M. Kobya

Treatment of textile wastewaters by electrocoagulation using iron and aluminum electrodes

Treatment of textile wastewaters by electrocoagulation using iron and of aluminum electrode materials has been investigated in this paper. The effects of relevant wastewater characteristics such as conductivity and pH, and important process variables such as current density and operating time on the chemical oxygen demand (COD) and turbidity removal efficiencies have been explored. Furthermore, the electrode and energy consumptions for each electrode have been calculated. The results show that iron is superior to aluminum as sacrificial electrode material, from COD removal efficiency and energy consumption points.

Removal of Ni(II) from aqueous solution by adsorption onto hazelnut shell activated carbon: equilibrium studies

Activated carbon prepared from hazelnut shell was used as an adsorbent for the removal of Ni(II) from aqueous solution. Batch mode adsorption studies were carried out by varying initial metal ion concentration, agitation speed, temperature and particle size. A contact time of 180 min was required to reach equilibrium. The equilibrium data were analysed using the Langmuir, Freundlich and Temkin isotherms. The characteristic parameters for each isotherm were determined. The Langmuir isotherm provided the best correlation for Ni(II) onto the activated carbon. Thermodynamical parameters revealed that the adsorption of Ni(II) is exothermic in nature.

Adsorption, Kinetic and Equilibrium Studies of Cr(VI) by Hazelnut Shell Activated Carbon

The adsorption of chromium(VI) from aqueous solutions on to hazelnut shell activated carbon (HSAC) was investigated. The adsorption was carried out by varying parameters such as the agitation time, the initial solution pH, the initial Cr(VI) concentration and the temperature. The experimental data were well fitted by the pseudo-first-order kinetic model allowing the rate constants to be evaluated. The Langmuir isotherm provided the best correlation for the adsorption of Cr(VI) onto the activated carbon. The adsorption of Cr(VI) was pH-dependent. The adsorption capacity as calculated from the Langmuir isotherm was 170 mg/g at an initial pH of 1.0 for a Cr(VI) solution of 1000 mg/l concentration. Thermodynamic parameters were evaluated, indicating that the adsorption was endothermic and involved monolayer adsorption of Cr(VI).

Treatment of rinse water from zinc phosphate coating by batch and continuous electrocoagulation processes.

Treatment of spent final rinse water of zinc phosphating from an automotive assembly plant was investigated in an electrochemical cell equipped with aluminum or iron plate electrodes in a batch mode by electrocoagulation (EC). Effects of the process variables such as pH, current density, electrode material and operating time were explored with respect to phosphate and zinc removal efficiencies, electrical energy and electrode consumptions. The optimum operating conditions for removal of phosphate and zinc were current density of 60.0 A/m(2), pH 5.0 and operating time of 25.0 min with Al electrode and current density of 60.0 A/m(2), pH 3.0 and operating time of 15.0 min with Fe electrode, respectively. The highest phosphate and zinc removal efficiencies at optimum conditions were 97.7% and 97.8% for Fe electrode, and 99.8% and 96.7% for Al electrode. The electrode consumptions increased from 0.01 to 0.35 kg electrode/m(3) for Al electrode and from 0.20 to 0.62 kg electrode/m(3) for Fe electrode with increasing current density from 10.0 to 100.0 A/m(2). The energy consumptions were 0.18-11.29 kWh/m(3) for Al electrode and 0.24-8.47 kWh/m(3) for Fe electrode in the same current density range. Removal efficiencies of phosphate and zinc were found to decrease when flow rate was increased from 50 to 400 mL/min in continuous mode of operation. The morphology and elements present in the sludge was also characterized by using SEM and EDX.

Treatment of cadmium and nickel electroplating rinse water by electrocoagulation.

Treatments of cadmium‐cyanide and nickel‐cyanide electroplating rinse water were investigated in an electrochemical reactor equipped with iron plate electrodes in a batch mode by electrocoagulation (EC). Effects of the process variables such as pH, current density, and operating time were explored with respect to removal efficiencies of cadmium, nickel and cyanide in electroplating rinse water and operating costs as well. Removal efficiencies and operating costs under the optimum conditions (30 A/m2, 30 min and pH 8–10 for cadmium; 60 A/m2, 80 min and pH 8–10 for nickel) for the EC process in electroplating rinse water were determined as 99.4% and 1.05 /m3 for cadmium, 99.1% and 2.45 /m3 for nickel and >99.7% for cyanide, respectively. The results indicated that EC was very effective treatment for the removals of cadmium, nickel, and cyanide ions from the electroplating rinse water.

Electrochemical treatment and operating cost analysis of textile wastewater using sacrificial iron electrodes

Electrocoagulation (EC) method with iron electrode was used to treat the textile wastewater in a batch reactor. Iron electrode material was used as a sacrificial electrode in monopolar parallel mode in this study. The removal efficiencies of the wastewater by EC were affected by initial pH of the solution, current density, conductivity and time of electrolysis. Under the optimal experimental conditions (initial pH 6.9, current density of 10 mA/cm(2), conductivity of 3,990 microS/cm, and electrolysis time of 10 min), the treatment of textile wastewater by the EC process led to a removal capacity of 78% of chemical oxygen demand (COD) and 92% of turbidity. The energy and electrode consumptions at the optimum conditions were calculated to be 0.7 kWh/kg COD (1.7 kWh/m(3)) and 0.2 kgFe/kg COD (0.5 kgFe/m(3)), respectively. Moreover, the operating cost was calculated as 0.2 euro/kg removed COD or 0.5 euro/m(3) treated wastewater. Zeta potential measurement was used to determine the charge of particle formed during the EC which revealed that Fe(OH)(3) might be responsible for the EC process.

