9848
Ind. Eng. Chem. Res. 2008, 47, 9848–9853
Electrochemical Oxidation of Lignosulfonate: Total Organic Carbon Oxidation Kinetics A. Dominguez-Ramos,* R. Aldaco, and A. Irabien Departamento de Ingenierı´a Quı´mica y Quı´mica Inorga´nica, UniVersidad de Cantabria, ETSIIT, AVda. de Los Castros s/n, 39005, Santander, Spain
Lignin derivatives account for a significant fraction of biorefractory pollutants in wastewater from the pulp and paper industry. Electrochemical oxidation has been described as an efficient alternative in wastewater treatment based on electrogenerated oxidation. Lignosulfonate was selected in this work as a biorefractory reference pollutant. Total organic carbon (TOC) removal was higher than 80% under the selected experimental conditions, where chemical oxygen demand (COD) was in the range 500-1500 mg O2 L-1, current density was between 30 and 60 mA cm-2, and the concentrations of sodium sulfate and sodium chloride supporting electrolytes were 2500 and 5000 mg L-1. Experimental conditions were selected to evaluate the technical suitability of the process and to establish a kinetic model and parameters. Experiments were carried out in a laboratory scale single cell flow electrochemical reactor with boron-doped diamond electrodes. A first-order kinetic model is in good agreement with previously reported results, and kinetic parameters depending mainly on the current density agree well with previous references. A model describing the influence of the current density in the kinetic parameters allows us to calculate the surface electrochemical reaction kinetic constant and the mass transfer coefficient. Introduction During the past 40 years, the field of electrochemical oxidation has been very active in the search for new materials to manufacture energy-efficient and mechanically resistant electrodes. Controlling factors of the process and kinetics of different pollutant degradation have also been studied.1 In recent years, the electrochemical oxidation of a large number of industrial wastewater and chemical pollutants has been reported as it is shown in Table 1. Additionally, references of pilot plant scale units for tertiary electrochemical oxidation are also available.2 Electrochemical oxidation has been included within the advanced oxidation processes (AOP)17,41 under the name electrochemical advanced oxidation processes (EAOP). When COD is below 5000 mg O2 L-1, electrochemical oxidation appears to be an interesting alternative to AOP,42 but a wide range of applications ranging from 100000 to 1000 mg O2 L-1 have been suggested,43 although the technical range is generally lower, close to the former reference of 5000 mg O2 L-1. In the comparison among AOP, the reduction of sludge formation and consumption of chemicals are very attractive features of electrochemical oxidation.41,44 On the other hand, the main drawbacks of the electrochemical oxidation for the treatment of wastewater are the energy consumption per unit of wastewater volume8,18,45,46 and the investment costs,18 but practical applications of the technology in a wider extension have been limited by the use of low efficiency electrodes.47 Boron-doped diamond (BDD) has been widely recognized as an excellent material for electrodes to perform electrochemical oxidation, not only in electroanalysis or preparation of powerful oxidants, but also for the removal of organics from wastewater due to its high anodic stability and wide potential window.1,48 Derived from the unique surface properties, BDD electrodes * To whom correspondence should be addressed. Tel.: +34 942200931. Fax: +34 942201591. E-mail:
[email protected].
can perform the electro-combustion of the organic matter with energetic efficiency under the appropriate operational conditions.49 Two basic mechanisms take place in electrochemical oxidation in aqueous media which are related to the electrode, the applied potential, and the supporting electrolyte: the direct and the indirect oxidation.8,22,29,41,50 Wastewater characteristics (concentration of organic matter, pH) and other operating parameters such as temperature, flowrate, and cell configuration severely affect the extension of each mechanism. Kinetic studies of lumped variables such as total organic carbon (TOC) in well-defined synthetic effluents are a first approach to evaluate the technical viability of flow electrochemical reactors using boron-doped diamond electrodes. Phenol has been widely used as reference substance in the field of electrochemical oxidation to evaluate effluents with hazardous pollutants.8,10,47 This study takes lignin derivatives like lignosulfonate (lignin derivative in sulfite mills) as a specific biorefractory compound to be removed.51,52 Some studies of the electrochemical oxidation of lignin derivatives have been reported in the literature: lignin by lead-dioxide-coated titanium electrodes53 and the transformation of lignosulfonate into lower molecular weight products by electro-oxidation with PbO2 Table 1. Electrochemical Oxidation of Industrial Wastewater and Chemical Pollutants industrial wastewater
ref
chemical pollutant
ref
olive mill pulp and paper textile pharmaceutical landfill leacheate leather phenol formaldehyde oil refinery bulk drug manufacture
3, 4 6, 7 11-16 18 20-24 26-29 31 31 31
cyanides phenol chlorophenol 2-naphtol 3-methylpyridine glucose polyhydroxybenzenes histidine synthetic dyes
carwash motor industry
60 61
herbicides drugs
5 8-10 17 19 25 30 32 33 12, 14, 15, 34, 35 36-39 40
10.1021/ie801109c CCC: $40.75 2008 American Chemical Society Published on Web 11/17/2008
Ind. Eng. Chem. Res., Vol. 47, No. 24, 2008 9849
Figure 1. Experimental setup: (1) power supply, (2) single-compartment flow electrochemical reactor, (3) flowmeter, (4) centrifugal pump, (5) refrigerated glass tank, (6) absorber.
