Nihal Bektaş

Single electrode conductivity detection for electrophoretic separation systems

Various types of detectors have been utilised in electrophoretic separation systems, but conductivity detection provides the obvious choice for detecting ionic substances. This paper describes a new design of conductivity detector utilising a single, on column, sensing electrode. This new design is seen as offering the twin advantages of much higher resolution, than has previously been possible, and simple construction. The detector has been evaluated using separations of sodium and potassium in capillary isotachophoretic and miniaturised planar polymer isotachophoretic separation systems. Good linearity has been found and the limit of detection of sodium calculated to be 0.43 mM.

Isotachophoresis on Planar Polymeric Substrates

The work presented here describes the design, fabrication, evaluation and use of miniaturised polymeric devices, for performing capillary isotachophoresis (CITP). CITP is an electrophoretic separation method that provides a simple technique for the analysis of ionic substances. The two principal advantages of CITP over capillary zone electrophoresis (CZE) are that it allows larger volumes of dilute sample solutions to be loaded into the separation channel and the electrolyte system can be chosen to eliminate sample matrix constituents which are not of interest. In addition CITP can be used as a preconcentration technique to provide a narrow sample band for subsequent on-line CZE separation. The devices are fabricated from silicone elastomer with on-chip conductivity detection. The resulting system has been used to separate simple mixtures of ions.

The Adsorption of Arsenic Ions Using Beidellite, Zeolite, and Sepiolite Clays: A Study of Kinetic, Equilibrium and Thermodynamics

Arsenic contamination in drinking water resources is a global problem; therefore, its removal from drinking water has become an important sustainable matter. The adsorption process can be more cost-effective and applicable, especially, if the absorbents used in the process are low-cost natural geo-materials. Beidellite, zeolite, and sepiolite are inexpensive and natural minerals available locally, modified, and used as adsorbents for the removal of arsenic ions from aqueous solutions in batch experiments. The kinetics of the adsorption process was separately tested for the pseudo-first order and pseudo-second order reactions and intra-particle diffusion models. The rate constants of adsorption for all these kinetic models were calculated. The comparison among the models showed that the pseudo second-order model best described the adsorption kinetics. Applied to the experimental equilibrium, at different temperatures were the Langmuir and Freundlich isotherm models. The Langmuir isotherm was used to calculate the adsorption capacities (Q°) of minerals for arsenic ions. The adsorption capacities of these three modified minerals, at different temperatures, ranged from 476 to 841 µg/g. Thermodynamic studies showed that the arsenic uptake reactions by minerals were endothermic and spontaneous in nature. Bottled spring water containing arsenic, sold in markets, was used to conduct the arsenic adsorption study beidellite, zeolite, and sepiolite, minerals which efficiently removed the arsenate ions from the bottled drinking water. The use of modified beidellite, zeolite, and sepiolite as adsorbents in the arsenic ion removal processes is possible, based on the optimum parameters found.

Determination of gaseous sulphur dioxide by capillary isotachophoresis

Abstract An isotachophoretic method is described for the analysis of sulphur dioxide, a major contributor to air pollution and acid rain. Two different sampling procedures are presented: an absorbing bottle equipped with a fritted glass bubbler and a counter-current membrane collection chamber constructed from Kel–F. The sample is collected in a dilute solution of H 2 O 2 and analysed as sulphate by capillary isotachophoresis (cITP). The limit of detection for the cITP method used was found to be 2.4 ppm. The range of sulphate concentrations analysed by cITP spanned 5–100 ppm; the gas flow-rates used for SO 2 sampling varied from 170 to 660 ml/min. Good absorbing efficiency is observed for the absorbing bottle sampling system. Initial work on the membrane sampling system is also described. Under the conditions used in this initial study overall limits of detection were 1 ppm SO 2 for the absorber bottles (with an 80 min sampling time) and 17 ppm for the membrane collection chamber. The method is low-cost, easily operated and needs no sample pre-treatment.