Removal of thiocyanate from aqueous solutions by ion exchange

The adsorption kinetics and equilibrium of thiocyanate in aqueous solutions onto an anion-exchange resin (Purolite A-250) were investigated in a batch-mode operation to assess the possible use of this adsorbent. The effect of various parameters such as initial thiocyanate concentration, contact time, pH, particle size, resin dosage and temperature were studied. A comparison of four kinetic models, the pseudo-first-order, second-order, Elovich and diffusion controlled kinetic models, on the thiocyanate-resin system was used to determine the rate constants and the adsorption mechanism. The kinetic results correlated well with pseudo-second-order model. The experimental parameters had also an effect on the pore and surface diffusivities. The optimum conditions for removal of thiocyanate were found to be pH 8, 2g/l of adsorbent dosage, 355-500 microm of particle size and equilibrium time of 30 min, respectively. The column capacity and performance by the bed depth service time model using bed depth and flow rate as variables were evaluated. The adsorption isotherm data were fitted well to Langmuir and Freundlich isotherms. The adsorption capacity was calculated as 191.20mg/g at 323 K. Thermodynamics parameters such as free Delta G(0), Delta H(0) and DeltaS(0) for the adsorption were evaluated. The positive value of Delta H(0) indicated that the process was endothermic in nature.

Optimization of arsenic removal from drinking water by electrocoagulation batch process using response surface methodology

AbstractIn this investigation, arsenic removal from drinking water using electrocoagulation (EC) in a batch mode was studied by response surface methodology (RSM). The RSM was applied to optimize the operating variables viz. current density (CD, A/m2), operating time (tEC, min) and arsenic concentration (Co, μg/L) on arsenic removal in the EC process using iron electrodes. The combined effects of these variables were analyzed by the RSM using quadratic model for predicting the highest removal efficiency of arsenic from drinking water. The proposed model fitted very well with the experimental data. R2 adjusted correlation coefficients (AdjR2: 0.93) for arsenic removal efficiency showed a high significance of the model. The model predicted for a maximum removal of arsenic at the optimum operating conditions (112.3 μg/L, 5.64 A/m2 and 5 min) after the EC process was 93.86% which corresponded to effluent arsenic concentration of 6.9 μg/L. The minimum operating cost (OC) of the EC process was 0.0664 €/m3. This...

An evaluation on different origins of natural organic matters using various anodes by electrocoagulation.

In this investigation, natural organic matters (NOM) of different origins (commercial, terrestrial and natural water) were treated by electrocoagulation (EC) process using aluminum, iron and hybrid electrodes. Electrode type effect on removal efficiency was observed for each NOM (commercial, terrestrial, and natural). The results were presented as dissolved organic carbon (DOC) (mg L(-1)) and UV/VIS absorbance (cm(-1)). The specific UV absorbance (SUVA) was determined before and after treatment of water. The lowest effluent concentration was obtained as 5.05 mg L(-1) with hybrid electrode for natural NOM source at its original pH 7.3. In addition, among the metal types, the best UV-abs-254 removal efficiency was obtained as 92.4% with 0.0312 cm(-1) by hybrid electrode at the end of the process. The color removal efficiency of water occurred successfully by Al and hybrid electrodes. Aquatic NOM source was the most resistant to EC treatment with DOC reduction of 71.1%, 59.8%, and 68.6% for Al, Fe and hybrid electrodes, respectively. Zeta potential and floc size of colloids were observed during the process for the determination of destabilization level of natural organic matters in EC process. Fast coagulation or flocculation and incipient instability were formed during electrolysis time for Al and Fe electrode, respectively. SUVA value was reduced to below 2 for three NOM sources studied. The EC process was shown to be a viable for different NOM sources with various metals.

Decolourization of melanoidins by a electrocoagulation process using aluminium electrodes

The decolourization of melanoidins was studied with a batch electrocoagulation (EC) process using aluminium electrodes. The effects of conductivity (κ=500–3000 μS/cm), initial pHi (4.2–8.2), current density (j=2.5–7.5 A/m2), initial melanoidin concentration (C 0=100–800 mg/L) and operating time (t EC =0–60 min) were investigated on the decolourization efficiency. The results obtained from the EC process were extremely efficient and able to achieve a decolourization efficiency of>98% at pHi=4.2, j=5 A/m2, κ=2500 μ S/cm, C 0=100 mg/L and t EC =10 min. The decolourization performance was dependent on pHi value since the lower pH values led to faster reactions and higher decolourization efficiency. Melanoidins in the EC process were removed by precipitation and charge neutralization at pH<6.5, and both adsorption and sweep coagulation by amorphous Al(OH)3(s) occurred at pH>6.5. The operating cost was calculated as 0.0096 €/m3.