membrane electrodes.54 Lignin derivatives have been largely described as responsible for a representative fraction of the biorefractory content in the paper industry wastewater55,56 related to the inherent difficulties in breaking down the strong aryl linkages and reducing the color of the effluents.56,57 The main objective of this study is the kinetic analysis and modeling of the removal of the TOC from lignosulfonate solutions with BDD electrodes in a single compartment flow electrochemical reactor. To describe the degradation process of lignosulfonate, TOC has been evaluated to describe the organic matter evolution with time, which is a common reference parameter in environmental regulations. Materials and Methods Laboratory-Scale Experimental Setup. Lignosulfonate solutions were introduced in a single compartment flow electrochemical reactor from Adamant Technologies SA operating in a semibatch mode. Figure 1 shows the basic layout of the laboratory scale plant. The cell is equipped with two parallel thin-film boron-doped diamond electrodes supported on silicon with an interelectrode gap of 1 mm: anode and cathode are both circular, and they have an area of 70 cm2 per electrode. Borondoped diamond electrodes are well-known for their mechanical and chemical stability under extreme high current densities,1 and in the present work no alteration of the active surface was noticed. A centrifugal pump is responsible for the circulation of the 2 L storage tank solution through the cell (a rotameter was measuring the flowrate). Galvanostatic conditions were applied by using an Agilent power supply 6554A. In the experiments, the flowrate through the cell was kept constant at 300 L h-1, and the temperature was maintained constantly at 22 ( 2 °C. The solution pH slightly changed at the end of the experimental time, which was set up in 8 h and verified to be enough for the kinetic study (TOC removal higher than 80% in all experiments). Samples were withdrawn from the glass tank at regular times preventing the surface electrode to solution volume ratio from changing more than 10%. Analytical Procedure. Total organic carbon (TOC) was measured in the experimental runs. TOC was monitored using a Shimadzu TOC-V CPH with ASI-V operating with synthetic air (pressure, 200 KPa; flowrate, 150 mL min-1). Chemical oxygen demand (COD) was monitored at the beginning of each experiment according to standard methods (5220D Close reflux, colorimetric method)58 by using a Hanna COD-reactor HI839800 for digestion and a Merck Spectroquant NOVA 600 for
colorimetric measurements. The initial and final pH and conductivity were measured at the beginning and at the end of each experimental run. A Crison pH meter GLP22 with pH 52-02 electrodes and a Crison CM35 were used for pH and conductivity measurements, respectively. A commercial Borrebond 55S calcium-magnesium lignosulfonate (molecular weight about 3000 Daltons) coming from Eucalyptus globulus (sulfite process) was obtained from Lignotech Iberica S.A. (Torrelavega, Spain). This product is water soluble in all proportions and has a residual concentration of reduced sugars (it was utilized as received without additional purification). Synthetic air was from Air Liquide S.A., Spain. The rest of the reagents were purchased from Panreac Quı´mica, S.A., with required quality grades. Ultrapure water from Milli-Q was employed for the lignosulfonate solutions. Selection of Variables. Three variables were selected to be studied at two different levels: initial chemical oxygen demand, current density, and concentration of supporting electrolyte. The initial chemical oxygen demand [COD]0 was studied in the range 500-1500 mgO2 L-1, as the lower level would be representative of the COD effluent from the pulp and paper industry.59 The range of the applied current density j was between 30 and 60 mA cm-2 to guarantee that the anodic potential was above 2.3 V versus SHE at the selected supporting electrolyte concentrations (out of the region of water stability on BDD). Finally, the concentration of supporting electrolyte was 2500-5000 mg L-1, which is typical for electrochemical oxidation,8,30 and it allows the conductivity to be above the minimum conductivity (2 mS cm-1) established by the supplier. For electrochemical purposes, a concentration of sodium chloride below 3000 mg L-1 is typically well established.1 Additionally, two different supporting electrolytes were studied: sodium sulfate and sodium chloride. Table 2 summarizes the set of experimental runs, including the ratio ϑ ) (j/[COD]0)(A/V) (mA