Mahir Alkan

Adsorption kinetics of methyl violet onto perlite

This study examines adsorption kinetics and activation parameters of methyl violet on perlite. The effect of process parameters like contact time, concentration of dye, temperature and pH on the extent of methyl violet adsorption from solution has been investigated. Results of the kinetic studies show that the adsorption reaction is first order with respect to dye solution concentration with activation energy of 13.2 kJ mol(-1). This low activation energy value indicates that the adsorption reaction is diffusion controlled. The activation parameters using Arrhenius and Eyring equations have been calculated. Adsorption increases with increase of variables such as contact time, initial dye concentration, temperature and pH.

Adsorption of methylene blue onto hazelnut shell: Kinetics, mechanism and activation parameters.

The adsorption kinetics of methylene blue (MB) on the hazelnut shell with respect to the initial dye concentration, pH, ionic strength, particle size and temperature were investigated. The rate and the transport/kinetic processes of MB adsorption were described by applying the first-order Lagergren, the pseudo-second-order, mass transfer coefficient and the intraparticle diffusion models. Kinetic studies showed that the kinetic data were well described by the pseudo-second-order kinetic model. Significant increases in initial adsorption rate were observed with the increase in temperature followed by pH and initial MB concentration. The intraparticle diffusion was found to be the rate-limiting step in the adsorption process. Adsorption activation energy was calculated to be 45.6kJmol(-1). The values of activation parameters such as free energy (DeltaG(*)), enthalpy (DeltaH(*)) and entropy (DeltaS(*)) were also determined as 83.4kJmol(-1), 42.9kJmol(-1) and -133.5Jmol(-1)K(-1), respectively.

ADSORPTION OF METHYLENE BLUE FROM AQUEOUS SOLUTION ONTO PERLITE

Adsorption of methylene blue from aqueous solutionsonto unexpanded and expanded perlite samples activatedby H2SO4 and NaCl solutions has beeninvestigated, to assess the possibility of usingperlite for removing cationic dyes from aqueoussolutions. The effects of pH and temperature of dyesolution on the adsorption capacities have beenevaluated. The experimental data were correlatedreasonably well by the Langmuir adsorption isothermand the isotherm parameters (Qm and K) have beencalculated. The removal efficiency (P) anddimensionless separation factor (R) have shown thatperlite can be used for removal of methylene blue fromaqueous solutions, but unexpanded perlite is more effective.

Removal of methyl violet from aqueous solution by perlite

The use of perlite for the removal of methyl violet from aqueous solutions at different concentration, pH, and temperature has been investigated. Adsorption equilibrium is reached within 1 h. The capacity of perlite samples for the adsorption of methyl violet was found to increase with increasing pH and temperature and decrease with expansion and increasing acid-activation. The adsorption isotherms are described by means of the Langmuir and Freundlich isotherms. The adsorption isotherm was measured experimentally at different conditions and the experimental data were correlated reasonably well by the adsorption isotherm of Langmuir. The order of heat of adsorption corresponds to a physical reaction. It is concluded that the methyl violet is physically adsorbed onto the perlite. The removal efficiency (P) and dimensionless separation factor (R) have shown that perlite can be used for removal of methyl violet from aqueous solutions, but unexpanded perlite is more effective.

The Removal of Victoria Blue from Aqueous Solution by Adsorption on a Low-Cost Material

The use of perlite for the removal of victoria blue from aqueous solution at different concentration, ionic strength, pH and temperature has been investigated. Adsorption process is attained to the equilibrium within 1 h. It is found that the adsorption capacity of perlite samples for the removal of victoria blue increased by increasing pH and temperature, and decreased by expansion and ionic strength. The adsorption isotherms are described by means of the Langmuir and Freundlich isotherms. The adsorption isotherm was measured experimentally at different conditions, and the experimental data were correlated reasonably well by the adsorption isotherm of the Langmuir, and the isotherm parameters (Qm and K) have been calculated for perlite samples as well. It is concluded that victoria blue is physically adsorbed onto the perlite. The removal efficiency (P) and dimensionless seperation factor (R) have shown that perlite can be used for removal of victoria blue from aqueous solutions, but unexpanded perlite is more effective.

