Adsorption of Malachite Green by Diatomite: Equilibrium Isotherms and Kinetic Studies

The utilization of diatomite as potential adsorbent to remove malachite green (MG) from aqueous solution was developed. The characterization of the diatomite was evaluated by scanning electron microscope (SEM) and Brurauer Emmerr Teller (BET). The operating variables of pH, diatomite mass, initial MG concentration, and adsorption reaction time were studied. The equilibrium, kinetics, and thermodynamic parameters were investigated as well. It was found that the diatomite was composed of integral and almost circle sieve tray with lots of small pores on it, which afforded the diatomite high specific surface area of 46.09 m² g^?1. The optimum pH and reaction time were 7 and 90 minutes, respectively. The MG removal increased accordingly as the diatomite mass increased. The isotherm results showed that the equilibrium data were fitted to Langmuir model better, indicating the MG adsorption was better characterized by mono-layer. The maximum mono-layer capacity obtained from Langmuir was 23.64 mg g^?1 at 25°C. The kinetic studies indicated that experiment data followed pseudo-second-order model better. It also revealed that intraparticle diffusion was not the only rate-controlling step. The thermodynamic results concluded that the adsorption process was endothermic and more favorable at high temperature. Researches confirmed the applicability of diatomite as an efficient adsorbent and low-cost process to remove hazardous materials.     

Adsorption of tartrazine from an aqueous solution by octadecyltrimethylammonium bromide-modified bentonite: Kinetics and isotherm modeling

A modified bentonite was prepared at different surfactant (ODTMA) loadings through ion exchange. The obtained organobentonite adsorbent materials were then used for the removal of an anionic dye, tartrazine, from an aqueous solution. The bentonite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and Brunauer- Emmett-Teller (BET) method. The modification of organophilic bentonite by ODTMA increases the basal spacing d₀₀₁ from 24.1 to 39.1 Å when the cation exchange capacity increases from 1 to 4. The increase in the spacing, due to the basic organic modifications, was confirmed by the results of thermogravimetric analysis, Fourier transform infrared spectroscopy, and BET. The effects of contact time, initial concentration, and solution pH onto an adsorbed amount of tartrazine were investigated. To predict adsorption isotherm, the experimental data were analyzed using the Langmuir and Freundlich isotherm equations. It was determined that the isotherm data were fitted to the Langmuir isotherm. The adsorption process was also found to follow a pseudo-second-order kinetic model.     

Effect of Direct yellow 50 removal from an aqueous solution using nano bentonite; adsorption isotherm,kinetic analysis and also thermodynamic behavior

The developing countries are suffering from the toxicity of different industrial effluents, especially dyes that contaminate water systems. This study successfully explained the preparation and characterization of nano bentonite to extract Direct Yellow Fifty (DY50). Direct Yellow 50 is an organic contaminant that may affect the quality of water. The characterization of prepared nanoparticles was done using Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR). The impact of different operating conditions was studied using different pH, dose, temperature, contact time, and initial DY50 concentrations. The obtained results indicated that nano bentonite could adsorb about 94 % at initial concentrations of 40 mg/L, respectively. The optimum removal conditions were observed at an acidic pH (pH 3) using a sorbent material dosage of 0.05 g for 4 h at 30 °C. The adsorption isotherm, kinetic analysis, and thermodynamic behavior were studied using linear equation form, and the adjusted R² was compared to detect the preferred models. The adsorption behavior pseudo-second order kinetics, and fitted Langmuir isotherm model, respectively, showed the chemisorption interactions between adsorbed and sorbed molecules. Thermodynamic behavior indicated that the reaction was exothermic. Finally, this study strongly recommended using nano bentonite for DY50 removal from an aqueous solution.     

Optimizing adsorptive removal of malachite green and methyl orange dyes from simulated wastewater by Mn‐doped CuO‐Nanoparticles loaded on activated carbon using CCD‐RSM: Mechanism,regeneration, isotherm,kinetic, and thermodynamic studies

