• Clean Technology
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• v.18 no.3
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• pp.312-319
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• 2012

Malachite green is used a dye but malachite green is harmful toxic substance. In this study, the adsorption characteristics of zeolite has been investigated for the adsorption of malachite green dissolved in water. The effects of initial dye concentration, contact time, pH and temperature on adsorption of malachite green by a fixed amount of zeolite have been studied in batch adsorber and fixed bed. The adsorption equilibrium data are successfully fitted to the Freundlich isotherm equation in the temperature range from 25 to $45^{\circ}C$. The estimated values of k and ${\beta}$ are 23.60-46.88, 0.225-0.347, respectively. The mechanism of the adsorption process was determined from the intraparticle diffusion model. The effects of the operation conditions of the fixed bed on the breakthrough curve were investigated. When the inlet concentration and initial flow rate of malachite green are increased, the corresponding adsorption breaktime appears to decrease. Breaktime increased with increasing bed height and length of adsorption zone showed similar patterns.

• Clean Technology
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• v.18 no.1
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• pp.76-82
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• 2012

The paper includes utlization of zeolite as potential adsorbent to remove a hazardous malachite green from waste water. The adsorption studies were carried out at 298, 308 and 318 K and effects of temperature, contact time, initial concentration on the adsorption were measured. On the basis of adsorption data Langmuir and Freundlich adsorption isotherm model were also confirmed. The equilibrium process was described well by Freundlich isotherm model, showing a selective adsorption by irregular energy of zeolite surface. From determined isotherm constants, zeolite could be employed as effective treatment for removal of malachite green. From kinetic experiments, the adsorption process followed the pseudo second order model, and the adsorption rate constant ($k_2$) decreased with increasing initial concentration of malachite green. Thermodynamic parameters like activation energy, change of free energy, enthalpy, and entropy were also calculated to predict the nature adsorption. The activation energy calculated from Arrhenius equation indicated that the adsorption of malachite green on the zeolite was physical process. The negative free energy change (${\Delta}G^{\circ}$ =-6.47~-9.07 kJ/mol) and the positive enthalpy change (${\Delta}H^{\circ}$ = +32.414 kJ/mol) indicated the spontaneous and endothermic nature of the adsorption in the temperature range 298~318 K.

• Applied Chemistry for Engineering
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• v.24 no.2
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• pp.184-189
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• 2013

In the present study, batch experiments were carried out for the utilizatioin of activated carbon as a potential adsorbent to remove a hazardous malachite green from an aqueous solution. The effects of various parameters such as temperature, contact time, initial concentration on the adsorption system were investigated. On the basis of adsorption data Langmuir and Freundlich adsorption isotherm model were also confirmed. The equilibrium process was described well by Langmuir isotherm model. From determined separation factor, the activated carbon could be employed as an effective treatment for removal of malachite green. From kinetic experiments, the adsorption process followed the pseudo second order model, and the adsorption rate constant ($k_2$) decreased with increasing both the initial concentration of malachite green and the adsoprtion temperature. Thermodynamic parameters like that activation energy, change of free energy, enthalpy, and entropy were also calculated to predict the adsorption nature. The activation energy calculated from Arrhenius equation indicated that the adsortpion of malachite green on the zeolite was physical process. The negative Gibbs free energy change ($\Delta$G = -3.68~-7.76 kJ/mol) and the positive enthalpy change ($\Delta$H = +26.34 kJ/mol) indicated the spontaneous and endothermic nature of the adsorption in the temperature range of 298~318 K.

• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.216-221
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• 2007

The adsorption characteristics of malachite green on waste garnet have been investigated for its treatment from aqueous solution by employing waste garnet which is generated from the abrasive production process as an adsorbent. The influential factors examined were the initial concentration of malachite green in solution, reaction temperature, and the amount of adsorbent. Also, the effect of the modification of the surface of adsorbent on adsorption was examined. As the initial malachite green was increased with reaction temperature and the color removal of malachite green-containing solution was promoted with the amount of adsorbent. Finaly, increased adsorption of malachite green could be attained when the surface of glass was modified by hexamethyldisilazane.

