specific techniques were used to characterize the functionalized magnetic particles.     

Synthesis of High Surface Area MgAl2O4 Nanopowder as Adsorbent for Leather Dye Removal

Abstract

MgAl₂O₄ nanopowder has been prepared by alkoxides hydrolysis with further calcination at temperature of 700°C. The adsorption of a leather dye, Direct Black 38, onto this material was investigated. The sample was characterized by X-ray-diffraction (XRD), N₂ adsorption–desorption isotherm and Fourier transform infrared spectroscopy. The results showed that sample present a pure phase, and the average nanocrystal size of 8 nm, the BET surface area is about 206.5 m² · g^?1 and total pore volume is about 1.44 cm³ · g^?1. Adsorption kinetics data were modeled by film and pore diffusion model. The experimental isotherm was described by the Langmuir model. MgAl₂O₄ nanopowder presented a great removal efficiency of leather dye by adsorption process, with a maximum adsorption capacity of 833 mg of dye per gram of adsorbent.     

Adsorptive removal of alizarin dye from wastewater using maghemite nanoadsorbents

ABSTRACT

This is an investigation of the adsorptive removal of anthraquinone dyes, resembled by Alizarin, by utilizing maghemite iron oxide (γ-Fe₂O₃) nanoparticles in aqueous media. The adsorption process was affected by several parameters such as solution pH, adsorbent amount, contact time, and temperature. After optimizing the parameters affecting the adsorption, the process was successful in removing Alizarin dye with an efficiency exceeding 95%. Best adsorption results were achieved at a pH of 11 and contact time of 60 min. The adsorption was shown to follow the Langmuir model suggesting a monolayer and homogeneous coverage. The maximum adsorption capacity (q_m ) was found to be 23.2 mg/g at pH = 11. A thermodynamic study showed that the adsorption process is exothermic and spontaneous at room temperature. The Gibbs free energy of adsorption (-6.79 kJ/mol) obtained in this study suggests a physisorption process. This finding has facilitated the regeneration of the Fe₂O₃ nanocatalyst. Both NaOH and HNO₃ at dilute levels were tested for the regeneration of the nanocatalyst. Regeneration with HNO₃ was successful up to four successive removal cycles with an efficiency >80%. Photodegradation experiments utilizing a UV light were also successful in maximizing the adsorption removal efficiency. A sorption mechanism based on the results obtained in this work is also proposed.     

Template-free synthesis of MgO mesoporous nanofibers with superior adsorption for fluoride and Congo red

MgO mesoporous nanofibers were obtained by a template-free electrospinning method. The unique bumpy-structure was obtained on the surface of nanofibers that could enhance the surface area and provide more active sites for adsorption. The formation mechanism of the bumpy-structure has been investigated. The as-prepared MgO nanofibers with a high surface area of 194.17?m² g^?1 exhibited excellent adsorption capacities for fluoride of 237.49?mg?g^?1. Furthermore, the MgO nanofibers showed selective adsorption for different organic dyes and have superior adsorption capacity for Congo red (4802.27?mg?g^?1). The adsorption processes for both fluoride and Congo red were systematically investigated, which were found to follow the pseudo-second-order kinetic model. By comparison with the reported fabrication routes and adsorption capacities of mesoporous MgO, the synthesis process is simple, controllable and template-free, and the superior adsorption performance provided a potential adsorbent for the removal of fluoride and Congo red in wastewater treatment. The high surface area of the MgO mesoporous nanofibers might also promote its application in basic catalysis and other fields.     

Adsorptive removal of cationic dye from aqueous solutions by ZnO/ZnMn2O4 nanocomposite

The ZnO/ZnMn₂O₄ nanocomposite (ZnMn) was used as adsorbent for the removal of cationic dye Basic Yellow 28 (BY28) from aqueous solutions. The adsorbent was characterized by X-ray diffraction, scanning electron microscope, TEM, Fourier transform infrared ray, BET, particle size distribution and zeta potential measurements. The adsorption parameters, such as temperature, pH and initial dye concentration, were studied. Kinetic adsorption data were analyzed using the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The Langmuir and Freundlich isotherm models were applied to fit the equilibrium data. The maximum adsorption capacity of BY28 was 48.8 mg g^?1. Various thermodynamic parameters, such as ΔG°, ΔH° and ΔS°, were calculated.     