mg O2-1). Experimental run Si stands for test i using sodium sulfate as supporting electrolyte and Ci for sodium chloride (i ) 1-8). Kinetic Model and Parameters. Figures 2 and 3 show the time profile of the dimensionless total organic carbon, τ (TOC · TOC0-1), for the sodium sulfate (Si) and sodium chloride (Ci) electrolytes. As can be seen in Figures 2 and 3, TOC may be removed, showing an exponential trend. In Table 3, the initial and final pH and average voltage during the experimental runs are summarized. A variability in the initial pH, ranging from 3.60 to 4.26, is observed, leading to minor changes in the final pH. In the sulfate series, the pH decreases slightly during the electrochemical oxidation within the range 2.81-3.62 due to the presence of relatively strong acids such as sulfuric and peroxodisulphuric acid, but in the chloride medium the pH is higher in the range 3.96-6.78 due to weak acids such as hypochlorous acid. Once the experiments were completed, a small amount of black thin films was observed during the washing of the electrode with distilled water. In order to describe the kinetics of the electrochemical oxidation processes, different models have been proposed in the literature.9,12,15,22,49 Table 4 summarizes the main assumptions of the primary oxidation and secondary oxidation models. In the experimental cell described in Figure 1, the fluid phase flows parallel to the surface of the circular electrodes (70 cm2 per electrode) with an interelectrode gap of 1 mm. A minimum flowrate (from bottom input to top output as shown in Figure 1) must be set up to guarantee the contact between the liquid phase and the electrode surface so the total area takes part in the oxidation process. A boundary layer between the circular electrode surface and the bulk of the aqueous phase is
9850 Ind. Eng. Chem. Res., Vol. 47, No. 24, 2008 Table 2. Experimental Variables expt run
[COD]0 (mg O2 L-1)
j (mA cm-2)
[Na2SO4]/[NaCl] (mg L-1)
ϑ (mA mg O2-1)
S1, C1 S2, C2 S3, C3 S4, C4 S5, C5 S6, C6 S7, C7 S8, C8
500 500 500 500 1500 1500 1500 1500
30 30 60 60 30 30 60 60
5000 2500 5000 2500 5000 2500 5000 2500
0.21 0.21 0.42 0.42 0.07 0.07 0.14 0.14
established, which implies a resistance to the mass transfer of organic matter to the electrode surface. After fitting the experimental results with MATLAB v7.5.0 R2007b (Levenberg-Marquardt algorithm) to an exponential equation in all individual runs for the sulfate and chloride series, kinetic constants are shown in Table 5. The confidence range for the kinetic parameters is set up to 95%. The kinetic constant is corrected by the extensive magnitude (A/V)-1 to be expressed in terms of a mass transfer coefficient leading to k (m min-1). The experimental kinetic constants referred to the electrode surface are within the range of values shown in Table 6 for electrochemical oxidation. As it is shown in Table 6, electrodes
Table 3. Initial and Final pH and Average Voltage Vaverage (V) between Electrodes (Flowrate ) 300 L h-1, T ) 22 °C) expt run
initial pH
final pH
Vaverage (V)
S1 S2 S3 S4 S5 S6 S7 S8 C1 C2 C3 C4 C5 C6 C7 C8
4.19 4.15 4.26 4.22 3.98 3.84 4.01 4.00 3.71 3.91 3.70 4.19 3.64 3.83 3.64 3.60
3.30 3.33 3.62 3.41 3.06 2.93 2.81 2.82 6.6 3.96 6.78 5.92 5.95 4.32 6.22 4.29
5.750 6.093 6.850 7.594 5.193 5.275 6.763 7.313 4.931 5.78 7.385 7.561 5.795 5.322 6.379 6.822
Table 4. Summary of the Main Mechanism of the Electrochemical Oxidation Kinetics approach
Figure 2. Dimensionless TOC (τ) versus time (low initial COD): (inverted open triangle) S1-2; (upright open triangle) C1-2; (cross) S3-4; (small solid circle) C3-4; (solid line) fitting curve for S1-2, C1-2; (dashed line) fitting curve for S3-4, C3-4.
contribution of hydroxyl radicals (from water) contribution of electrogenerated reagents relevance of the nature organic matter distinction between current controlled and mass transfer controlled operations regimes COD value at which the transition between controlling regimes takes place type of electrodes for which the model has been successfully applied
primary oxidation
secondary oxidation
yes
no
yes
yes
yes
no
yes
no
COD experimental nonactive (i.e., BDD)
low overpotential for Cl2 evolution (i.e., DSA)
based on boron-doped diamond lead to similar kinetic constants in the removal of organic compounds. Discussion
Figure 3. Dimensionless TOC (τ) versus time (high initial COD): (leftpointing triangle) S5-6; (right-pointing triangle) C5-6; (open circle) S7-8; (open square) C7-8; (dotted line) fitting curve for S5-6, C5-6; (dashed line) fitting curve for S7-8, C7-8.
