I. Ayhan Şengil

Adsorption of reactive dyes on calcined alunite from aqueous solutions

An attempt to alleviate the problem caused by the presence of reactive dyes in textile effluents was undertaken. Since alunite is a very abundant and inexpensive, we decided to experiment with it as a potential adsorbent for a certain type of the supracited pollutants used in cellulose fibers dyeing. The adsorption of Reactive Blue 114 (RB114), Reactive Yellow 64 (RY64) and Reactive Red 124 (RR124) by calcined alunite was studied by varying parameters such as the calcination temperature and time, particle size, pH, agitation time and dye concentration. Acidic pH was favorable for the adsorption of RB114 and alkaline pH was favorable to both RY64 and RR124. The equilibrium data fit the Langmuir isotherm. The adsorption capacities were found to be 170.7, 236 and 153 mg dye per gram of calcined alunite for RB114, RY64 and RR124, respectively. The pseudo first- and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data were fitted by the second-order kinetic model, which indicates that chemicalsorption is the rate limiting step, inside of mass transfer.

The decolorization of C.I. Reactive Black 5 in aqueous solution by electrocoagulation using sacrificial iron electrodes

The removal of color from synthetic wastewater containing Reactive Black 5 was experimentally investigated using direct current electrocoagulation at iron electrodes. The effects of operational parameters such as current density, initial pH, electrolysis time, initial dye concentration and solution conductivity on color removal efficiency were investigated in this study. The optimum operating range for each of these operating variables was experimentally determined. The experimental results show that the color of Reactive Black 5 in the aqueous phase was removed effectively. Under the conditions of an initial dye concentration of 100 mg L(-1), initial pH of 5, current density of 4.575 mAcm(-2), salt concentration of 3000 mg L(-1), temperature of 20 degrees C, and interelectrode distance of 2.5 cm, the color removal efficiency reached 98.8%. Electrical energy consumption in the above conditions for the decolorization of the dye solution containing Reactive Black 5 was 4.96 kWh/kg dye. Results show that the first-order rate equation provides the best correlation for the decolorization rate of Reactive Black 5.

Biosorption of Pb(II) ions by modified quebracho tannin resin.

In this study, the effect of temperature, pH and initial metal concentration on Pb(II) biosorption on modified quebracho tannin resin (QTR) was investigated. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to investigate QTR structure and morphology. Besides, the specific BET surface area and zeta-potential of the QTR were analysed. Thermodynamic functions, the change of free energy (DeltaG degrees), enthalpy (DeltaH degrees) and entropy (DeltaS degrees) of Pb adsorption on modified tannin resin were calculated as -5.43 kJ mol(-1) (at 296+/-2K), 31.84 kJ mol(-1) and 0.127 J mmol(-1) K(-1), respectively, indicating the spontaneous, endothermic and the increased randomness nature of Pb(2+) adsorption. The kinetic data was tested using pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion model. The results suggested that the pseudo-second-order model (R(2)>0.999) was the best choice among all the kinetic models to describe the adsorption behavior of Pb(II) onto QTR. Langmuir, Freundlich and Tempkin adsorption models were used to represent the equilibrium data. The best interpretation for the experimental data was given by the Langmuir isotherm and the maximum adsorption capacity (86.207 mg g(-1)) of Pb(II) was obtained at pH 5 and 296 K.

Adsorption of Acid Dyes from Aqueous Solutions by Calcined Alunite and Granular Activated Carbon

Dyestuff production units and dyeing units have always had a pressing need for techniques that allow economical pretreatment for color in the effluent. The effectiveness of adsorption for dye removal from wastewaters had made it an ideal alternative to other expensive treatment options. This paper deals with an investigation on alunite, existing wide reserves in Türkiye and in the world, for dye removal. Calcined alunite was utilized for this study and its performance evaluated against that of granular activated carbon (GAC). The use of calcined alunite for the removal of Acid Blue 40 and Acid Yellow 17 (AB 40 and AY 17) from aqueous solution at different calcination temperature and time, particle size, pH, agitation time and dye concentration has been investigated. The adsorption followed by Langmuir and Freundlich isotherms. The process follows first order adsorption rate expression and the rate constant was found to be 7.65 × 10−2 and 5.74 × 10−2 min−1 for adsorption of AB 40 and AY 17 on calcined alunite, and 8.41 × 10−2 and 10.04 × 10−2 min−1 for adsorption of AB 40 and AY 17 on GAC, respectively. The equilibrium saturation adsorption capacities were 212.8 mg dye/g calcined alunite and 151.5 mg dye/g calcined alunite for AB 40 and AY 17, respectively. The adsorption capacities were found to be 57.47 mg and 133.3 mg dye per g of GAC for AB 40 and AY 17, respectively. The results indicate that, for the removal of acid dye, calcined alunite was most effective adsorbent, although comparable dye removals were exhibited by GAC.

Biosorption of Cu(II) from aqueous solutions by mimosa tannin gel.

The biosorption of Cu(II) from aqueous solutions by mimosa tannin resin (MTR) was investigated as a function of particle size, initial pH, contact time and initial metal ion concentration. The aim of this study was to understand the mechanisms that govern copper removal and find a suitable equilibrium isotherm and kinetic model for the copper removal in a batch reactor. The experimental isotherm data were analysed using the Langmuir, Freundlich and Temkin equations. The equilibrium data fit well in the Langmiur isotherm. The experimental data were analysed using four sorption kinetic models -- the pseudo-first- and second-order equations, and the Elovich and the intraparticle diffusion equation -- to determine the best fit equation for the biosorption of copper ions onto mimosa tannin resin. Results show that the pseudo-second-order equation provides the best correlation for the biosorption process, whereas the Elovich equation also fits the experimental data well. Thermodynamic parameters such as the entropy change, enthalpy change and Gibbs free energy change were found out to be 153.0 J mol(-1)K(-1), 42.09 kJ mol(-1) and -2.47 kJ mol(-1), respectively.