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.300-309
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• 2010

The ability of sodium-exchanged clay particles as an adsorbent for the removal of commercial dyes, Methylene blue (MB) and Malachite green oxalate (MG) from aqueous solutions has been investigated under various experimental conditions. The effect of the experimental parameters, such as pH solution, agitation time, adsorbate concentration and adsorbent dose were examined. Maximum adsorption of dyes, i.e. >90% has been achieved in aqueous solutions using 0.03 g of clay at a pH of 7 and 298 K for both dyes. The adsorption process was a fast and the equilibrium was obtained within the first 5 min. For the adsorption of both MB and MG dyes, the pseudo-second-order reaction kinetics provides the best correlation of the experimental data. The adsorption equilibrium results follow Langmuir and Dubini-Radushkevich (D-R) isotherms with high regression coefficients $R^2$ > 0.98. The mean free energies $E_a$ of adsorption from D-R model were 3.779 and 2.564 kj/mol for MB and MG respectively, which corresponds to a physisorption process.

• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.151-158
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• 2022

In this paper, parameter characteristics such as pH effect, isotherm, kinetic and thermodynamic parameters and competitive adsorption of dyes including malachite green (MG), direct red 81 (DR 81) and thioflavin S (TS), which have different functional groups, being adsorbed onto activated carbon were investigated. Langmuir, Freundlich and Temkin isotherm models were employed to find the adsorption mechanism. Effectiveness of adsorption treatment of three dyes by activated carbon were confirmed by the Langmuir dimensionless separation factor. The mechanism was found to be a physical adsorption which can be verified through the adsorption heat calculated by Temkin equation. The adsorption kinetics followed the pseudo second order and the rate limiting step was intra-particle diffusion. The positive enthalpy and entropy changes showed an endothermic reaction and increased disorder via adsorption at the S-L interface, respectively. For each dye molecule, negative Gibbs free energy increased with the temperature, which means that the process is spontaneous. In the binary component system, it was found that the same functional groups of the dye could interfere with the mutual adsorption, and different functional groups did not significantly affect the adsorption. In the ternary component system, the adsorption for MG lowered a bit, likely to be disturbed by the other dyes meanwhile DR 81 and TS were to be positively affected by the presence of MG, thus resulting in much higher adsorption.

• Journal of Korean Society on Water Environment
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• v.25 no.3
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• pp.459-463
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• 2009

The adsorption features of malachite green onto activated carbon have been investigated for its treatment from aqueous solution. The influential factors were examined the initial concentration of malachite green, reaction temperature, and pH. Under experimental conditions, adsorption equilibrium of malachite green was attained within 2 hr after the adsorption started. The adsorption reaction of malachite green followed the pseudo-second order rate model, and the adsorption rate constants(k2) decreased with increasing initial concentrations of malachite green. Adsorption behavior of malachite green on activated carbon was found to follow the Freundlich model well in the initial adsorbate concentration range. With increase in temperature, the adsorbed amount of malachite green at equilibrium increased, which indicate that the adsorption reaction was endothermic reaction. Thermodynamic parameters for malachite green adsorption reaction were estimated at varying temperatures, and in the pH range of 2-10, adsorption of malachite green increased.

• Composites Research
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• v.35 no.2
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• pp.98-105
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• 2022

In this study, polyvinyl alcohol (PVA)/graphene oxide (GO)/iron oxide (Fe₃O₄) magnetic microgels were prepared using a microfluidic approach and the dye adsorption capacity of the microgels was confirmed. The adsorption capacity (q_e) of the gels was evaluated by varying the dye concentration, pH, and contact time with the microgels. The dyes used in this work were methylene blue (MB), crystal violet (CV), and malachite green (MG), and microgels showed the highest adsorption capacity (191.1 mg/g) in methylene blue. The microgels exhibited the highest adsorption capacity in the dye aqueous solution at pH 10 due to the presence of atomic nitrogen ions (N⁺) on the dye molecules. The adsorption isotherm studies revealed that the Langmuir isotherm is the best fit isotherm model for the dye adsorption on the microgels, indicative of monolayer adsorption. The kinetic analysis exhibited that the pseudo-second order model fits better than the pseudo-first order model, confirming that the adsorption process is chemisorption. In addition, the magnetic microgels showed good reusability and recovery efficiency. It was confirmed that the adsorption capacity of the gels maintains more than 70% of the initial capacity after 5 times of cycle experiments.