Francesc Torrades - Academia.edu (original) (raw)

Papers by Francesc Torrades

Research paper thumbnail of Decolorization and mineralization of commercial reactive dyes under solar light assisted photo-Fenton conditions

Solar Energ, 2004

The degradation of different commercial reactive dyes: a monoreactive dye (Procion Red H-E7B), an... more The degradation of different commercial reactive dyes: a monoreactive dye (Procion Red H-E7B), an hetero-bireactive dye (Red Cibacron FN-R) and a Standard Trichromatic System, by using solar light assisted Fenton and photo-Fenton reaction is investigated. The reaction efficiencies have been compared with the ones obtained for the same system in the dark or under the assistance of an artificial light source. The use of solar light is clearly beneficial for the removal of color, aromatic compounds (UV254), total organic carbon (TOC), and the increase of the BOD5/COD ratio. The possibility of a combined advanced oxidation process (AOP)/biological treatment based on the use of sunlight is suggested.

Research paper thumbnail of A Model to Establish the Limit of Decision and the Limit of Detection for Straight-Line Curves in a Case of Heteroscedasticity

Anal Lett, 1993

ABSTRACT A problem arises when determining the decision and detection limits in a series of resul... more ABSTRACT A problem arises when determining the decision and detection limits in a series of results where the variance of the error distribution of the analytical signals around their expectation is not a constant when applying a method proposed by Hubaux and Vos. In this paper an approach is proposed to overcome this difficulty, that involves the use of a transform method to convert heteroscedastic data to homoscedastic data so that the limit of detection can be obtained by projection of the confidence band about the linear regression. This approach is applied to the case of a gravimetric determination of sulphate ion in the 1 – 5 mgL SO4 range. The results obtained from this approach are compared from others obtained previously.

Research paper thumbnail of Limit of detection and limit of identification for straight-line calibration curves

Peer Reviewed Postprint (published version)

Research paper thumbnail of Mineralization of Hetero BI-Functional Reactive Dye in Aqueous solution by Fenton and Photo-Fenton Reactions

Environmental Technology, 2015

This study focused on the advanced oxidation of the hetero bi-functional reactive dye Sumifix Sup... more This study focused on the advanced oxidation of the hetero bi-functional reactive dye Sumifix Supra Yellow 3RF (CI Reactive Yellow 145) using dark Fenton and photo-Fenton conditions in a lab-scale experiment. A 2(3) factorial design was used to evaluate the effects of the three key factors: temperature, Fe(II) and H2O2 concentrations, for a dye concentration of 250 mg L(-1) with chemical oxygen demand (COD) of 172 mg L(-1) O2 at pH = 3. The response function was the COD reduction. This methodology lets us find the effects and interactions of the studied variables and their roles in the efficiency of the treatment process. In the optimization, the correlation coefficients for the model (R(2)) were 0.948 and 0.965 for Fenton and photo-Fenton treatments, respectively. Under optimized reaction conditions: pH = 3, temperature = 298 K, [H2O2] = 11.765 mM and [Fe(II)] = 1.075 mM; 60 min of treatment resulted in a 79% and 92.2% decrease in COD, for the dye taken as the model organic compound, after Fenton and photo-Fenton treatments, respectively.

Research paper thumbnail of Fenton and photo-Fenton oxidation of textile effluents

Water Research, 2002

The simultaneous use of Fenton reagent and irradiation for the treatment of textile wastewaters g... more The simultaneous use of Fenton reagent and irradiation for the treatment of textile wastewaters generated during a hydrogen peroxide bleaching process is investigated. The experimental conditions tested during this study provide the simultaneous occurrence of Fenton, Fenton-like and photo-Fenton reactions. The batch experimental results are assessed in terms of total organic carbon reduction. Identification of some of the chemical constituents of the effluent was performed by means of GC-MS. Other pollution related features of the initial effluent-like COD and color were also measured. The main parameters that govern the complex reactive system, i.e., light intensity, temperature, pH, Fe(II) and H 2 O 2 initial concentrations have been studied. Concentrations of Fe(II) between 0 and 400 ppm, and H 2 O 2 between 0 and 10,000 ppm were used. Temperatures above 251C and up to 701C show a beneficial effect on organic load reduction. A set of experiments was conducted under different light sources with the aim to ensure the efficiency of using solar light irradiation. The combination of Fenton, Fenton-like and photon-Fenton reactions has been proved to be highly effective for the treatment of such a type of wastewaters, and several advantages for the technique application arise from the study. r