In the present work, Mn‐doped CuO‐NPs‐AC was prepared by a simple method, characterized using various techniques such as FESEM, EDX, XRD, PSD, and pH_pzc and finally used for the adsorption of malachite green (MG) and methyl orange (MO) in a number of single and binary solutions. A series of adsorption experiments were conducted to investigate and optimize the influence of various factors (such as different pH, concentration of MG and MO, adsorbent mass, and sonication time) on the simultaneous adsorption of MG and MO using response surface methodology. Under optimal conditions of pH 10, adsorbent dose of 0.02 g, MG concentration of 30 mg L^?1, MO concentration of 30 mg L^?1, and sonication time of 4.5 min at room temperature, the maximum predicted adsorption was observed to be 100.0%, for both MG and MO, showing that there is a favorable harmony between the experimental data and model predictions. The adsorption isotherm of MO and MG by Mn‐doped CuO‐NPs‐AC could be well clarified by the Langmuir model with maximum adsorption capacity of 320.69 mg g^?1 and 290.11 mg g^?1 in the single solution and 233.02 mg g^?1 and 205.53 mg g^?1 in the binary solution by 0.005 g of adsorbent mass for MG and MO, respectively. Kinetic studies also revealed that both MG and MO adsorption were better defined by the pseudo‐second order model for both solutions. In addition, the thermodynamic constant studies disclosed that the adsorption of MG and MO was likely to be influenced by a physisorption mechanism. Eventually, the reusability of the Mn‐doped CuO‐NPs‐AC after six times showed a reduction in the adsorption percentage of MG and MO.     

A kinetics,isotherms, and thermodynamic study of diclofenac adsorption using activated carbon prepared from olive stones

The objective of this work was to study the efficiency of activated carbon prepared from agricultural waste (olive stones; OS) on diclofenac (DCF) adsorption in aqueous solutions. The prepared charcoals were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM)/Energy Dispersive X-Ray Analyser (EDX), and Brunauer–Emmett–Teller (BET) analysis techniques. The results show that DCF adsorption is favorable in acid medium and low temperature. The adsorption kinetics follows a pseudo-second-order kinetic model. The adsorption was found to be spontaneous (ΔG°?相似文献   

The use of starch‐modified magnetic Fe0 nanoparticles for naphthalene adsorption from water samples: Adsorption isotherm,kinetic and thermodynamic studies

This study was aimed at investigating the effectiveness of starch‐modified magnetic nanoparticles for the removal of naphthalene, which is a polycyclic aromatic hydrocarbon present in the majority of water sediments, from water resources. Magnetic Fe⁰ nanoparticles have recently been considered because of their high efficiency for contaminant removal. In the present study, Fe⁰ nanoparticles were synthesized using sulfate method and starch was used as a stabilizer. The size of the Fe⁰ nanoparticles was measured as approximately 45 nm using X‐ray diffraction and scanning electron microscopy analyses. The removal efficiency of naphthalene from water using the nanoparticles was evaluated based on various factors including the viscosity of naphthalene dissolved in water, and operation factors such as nanoparticle dosage, contact time, initial naphthalene concentration and pH in non‐continuous reactors were optimized. The results revealed that the starch‐modified nanoparticles have high efficiency for removal of dissolved naphthalene from aqueous solution. Under the optimum conditions, more than 99% of naphthalene at a pH of 5.0 with nanoparticle dosage of 0.05 g was removed from aqueous solution in 5 min. The equilibrium adsorption data were interpreted in terms of Langmuir, Freundlich and Temkin isotherm models and the goodness of fit was inspected using linear regression analysis. Our results indicated that the Langmuir model with maximum adsorption capacity was best fitted, suggesting monolayer adsorption. Moreover, it was found that the adsorption process followed the pseudo‐second‐order kinetic model. In addition, a thermodynamic study indicated that the adsorption process of naphthalene from aqueous solution by the starch‐modified nanoparticles was spontaneous and exothermic.     

Removal of thorium(IV) from aqueous solution by biosorption onto modified powdered waste sludge: experimental design approach

The biosorption of radioactive Th(IV) ions in the aqueous solutions onto the modified powdered waste sludge (MPWS) has been examined. In this context, the parameters affecting biosorption of Th(IV) from aqueous solutions has been examined by using MPWS biosorbent in Box Behnken statistical experimental design. The structure of MPWS biosorbent was characterized by using SEM and BET techniques. According to the experimental design results, MPWS and Th(IV) concentrations should be kept high to achieve the maximum efficiency in Th(IV) biosorption. On the other hand, MPWS, which is also used as a biosorbent, is an economical, effective and natural biosorbent.

