Ismail Ozbay

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 ...

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.

Temporal variation of decomposition gases from baled municipal solid wastes

In this study, after nine cylindrical bales containing a mix of different waste materials were constructed, they were stored in the open air and temporal variations of CO(2), CH(4), O(2), and N(2) were monitored over 10 months. In each bale, different waste fractions were considered in order to represent different moisture contents. The results showed that CO(2) increased within very few days to approximately 80% and stabilized later in the range of between 10% and 35% in a month. The O(2) levels dropped from approximately 15% to significantly less than 1%. There was no significant anaerobic decomposition since CH(4) did not exceed 5% during the whole test period. N(2) exhibited an opposite pattern with CO(2). In addition, relationships between waste species in the bales and gas formations were determined by a bivariate correlation analysis. An empirical prediction model for the maximum CO(2) production was also developed.

Energy content of municipal solid waste bales

Baling technology is a preferred method for temporary storage of municipal solid waste (MSW) prior to final disposal. If incineration is intended for final disposal of the bales, the energy content of the baled MSW gains importance. In this study, nine cylindrical bales containing a mix of different waste materials were constructed and several parameters, including total carbon (TC), total organic carbon (TOC), total Kjeldahl nitrogen, moisture content, loss on ignition, gross calorific value and net calorific value (NCV) were determined before the baling and at the end of 10 months of storage. In addition, the relationships between the waste materials and the energy contents of the bales were investigated by the bivariate correlation analyses. At the end, linear regression models were developed in order to forecast the decrease of energy content during storage. While the NCVs of the waste materials before the baling ranged between 6.2 and 23.7 MJ kg−1 dry basis, they ranged from 1.0 to 16.4 MJ kg−1 dry basis at the end of the storage period. Moreover, food wastes exhibited the highest negative correlation with NCVs, whereas plastics have significant positive correlation with both NCVs and TCs. Similarly, TOCs and carbon/nitrogen ratios decreased with the increase in food amounts inside the bales. In addition, textile, wood and yard wastes increase the energy content of the bales slightly over the storage period.

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.

Possibility of the most cost efficient choice: A divided process approach to method and location selection for municipal solid waste management

As studies on municipal solid waste management increased in recent years, many new mathematical models and approaches with a focus on determining the best treatment and disposal scenario were developed and applied. In this study, a mixed integer linear programming model was developed to be used as a facilitative tool for the cost minimisation of municipal solid waste management practices. Since municipal solid waste mass is a mixed composition of various types of waste components with different physical and chemical properties, the model was designed to include all the suitable treatment and disposal methods for these different waste components. The method alternatives with multiple waste inputs, such as aerobic biological treatment and the thermal processes, were divided into a number of inputs to remove their non-linear structures. This way, linear programming could be used, and the linear cost function could be minimised over a set of linear constraints with integer variables. The model was applied to the city of Kocaeli, which will require a new waste management application in the future, beginning from 2015. The results obtained for different haul distance constraints in the study area were presented and assessed. The results showed that all the information required for a comprehensive management task could be modelled by a linear optimisation model with a divided processes approach easily.

Effect of waste matrix for the optimization of moisture content and calorific value of biodried material using Taguchi DOE

Abstract In this study, Taguchi approach was used to determine the influence of waste composition for the optimization of moisture content (MC) and calorific value (CV) of food waste via bio-drying process. The objective was to reduce MC and increase CV of the bio-dried material. The effect of three different levels of four factors including food (FW), paper (Pa), plastic (Pl) waste, and bulking agent (BA) were studied and optimized. The moisture content of the bio-dried material varied between 8.59 and 50.93%, whereas that of the calorific value was 11–25 MJ/kg. The results revealed optimum configurations for MC and CV as FW1Pa3Pl3BA3 and FW1Pa1Pl3BA1, respectively. Regression analysis revealed MC as a positive function of FW and BA with plastic positively correlated with calorific value. ANOVA analysis indicated that FW had more prominent effect on both MC and CV. The predicted and measured values were very close to each other. Additionally, the results realized in the confirmatory experiments at optimized conditions of CV was found to be higher than the test runs of Taguchi design, suggesting that Taguchi method was very successful in the optimization of bio-drying factors for MC and CV.