Effectiveness of tannins obtained from valonia as a coagulant aid for dewatering of sludge

Abstract For evaluating the tannin (natural polyelectrolyte) and AN913 (synthetic anionic polyelectrolyte) as a coagulant aid for treating raw water to remove suspended matter the tannin or AN913 was added to the synthetic water sample which was stirred and then allowed to settle. After a settled time a sample of the supernatant liquid was removed and its turbidity determined. For use as sludge conditioners the optimum polymer dose was determined. Formed sludge dewatering investigated for optimum pH and optimum dose of coagulant and coagulant aids. The sludge filterability was determined by specific resistance measurements. Tannin and Al 2 (SO 4 ) 3 together gave a significant improvement comparing with Al 2 (SO 4 ) 3 only. As coagulant aids, tannin was more effective than AN913.

Kinetic and isotherm studies of Cu(II) biosorption onto valonia tannin resin

The biosorption of Cu(II) from aqueous solutions by valonia tannin resin was investigated as a function of particle size, initial pH, contact time and initial metal ion concentration. The aim of this study was to understand the mechanisms that govern copper removal and find a suitable equilibrium isotherm and kinetic model for the copper removal in a batch reactor. The experimental isotherm data were analysed using the Langmuir, Freundlich and Temkin equations. The equilibrium data fit well in the Langmuir isotherm. The experimental data were analysed using four sorption kinetic models - the pseudo-first- and second-order equations, the Elovich and the intraparticle diffusion model equation - to determine the best fit equation for the biosorption of copper ions onto valonia tannin resin. Results show that the pseudo-second-order equation provides the best correlation for the biosorption process, whereas the Elovich equation also fits the experimental data well.

Enhancing phosphate removal from wastewater by using polyelectrolytes and clay injection

Aluminum sulfate, alum, is a common chemical coagulant used for coagulation. Recently, polymers have been utilized in coagulation/flocculation processes for water purification. In this study, the ability of two organic polymers, tannin (natural polyelectrolyte) and AN913 (synthetic anionic polyelectrolyte), and clay to act as coagulant aids was tested, in the removal of phosphate from synthetic wastewater. Contaminants in synthetic waters were coagulated using alum, alum+clay, alum+tannin, alum+AN913, alum+tannin+clay and alum+AN913+clay. Alum together with polymers as coagulant aids yielded a significant improvement in phosphate removal compared with alum alone, for initial phosphate concentrations of 5-15 mg/l PO(4)(3-). The use of clay and polyelectrolytes improved the efficiency of phosphate removal and lowered the required alum dose. Fourier transform infrared (FTIR) spectroscopy was used for the identification and characterization of the aluminum species formed during dephosphorization of the synthetic wastewater with and without tannin, AN913 and clay. Evidence from FTIR spectroscopy showed the formation of aluminum hydroxyphosphate, hydroxy-Al-tannate and aluminum complexes containing phosphorus, tannin and AN913.

Treatment of tannery liming drum wastewater by electrocoagulation

The removal of COD, suphide and oil-grease from tannery liming drum wastewater was experimentally investigated using direct current (DC) electrocoagulation (EC). In the EC of the wastewater, the effects of initial pH, electrolysis time and current density were examined. The COD, sulphide and oil-grease in the aqueous phase were effectively removed when mild steel electrodes were used as sacrificial anode. The optimum operating range for each operating variable was experimentally determined. The experimental results show that COD, sulphide and oil-grease was removed effectively. The overall COD, sulphide and oil-grease removal efficiencies reached 82%, 90% and 96%, respectively. The optimum current density for removal of COD, sulphide and oil-grease in the tannery liming drum wastewater were 35 mA/cm(2), 35 mA/cm(2) and 3.5 mA/cm(2) at 10 min electrolysis time and pH 3, respectively. Mean energy consumptions were 5.768 kWh/m(3) of COD, 0.524 kWh/m(3) of sulphide and 0.00015 kWh/m(3) of oil-grease. Results show that the pseudo-second-order rate equation provides the best correlation for the removal rate of the parameters.

Simultaneous decolorization of binary mixture of blue disperse and yellow basic dyes by electrocoagulation

Abstract In this paper, electrocoagulation (EC) has been used for the removal of color from solution containing a disperse dye (Disperse blue 56) and a basic dye (Basic Yellow 28) in the same solution. Iron electrodes were arranged in a monopolar fashion. In the EC of the dye mixture, the effects of the supporting electrolyte, initial pH, electrolysis time, and current density were examined. The results indicated that the majority of the aforementioned dyes in the synthetic wastewater were effectively removed when iron electrodes were used as a sacrificial anode. The amount of dye removed was found by the application of the first derivative spectrophotometric method to the synthetic dye mixtures. In the presence of both dye molecules, the optimum pH was found to be 7, optimum NaCl concentration was 3,000 mg L−1, and optimum current density was 10.89 mA cm−2. The experimental data were fit to a variety of isotherm models to determine the characteristics of the EC process. The results indicated that the mod...