Erhan Gengec

Optimizing Dye Adsorption Onto a Waste-Derived (Modified Charcoal Ash) Adsorbent Using Box-Behnken and Central Composite Design Procedures

The objective of this work was to optimize the experimental conditions for adsorption of reactive azo dye using a waste-derived adsorbent, modified charcoal ash. With this aim, Box–Behnken and Central Composite Design models were applied to achieve maximum dye adsorption and minimum operation costs. In the models studied, independent variables were pH (1–12), ash dosage (0.02–0.1xa0g/50xa0ml), dye concentration (10–200xa0mg/L), and operation time (10–130xa0min). The quadratic models were developed for the predetermined responses (dye removal and operation cost), and it was clearly seen that the experimental data fit well to model predictions statistically (R2u2009≥u20090.89 and “Probu2009>u2009F”u2009<u20090.005). Experimental conditions for optimum dye removal of 90.2xa0% were determined as pH 2, 0.08xa0mg/50xa0ml ash dosage, 80.5xa0mg/L dye concentration, and 100xa0min agitation period. Operating cost which includes expenses for modification of adsorbent, arrangement of solution pH, and sample shaking was calculated as 1.17 €/m3 for optimized conditions.

Treatment of Baker's Yeast Wastewater by Electrocoagulation and Evaluation of Molecular Weight Distribution with HPSEC

In the present paper, the molecular weight distributions (MWDs) of Bakers yeast wastewater (BYW) during electrocoagulation (EC) are investigated by High Performance Size Exclusion Chromatography (HPSEC) with ultraviolet diode array (DAD) and refractive index detectors (RID). The results of this study show that using DAD and RID in HPSEC are quite useful in order to reveal changes in MWDs of all components (whether UV-Vis absorption or not) by RID, and colored (strongly absorb UV-Vis radiation) by DAD. Molecular Weights (MW) of components are varied in a wide range of 92.0 Da – 2.1 × 106 Da. The high molecular weight components (HMWCs) and low molecular weight components (LMWCs) are present in low concentrations but they contribute high amount to color intensity (total contribution of two fractions are about 80%) whereas the intermediate molecular weight components (IMWCs) have high concentration with low amount to color intensity. The optimum operating conditions for the removal of color and COD are found as 86% and 43% at 80 A/m2, pHi 4 and 20 min in EC process with Al electrode. The EC process remove the HMWCs more efficiently; thus color removal efficiencies are high with respect to COD and TOC removal efficiencies during EC.

Electrochemical treatment of Baker's yeast wastewater containing melanoidin: optimization through response surface methodology

Effluents from Bakers yeast production plant contain a high percentage of color and a large amount of organic load. In the present study, Bakers yeast wastewater (BYW) is treated with the electrocoagulation (EC) process using Al electrodes. Operating parameters (pH, current density, color intensity and operating time) are optimized by response surface methodology (RSM). Quadratic models are developed for the responses which are removal efficiencies of color, chemical oxygen demand (COD) and total organic carbon (TOC) and operating cost (OC). Optimum operating parameters and responses are determined as initial pH 5.2, current density of 61.3 A/m(2) and operation time of 33 min, and 71% of color, 24% of COD, 24% of TOC removal efficiencies and OC of 0.869 €/m(3), respectively. The quadratic model fits for all responses very well with R(2) (>0.95). This paper clearly shows that RSM is able to optimize the operating parameters to maximize the color, COD and TOC removal efficiencies and minimize the OC.

Evaluation of wet air oxidation variables for removal of organophosphorus pesticide malathion using Box-Behnken design

This paper deals with finding optimum reaction conditions for wet air oxidation (WAO) of malathion aqueous solution, by Response Surface Methodology. Reaction conditions, which affect the removal efficiencies most during the non-catalytic WAO system, are: temperature (60-120 °C), applied pressure (20-40 bar), the pH value (3-7), and reaction time (0-120 min). Those were chosen as independent parameters of the model. The interactions between parameters were evaluated by Box-Behnken and the quadratic model fitted very well with the experimental data (29 runs). A higher value of R2 and adjusted R2 (>0.91) demonstrated that the model could explain the results successfully. As a result, optimum removal efficiency (97.8%) was obtained at pH 5, 20 bars of pressure, 116 °C, and 96 min. These results showed that Box-Behnken is a suitable design to optimize operating conditions and removal efficiency for non-catalytic WAO process. The EC20 value of raw wastewater was measured as 35.40% for malathion (20 mg/L). After the treatment, no toxicity was observed at the optimum reaction conditions. The results show that the WAO is an efficient treatment system for malathion degradation and has the ability of converting malathion to the non-toxic forms.

