• Corrosion Science and Technology
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• v.21 no.1
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• pp.9-20
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• 2022

The aim of this paper is to study corrosion inhibition of Aluminum with Capparis decidua extract. The study was performed in a 1.0 M solution of hydrochloric acid (HCl) and was monitored both by measuring mass loss and by using electrochemical and polarization methods. A scanning electron microscopy (SEM) technique was also applied for surface morphology analysis. The results revealed high inhibition efficiency of Capparis decidua extract. Our data also determined that efficiency is governed by temperature and concentration of extract. Optimum (88.2%) inhibitor efficiency was found with maximum extract concentration at 45 o C. The results also showed a slight diminution of aluminum dissolution when the temperature is low. Based on the Langmuir adsorption model, Capparis decidua adsorption on the aluminum surface shows a high regression coefficient value. From the results, the activation enthalpy (∆H#) and activation entropy (∆S#) were estimated and discussed. In conclusion, the study clearly shows that Capparis decidua extract acted against aluminum corrosion in acidic media by forming a protective film on top of the aluminum surface.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.667-674
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• 2020

The adsorption of reactive orange 16 (RO 16) dye by activated carbon was investigated using the amount of adsorbent, pH, initial concentration, contact time and temperature as adsorption variables. The investigated process parameters were separation coefficient, rate constant, rate controlling step, activation energy, enthalpy, entropy, and free energy. The adsorption of RO 16 was the highest at pH 3 due to the electrostatic attraction between the cations (H⁺) on the surface of the activated carbon and the sulfonate ions and hydroxy ions possessed by RO 16. Isotherm data were fitted into Langmuir, Freundlich and Temkin isotherm models by applying the evaluated separation factor of Langmuir (RL=0.459~0.491) and Freundlich (1/n=0.398~0.441). Therefore, the adsorption operation of RO 16 by activated carbon was confirmed as an appropriate removal method. Temkin's adsorption energy indicated that this adsorption process was physical adsorption. The adsorption kinetics studies showed that the adsorption of RO 16 follows the pseudo-second-order kinetic model and that the rate controlling step in the adsorption process was the intraparticle diffusion step. The positive enthalpy change indicated an endothermic process. The negative Gibbs free energy change decreased in the order of -3.16 <-11.60 <-14.01 kJ/mol as the temperature increased. Therefore, it was shown that the spontaneity of the adsorption process of RO 16 increases with increasing temperature.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.9
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• pp.623-629
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• 2011

The adsorption characteristics of tricyclazole by granular activated carbon were experimently investigated in the batch adsorption. Kinetic studies of adsorption of tricyclazole were carried out at 298, 308 and 318 K, using aqueous solutions with 250, 500 and 1,000 mg/L initial concentration of tricyclazole. It was established that the adsorption equilibrium of tricyclazole on granular activated carbon was successfully fitted by Freundlich isotherm equation at 298 K. The pseudo first order and pseudo second order models were used to evaluate the kinetic data and the pseudo second order kinetic model was the best with good correlation. Values of the rate constant ($k_2$) have been calculated as 0.1076, 0.0531, and 0.0309 g/mg h at 250, 500 and 1,000 mg/L initial concentration of tricyclazole, respectively. Thermodynamic parameter such as activation energy, standard enthalpy, standard entropy and standard free energy were evaluated. The positive value for enthalpy, -66.43 kJ/mol indicated that adsorption interaction of tricyclazole on activated carbon was an exothermic process. The estimated values for standard free energy were -5.08~-8.10 kJ/mol over activated carbon at 200 mg/L, indicated toward a exothermic process.

• Applied Chemistry for Engineering
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• v.25 no.6
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• pp.632-638
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• 2014

Batch adsorption studies including equilibrium, kinetics and thermodynamic parameters for the adsorption of new fuchsin dye using granular activated carbon were investigated with varying the operating variables such as initial concentration, contact time and temperature. Equilibrium adsorption data were fitted into Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherms. Adsorption equilibrium was mostly well described by Langmuir Isotherm. From the estimated separation factor of Langmuir ($R_L$ = 0.023), and Freundlich (1/n = 0.198), this process could be employed as an effective treatment for the adsorption of new fuchsin dye. Also based on the adsorption energy (E = 0.002 kJ/mol) from Dubinin-Radushkevich isotherm and the adsorption heat constant (B = 1.920 J/mol) from Temkin isotherm, this adsorption is physical adsorption. From kinetic experiments, the adsorption reaction processes were confirmed following the pseudo second order model with good correlation. The intraparticle diffusion was a rate controlling step. Thermodynamic parameters including changes of free energy, enthalpy, and entropy were also calculated to predict the nature of adsorption. The change of enthalpy (92.49 kJ/mol) and activation energy (11.79 kJ/mol) indicated the endothermic nature of adsorption processes. The change of entropy (313.7 J/mol K) showed an increasing disorder in the adsorption process. The change of free energy found that the spontaneity of process increased with increasing the adsorption temperature.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.430-436
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• 2014

Allura Red (AR) is a water-soluble harmful tar-based food colorant (FD & C Red 40). Batch adsorption studies were performed for the removal of AR using bituminous coal based granular activated carbon as adsorbent by varying the operation parameters such as adsorbent dosage, initial concentration, contact time and temperature. Experimental equilibrium adsorption data were analyzed by Langmuir, Freundlich and Temkin isotherms. The equilibrium process was described well by Freundlich isotherm. From determined separation factor ($R_L$), adsorption of AR by granular activated carbon could be employed as effective treatment method. Temkin parameter, B was determined to 1.62~3.288 J/mol indicating a physical adsorption process. By estimation of adsorption rate experimental data, the value of intraparticle diffusion rate constant ($k_m$) increased with the increasing adsorption temperature. The adsorption process were found to confirm to the pseudo second order model with good correlation. Thermodynamic parameters like change of free energy, enthalpy, and entropy were also calculated to predict the nature adsorption in the temperature range of 298~318 K. The negative Gibbs free energy change (${\Delta}G$ = -2.16~-6.55 kJ/mol) and the positive enthalpy change (${\Delta}H$ = + 23.29 kJ/mol) indicated the spontaneous and endothermic nature of the adsorption process, respectively.

