Yilmaz Yildirim

Optimization of arsenic removal from drinking water by electrocoagulation batch process using response surface methodology

AbstractIn this investigation, arsenic removal from drinking water using electrocoagulation (EC) in a batch mode was studied by response surface methodology (RSM). The RSM was applied to optimize the operating variables viz. current density (CD, A/m2), operating time (tEC, min) and arsenic concentration (Co, μg/L) on arsenic removal in the EC process using iron electrodes. The combined effects of these variables were analyzed by the RSM using quadratic model for predicting the highest removal efficiency of arsenic from drinking water. The proposed model fitted very well with the experimental data. R2 adjusted correlation coefficients (AdjR2: 0.93) for arsenic removal efficiency showed a high significance of the model. The model predicted for a maximum removal of arsenic at the optimum operating conditions (112.3 μg/L, 5.64 A/m2 and 5 min) after the EC process was 93.86% which corresponded to effluent arsenic concentration of 6.9 μg/L. The minimum operating cost (OC) of the EC process was 0.0664 €/m3. This...

A modeling approach for iron concentration in sand filtration effluent using adaptive neuro-fuzzy model

Effluent iron concentration is an important water quality criterion used for the assessment of the performance of rapid sand filters, in addition to other criteria. This study deals with the prediction of effluent iron concentrations by adaptive neuro-fuzzy (ANFIS) model with input parameters including filter hydraulic loading rate, influent iron concentration, bed porosity and operation time. With trying various types of membership functions, two rule base generation methods, namely subtractive clustering and grid partition were used for a first order Sugeno type inference system. Models were evaluated using root mean squared error (RMSE), index of agreement (IA) and R^2 as statistical performance parameters. The fit between experimental results and model outputs showed good agreement for tap water and deionized water; testing RMSE values were 36.33 and 7.66@mg/L, the IA values were 0.996 and 0.971, and R^2 values were 0.99 and 0.89, respectively. It was concluded that neuro-fuzzy modeling may be successfully used to predict effluent iron concentration in sand filtration.

Facilitated Transport of Cd(II) Through a Supported Liquid Membrane with Aliquat 336 as a Carrier

Selective removal of cadmium from wastewaters is very important, because cadmium is toxic for the environment and for human health. This work is a comprehensive study on the selective removal of Cd(II) from aqueous solutions by using a co-current flow flat sheet supported liquid membrane system. 4.4 × 10−4 M Cd(II) concentration was used as a feed solution in the experiments. Toluene containing Aliquat 336 was used as the membrane liquid in the membrane system. Parameters such as the properties of feed and stripping solutions, carrier concentration, and flow rate, which have roles in transport of Cd(II) ions, were optimized. The efficiency of the system is expressed in terms of permeability and flux values, and transport efficiency. The optimum process conditions for the Cd(II) transport are experimentally found as follows: The feed solution as 2 M HCl, the carrier concentration as 0.1 M Aliquat 336, the stripping solution as 0.06 M EDTA, and the flow rates for the feed and stripping solutions as 50 mL/min and 80 mL/min, respectively. Under these conditions, the Cd(II) transport efficiency is found to be 82%.

A mathematical modeling of sulphur dioxide pollution in Erzurum City.

A non-linear simple air-quality model was developed by applying the continuity equation for the air control volume over Erzurum city center and tested using daily average values of SO2 and meteorological data obtained during the winter seasons in Erzurum, Turkey from 1994 to 1998. Model parameters are estimated by non-linear regression analysis. Agreement between model predictions and measured data was found very satisfactory with standard deviations less than 20 microg/m3.

Effect of carrier type on coupled transport kinetics of thiocyanate ions through liquid membranes

Abstract Coupled transport of thiocyanate ions through a liquid membrane containing quaternary ammonium chloride salts in chloroform was examined. The influences of the carrier type in the membrane phase on the coupled transport of thiocyanate ions were investigated. The kinetics of the coupled transport were analyzed in the formalism of two consecutive irreversible first-order reactions and the kinetic parameters ( k 1 d , k 2 m , k 2 a , R m max , t max , J d max , J a max) were also calculated. For the coupled transport of thiocyanate ions, quaternary ammonium chloride salts having different carbon atom numbers ( C n ) used as carriers were found to increase thiocyanate ions transport efficiency with increasing carbon atom numbers. Tetradecyl trimethylammonium chloride (TDTMACl), hexadecyl trimethylammonium chloride (HDTMACl), and tetraoctyl ammonium chloride (TOACl) were found to be the most effective carrier types for transport of thiocyanate ions when C n is greater than 16. The activation energies for maximum membrane entrance and exit fluxes were calculated as 32.45 kJ/mol and 34.75 kJ/mol, respectively. The values of the activation energy indicate that the process is controlled by species diffusion.

Silica Modified Membrane for Carbon Dioxide Separation from Natural Gas

A dip-coating technique was applied to prepare a selective membrane on a commercial ceramic mesoporous support. Single gas components used for permeance and selectivity were CH4, CO2, H2, He, N2, and O2 (BOC UK) with at least 99.999 (% v/v) purity. The permeances and selectivities were obtained at room temperature and transmembrane pressure differences between 0.05 up to 5.0 barg. Gas permeation experiments showed the permeance of CO2 to be strongly influenced by surface diffusion mechanism. Single gas experiment showed linear flow dependence on the inverse square root of molecular weight at room temperature and 1.0 barg. The single gas selectivities were found to be higher than the ideal Knudsen separation mechanism. The highest CO2/CH4 selectivity value of 24.07 was obtained at 0.7 barg and room temperature.

Statistical Modeling of Winter Air- Pollution Study in Urban Area of Sivas, Turkey

In this study air pollution level in the city center of Sivas for a 10 years’ period was analyzed. Winter season’ and annual averages of sulfur dioxide and particulate matter measurements have been carried out in central area of Sivas by City Health Management. Specifically the winter seasons’ concentrations are presented and their causes and their change with respect to meteorological parameters are discussed. The statistical relations between pollutants and meteorological parameters have been found to be significant.

Adaptive Neuro-Fuzzy Based Method for Daily Estimation of So2 Concentration in City of Zonguldak

Air pollution continues to be a major problem in many countries. Mathematical models are useful in relating emissions to air quality under a variety of meteorological conditions and source emission concentrations over an urban area. Meanwhile, the forecasting capability of sophisticated models is limited to very large and complex terrains. In this study, adaptive neuro- fuzzy logic method has been proposed to estimate the impact of meteorological factors on SO2 pollution levels. The model forecasts satisfactorily the trends in SO2 concentration levels, with performance between 78–90%.