Adsorption kinetics of maxilon yellow 4GL and maxilon red GRL dyes on kaolinite

Kaolinite, a low-costly material, is the most abundant phyllosilicate mineral in highly weathered soils. In this work, the adsorption kinetics of maxilon yellow 4GL (MY 4GL) and maxilon red GRL (MR GRL) dyes on kaolinite from aqueous solutions was investigated using the parameters such as contact time, stirring speed, initial dye concentration, initial pH, ionic strength, acid-activation, calcination and solution temperature. The equilibrium time was 150 min for both dyes. The results showed that alkaline pH was favorable for the adsorption of MY 4GL and MR GRL dyes and physisorption seemed to play a major role in the adsorption process. It was found that the rate of adsorption decreases with increasing temperature and the process is exothermic. The adsorption kinetics followed the pseudo-second-order equation for both dyes investigated in this work with the k(2) values lying in the region of 1.79 x 10(4) to 107.87 x 10(4)g/mol min for MY 4GL and 3.44 x 10(4) to 72.09 x 10(4)g/mol min for MR GRL. The diffusion coefficient values calculated for the dyes were in the range of 3.76 x 10(-9) to 62.50 x 10(-9)cm(2)/s for MY 4GL and 1.98 x 10(-9) to 44.00 x 10(-9)cm(2)/s for MR GRL, and are compatible with other studies reported in the literature. The thermodynamic activation parameters such as the enthalpy, entropy and free energy were determined. The obtained results confirmed the applicability of this clay as an efficient adsorbent for cationic dyes.

Preconcentration and separation of copper (II) with solvent extraction using N,N′-bis(2-hydroxy-5-bromo-benzyl)1,2 diaminopropane

Abstract Preconcentration and separation with solvent extraction of Cu(II) from aqueous solution using N,N′-bis(2-hydroxy-5-bromo-benzyl)1,2 diaminopropane (H2L) as the new extractant has been studied. Separation of Cu(II) from other metal ions such as Cd(II), Ni(II), Zn(II), Pb(II), Cr(III), Co(II) and Mn(II) at aqueous solutions of various pH values and complexing agent H2L, has been described. The possible extraction mechanism and the compositions of the extracted species have been determined. The separation factors for these metals using this reagent are reported while efficient methods for the separation of Cu(II) from other metal ions are proposed. From the loaded organic phase, Cu(II) stripping was carried out in one stage with different mineral acid solutions. The stripping efficiency was found to be quantitative in case of HNO3 and HCl. From quantitative evaluation of the extraction equilibrium data, it has been deduced that the complex extracted is the simple 1:1 chelate, CuL. The extraction constant has a value of logKex=−4.05±0.04.

Dissolution kinetics of colemanite in oxalic acid solutions

Abstract Colemanite is one of the most important underground riches of Turkey, having approximately 60% of the world boron deposits, and it has a large portion in the deposits. When colemanite having a 2CaO·3B 2 O 3 ·5H 2 O formula is mined naturally, it contains various clay minerals. In this study, the dissolution of colemanite in aqueous oxalic acid solutions was investigated in a batch reactor employing the parameters of stirring speed, particle size, temperature and acid concentration. It was found that the dissolution rate increases with increasing temperature and decreasing particle size. The conversion rate increased until 250 mol m −3 with increasing acid concentration and then decreased with increasing acid concentration. No important effect of stirring speed was observed. The dissolution kinetics of colemanite was examined according to heterogeneous and homogeneous reaction models, and it was found that the dissolution rate was controlled by product layer (or ash layer) diffusion process. The activation energy of the process was determined to be 9.50 kcal mol −1 . The experimental data were tested by graphical and statistical methods and it was found that the following model best fit the experimental data t = t *[1−3(1− X ) 2/3 +2(1− X )].

Dissolution kinetics of colemanite in SO2 saturated water

Abstract The kinetics of dissolution of colemanite (a borate mineral) in water saturated with SO2 were studied. The effects of particle size, temperature and stirring rate were determined. It was found that the rate of dissolution increases with decreasing particle size and with increasing temperature, but is unaffected by stirring rate. The dissolution rate was chemically controlled. The activation energy and pre-exponential factor were calculated as 53.97 kJ mol−1 and 26.1 km s−1, respectively.

Determination of acidity constants of acid-base indicators by second-derivative spectrophotometry.

A method for calculation of acid-base dissociation constants of monoprotic weak organic acids whose acid and base species have overlapping spectra from absorptiometric and pH measurements is described. It has been shown that the second-derivative spectrophotometry can effectively be used for determining the dissociation constants, when dissociation constants obtained for methyl orange and bromothymol blue were compared with the values given in the literature.