• Clean Technology
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• v.20 no.1
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• pp.35-41
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• 2014

Batch adsorption studies were carried out for equilibrium, kinetic and thermodynamic parameters for quinoline yellow adsorption by granular activated carbon ($8{\times}30mesh$, $1,578m^2/g$) with varying the operating variables like initial concentration, contact time and temperature. Equilibrium adsorption data were fitted into Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms. From estimated Langmuir constant ($R_L=0.0730{\sim}0.0854$), Freundlich constant (1/n = 0.2077~0.2268), this process could be employed as effective treatment for removal of quinoline yellow. From calculated Temkin constant (B = 15.759~21.014 J/mol) and Dubinin-Radushkevich constant (E = 1.0508~1.1514 kJ/mol), this adsorption process is physical adsorption. From kinetic experiments, the adsorption process were found to confirm to the pseudo second order model with $r^2$ > 0.99 for all concentrations and temperatures. Thermodynamic parameters like activation energy, change of free energy, enthalpy, and entropy were also calculated to predict the nature adsorption. The activation energy value (+35.137 kJ/mol) and enthalpy change (35.03 kJ/mol) indicated endothermic nature of the adsorption process. Entropy change (+134.38 J/mol K) showed that increasing disorder in process. Free energy change found that the spontaneity of process increased with increasing adsorption temperature.

• Applied Chemistry for Engineering
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• v.2 no.4
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• pp.385-392
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• 1991

Nonstoichiometry and defect model for $Ni_{1-x}O$ were determined by coulometric titration method. In the temperature range of 1123-1198K and oxygen partial pressure of 0.21-0.1 atm, the nonstoichiometry was found to be proportional to the fourth root of the oxygen partial pressure. This pressure dependence can be explained by the fact that nonstoichiometric $Ni_{1-x}O$ contains singly ionized metal vacancies as the predominant point defects. At T=1173K and $Po_2=0.21atm$, the nonstoichiometry, x was $1.21{\times}10^{-4}$. The standard formation enthalpy of defects in $Ni_{1-x}O$ was found, on the basis of this defect model, to be 0.95 eV. Also the result indicates that both of singly and doubly ionized metal vacancies are simultaneously present at above 1248K.

• Journal of Environmental Science International
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• v.25 no.12
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• pp.1613-1622
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• 2016

Zeolite (FZ), prepared from fly ash, was immobilized with polyacrylonitrile (PAN) to fabricate PAN/FZ beads. The prepared PAN/FZ beads were characterized by scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The optimum ratio to prepare PAN/FZ beads was 0.3 g of PAN to 0.3 g of FZ. The diameter of the prepared PAN/FZ beads was about 3 mm. Sr and Cu ion adsorption experiments were conducted with PAN/FZ beads. A pseudo-second-order model fit the kinetic data for Sr and Cu ion adsorption by PAN/FZ beads well. The equilibrium data fitted well with the Langmuir isotherm model, and the maximum adsorption capacities were 96.5 mg/g and 74.6 mg/g for the Sr and Cu ions, respectively. Additionally, the values of thermodynamic parameters such as Gibbs free energy (${\Delta}G^o$), enthalpy (${\Delta}H^o$) and entropy (${\Delta}S^o$) were determined. The positive values of ${\Delta}H^o$ revealed the endothermic nature of the adsorption process and the negative values of ${\Delta}G^o$ were indicative of the spontaneity of the adsorption process.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.309-314
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• 2015

Adsorption of brilliant blue FCF dye from aqueous solution using coconut shell based activated carbon was investigated. Batch experiments were carried out as function of adsorbent dose, initial concentration, contact time and temperature. The equilibrium adsorption data were analyzed by Langmuir and Freundlich model. The results indicate that Freundlich model provides the best correlation of the experimental data. Base on the estimated Freundlich constant (1/n=0.129~0.212), this process could be employed as effective treatment method. Adsorption kinetics experimental data were modeled using the pseudo-first-order and pseudo-second-order kinetic equation. It was shown that pseudo-second-order kinetic equation could best describe the adsorption kinetics. Base on the negative Gibbs free energy value (-4.81~-10.33 kJ/mol) and positive enthalpy value (+78.59 kJ/mol) indicate that the adsorption is spontaneous and endothermic process.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.199-204
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• 2016

The adsorption of Rhodamine-B dye using granular activated carbon from aqueous solution was investigated. Adsorption experiments were carried out as a function of the adsorbent dose, pH initial concentration, contact time and temperature. The equilibrium adsorption data showed a good fit to Langmuir isotherm model. Based on the estimated Langmuir separation factor ($R_L$ = 0.0164~0.0314), our adsorption process could be employed as an effective treatment method. The kinetics of adsorption followed the pseudo first order model. Also, the negative values of Gibbs free energy (-4.51~-13.44 kJ/mol) and positive enthalpy (128.97 kJ/mol) indicated that the adsorption was spontaneous and endothermic process. The isosteric heat of adsorption increased with increase in the surface loading indicating lateral interactions between the adsorbed dye molecules.