Mehmet Yalcin

Electrocoagulation of some reactive dyes: a statistical investigation of some electrochemical variables.

In this study, the decolorization of strong colored solutions containing the reactive textile dyes by electrocoagulation was investigated. The experiments were statistically designed and carried out according to a 2(4) full factorial design with two replicate and four center points. This design was extended with eight additional axial points. Then, the non-linear regression was applied on the data by using MINITAB software. The variables chosen for this work are mixing rate, cell voltage, electrolysis time and current density. Results showed that the effective variables on decolorization process are cell voltage, electrolysis time and current density. In addition, to determine the effect of dye and electrode type on decolorization, the additional experiments were carried out. It was determined the dye and electrode type are important on the decolorization process.

The investigation of adsorption thermodynamics and mechanism of a cationic surfactant, CTAB, onto powdered active carbon

In this study, the adsorption mechanism of cethyltrimethylammonium bromide (CTAB), a cationic surfactant, onto powdered active carbon (PAC) from aqueous solution was investigated and also some thermodynamic quantities such as isosteric adsorption enthalpy and entropy for this system were determined. In addition, the mechanistic and thermodynamic results of the experiments were supported with the surface zeta potential measurements. It was found that 5 min is sufficient in order to reach adsorption equilibrium. The adsorption of CTAB onto active carbon/water interface mainly takes place through ion exchange, the ion pairing and hydrophobic bonding. The predominant mechanisms in the lower CTAB concentrations are probably ion exchange and ion pairing. The hydrophobic bonding mechanism predominates with the increasing CTAB concentration. It was determined that the signs of isosteric adsorption enthalpy (ΔHζ) and isosteric adsorption entropy (ΔSζ) for adsorption of CTAB onto PAC are negative and positive, respectively. As temperature increases, the amount of CTAB adsorbed is decreased indicating the exothermic nature of adsorption process. This decreasing verifies the negative sign expected of (ΔHads)ζ. As a result of the adsorption, since the number of the water molecules surrounding the hydrocarbon tails of CTAB molecules decreases and thus the degree of freedom of the water molecules increases, the positive sign of (ΔSads)ζ points out the hydrophobic bonding mechanisms.

Removal of Phosphate from Waste Waters by Adsorption

In this study, the adsorption of phosphate on gas concrete from aqueous solutions has been studied as functions of temperature, mixing rates and suspension pH. Over 99% of phosphate removal was found. The chemical composition of the gas concrete has been defined by X-ray analysis. Experimental data was fitted to the Langmuir equation in order to Langmuir coefficients. After calculating Langmuir coefficients, adsorption free energy (Δ G0ads.) has been determined. In order to gather information about adsorption mechanism, electrophoretic mobilites of particles were measured at various pHs by using Zeta meter 3.0+. It has been found that the adsorption is driven by the interactions between the ionizations of CaO and Al2O3 and the formation of AlPO4. According to the BET (N2) measurements, the specific surface area of gas concrete was found as 22 m2g-1. The surface area after adsorption has been found as 17 m2g-1. The surface area covered by adsorbate has been found as 5.23 m2g-1 by usingas = nsm. am. NA. These two areas determined by BET and Langmuir model were close to each other (BET: 22 m2g-1–17 m2g-1).

Removal of Remazol Red Rb by using Al (III) as Coagulant-Flocculant: Effect of Some Variables on Settling Velocity

This study addresses the research of the removal of a textile dye from aqueous solutions by using aluminum ions as coagulant-flocculant. A simulated textile wastewater was prepared from Remazol Red RB textile dye. The purpose of this study was to investigate the effects of temperature, pH, and concentrations of the cationic surfactant and electrolyte concentration on the settling velocity ofthe simulated textile wastewater. While investigating these factors, levels of variables were determined by considering the characteristicsof traditional textile wastewater like pH, temperature, and dye concentration. Although traditional coagulation-flocculation processesmake use of different aluminium salts as coagulant-flocculent, in this study, Al ions dissolved in pH and temperature of traditional textilewastewater were used. Furthermore, sludge volume index values (SVI) were determined and conductivity measurements carried out. The resultsshowed that, in the working range of these variables, the spectroscopic color measurement revealed 100% decolorization yieldof wastewater. In conclusion, researchers found that the optimum settling velocity conditions were as follows: low temperature (273K),surfactant concentration of 0.10 g L-1, electrolyte concentration of 0.10 g L-1, dye concentration of 0.025 g L-1 and a pH of 10.05. Finally, by conducting experiments twice under the obtained optimum values, mean settling velocity was 0.014 m min-1 and the mean sludge volume index 140 mL g-1.

Investigation of agglomeration rates of two Turkish lignites

Abstract Oil agglomeration is an effective technique for recovering and reducing the ash of coal fines. In this study, the effects of some parameters that markedly influence the effectiveness of selective oil agglomeration, such as solids concentration, amount of agglomeration oil and agglomeration time, on the recovery of agglomerate and the ash and the pyritic sulphur content of the agglomerates were investigated. In order to delineate the relation between the formation rate of coal–oil agglomerates and the removal of ash and pyritic sulphur, the rates of agglomeration for Balkaya and Askale lignites were also calculated by using experimental data. It was found that the success of the process in terms of both recovery and selectivity for lignites was highly dependent on the parameters and control of the agglomeration rate.