Treatment of highly toxic cardboard plant wastewater by a combination of electrocoagulation and electrooxidation processes

The objective of this study was to investigate the removal efficiencies of the electrochemical treatment systems as an alternative for the treatment of cardboard plant wastewater (CPW). In accordance with this purpose, CPW was treated by electrocoagulation (EC) with Al electrodes and the effects of current density (CD), operating time (t), and initial pH (pHi) were investigated. The results showed that EC at optimum treatment conditions (CD: 7.5mA/cm2, pHi: 7.0 and t: 60min) have limited removal efficiencies for total organic carbon (TOC; 17.1%) and chemical oxygen demand (COD, 14.2%), on the contrary of turbidity (98.7%). Due to the low TOC and COD removal efficiencies, a secondary treatment was needed and the electrocoagulated effluent was subjected to electrooxidation (EO) by using a boron doped diamond (BDD) electrode for investigating the effect of CD, t, pHi and electrolyte concentration (Ce). Higher TOC (83.7%) and COD (82.9%) removal efficiencies were obtained by EO under the optimum treatment conditions (CD: 100mA/cm2, pHi: 7.2, Ce: 5.0g/L Na2SO4 and t: 180min). In addition, a toxicity test was carried out to the raw and treated wastewater under the optimum operating conditions. This study demonstrated that the combination of EC and EO have a satisfactory potential for real industrial wastewater with a high organic content, suspended solids and toxicity.

Heterogeneous Activation of Persulfate by Graphene Oxide-TiO2 Nanosheet for Oxidation of Diclofenac: Optimization by Central Composite Design

In this study, the performance of oxidation with actived persulfate (PS) by graphene oxide-TiO2 nanosheet (GO-TiO2) was investigated for diclofenac (DCF) removal, an anti-inflammatory analgesic being widely used in human health care and veterinary treatment. GO-TiO2 containing oxygen functional groups is employed as an activator for the activation of PS used as the oxidizing agent. Modeling and optimization of the process were performed by central composite design (CCD) as a response surface methodology (RSM). The effects of various factors, including PS concentration, GO-TiO2 amount, initial pH of DCF solution, and reaction time on DCF oxidation, were evaluated. When the estimated values of the full quadratic model obtained with CCD were compared with the actual experimental results, a strong agreement was obtained with an R2 value of 0.9553. Besides, the model consistency was verified by analysis of variance (ANOVA) with a value of 20.17 of F value and P value of less than 0.05. After the optimization run, maximum DCF removal of 93.06% occurred with contact time of 14xa0min, pH of 5.54, PS concentration of 10xa0g/L, and 0.1xa0g of GO-TiO2 as optimal variable values.

Optimization of Beidellite/Polyaniline Production Conditions by Central Composite Design for Removal of Acid Yellow 194

In the adsorption process, the adsorbent structure and its interaction with wastewater are the main determinant of the process efficiency. For this reason, the correct selection of the production conditions for the produced adsorbents is critical. In this study, the reaction time and the concentration of acid, oxidant, substrate, and monomer were selected as independent variables which effect the structure of the polyaniline based composite material. These production variables of polyaniline/beidellite (PANI/BEI) composites were designed by response surface methodology (RSM). According to RSM, 46 different PANI/BEI composites were synthesized and were used as an adsorbent in the removal of acid yellow 194. Thus, the optimum PANI/BEI production conditions were determined. After the identification of the optimum PANI/BEI production conditions, the effect of adsorption conditions such as pH, mixing time, and dye concentration were studied by batch experiments. The maximum adsorption capacity was obtained as 123 (mgxa0g−1) at the Tu2009=u200925xa0°C, tu2009=u200924xa0h, pH 3,

Optimization of baker's yeast wastewater using response surface methodology by electrocoagulation

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