Research paper thumbnail of Use of the blank test for detecting threshold effects in the indirect spectrophotometric determination of sulfate ions in tap water

Research paper thumbnail of Study of the coprecipitation of calcium, potassium, sodium and chloride with barium sulfate using atomic spectrometry and visible spectrophotometry

The Analyst, 1993

ABSTRACT Sulfate ions at the 50 and 250 mg l–1 SO42– levels are precipitated gravimetrically as B... more ABSTRACT Sulfate ions at the 50 and 250 mg l–1 SO42– levels are precipitated gravimetrically as BaSO4 from 200 ml samples using a large excess of BaCl2. Atomic absorption or emission spectrometry and visible spectrophotometry are applied to ten pairs of BaSO4 precipitates obtained from each of two concentration levels of standard Na2SO4 solution with or without 4 g of the cation being studied, to determine the Na, K, Ca and Cl ions present as impurities, after dissolution of the BaSO4 precipitates with hot, concentrated H2SO4. The experimental results, Δexp, are compared with the theoretical values, Δcalc, calculated from a model that assumes that all the anion precipitates as BaCl2 and all the cation as the sulfate of the respective cation. Good agreement with the model is found for the cations studied.

Research paper thumbnail of Limit of detection in barium sulphate gravimetry for water analysis

The Analyst, 1985

ABSTRACT Sulphate ions in the 1–5 mg l–1 SO42– range can be determined gravimetrically in 200-ml ... more ABSTRACT Sulphate ions in the 1–5 mg l–1 SO42– range can be determined gravimetrically in 200-ml samples using a large excess of barium chloride. From ten determinations at each of three concentration levels of standard sodium sulphate solution, the analytical calibration function calculated by weighted least squares is xc(mg l–1 SO42– found)=(0.093 ± 0.064)+(1.008 ± 0.039)c(mg l–1 SO42– added) with 95% confidence intervals. The limit of detection is cL= 1 mg l–1 SO42–(k= 3). A systematic approach is suggested for determining the limit of detection, by considering the variance of both the blank and the calibration function.

Research paper thumbnail of Use of the correct blank test in the determination of COD and AOX in bleached kraft mill D stage effluents

The Analyst, 2001

A study of four types of blank, two of which (the placebo blank and the method blank) are amenabl... more A study of four types of blank, two of which (the placebo blank and the method blank) are amenable to direct measurements and the other two [the total Youden blank (TYB) and system blank] to extrapolation, revealed the need to use a correct blank test, the TYB, in order to eliminate the constant error component. The conclusions drawn here are demonstrated for the microcoulometric determination of adsorbable organic halogen (AOX), according to Scandinavian standard SCAN-W 9+89, and in the spectrophotometric determination of chemical oxygen demand (COD) following a closed reflux spectrophotometric method. These environmental analytical parameters (AOX and COD) were determined in two different bleached kraft mill effluents: one from stage D (100% ClO 2 ) of the bleaching sequence AOD of the elemental chlorine-free type and the other for the chlorination step, the first in the conventional sequence (D 20 C 80 )(E 0 )D 1 D 2 , applied to kraft pulp from Populus spp.