     

Removal of Cd(II), Cu(II), and Pb(II) by adsorption onto natural clay: a kinetic and thermodynamic study

In this work, we study the elimination of three bivalent metal ions (Cd²⁺, Cu²⁺, and Pb²⁺) by adsorption onto natural illitic clay (AM) collected from Marrakech region in Morocco. The characterization of the adsorbent was carried out by X-ray fluorescence, Fourier transform infrared spectroscopy and X-ray diffraction. The influence of physicochemical parameters on the clay adsorption capacity for ions Cd²⁺, Cu²⁺, and Pb²⁺, namely the adsorbent dose, the contact time, the initial pH imposed on the aqueous solution, the initial concentration of the metal solution and the temperature, was studied. The adsorption process is evaluated by different kinetic models such as the pseudo-first-order, pseudo-second-order, and Elovich. The adsorption mechanism was determined by the use of adsorption isotherms such as Langmuir, Freundlich, and Temkin models. Experiments have shown that heavy metals adsorption kinetics onto clay follows the same order, the pseudo-second order. The isotherms of adsorption of metal cations by AM clay are satisfactorily described by the Langmuir model and the maximum adsorption capacities obtained from the natural clay, using the Langmuir isotherm model equation, are 5.25, 13.41, and 15.90 mg/g, respectively for Cd(II), Cu(II), and Pb(II) ions. Adsorption of heavy metals on clay is a spontaneous and endothermic process characterized by a disorder of the medium. The values of ΔH are greater than 40 kJ/mol, which means that the interactions between clay and heavy metals are chemical in nature.     

Thermodynamic and Kinetic Studies on the SiH + XH_3 (X=N, P) Reactions

Silicon chemistry has been attracted more attention because of its applications to the production of thin silicon films and the etching of silicon wafers in micro-electronics1. Silylidyne (SiH), which plays an important role in plasma chemical vapor deposition (CVD) processes, has been investigated in experimental research2-5. The reaction mechanism of SiH insertion reaction with small molecules such as XH3 (X=N, P) was recently studied by means of M豯ler-Plesset perturbation theory6.…     

Adsorption of uranium from aqueous solution using HDTMA+-pillared bentonite: isotherm, kinetic and thermodynamic aspects

The ability of hexadecyltrimethylammonium cation pillared bentonite (HDTMA⁺-bentonite) has been explored for the removal and recovery of uranium from aqueous solutions. The adsorbent was characterized using small-angle X-ray diffraction, high resolution transmission electron microscopy, and Fourier transform infrared spectroscopy. The influences of different experimental parameters such as solution pH, initial uranium concentration, contact time, dosage and temperature on adsorption were investigated. The HDTMA⁺-bentonite exhibited the highest uranium sorption capacity at initial pH of 6.0 and at 80?min. Adsorption kinetics was better described by the pseudo-second-order model and adsorption process could be well defined by the Langmuir isotherm. The thermodynamic parameters, ??G° (308?K), ??H°, and ??S° were determined to be ?31.64, ?83.84?kJ/mol, and ?169.49?J/mol/K, respectively, which demonstrated the sorption process of HDTMA⁺-bentonite towards U(VI) was feasible, spontaneous, and exothermic in nature. The adsorption on HDTMA⁺-bentonite was more favor than Na-bentonite, in addition the saturated monolayer sorption capacity increased from 65.02 to 106.38?mg/g at 298?K after HDTMA⁺ pillaring. Complete removal (??100%) of U(VI) from 1.0?L simulated nuclear industry wastewater containing 10.0?mg U(VI) ions was possible with 1.5?g HDTMA⁺-bentonite.     

Magnetically assisted removal and separation of cationic dyes from aqueous solution by magnetic nanocomposite hydrogels

Magnetic poly(acrylic acid‐acrylamide‐butyl methacrylate) (P(AAB)) nanocomposite hydrogels were prepared and used as adsorbents for removal and separation of cationic dyes from aqueous solution. These magnetic P(AAB) nanocomposite hydrogels were characterized by scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). It was found that these magnetic P(AAB) nanocomposite hydrogels had magnetic responsive characters. The dynamic swelling, removal, and separation of cationic dye, crystal violet (CV), and basic magenta (BM) by these magnetic nanocomposite hydrogels were studied. The adsorption capacity and isotherm studies of cationic dyes onto magnetic P(AAB) nanocomposite hydrogels have been evaluated. The magnetic P(AAB) nanocomposite hydrogels containing Fe₃O₄ particles can be easily manipulated in magnetic field for removal and separation of cationic dyes from aqueous solution. Adsorption process agreed very well with the Langmuir and Freundlich models. Copyright © 2010 John Wiley & Sons, Ltd.     

