A comparison of the electrolysis of soil washing wastes with active and non-active electrodes.

A comparison between the performance of electrolysis of three different soil-washing wastes with platinum and boron doped diamond (BDD) anodes is carried out in this work. Results demonstrate that the treatment is more efficient with BDD for perchloroethylene and clopyralid but not for the case of lindane, because in this case there is a competitive oxidation between lindane and Sodium Dodecyl Sulfate used to extract this pollutant from soil. First order kinetics are observed in each compound with higher removal at the early stages and generally better results are obtained when using BDD as anode. The evolution of pH and a voltammetry study indicate a higher direct oxidation rate in the case of platinum and more importance of hydroxyl radical mediated processes with diamond anodes. Similar speciation is obtained during the electro-oxidation using BDD and platinum electrodes although the concentration of intermediates vary significantly.

Electrochemical Oxidation of Resorcinol in Aqueous Medium Using Boron-Doped Diamond Anode: Reaction Kinetics and Process Optimization with Response Surface Methodology.

Electrochemical oxidation of resorcinol in aqueous medium using boron-doped diamond anode (BDD) was investigated in a batch electrochemical reactor in the presence of Na2SO4 supporting electrolyte. The effect of process parameters such as resorcinol concentration (100-500 g/L), current density (2-10 mA/cm2), Na2SO4 concentration (0-20 g/L), and reaction temperature (25-45°C) was analyzed on electrochemical oxidation using response surface methodology (RSM). The optimum operating conditions were determined as 300 mg/L resorcinol concentration, 8 mA/cm2 current density, 12 g/L Na2SO4 concentration, and 34°C reaction temperature. One hundred percent of resorcinol removal and 89% COD removal were obtained in 120 min reaction time at response surface optimized conditions. These results confirmed that the electrochemical mineralization of resorcinol was successfully accomplished using BDD anode depending on the process conditions, however the formation of intermediates and by-products were further oxidized at much lower rate. The reaction kinetics were evaluated at optimum conditions and the reaction order of electrochemical oxidation of resorcinol in aqueous medium using BDD anode was determined as 1 based on COD concentration with the activation energy of 5.32 kJ/mol that was supported a diffusion-controlled reaction.

Electrochemical oxidation of ampicillin antibiotic at boron-doped diamond electrodes and process optimization using response surface methodology.

Electrochemical oxidation and process optimization of ampicillin antibiotic at boron-doped diamond electrodes (BDD) were investigated in a batch electrochemical reactor. The influence of operating parameters, such as ampicillin concentration, electrolyte concentration, current density, and reaction temperature, on ampicillin removal, COD removal, and energy consumption was analyzed in order to optimize the electrochemical oxidation process under specified cost-driven constraints using response surface methodology. Quadratic models for the responses satisfied the assumptions of the analysis of variance well according to normal probability, studentized residuals, and outlier t residual plots. Residual plots followed a normal distribution, and outlier t values indicated that the approximations of the fitted models to the quadratic response surfaces were very good. Optimum operating conditions were determined at 618 mg/L ampicillin concentration, 3.6 g/L electrolyte concentration, 13.4 mA/cm(2) current density, and 36 °C reaction temperature. Under response surface optimized conditions, ampicillin removal, COD removal, and energy consumption were obtained as 97.1 %, 92.5 %, and 71.7 kWh/kg CODr, respectively.

Continuous electrochemical treatment of simulated industrial textile wastewater from industrial components in a tubular reactor.

The continuous electrochemical treatment of industrial textile wastewater in a tubular reactor was investigated. The synthetic wastewater was based on the real process information of pretreatment and dyeing stages of the industrial mercerized and non-mercerized cotton and viscon production. The effects of residence time on chemical oxygen demand (COD), color and turbidity removals and pH change were studied under response surface optimized conditions of 30 degrees C, 25 g/L electrolyte concentration and 3505 mg/L COD feed concentration with 123.97 mA/cm(2) current density. Increasing residence time resulted in steady profiles of COD and color removals with higher treatment performances. The best column performance was realized at 3h of residence time as 53.5% and 99.3% for COD and color removals, respectively, at the expense of 193.1 kWh/kg COD with a mass transfer coefficient of 9.47 x 10(-6) m/s.