Highly Efficient Adsorption of Anionic Dyes from Aqueous Solutions Using Sawdust Modified by Cationic Surfactant of Cetyltrimethylammonium Bromide

In the present study, the adsorption behavior of Congo Red (CR) dye from aqueous systems onto sawdust modified by cetyltrimethylammonium bromide, CH₃(CH₂)₁₅N(CH₃)₃Br (CTAB) was attempted. Adsorption experiments were carried out using both batch and column modes under various operating conditions. The effects of some important parameters such as solution pH, adsorbent dosage, initial dye concentration and contact time were investigated. Treatment of the equilibrium data obtained in batch experiments was carried out using Langmuir and Freundlich isotherm equations. Based on the isotherm analysis, it was found that the adsorption of CR dye onto SD fits well to the Langmuir model and the adsorption pattern on CTAB modified sawdust (CTAB/SD) followed the Freundlich isotherm which is indicative of heterogeneity of the adsorption sites on the surfactant-modified sawdust. The maximum adsorption capacity of SD and CTAB/SD were found to be 5.2 and 9.1?mg?g^?1, respectively, according to the Langmuir model. However, much higher differences in sorption capacities were observed for CTAB/SD and SD in the column system (66.73?mg?g^?1). In order to find out the possibility of the exhausted column for frequent use, a regeneration study was also carried out. It was found that the dye uploaded column can be easily regenerated with a high performance using ethanol as the washing solution.     

Synthesis of Fe2O3-coated and HCl-treated bauxite ore waste for the adsorption of arsenic (III) from aqueous solution: Isotherm and kinetic models

The present work has focused on the removal of arsenic (III) using two effective adsorbents such as red mud treated with HCl and coated with Fe₂O₃. Adsorption of As (III) was performed by the function of pH, adsorbent dose, contact time, initial ion concentration, and the appropriate conditions for adsorption were determined. The characterization studies of the adsorbent were analyzed using X-ray diffraction, X-ray fluorescence, Brauner–Emmett–Teller, scanning electron microscope, and FTIR spectroscopy. The result of the studies shows that the adsorbent is suitable for the effective removal of As (III) ions. Batch adsorption process showed that the maximum adsorption occurred at Fe₂O₃-coated red mud. The equilibrium data were well fitted to the nonlinear Langmuir isotherm model and the maximum adsorption capacity (q_m) of Fe₂O₃-coated red mud was found to be 21.85?mg?g^?1 which indicates that Fe₂O₃-coated red mud had more adsorption capacity. In the Freundlich isotherm, the experimentally obtained n value of Fe₂O₃-coated red mud was 2.393 which indicates the favorable adsorption of As (III) on the adsorbent. Dubinin–Radushkevich isotherm confirms that the adsorption process is physical in nature. Furthermore, the adsorption kinetic studies followed the pseudo-first-order model. All the results concluded that Fe₂O₃-coated red mud can be considered as a cost-effective and potential adsorbent for As (III) removal.     

Low cost adsorbents obtained from ash for copper removal

We investigated the utilization of ash and modified ash as a low-cost adsorbent to remove copper ions from aqueous solutions such as wastewater. Batch experiments were conducted to determine the factors affecting adsorption of copper. The influence of pH, adsorbent dose, initial Cu²⁺ concentration, type of adsorbent and contact time on the adsorption capacity of Cu²⁺ from aqueous solution by the batch adsorption technique using ash and modified ash as a low-cost adsorbent were investigated. The optimum pH required for maximum adsorption was found to be 5. The results from the sorption process showed that the maximum adsorption rate was obtained at 300 mg/L when a different dosage of fly ash was added into the solution, and it can be concluded that decreasing the initial concentration of copper ion is beneficial to the adsorption capacity of the adsorbent. With the increase of pH value, the removal rate increased. When the pH was 5, the removal rate reached the maximum of over 99%. When initial copper content was 300 mg/L and the pH value was 5, the adsorption capacity of the zeolite Z 4 sample reached 27.904 mg/g. The main removal mechanisms were assumed to be the adsorption at the surface of the fly ash together with the precipitation from the solution. The adsorption equilibrium was achieved at pH 5 between 1 and 4 hours in function of type of adsorbent. A dose of 1: 25 g/mL of adsorbent was sufficient for the optimum removal of copper ions. For all synthesized adsorbents the predominant mechanism can be described by pseudo-second order kinetics.     

Synthesis of cationic polymeric adsorbent and dye removal isotherm,kinetic and thermodynamic

Poly(quaternary ammonium salt) (PQAS) as a cationic polymeric adsorbent was synthesized and characterized by FTIR. Isotherm, kinetic and thermodynamic of dye removal from single and binary systems was investigated. Acid Blue 25 (AB25) and Acid Red 18 (AR18) were used. The effect of operational parameters (adsorbent dose, pH, dye concentration and salt) on dye removal was studied. The dye removal followed the Langmuir isotherm and pseudo-first order kinetics. The adsorbent maximum dye adsorption capacity (Q₀) was 2000 and 1667 mg/g for AB25 and AR18, respectively. The thermodynamic data showed that dye adsorption was spontaneous, endothermic, and a physisorption reaction.     