Kinetic results from Table 5 for the electrochemical oxidation of lignosulfonate do not show any influence of the electrolyte concentration. The kinetic constant k is therefore independent of the electrolyte in both sulfate and chloride series at a fixed initial COD and current density. Hereby, kinetic results shown in Table 5 show that the concentration of sodium sulfate and sodium chloride supporting electrolyte between 2500 and 5000 mg L-1 at each level of initial COD and applied current density does not have any influence on the kinetic parameter k, and consequently, the influence of the electrolyte can be neglected in the studied range of variables. This negligible influence of the supporting electrolyte concentration above certain values
Ind. Eng. Chem. Res., Vol. 47, No. 24, 2008 9851 Table 5. First-Order Kinetic Parameters of τ versus Time (Flowrate ) 300 L h , T ) 22 °C, Confidence Range ) 95%) -1
expt run
k × 103 (m min-1)
r2
kS/C × 103 (m min-1)
r2
kϑ × 103 (m min-1)
r2
ϑ (m mg O2-1)
S1 S2 C1 C2 S3 S4 C3 C4 S5 S6 C5 C6 S7 S8 C7 C8
1.22 ( 0.07 1.27 ( 0.08 1.73 ( 0.15 1.17 ( 0.05 1.55 ( 0.10 1.62 ( 0.09 1.45 ( 0.12 1.44 ( 0.08 0.81 ( 0.06 0.88 ( 0.06 1.03 ( 0.19 0.79 ( 0.08 1.18 ( 0.07 1.34 ( 0.08 1.48 ( 0.10 1.37 ( 0.21
0.992 0.991 0.987 0.996 0.993 0.994 0.983 0.993 0.987 0.988 0.945 0.974 0.992 0.993 0.992 0.965
1.24 ( 0.05
0.991
1.33 ( 0.07
0.972
0.21
1.42 ( 0.14
0.958
1.58 ( 0.07
0.993
1.51 ( 0.05
0.989
0.42
1.44 ( 0.07
0.989
0.84 ( 0.04
0.985
0.87 ( 0.05
0.958
0.07
0.91 ( 0.10
0.940
1.26 ( 0.06
0.988
1.33 ( 0.06
0.979
0.14
1.42 ( 0.11
0.976
Table 6. Reported Kinetic Constants (kR’s) in the Oxidation of Lignin-Related Biorefractory Compounds by Electrochemical Oxidation (EO) electrode
substance
variable
kR × 105 (m min-1)
ref
Ti/PbO2 Si/BDD Si/BDD DiaChem DiaChem Si/BDD
lignin solution phenol solution phenol solution phenol solution AO7 solutions lignosulfonate solutions
COD COD phenol COD COD TOC
2-6 170 127-769 114 88 87-151
53 8 47 10 34 this work
has been recognized as a general behavior in electrochemical processes. No significant effect of increasing the concentration of sodium sulfate from 2% to 3% was found during the electrochemical oxidation of olive mill wastewater (OMW) at Ti-Ta/Pt-Ir electrodes.4 In this work, a concentration of 2500 mg L-1 of the selected electrolytes leads to the same value of the kinetic constants represented by kS/C, which refers to the sulfate or the chloride media. From Table 5 it can be deduced that there is not any influence of the selected supporting electrolyte on the TOC removal rate. The electrochemical reactions for hypochlorous anion are summarized in eqs 1-3 throughout the generation of dissolved chlorine and the later disproportionation reaction of chlorine in the aqueous phase: 2Cl- f Cl2(l) + 2e-
(1)
Cl2(l) + H2O f HCl + HClO
(2)
+
-
in relation to the organic matter reaching the electrode surface. In this case, the process becomes mass-transfer-controlled. According to this statement, decreasing the initial COD from 1500 to 500 mg O2 L-1 increases ϑ, and the process becomes mass-transfer-controlled. In the same way, increasing the current density from 30 to 60 mA cm-2 increases ϑ so the oxidation would be mass-transfer-controlled and a higher kinetic constant is obtained. The kinetic constants for TOC removal as a function of ϑ (kϑ) are shown in Figure 4. Kinetic constants are associated with ϑ, which corresponds with each individual combination of j and [COD]0 studied in this work. According to the evolution of Figure 4, a hyperbolic function as is shown in eq 5 describes the experimental behavior Rϑ (5) 1 + βϑ where R represents the kinetic constant of the electrochemical oxidation at the electrode surface kA and β represents the ratio between kA and the mass transfer coefficient km. For the fitting of the kinetic constants to ϑ, R ) (28.39 ( 9.51) × 10-3 (mg O2 m)(mA min)-1 and β ) 16.13 ( 7.05 mg O2 mA-1 are obtained (r2 ) 0.988, confidence range ) 80%, LevenbergMarquardt algorithm). From Figure 3 it is observed that, at high values of ϑ, the process becomes mass-transfer-controlled: there is an excess of current density in the system, and therefore, the transfer of organic matter to the electrode surface is the limiting step to the TOC degradation. At low values of ϑ, the process becomes current-density-controlled: the applied current density kϑ )
(3) HClO f H + ClO The corresponding equation for the generation of peroxodisulphate in aqueous phase is shown in eq. 4: 22SO24 f S2O8 + 2e
(4)
Experimental kinetic constants can be considered taking into account those experiments with similar current densities and initial COD but different electrolytes. Consequently, kinetic constants for TOC can be grouped up to 4 values (kϑ), which show the possible combinations summarized in Table 5. These results are in a good agreement with previous results,8,12 which states that the ratio of applied current density to concentration of organic matter (ϑ) determines the way in which the COD is removed. When the ratio ϑ is relatively low, there are no available hydroxyl radicals to oxidize all the organic matter reaching the electrode surface, so the process is kinetically controlled by the applied current. On the other hand, when the ratio ϑ is relatively high, there is an excess of hydroxyl radicals
Figure 4. Kinetic constant kϑ as a function of ϑ. The error bars describe the maximum and minimum values of k.
