Bahdişen GEZER, Başak URHAN, Yusuf ERSOY
Abstract: Introduction: In recent years industrial wastes have emerged as a result of the rapid growth of the industry. Hexavalent chromium salts are mainly used in paint, paper production, leather technology, explosives and corrosion prevention methods. The mixing of these heavy metal ions into the water is a life-threatening threat to all life on the planet. The human body is absorbed through water and food. This chromium (VI) heavy metal ion, which accumulates in the body, affects a large number of organs with the possible cause of a tendency to accumulate but not biodegrade. This situation has led the studies to be made about the water resources to be well evaluated and reusable. Goal: In this study, adsorption technique, which is a widely used method to remove heavy metals from waste water, was chosen. Adsorption technique is very effective in removing contaminants such as biodegradable dyes, heavy metals, pesticides, easy to apply and economically inexpensive. Scope: The most important treatment for chromium (VI) removal from waste water is catalysis. Due to the large internal surface area of the catalyst to be used and the pore structure of different diameters, the adsorption capacity of the organic and inorganic materials in the liquid is high. Method: As an adsorbent, PdAuNi catalyst was synthesized by ultrasonics. At each stage of the adsorption experiment, catalysts synthesized in 16 nm particle size were used. In the adsorption of chromium (VI); The effects of solution pH (2-4-6), adsorbent amount (2-6-10 mg / L) and adsorption temperature (25-35-45 ° C) on the adsorption process were investigated as experimental parameters. Chromium (VI) concentration was determined by spectrophotometric method. The prepared solution was read at 540 nm wavelength in ultraviolet and visible light (UV-Vis) absorption spectrophotometer. The chromium (VI) removal yield was calculated as% by performing 17 different experiments with different parameter values. Experimental parameters affecting the adsorption, together with the obtained results, have been optimized using Response Surface Mothodology program. Experiments were statistically designed and the effect of the parameters examined. A statistical model was established with the help of analysis of variance (ANOVA) between the parameters related to chromium (VI) adsorption and this optimization model was used to find the optimum experimental conditions. Discussion: Characterization analyzes of the synthesized catalyst were carried out. Scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD) methods were used to determine the suitability of the catalyst for adsorption experiments. The duration of contact in adsorption process is one of the important parameters to be determined. Experiments were carried out with this parameter at normal room temperature. To determine the equilibrium time for chromium (VI) removal with PdAuNi catalyst, 30 mg / L metal concentration and 3 g / L adsorbent concentration were taken at room temperature (~ 25 ° C). The working time was continued for up to 250 minutes to see where the work adsorption was at equilibrium. It was observed that the adsorption reached 110 minutes. The adsorption of catalyst solutions prepared by ultrasound was investigated. The amounts of chromium removal are calculated. The data were analyzed using the statistical design model. Interactions on the chromium (VI) adsorption of the parameters were developed with second order model with effective parameters at 96% confidence level. Statistical analysis of the model was performed. The suitability of the experimental data model was found to be sufficient. Correlation coefficient was found to be 0.9654. Result: As a result of the work done, it has been shown that the aqueous solution prepared by ultrasonics can effectively use the catalyst synthesized for chromium (VI) adsorption. High yield of chromium (VI) removal has been achieved. As the amount of adsorbent increases, the removal is seen to increase. The established model and optimum operating conditions are important in terms of being able to be used in determining the appropriate process conditions that can be set as starting point in detailed work to be carried out in industrial scale applications and in larger sizes and also as an important source of information for feasibility studies.

Anahtar Kelimeler: Leather wastewater, Cr (VI), PdAuNi catalyst, Response Surface Methodology