Research paper thumbnail of Environmental assessment of different solar driven advanced oxidation processes

Solar Energy, 2005

In this work a comparative environmental assessment of different advanced oxidation processes (AO... more In this work a comparative environmental assessment of different advanced oxidation processes (AOPÕs) is performed. Two energy scenarios have been considered according to the energy source used: solar energy and electricity (UVA lamp). A life cycle assessment (LCA) is carried out in order to quantify the environmental impacts of the AOPÕs. The treatments considered are heterogenous photocatalysis, photo-Fenton reactions, the coupling of heterogeneous photocatalysis and photo-Fenton, and heterogeneous photocatalysis in combination with hydrogen peroxide. These AOPÕs are applied to the treatment of kraft mill bleaching wastewaters. The system under study includes the production of the catalysts, reagents as well as the production of electricity; eight environmental impact categories are assessed for each AOP: global warming, ozone depletion, aquatic eutrophication, acidification, human toxicity, freshwater aquatic toxicity, photochemical ozone formation, and abiotic resource depletion. the results of the LCA show that the environmental impact of AOPÕs is caused mainly by the amount of electricity consumed, whereas the impact of producing the reagents and catalysts is comparatively low. For this reason, the solar energy scenario reduces the impact more than 90% for almost all AOPÕs and impact categories. None of the solar driven AOPÕs can be identified as the best in all impact categories, but heterogenous photocatalysis and photo-Fenton reactions obtain better results than the remaining treatments, since these treatments do not consume simultaneously both TiO 2 and H 2 O 2 , the chemicals with highest environmental burdens in the system.

Research paper thumbnail of Decolorization and mineralization of commercial reactive dyes under solar light assisted photo-Fenton conditions

Solar Energy, 2004

The degradation of different commercial reactive dyes: a monoreactive dye (Procion Red H-E7B), an... more The degradation of different commercial reactive dyes: a monoreactive dye (Procion Red H-E7B), an hetero-bireactive dye (Red Cibacron FN-R) and a Standard Trichromatic System, by using solar light assisted Fenton and photo-Fenton reaction is investigated. The reaction efficiencies have been compared with the ones obtained for the same system in the dark or under the assistance of an artificial light source. The use of solar light is clearly beneficial for the removal of color, aromatic compounds (UV 254 ), total organic carbon (TOC), and the increase of the BOD 5 /COD ratio. The possibility of a combined advanced oxidation process (AOP)/biological treatment based on the use of sunlight is suggested.

Research paper thumbnail of Pilot plant scale reactive dyes degradation by solar photo-Fenton and biological processes

Journal of Photochemistry and Photobiology A: Chemistry, 2008

Solar photo-Fenton reactions as a stand-alone process and as a pre-treatment of an aerobic biolog... more Solar photo-Fenton reactions as a stand-alone process and as a pre-treatment of an aerobic biological treatment for Procion Red H-E7B and Cibacron Red FN-R reactive dyes degradation have been carried out at pilot plant scale. Photo-Fenton oxidation was conducted using a Compound Parabolic Collector (CPC) solar photo-reactor and the biological treatment was carried out with an Immobilised Biomass Reactor (IBR). Artificial light photo-Fenton experiments carried out at laboratory scale have been taken as starting point. When applying photo-Fenton reaction as a single process, 10 mg L −1 Fe (II) and 250 mg L −1 H 2 O 2 for 250 mg L −1 Procion Red H-E7B treatment, and 20 mg L −1 Fe (II) and 500 mg L −1 H 2 O 2 for 250 mg L −1 Cibacron Red FN-R treatment closely reproduced the laboratory mineralisation results, with 82 and 86% Dissolved Organic Carbon (DOC) removal, respectively. Nevertheless, the use of sunlight with the CPC photo-reactor increased the degradation rates allowing the reduction of Fe (II) concentration from 10 to 2 mg L −1 (Procion Red H-E7B) and from 20 to 5 mg L −1 (Cibacron Red FN-R) without yield loses. Carboxylic acids, SO 4 2− , NH 4 + and NO 3 − generation was monitored along with dye mineralisation. Finally, in the combined photo-Fenton/biological system, reagents doses of 5 mg L −1 Fe (II) and 225 mg L −1 H 2 O 2 for Cibacron Red FN-R and 2 mg L −1 Fe (II) and 65 mg L −1 H 2 O 2 for Procion Red H-E7B were enough to generate biodegradable solutions that could be fed to the IBR, even improving bench-scale results.