Determination of optimum operating conditions of carmine decoloration by UV/H2O2 using response surface methodology.

In this study, the photolytic decoloration of carmine (C.I. Natural Red 4) via UV radiation in the presence of H2O2 was optimized using response surface methodology (RSM). According to analysis of variance (ANOVA) results, the proposed model can be used to navigate the design space. It was found that the response of carmine degradation is very sensitive to the independent factors of carmine concentration, H2O2 concentration, pH and reaction time. The proposed model for D-optimal design fitted very well with the experimental data with R2 and R(adj)2 correlation coefficients of 0.998 and 0.997, respectively.

Photolytic decolorization of Rose Bengal by UV/H(2)O(2) and data optimization using response surface method.

Rose Bengal (C.I. name is Acid Red 94) was irradiated with UV light in the presence of hydrogen peroxide. The photoinduced decolorization of the dye was monitored spectrophotometrically. The apparent rate of decolorization was calculated from the observed absorption data and was found to be pseudo first order. A systematic study of the effect of dye concentration and H(2)O(2) concentration on the kinetics of dye decolorization was also carried out. Dye decolorization increased with increasing H(2)O(2) concentration and decreasing dye concentration. The maximum dye decolorization was determined as 90% with 0.005 mM dye at optimum 0.042 M H(2)O(2) and pH 6.6. Additionally, the effect on decolorization of this dye in the presence of some additives (ions) was also investigated. It was seen that sulphite caused a maximum effect on % decolorization of the dye solution. A plausible explanation involving the probable radical initiated mechanism was given to explain the dye decolorization. The experimental data was also optimized using the response surface methodology (RSM). According to ANOVA results, the proposed model can be used to navigate the design space. It was found that the response of Rose Bengal degradation is very sensitive to the independent factors of dye concentration, H(2)O(2) concentration, pH and reaction time. The proposed model for D-optimal design fitted very well with the experimental data with R(2) and R(adj)(2) correlation coefficients of 0.85 and 0.80, respectively.

Electrochemical treatment of simulated textile wastewater with industrial components and Levafix Blue CA reactive dye: optimization through response surface methodology.

The electrochemical oxidation of simulated textile wastewater was studied on iron electrodes in the presence of NaCl electrolyte in a batch electrochemical reactor. The simulated textile wastewater was prepared from industrial components based on the real mercerized and non-mercerized cotton and viscon process, being first in literature. The highest COD, color and turbidity removals were achieved as 93.9%, 99.5%, and 82.9%, respectively, at 40% pollution load, 8 V applied potential, 37.5 g/L electrolyte concentration and 30 degrees C reaction temperature. The electrochemical treatment of industrial textile wastewater was optimized using response surface methodology (RSM), where applied potential and electrolyte concentration were to be minimized while COD, color and turbidity removal percents were maximized at 100% pollution load. In a specific batch run under the optimum conditions of 30 degrees C reaction temperature, 25 g/L electrolyte concentration and 8 V applied potential applied with 35.5 mA/cm2 current density at 100% pollution load, COD, color and turbidity removals were realized as 61.6%, 99.6% and 66.4%, respectively.

Investigation of nickel(II) biosorption on Enteromorpha prolifera: optimization using response surface analysis.