Removal of Cr(VI) from aqueous solutions using EDCC-MCM-41: Isotherm,kinetics and thermodynamic evaluation

Abstract

EDCC-MCM-41, a novel ethylenediamine derivative of MCM-41 was synthesized from a sugar industry waste, bagasse fly ash. Studies were carried out on its ability to remove Cr(VI) from aqueous solution. Its performance was also compared with that of unmodified MCM-41 and an already known derivative NH₂-MCM-41 (both also synthesized from bagasse fly ash) at the same experimental conditions. Results show that the novel adsorbent produced a better sorption performance (adsorption capacity of 49.04?mg g^?1) than MCM-41 and NH₂-MCM-41 which produced adsorption capacities of 13.78?mg g^?1 and 25.29?mg g^?1 respectively. Thermodynamics, kinetics and isotherm studies confirm that the sorption process involving the novel adsorbent is favorable for Cr(VI) and can best be represented by pseudo-second-order kinetics model. The sorption process was also found to be multistep, involving both film diffusion and intraparticle diffusion into the pores on the adsorbent’s surface.

Abbreviations: BFA: Bagasse Fly Ash; MCM-41: Mobil Composition of matter no. 41; NH2-MCM-41: mine functionalized MCM-41; EDCC-MCM-41: Ethylenediamine grafted MCM-41; qe: Mass of material adsorbed at equilibrium per mass of adsorbent; qt: Mass of material adsorbed at any time t per mass of adsorbent; C0: The initial concentration; Ce: The residual concentration at equilibrium; Ct: Residual concentration at any time t; W: The weight of adsorbents; rRMSD: Root mean square deviation; R: Gas constant     

Removal of zinc metal ion (Zn) from its aqueous solution by kaolin clay mineral: A kinetic and equilibrium study

A laboratory batch study has been performed to study the effect of various physic-chemical factors such as initial metal ion concentration, solution pH, and amount of adsorbent, contact time and temperature on the adsorption characteristics of zinc (Zn²⁺) metal ions onto kaolin. It has been found that the amount of adsorption of zinc metal ion increases with initial metal ion concentration, contact time, solution pH but decreases with the amount of adsorbent and temperature of the system. Kinetic experiments clearly indicate that adsorption of zinc metal ion (Zn²⁺) on kaolin is a two steps process: a very rapid adsorption of zinc metal ion to the external surface is followed by possible slow decreasing intra-particle diffusion in the interior of the adsorbent which has also been confirmed by intra-particle diffusion model. The equilibrium time is found to be in the order of 60 min. Overall the kinetic studies showed that the zinc adsorption process followed pseudo-second-order kinetics among pseudo-first-order and intra-particle diffusion model. The different kinetic parameters including rate constant are determined at different initial metal ion concentration, solution pH, amount of adsorbent and temperature respectively. The equilibrium adsorption results are analyzed by both Langmuir and Freundlich models to determine the mechanistic parameters associated with the adsorption process. The value of separation factor, R_L from Langmuir equation also gives an indication of favorable adsorption. Finally thermodynamic parameters are determined at three different temperatures and it has been found that the adsorption process is exothermic due to negative ΔH° accompanied by decrease in entropy change and Gibbs free energy change (ΔG°).     

Adsorption of Fe(III) from Aqueous Medium onto Glycine-Modified Chitosan Resin: Equilibrium and Kinetic Studies

The adsorption of Fe(III) onto glycine-modified chitosan (G@Chs) resin has been investigated. The parameters studied include the effects of pH, contact time, and initial metal ion concentrations by batch method. The optimal pH for the adsorption of Fe(III) was found to be 2.5. The results obtained from equilibrium adsorption studies are fitted in various adsorption models such as Langmuir and Freundlich, and each model parameter were evaluated. Kinetics and thermodynamic parameters of the adsorption process were also investigated. The maximum uptake was found to be 0.9 mmol g^?1 at 25°C.     