Photocatalytic Fenton oxidation of sodium dodecyl sulfate solution using iron-modified zeolite catalyst

Abstract The heterogeneous photo-Fenton oxidation of sodium dodecyl sulfate (SDS) solutions was investigated in a quartz batch reactor using an artificial UV light source. Fe-modified zeolite was used as a heterogeneous catalyst in the process. The effect of various process variables on SDS removal performance was evaluated by examining temperature, pH, H2O2 dosage, catalyst loading, initial SDS concentration and light intensity. The optimal operational parameters were found as follows: temperature 35°C, solution pH 7.5, 15 mmol H2O2 dosage, and 1 g/L catalyst loading. Stability and the reuse of the catalyst were also tested. Comparison with homogenous photo-Fenton process was also performed by analyzing SDS removal rate. Kinetic investigation of removal process based on different kinetic models was evaluated. The results showed that the first-order kinetic model was in good correlation with experimental data.

Determination of physical and chemical properties of waste tyres in usage/storage areas

Used tyres interact with soil, water and the atmosphere during temporary or permanent storage and also when used as additive or paving materials in landscapes, asphalt, concrete and for coastal protection. Various organic and inorganic compounds can penetrate into the environment from used tyres at various rates dependent on climatic and soil conditions. In this study, laboratory leaching batch experiments were conducted to determine the heavy metals and other constituents that could possibly penetrate into the leachate created during tyre usage/storage. The results obtained in this study showed that tyres were dissolved due to their usage and the climatic and environmental conditions thus leading to soil and groundwater pollution in their usage/reuse/storage/disposal areas. Zinc concentrations were the highest among the heavy metals measured in the simulated leachate. The average weight loss for all tyre samples was calculated as 3.6‰.

Investigation of shipyard wastewater treatment using electrocoagulation process with Al electrodes

ABSTRACT In this study, shipyard oily wastewater treatment was investigated by electrocoagulation (EC) using aluminum electrodes in a batch reactor by evaluating different operation conditions. The maximum chemical oxygen demand (COD) removal efficiency of 88.83% was obtained at current density of 3 mA/cm2. The removal efficiency was gradually improved with increasing current density and decreased with increasing COD concentration. However, initial pH value was not determinant factor for this process. Total energy and electrode cost were calculated as

Hazardous Wastes and Waste Generation Factors Originating from Battery and Accumulator Manufacturing Sector in Turkey

0.88 per m3 treated wastewater. The result of this research shows that EC process seems to be an efficient method for the oily wastewater treatment.

Removal of Direct Orange-46 from Aqueous Solutions Using MN-Diatomite

RESEARCH ARTICLE Hazardous Wastes and Waste Generation Factors Originating from Battery and Accumulator Manufacturing Sector in Turkey Senem Bayar, Nihal Bektaş, Mehmet S. Öncel, Güleda O. Engin, Yasemin Ç and Emin E. Çelebi Department of Environmental Engineering, Gebze Tecnical University, 41400, Gebze, Kocaeli, Turkey Department of Environmental Engineering, Yildiz Tecnical University, Esenler, Istanbul, Turkey

Kinetic and equilibrium studies in removing lead ions from aqueous solutions by natural sepiolite

Textile industry wastewater is an important pollution source that contains high concentration of inorganic and organic chemical species. Clay minerals are useful due to their chemical and mechanical stability, high surface area and structural properties. Diatomite is a pa1e-coloured, soft, lightweight sedimentary rock composed principally of silica microfossils of aquatic unicellular algae. Diatomite can be used as an adsorbent in wastewater treatment due to its unique combination of physical and chemical properties such as highly porous structure, low density and high surface area. Naturally occurring low cost diatomite as an adsorbent offers great potential for removing dyes from industrial wastewater. The aim of this work is to evaluate the removal of direct orange-46 from aqueous solution using manganese conditioned diatomite. The results from isotherm studies were evaluated with different isotherm models. The constants and correlation coefficients of these isotherm models for the present system were calculated and compared.