Removal of water‐soluble azo dye by the magnetic material MnFe2O4

Magnetic ferrite material, MnFe₂O₄, as a novel adsorbent was prepared and characterized. Adsorption tests indicated that it is an excellent adsorbent for the removal of the azo dye Acid Red B (ARB) from water. After adsorbing ARB and recovery by the magnetic separation method, it can be regenerated by Fenton's reagent. The pseudo‐first‐order and second‐order kinetic models were used to describe the kinetic data and the rate constants were evaluated. The adsorption capacity was highly affected by the pH of the solution, and pH 3.8 was optimal. After regeneration, the adsorption capacity of MnFe₂O₄ increased significantly, which was the result of a decrease in average pore diameter, an increase in surface area of the adsorbent and the adsorption of ferric hydroxide produced in the regeneration reaction. The adsorption can be described with the Langmuir model and the maximum adsorption capacity for ARB was 53.8 mg g^?1 adsorbent. FTIR study for ARB on MnFe₂O₄ indicated that the adsorption of ARB occurred via the azo group and the sulfonic group of the dye through the formation of a complex with the adsorbent surface. Copyright © 2004 Society of Chemical Industry     

Novel porous organic triazine‐based polyimide with high nitrogen levels for highly efficient removal of Ni(II) from aqueous solution

In this study, a porous organic triazine‐based polyimide (PPI network) was prepared from 2,4,6‐tris(hydrazino)‐s‐triazine and 3,4,9,10‐perylenetetracarboxylic dianhydride. TGA, Fourier transform infrared spectroscopy, field emission SEM, XRD and a nitrogen sorption study confirmed the PPI network structure. Then, the synthesized PPI network was used to evaluate Ni²⁺ ion removal from aqueous solution and the effective parameters on adsorption functions of Ni²⁺ ions such as initial concentration, contact time and pH of the solution in batch adsorption experiments was studied. The results showed that the maximum adsorption capacity (q_m) of Ni²⁺ ions was 36.1 mg g^?1 in only 30 min with a pH of 7. The kinetics and adsorption isotherm were identified to be better fitted by the pseudo‐second‐order model and the Langmuir model, respectively. Based on the results, the proposed adsorbent has good potential for removing Ni²⁺ ions from aqueous solutions. © 2019 Society of Chemical Industry     

Adsorption d'un colorant textile réactif sur un biosorbant non‐conventionnel : Les fibres de Posidonia oceanica (L.) delile

The marine biomaterial Posidonia oceanica (L.) fibres were used as a novel low‐cost biological adsorbent for the removal of reactive textile dye (Cibacron Red) from aqueous solutions. Batch experiments were carried out for sorption kinetics and isotherms. Operating variables studied were contact time, fibres quantity, temperature, pH, and chemical pre‐treatment. The equilibrium state was reached within 48 h. Biosorption capacity seems to be enhanced by increasing the biosorbent mass. Rising the temperature has also a positive effect on dye removal rate. Maximum colour removal was observed at pH 5.5. Pre‐treating fibres with H₃PO₄ and HNO₃ solutions increased considerably the adsorption capacity. Kinetic and equilibrium data for raw fibres were well described by the pseudo‐second order and Freundlich models, respectively. Besides, the thermodynamic study has showed that the dye‐adsorption phenomenon onto P. oceanica biomass was favourable, endothermic and spontaneous.     

Synthesis and characterization of magnetic beads containing aminated fibrous surfaces for removal of Reactive Green 19 dye: kinetics and thermodynamic parameters

BACKGROUND: Poly(HEMA‐co‐MMA) beads were prepared from 2‐hydroxyethyl‐methacrylate (HEMA) and methylmethacrylate (MMA) in the presence of FeCl₃. Thermal co‐precipitation of Fe(III) ions containing beads with Fe(II) ions was carried out under alkaline conditions. The magnetic beads were grafted with poly(glycidylmethacrylate; p(GMA)), and the epoxy groups of the grafted p(GMA) brushes were converted into amino groups by reaction with ammonia. RESULTS: The magnetic beads were characterized by surface area measurement, electron spin resonance (ESR), Mössbauer spectroscopy and scanning electron microscopy (SEM). The maximum adsorption of Reactive Green‐19 (RG‐19) dye on the p(GMA) grafted and amine modified magnetic beads was around pH 3.0. The adsorption capacity of magnetic beads was 84.6 mg dye g^?1. The effects of adsorbent dosage, ionic strength and temperature have also been reported. Batch kinetic sorption experiments showed that a pseudo‐second‐order rate kinetic model was applicable. CONCLUSION: The p(GMA) grafted and amine modified magnetic beads (adsorbent) were expected to have the advantage of mobility of the grafted chains in the removal of acidic dyes from aqueous solutions. The magnetic beads have potential as an adsorbent for removal of pollutants under various experimental conditions without significant reduction in their initial adsorption capacity. Copyright © 2011 Society of Chemical Industry