9852 Ind. Eng. Chem. Res., Vol. 47, No. 24, 2008
is not enough to degrade the organic matter reaching the electrode surface. The ratio R/β ) 1.76 × 10-3 m min-1 describes therefore the mass transfer coefficient km when the process is mass-transfer-controlled at large ϑ values. As lignosulfonate is based on phenolic structures, it would be expected that different phenolic derivatives could appear after breaking into lower molecular weight species. The final steps of the reaction would include typical organic acids such as oxalic, maleic, etc., before the final mineralization to CO2. Conclusions In this work, the technical feasibility of removing the total organic carbon from dilute lignosulfonate solutions by means of a single compartment flow electrochemical cell in sodium sulfate and sodium chloride medium has been demonstrated in the studied range of variables. The oxidation process depends on the initial chemical oxygen demand and the applied current density. Both variables play a major role in the electrochemical oxidation of lignosulfonate with BDD electrodes. In the studied range of sodium chloride and sodium sulfate concentration, it has no significant effect so a concentration of 2500 mg L-1 is suitable to extend the removal percentage up to the desired values, and the supporting electrolyte does not have any influence on TOC removal. A first order kinetic model based on an exponential evolution of the dimensionless TOC with time has shown a good fitting of the experimental results leading to the experimental kinetic constants. Kinetics constants have been related to the current densities and initial chemical oxygen demand by a hyperbolic equation containing a first-order surface electrochemical reaction kinetic constant and a mass transfer coefficient. Acknowledgment This research is financially supported by the Spanish Ministry of Science and Technology (Project CONSOLIDER CTM200600317) and the Project CENIT SOSTAQUA. A.D.-R. thanks the Ministry of Education and Science for the FPU fellowship reference number AP-2005-1719. Nomenclature A/V ) electrode surface to solution volume ratio (m-1) [COD]0 ) initial COD (mg O2 L-1) j ) current density (mA cm-2) k ) kinetic constant for TOC removal (m min-1) kA ) kinetic constant of the electrochemical oxidation at the electrode surface (mg O2 m (mA min)-1 km ) mass transfer coefficient (m min-1) kS/C )kinetic constant for TOC removal independent of the selected supporting electrolyte (m min-1) kϑ ) kinetic constant for TOC removal as function of ϑ (m min-1) R ) adjusting parameter of kϑ as function of ϑ [(mg O2 m)(mA min)-1] β ) adjusting parameter of kϑ as function of ϑ (mg O2 mA-1) τ ) dimensionless TOC ϑ ) (j/[COD]0) · (A/V) (mA mg O2-1)
Literature Cited (1) Chen, G. Electrochemical technologies in wastewater treatment. Sep. Purif. Technol. 2004, 38, 11. (2) Chrysafopoulou, E.; Hourdakis, A.; Aghelopoulos, M.; Mantzavinos, D.; Kalogerakis, N. A pilot scale electrolytic unit for tertiary treatment of industrial effluents. Int. J. EnViron. Technol. Manage. 2006, 6, 480.