Research paper thumbnail of Removal of organic contaminants in paper pulp treatment effluents by TiO2 photocatalyzed oxidation

Journal of Photochemistry and Photobiology A: Chemistry, 1997

ABSTRACT TiO2 slurries under UV light irradiation were used for the oxidation and removal of the ... more ABSTRACT TiO2 slurries under UV light irradiation were used for the oxidation and removal of the organic load of effluent from the bleaching of paper pulp. TOC was the main analytical parameter used to characterize the reaction progress, although COD, AOX and color also received periodic attention. Conditions such as the catalyst load, light intensity, pH, temperature, and concentration of O2 and organic matter were changed through several series of experiments in order to determine their effect. A zero order kinetics accounts for the observed variation of TOC with time during most of the reaction, the rate constant being 0.25–0.40 ppm min−1 at 25 °C. This behavior is explained in terms of a Langmuir–Hinshelwood rate equation in a highly substrate concentrated system.

Research paper thumbnail of Environmental assessment of different photo-Fenton approaches for commercial reactive dye removal

Journal of Hazardous Materials, 2006

Research paper thumbnail of The testing of several biological and chemical coupled treatments for Cibacron Red FN-R azo dye removal

Journal of Hazardous Materials, 2008

Several biological and chemical coupled treatments for Cibacron Red FN-R reactive azo dye degrada... more Several biological and chemical coupled treatments for Cibacron Red FN-R reactive azo dye degradation have been evaluated. Initially, a two-stage anaerobic-aerobic biotreatment has been assessed for different dye concentrations (250, 1250 and 3135 mg l(-1)). 92-97% decolourisation was attained during the anaerobic digestion operating in batch mode. However, no dissolved organic carbon (DOC) removal neither biogas production was observed during the process, indicating that no methanogenesis occurred. Additionally, according to Biotox and Zahn-Wellens assays, the anaerobically generated colourless solutions (presumably containing the resulting aromatic amines from azo bond cleavage) were found to be more toxic than the initial dye as well as aerobically non-biodegradable, thus impeding the anaerobic-aerobic biological treatment. In a second part, the use of an advanced oxidation process (AOP) like photo-Fenton or ozonation as a chemical post-treatments of the anaerobic process has been considered for the complete dye by-products mineralisation. The best results were obtained by means of ozonation at pH 10.5, achieving a global 83% mineralisation and giving place to a final harmless effluent. On the contrary, the tested photo-Fenton conditions were not efficient enough to complete oxidation.

Research paper thumbnail of Degradation of Procion Red H-E7B reactive dye by coupling a photo-Fenton system with a sequencing batch reactor

Journal of Hazardous Materials, 2006

Research paper thumbnail of Bias-free results in the spectrophotometric determination of chemical oxygen demand in bleached textile mill effluents

Journal of Chemical Technology & Biotechnology, 2002

ABSTRACT A calibration methodology that enables validation of the analytical procedure used in th... more ABSTRACT A calibration methodology that enables validation of the analytical procedure used in those cases where no placebo or standard reference material is available is applied here. The total Youden blank is used to eliminate the constant error component, and analytical measurements in the presence of the matrix at two different levels of the test portion, in order to avoid its interactive interference, are made. Moreover, the results obtained in the determination of chemical oxygen demand following a closed reflux spectrophotometric method are compared with those obtained when a definitive analytical method is applied, in order to show the absence of direct interference from the matrix.© 2002 Society of Chemical Industry

Research paper thumbnail of Removal of organic contaminants in paper pulp effluents by AOPs: an economic study