In this study, the biosorption of nickel(II) ions on Enteromorpha prolifera, a green algae, was investigated in a batch system. The single and combined effects of operating parameters such as initial pH, temperature, initial metal ion concentration and biosorbent concentration on the biosorption of nickel(II) ions on E. prolifera were analyzed using response surface methodology (RSM). The optimum biosorption conditions were determined as initial pH 4.3, temperature 27 degrees C, biosorbent concentration 1.2 g/L and initial nickel(II) ion concentration 100 mg/L. At optimum biosorption conditions, the biosorption capacity of E. prolifera for nickel(II) ions was found to be 36.8 mg/g after 120 min biosorption. The Langmuir and Freundlich isotherm models were applied to the equilibrium data and defined very well both isotherm models. The monolayer coverage capacity of E. prolifera for nickel(II) ions was found as 65.7 mg/g. In order to examine the rate limiting step of nickel(II) biosorption, such as the mass transfer and chemical reaction kinetics, the intraparticle diffusion model, external diffusion model and the pseudo second order kinetic model were tested with the experimental data. It was found that for both contributes to the actual biosorption process. The pseudo second order kinetic model described the nickel(II) biosorption process with a good fitting.

Optimization of electrochemical treatment of industrial paint wastewater with response surface methodology.

The electrochemical oxidation of water-based paint wastewater was investigated batch-wise in the presence of NaCl electrolyte with carbon electrodes for the first time in literature. The electrochemical treatment conditions were optimized using response surface methodology where potential difference, reaction temperature and electrolyte concentration were to be minimized while chemical oxygen demand (COD), color and turbidity removal percents and initial COD removal rate were maximized at 100% pollution load. The optimum conditions were satisfied at 35 g/L external electrolyte concentration, 30 degrees C reaction temperature and 8 V potential difference (64.37 mA/cm(2) current density) realizing 51.8% COD and complete color and turbidity removals, and 3010.74 mg/Lh initial COD removal rate. According to these results, the electrochemical method could be a strong alterative to conventional physicochemical methods for the treatment of water-based paint wastewater.

Response surface optimization of electrochemical treatment of textile dye wastewater.

The electrochemical treatment of textile dye wastewater containing Levafix Blue CA, Levafix Red CA and Levafix Yellow CA reactive dyes was studied on iron electrodes in the presence of NaCl electrolyte in a batch electrochemical reactor. The wastewater was synthetically prepared in relatively high dye concentrations between 400mg/L and 2000mg/L. The electrochemical treatment of textile dye wastewater was optimized using response surface methodology (RSM), where current density and electrolyte concentration were to be minimized while dye removal and turbidity removal were maximized at 28 degrees C reaction temperature. Optimized conditions under specified cost driven constraints were obtained for the highest desirability at 6.7mA/cm(2), 5.9mA/cm(2) and 5.4mA/cm(2) current density and 3.1g/L, 2.5g/L and 2.8g/L NaCl concentration for Levafix Blue CA, Levafix Red CA and Levafix Yellow CA reactive textile dyes, respectively.

Continuous electrochemical treatment of phenolic wastewater in a tubular reactor.

The electrochemical treatment of phenolic wastewater in a continuous tubular reactor, constructed from a stainless steel tube with a cylindrical carbon anode at the centre, was investigated in this study, being first in literature. The effects of residence time on phenol removal was studied at 25 degrees C, 120 g l(-1) electrolyte concentration for 450 and 3100 mg l(-1) phenol feed concentrations with 61.4 and 54.7 mA cm(-2) current densities, respectively. The change in phenol concentration and pH of the reaction medium was monitored in every run and GC/MS analyses were performed to determine the fate of intermediate products formed during the electrochemical reaction in a specified batch run. During the electrolysis mono, di- and tri-substituted chlorinated phenol products were initially formed and consumed along with phenol thereafter mainly by polymerization mechanism. For 10 and 20 min of residence time phenol removal was 56% and 78%, respectively, with 450 mg l(-1) phenol feed concentration and above 40 min of residence time all phenol was consumed within the column. For 1, 1.5, 2 and 3h of residence time, phenol removal achieved was 42%, 71%, 81% and 98%, respectively, at 3100 mg l(-1) phenol feed concentration. It is noteworthy that more than 95% of the initial phenol was converted into a non-passivating polymer without hazardous end products in a comparatively fast and energy-efficient process, being a safe treatment.