(3) Can˜izares, P.; Martı´nez, L.; Paz, R.; Sa´ez, C.; Lobato, J.; Rodrigo, M. A. Treatment of Fenton-refractory olive oil mill wastes by electrochemical oxidation with boron-doped diamond anodes. J. Chem. Tech. Biotechnol. 2006, 81, 1331. (4) Giannis, A.; Kalaitzakis, M.; Diamadopoulos, E. Electrochemical treatment of olive mill wastewater. J. Chem. Technol. Biotechnol. 2007, 82, 663. (5) Perret, A.; Haenni, W.; Skinner, N.; Tang, X. ; Gandini, D.; Comninellis, C.; Correa, B.; Foti, G. Electrochemical behavior of synthetic diamond thin film electrodes. Diamond Relat. Mater. 1999, 8, 820. (6) Springer, A. M.; Hand, V. C.; Jarvis, T. S. Electrochemical removal of color and toxicity from bleached kraft effluents. Tappi J. 1995, 78, 85. (7) Buzzini, A. P.; Miwa, D. W.; Motheo, A. J.; Pires, E. C. Use of electrochemical oxidation process as post-treatment for the effluents of a UASB reactor treating cellulose pulp mill wastewater. Water Sci. Technol. 2006, 54, 207. (8) Can˜izares, P.; Dı´az, M.; Domı´nguez, J. A.; Garcı´a-Go´mez, J.; Rodrigo, M. A. Electrochemical oxidation of aqueous phenol wastes on synthetic diamond thin-film electrodes. Ind. Eng. Chem. Res. 2002, 41, 4187. (9) Can˜izares, P.; Lobato, J.; Paz, R.; Rodrigo, M. A.; Sa´ez, C. Electrochemical oxidation of phenolic wastes with boron-doped diamond anodes. Water Res. 2005, 39, 2687. (10) Mora˜o, A.; Lopes, A.; Pessoa de Amorim, M. T.; Gonc¸alves, I. C. Degradation of mixtures of phenols using boron doped diamond electrodes for wastewater treatment. Electrochim. Acta 2004, 49, 1587. (11) Vlyssides, A. G.; Israilides, C. J. Electrochemical oxidation of a textile dye and finishing wastewater using a Pt/Ti electrode. J. EnViron. Sci. Health, Part A: Toxic/Hazard. Subst. EnViron. Eng. 1998, 33, 847. (12) Can˜izares, P.; Gadri, A.; Lobato, J.; Nasr, B.; Paz, R.; Rodrigo, M. A.; Sa´ez, C. Electrochemical oxidation of azoic dyes with conductivediamond anodes. Ind. Eng. Chem. Res. 2006, 45, 3468. (13) Mohan, N.; Balasubramanian, N.; Basha, C. A. Electrochemical oxidation of textile wastewater and its reuse. J. Hazard. Mater. 2007, 147, 644. (14) Can˜izares, P.; Martı´nez, F.; Lobato, J.; Rodrigo, M. A. Electrochemically assisted coagulation of wastes polluted with eriochrome black T. Ind. Eng. Chem. Res. 2006, 45, 3474. (15) Rajkumar, D.; Kim, J. G. Oxidation of various reactive dyes with in situ electro-generated active chlorine for textile dyeing industry wastewater treatment. J. Hazard. Mater. 2006, 136, 203. (16) Malpass, G. R. P.; Miwa, D. W.; Mortari, D. A.; Machado, S. A. S.; Motheo, A. J. Decolorisation of real textile waste using electrochemical techniques: Effect of the chloride concentration. Water Res. 2007, 41, 2969. (17) Rodrigo, M. A.; Michaud, P. A.; Duo, I.; Panizza, M.; Cerisola, G.; Comninellis, C. Oxidation of 4-chlorophenol at boron-doped diamond electrode for wastewater treatment. J. Electrochem. Soc. 2001, 148, D60. (18) Can˜izares, P.; Paz, R.; Lobato, J.; Sa´ez, C.; Rodrigo, M. A. Electrochemical treatment of the effluent of a fine chemical manufacturing plant. J. Hazard. Mater. 2006, 138, 173. (19) Panizza, M.; Michaud, P. A.; Cerisola, G.; Comninellis, C. Anodic oxidation of 2-naphthol at boron-doped diamond electrodes. J. Electroanal. Chem. 2001, 507, 206. (20) Deng, Y.; Englehardt, J. D. Electrochemical oxidation for landfill leachate treatment. Waste Manage. 2007, 27, 380. (21) Lei, Y.; Shen, Z.; Huang, R.; Wang, W. Treatment of landfill leachate by combined aged-refuse bioreactor and electro-oxidation. Water Res. 2007, 41, 2417. (22) Chiang, L. C.; Chang, J. E.; Wen, T. C. Indirect oxidation effect in electrochemical oxidation treatment of landfill leachate. Water Res. 1995, 29, 671. (23) Chiang, L. C.; Chang, J. E.; Chung, C. T. Electrochemical oxidation combined with physical-chemical pretreatment processes for the treatment of refractory landfill leachate. EnViron. Eng. Sci. 2001, 18, 369. (24) Cabeza, A.; Urtiaga, A. M.; Ortiz, I. Electrochemical treatment of landfill leachates using a boron-doped diamond anode. Ind. Eng. Chem. Res. 2007, 46, 1439. (25) Iniesta, J.; Michaud, P. A.; Panizza, M.; Comninellis, C. Electrochemical oxidation of 3-methylpyridine at a boron-doped diamond electrode: Application to electroorganic synthesis and wastewater treatment. Electrochem. Commun. 2001, 3, 346. (26) Rao, N. N.; Somasekhar, K. M.; Kaul, S. N.; Szpyrkowicz, L. Electrochemical oxidation of tannery wastewater. J. Chem. Tech. Biotechnol. 2001, 76, 1124. (27) Szpyrkowicz, L.; Kaul, S. N.; Neti, R. N. Tannery wastewater treatment by electro-oxidation coupled with a biological process. J. Appl. Electrochem. 2005, 35, 381. (28) Szpyrkowicz, L.; Kaul, S. N.; Neti, R. N.; Satyanarayan, S. Influence of anode material on electrochemical oxidation for the treatment of tannery wastewater. Water Res. 2005, 39, 1601.