Effective removal of 4-Aminophenol from aqueous environment by pea (Pisum sativum) shells activated with sulfuric acid: Characterization,isotherm, kinetics and thermodynamics

The threat of phenol contamination in aquatic ecosystems is significant for the health of the earth's water systems as well as all humans on it. The present study was conducted to synthesize a cost-effective adsorbent (pea shells activated with sulfuric acid, PSASA) from agriculture waste (pea shells) and its use for effective removal of toxic 4-Aminophenol (4-AP). Newly designed PSASA exhibited significant adsorption of 4-AP which was confirmed by SEM, FT-IR, and XRD analysis. Surface topography confirmed high unevenness of the PSASA surface and the macroporous feature of the PSASA was confirmed by BET analysis. . Multiple testing was done to see how various factors affected adsorption such as adsorbent dose, temperature, pH, PZC, the effect of KCl and urea addition and the effect of the initial concentration of 4-AP. A drop in adsorption uptake of 4-AP was observed as the temperature increases from 25 °C to 45 °C. Maximum adsorption uptake (q_m) was found to be 106.11 mg/g at an optimum pH of 7.0 and 25 °C. Among various adsorption isotherm models tested, Langmuir Isotherm gave the best explanation with high R² values of experimental data. The pseudo-first-order model was found to explain the kinetics of adsorption well. The thermodynamic finding confirms the adsorption process was physical and exothermic. The adsorption of 4-AP was primarily governed by electrostatic interaction, hydrogen-bonding and π-π exchange mechanism. Because of the positive outcomes of the present research, we can use the PSASA as a cost-effective adsorbent for removing phenolic compounds.     

Evaluation of Pomegranate (Punica Granatum L.) Pulps for the Removal of Copper(II) Ions: Kinetic,Equilibrium, and Desorption Studies

Pomegranate pulp has been used as novel adsorbent for removing Cu(II) ions from aqueous solution. The optimum conditions for removal of Cu(II) ions were found to be pH 5.32, biosorbent dose 0.1 g, contact time 120 minutes, initial concentration 50 mg/L, and temperature 30°C. The kinetic data were well fitted to the pseudo-second-order model. The biosorption process agreed with the Langmuir isotherm model. Maximum monolayer biosorption capacity was 7.30 mg/g. Thermodynamic parameters suggest that the biosorption process is spontaneous and exothermic. Desorption studies were carried out with different desorbing agents.      

A four-coordinate cadmium(II) polymer for efficient adsorption of Congo red,kinetic, isotherm,fluorescence and antibacterial activity

A 3-D cadmium-based coordination polymer, [CdCl₂L]_n (1) (where L = 1,1-(1,6-hexanediyl)bis(1,3-dihydro-3-methyl-1H-imidazole-2-thione), was synthesized and structurally characterized. The capability of the polymer as an efficient sorbent for Congo red (CR) removal from aqueous solution has been evaluated. Compound 1 has a tetrahedral arrangement with a CdS₂Cl₂ core. L in 1 is bidentate to two neighboring Cd^II centers via the methimidazole sulfurs to create 1D chains propagating along the c-axis. The remaining coordination sites are occupied by two terminal chlorides. The chains are further stabilized by intermolecular C–H?Cl hydrogen bonds between the chlorides and hydrogens of the imidazole rings. Parallel chains stack in the 3-D structure. The Cd^II polymer sorbent was characterized by infrared spectroscopy, elemental analysis, UV–vis, solid fluorescence and X-ray single-crystal diffraction. Sorption kinetics were studied by three kinetic models, second order, Elovich and intraparticle diffusion. The results indicate that the mechanism of the sorption process followed Elovich kinetic model. Sorption equilibrium was also studied with Langmuir, Temkin, and Freundlich isotherm models. The sorption process followed the Temkin isotherm. MIC, MBC, and DNA cleavage activities of 1 were also studied. Furthermore, the UV–vis and solid state fluorescence spectra of 1 were measured.     

An evaluation of coal fly ash as an adsorbent for the removal of methylene blue from aqueous solutions: kinetic and thermodynamic studies

Abstract

In this study the effect of the dose and particle size of the adsorbent, initial dye concentration, initial pH, contact time and temperature were investigated for the removal of by means of fly ash (FA) methylene blue (MB) from an aqueous solution. The FA dose was found to be 2.0?g and the under 270 mesh sized particles were found to be effective particles for adsorption. The adsorption process reached its maximum value at 0.5?mg/L dye concentration and attained equilibrium within 10?minutes. The adsorption isotherm was found to follow the Langmuir model. The estimated adsorption free energy (ΔG^o), enthalpy change (ΔH^o), and entropy change (ΔS^o) for the adsorption process were ?37.77?kJ mol^?1, ?13.44?kJ mol^?1 and 122 J mol^?1 K^?1 respectively at 298 K. The maximum adsorption capacity is 0,12?mg g^?1 at 298 K and 0,07?mg g^?1 at 398 K. The adsorption process was exothermic, feasible and spontaneous. The positive value of ΔS^o shows the affinity of FA for MB while the low value of ΔG^o suggests a physical adsorption process.