Bilge Özbay

Kinetic, thermodynamic, and equilibrium studies for adsorption of azo reactive dye onto a novel waste adsorbent: charcoal ash

abstract This paper investigates the usability of activated charcoal ash for removal of reactive azo dye from aqueous solution. Firstly, elemental composition and surface characteristics of the ash have been examined by using X-ray fluorescence and scanning electron microscopy. The effects of pH, ash dosage, initial dye concentration, agitation period, agitation speed, and temperature were determined by batch experiments. Calculated thermodynamic parameters indicated exothermic and spontaneous characteristics of the adsorption process. Langmuir, Freundlich, and Temkin adsorption isotherms were applied to examine the efficiency of charcoal ash. The obtained correlation coefficients and the considered isotherm parameters showed fitness of the applied isotherm models. Pseudo-second-order kinetic model was found to best represent the kinetic data considering closer values of experimental and calculated dye amounts adsorbed by unit ash mass. Results of the study demonstrated usability of activated charcoal as ...

Predicting tropospheric ozone concentrations in different temporal scales by using multilayer perceptron models

article i nfo This study encompasses ozone modeling in the lower atmosphere. It was aimed to develop an appropriate neural network model in order to predict ozone concentrations in various temporal scales as a function of meteorological variables and air quality parameters. All data were collected from Dilovasi, Turkey as this site represents typical industrial regions with major air pollution problems. In the study performance of the multilayer perceptron models were tested for both annual and seasonal periods as meteorological conditions highly influence the ozone levels. Among the various architectures, a network of two hidden layers with fifteen neurons was found to give successful predictions. Modeling efficiency of the developed network was also evaluated for day light and night time data of warming season exhibiting highest ozone levels. Furthermore, principle component analysis was performed by using annual data in order to reduce the number of input variables describing ozone formation. Model run with principle components has also provided satisfying performance.

Application of economical models for dye removal from aqueous solutions: cash flow, cost–benefit, and alternative selection methods

Although there are numerous adsorption studies performed by using various adsorbents, there is no deterministic knowledge about selection of appropriate adsorbent type from present alternatives. In order to evaluate the advantages of the selected adsorbent species mathematically, researchers may use economical models such as cash flow diagrams, cost–benefit analyses, and alternative selection methods. In spite of the fact that these models have been used in many other engineering branches they are rarely applied in environmental research. In this study we have aimed to investigate usability of the mentioned economical models in adsorption of reactive azo dyes from aqueous solutions. Activated ash, a waste material, and commercial granular activated carbon were decided to be adsorbent alternatives. By applying economical models appropriate adsorbent type was selected considering both adsorption efficiencies and economical conditions. Although similar tendencies were monitored in cash flow diagrams; considering the amount of expenses activated ash exhibited remarkable advantages compared to granular activated carbon. Furthermore, results of cost–benefit analyses showed that activated ash has been advantageous when total costs and profits were evaluated together. Results of this study suggest usage of these economical models even in adsorption studies in order to provide accurate information on the selection of appropriate adsorbent type. These methods enable evaluation of economical conditions, which is generally neglected, together with the obtained removal efficiencies.

Photocatalytic activities of polyaniline-modified TiO2 and ZnO under visible light: an experimental and modeling study

In this study, photocatalytic activities of polyaniline-modified TiO2 and ZnO were examined by photodegradation of Sunfix red S3B reactive dye under visible light. The nanocomposites have been synthesized by in situ oxidative polymerization method. Structural, morphological, and optical characteristics of the prepared photocatalysts were analyzed by Fourier transform infrared spectroscopy and scanning electron microscopy techniques. The results showed that photocatalytic activities of the synthesized nanocomposites have increased due to increasing density of electrons in TiO2 and ZnO. Irradiation tests were performed to investigate the impacts of photocatalyst amount, initial dye concentration, and irradiation period on photodegradation efficiency. Strength and direction of the relationships between the experimental conditions and the obtained photocatalytic efficiencies were also examined by bivariate correlation analysis. Photocatalyst amount was found to be the most effective factor in the process with correlation coefficients of 0.76 and 0.77 for PANI/TiO2 and PANI/ZnO, respectively. In the final stage of the work, artificial neural networks were applied to predict the photodegradation efficiencies of the synthesized nanocomposites, individually. The chosen network architecture provided good prediction performances for both of the nanocomposite types.

Multilayer perceptrons and conventional biosorption equations for modeling removal of Ni(II) by terrestrial moss

AbstractIn this study, multilayer perceptrons (MLPs) and conventional isotherm equations were used to model bisorption of nickel using terrestrial moss. Characterization of the biosorbent was examined by scanning electron microscopy and Fourier transform infrared spectroscopy analyses. Batch biosorption tests were performed to examine the impacts of different experimental conditions. Thermodynamic calculations were made to evaluate the feasibility of the biosorption. All of the experimental data (total 86 data-sets) were used for MLP modeling purposes whereas equilibrium data were used in Langmuir, Freundlich, and Temkin models. Adsorption kinetic data were tested using pseudo-first-order and second-order kinetic models. Performances of the models were evaluated considering calculated R2 and mean standard error (MSE) values. Related isotherm and kinetic parameters were also calculated for conventional biosorption equations. In multilayer perceptron (MLP) modeling studies, network architecture with three h...