Ind. Eng. Chem. Res., Vol. 47, No. 24, 2008 9853 (29) Szpyrkowicz, L.; Kelsall, G. H.; Kaul, S. N.; De Faveri, M. Performance of electrochemical reactor for treatment of tannery wastewaters. Chem. Eng. Sci. 2001, 56, 1579. (30) Bonfatti, F.; De Battisti, A.; Ferro, S.; Lodi, G.; Osti, S. Anodic mineralization of organic substrates in chloride-containing aqueous media. Electrochim. Acta 2000, 46, 305. (31) Rajkumar, D.; Palanivelu, K. Electrochemical treatment of industrial wastewater. J. Hazard. Mater. 2004, 113, 123. (32) Can˜izares, P.; Sa´ez, C.; Lobato, J.; Rodrigo, M. A. Electrochemical oxidation of polyhydroxybenzenes on boron-doped diamond anodes. Ind. Eng. Chem. Res. 2004, 43, 6629. (33) Chen, L. C.; Chang, C. C.; Chang, H. C. Electrochemical oxidation of histidine at an anodic oxidized boron-doped diamond electrode in neutral solution. Electrochim. Acta 2007, 5, 2883. (34) Fernandes, A.; Morao, A.; Magrinho, M.; Lopes, A.; Gonc¸alves, I. Electrochemical degradation of C. I. Acid Orange 7. Dyes Pigm. 2004, 61, 287. (35) Panizza, M.; Barbucci, A.; Ricotti, R.; Cerisola, G. Electrochemical degradation of methylene blue. Sep. Purif. Technol. 2007, 54, 382. (36) Boye, B.; Brillas, E.; Marselli, B.; Michaud, P.; Comninellis, C.; Farnia, G.; Sandona`, G. Electrochemical incineration of chloromethylphenoxy herbicides in acid medium by anodic oxidation with boron-doped diamond electrode. Electrochim. Acta 2006, 51, 2872. (37) Brillas, E.; Ban˜os, M. A.; Skoumal, M.; Cabot, P. L.; Garrido, J. A.; Rodrı´guez, R. M. Degradation of the herbicide 2,4-DP by anodic oxidation, electro-Fenton and photoelectro-Fenton using platinum and boron-doped diamond anodes. Chemosphere 2007, 68, 199. (38) Brillas, E.; Boye, B.; Sire´s, I.; Garrido, J. A.; Rodrı´guez, R. M.; Arias, C.; Cabot, P.; Comninellis, C. Electrochemical destruction of chlorophenoxy herbicides by anodic oxidation and electro-Fenton using a boron-doped diamond electrode. Electrochim. Acta 2004, 49, 4487. (39) Flox, C.; Cabot, P. L.; Centellas, F.; Garrido, J. A.; Rodrı´guez, R. M.; Arias, C.; Brillas, E. Electrochemical combustion of herbicide mecoprop in aqueous medium using a flow reactor with a boron-doped diamond anode. Chemosphere 2006, 64, 892. (40) Weichgrebe, D.; Danilova, E.; Rosenwinkel, K.; Vedenjapin, A. A.; Baturova, M. Electrochemical oxidation of drug residues in water by the example of tetracycline, gentamicine and aspirin. Water Sci. Technol. 2004, 49, 201. (41) Marselli, B.; Garcia-Gomez, J.; Michaud, P. A.; Rodrigo, M. A.; Comninellis, C. Electrogeneration of hydroxyl radicals on boron-doped diamond electrodes. J. Electrochem. Soc. 2003, 150, D79. (42) Kapałka, A.; Fo´ti, G. Comninellis, C. Kinetic modelling of the electrochemical mineralization of organic pollutants for wastewater treatment. J. Appl. Electrochem. 2008, 38, 7. (43) Fryda, M.; Matthe´e, T.; Mulcahy, S.; Hampel, A.; Scha¨fer, L.; Tro¨ster, I. Fabrication and application of Diachem electrodes. Diamond Relat. Mater. 2003, 12, 1950. (44) Panizza, M.; Zolezzi, M.; Nicolella, C. Biological and electrochemical oxidation of naphthalenesulfonates. J. Chem. Technol. Biotechnol. 2006, 81, 225. (45) Can˜izares, P.; Sa´ez, C.; Lobato, J.; Rodrigo, M. A. Detoxification of synthetic industrial wastewaters using electrochemical oxidation with boron-doped diamond anodes. J. Chem. Technol. Biotechnol. 2006, 81, 352.
(46) DeLucas, A.; Can˜izares, P.; Rodrigo, M. A.; Garcı´a-Go´mez, J. Electrochemical treatment of aqueous phenol wastes: A preliminary economical outlook. Waste Manage. EnViron. 2002, 161. (47) Polcaro, A. M.; Vacca, A.; Palmas, S.; Mascia, M. Electrochemical treatment of wastewater containing phenolic compounds: Oxidation at borondoped diamond electrodes. J. Appl. Electrochem. 2003, 33, 885. (48) Iniesta, J.; Michaud, P. A.; Panizza, M.; Cerisola, G.; Aldaz, A.; Comninellis, C. Electrochemical oxidation of phenol at boron-doped diamond electrode. Electrochim. Acta 2001, 46, 3573. (49) Panizza, M.; Michaud, P. A.; Cerisola, G.; Comninellis, C. Electrochemical treatment of wastewaters containing organic pollutants on boron-doped diamond electrodes: Prediction of specific energy consumption and required electrode area. Electrochem. Commun. 2001, 3, 336. (50) Simond, O.; Comninellis, C. Anodic oxidation of organics on Ti/ IrO2 anodes using Nafion as electrolyte. Electrochim. Acta 1997, 42, 2013. (51) Gorenflo, A.; Li, Y.; Frimmel, F. H. Improved biodegradability of ligninsulfonic acid and wastewater after ozonation. Chem. Eng. Technol. 2003, 26, 11. (52) Machado, A. E. H.; de Miranda, J. A.; de Freitas, R. F.; Duarte, E.T.F.M.; Ferreira, L. F.; Albuquerque, Y. D. T.; Ruggiero, R.; Sattler, C.; de Oliveira, L. Destruction of the organic matter present in effluent from a cellulose and paper industry using photocatalysis. J. Photochem. Photobiol., A 2003, 155, 231. (53) Chiang, L. C.; Chang, J. E.; Tseng, S. C. Electrochemical oxidation pretreatment of refractory organic pollutants. Water Sci. Technol. 1997, 36, 123. (54) Chen, F.; Lu, Z.; Tu, B. Electro-degradation of sodium lignosulfonate. J. Wood Chem. Technol. 2003, 23, 261. (55) Lacorte, S.; Latorre, A.; Barcelo´, D.; Rigol, A.; Malmqvist, A.; Welander, T. Organic compounds in paper-mill process waters and effluents. TrAC, Trends Anal. Chem. 2003, 22, 725. (56) Kreetachat, T.; Damrongsri, M.; Punsuwon, V.; Vaithanomsat, P.; Chiemchaisri, C.; Chomsurin, C. Effects of ozonation process on ligninderived compounds in pulp and paper mill effluents. J. Hazard. Mater. 2007, 142, 250. (57) Ghoreishi, S. M.; Haghighi, M. R. Chromophores removal in pulp and paper mill effluent via hydrogenation-biological batch reactors. Chem. Eng. J. 2007, 127, 59. (58) APHA, AWWA, WEF. Standard Methods for the Examination of Water and Wastewater, 20th ed.; American Public Health Association: Washington, DC, 1998. (59) European Commission BREF (12.01) Integrated Pollution Prevention and Control, Reference Document on Best Available Techniques in the Pulp and Paper Industry; December 2001. (60) Panizza, M.; Deluchi, M.; Cerisola, G. Electrochemical degradation anionic surfactants. J. Appl. Electrochem. 2005, 35, 357. (61) Kraft, A.; Stadelmann, M.; Blaschke, M. Anodic oxidation with doped diamond electrodes: A new advanced oxidation process. J. Hazard. Mater. 2003, 103, 247.
ReceiVed for reView July 18, 2008 ReVised manuscript receiVed September 25, 2008 Accepted September 26, 2008 IE801109C