Journal of Chemical Technology & Biotechnology, 2002

ABSTRACT The degradation of the organic content of a bleaching Kraft mill effluent was carried ou... more ABSTRACT The degradation of the organic content of a bleaching Kraft mill effluent was carried out using Advanced Oxidation Processes (AOPs). The study was focused on the identification of the AOP, or combination of AOPs, that showed the highest efficiency together with the lowest cost. Direct UV photolysis (UV), TiO2 assisted-photocatalysis (TiO2/UV), Fenton, Fenton-like, and photo-Fenton reactions (Fe(II)/H2O/UV), UV-assisted ozonation (O3/UV) and addition of Fe2+ and/or H2O2 to the TiO2/UV and the O3/UV systems, were used for the degradation of a conventional cellulose bleaching effluent. The effluent was characterized by the general parameters TOC, COD and color, and analyzed for chlorinated low molecular weight compounds using GC–MS. The costs of the systems per unit of TOC reduction were compared. Fenton, Fenton-like and photo-Fenton reactions achieved better levels of TOC degradation than photocatalysis and with lower cost's than photocatalytic treatments. Ozonation is an effective but rather expensive process. The use of UVA light, however, increased the effectiveness of ozonation with a significant decrease (>25%) in the operational cost.© 2002 Society of Chemical Industry

Research paper thumbnail of Treatment of bleaching Kraft mill effluents and polychlorinated phenolic compounds with ozonation

Journal of Chemical Technology & Biotechnology, 2002

ABSTRACT The effect of the simultaneous use of ozone, UVA or visible light, and small quantities ... more ABSTRACT The effect of the simultaneous use of ozone, UVA or visible light, and small quantities of Fe(II)/Fe(III) ions in solution on the degradation rate of the organic content of a bleaching Kraft mill effluent was investigated. The same treatment was applied to synthetic samples of polychlorinated phenolic compounds, because these are one of the main groups of compounds found in real bleaching Kraft mill effluents. In order to improve the treatment efficiency and to lower the cost of the process several other strategies were investigated. It was found that a previous irradiation of the wastewater or the synthetic sample in the absence of ozone significantly improves the rate of removal of organic pollutants during the subsequent ozonation step.© 2002 Society of Chemical Industry

Research paper thumbnail of Degradation Pathways of the Commercial Reactive Azo Dye Procion Red H-E7B under Solar-Assisted Photo-Fenton Reaction

Environmental Science & Technology, 2008

Reactive azo dye Procion Red H-E7B solutions have been submitted to solar-assisted photo-Fenton d... more Reactive azo dye Procion Red H-E7B solutions have been submitted to solar-assisted photo-Fenton degradation. The solution color quickly disappears, indicating a fast degradation of the azo group. Nevertheless, complete DOC removal was not accomplished, in accordance with the presence of resistant triazine rings at the end of the reaction. The intermediates generated along the reaction time have been identified and quantified. LC-(ESI)-TOF-MS analysis allowed the detection of 18 aromatic compounds of different size and complexity. Some of them shared the same accurate mass, and consequently, the same empirical formula, but appeared at different chromatographic retention times, evidencing their different molecular structures. Heteroatom oxidation products like NH 4 + , NO 3 -, Cl -, and SO 4 2have also been quantified and explanations of their release are proposed. Short chain carboxylic acids are also detected at long reaction times, as a previous step to complete dye mineralization. A link between the disappearance of the largest intermediate products and the increase of the solutions biodegradability has been established. Finally, taking into account all the findings of the present study and previous related works, the evolution from the original dye to the final products (triazine and CO 2 ) is proposed in a general reaction scheme.

Research paper thumbnail of Decolorization and mineralization of commercial reactive dyes under solar light assisted photo-Fenton conditions

Solar Energ, 2004

The degradation of different commercial reactive dyes: a monoreactive dye (Procion Red H-E7B), an... more The degradation of different commercial reactive dyes: a monoreactive dye (Procion Red H-E7B), an hetero-bireactive dye (Red Cibacron FN-R) and a Standard Trichromatic System, by using solar light assisted Fenton and photo-Fenton reaction is investigated. The reaction efficiencies have been compared with the ones obtained for the same system in the dark or under the assistance of an artificial light source. The use of solar light is clearly beneficial for the removal of color, aromatic compounds (UV254), total organic carbon (TOC), and the increase of the BOD5/COD ratio. The possibility of a combined advanced oxidation process (AOP)/biological treatment based on the use of sunlight is suggested.

Research paper thumbnail of A Model to Establish the Limit of Decision and the Limit of Detection for Straight-Line Curves in a Case of Heteroscedasticity

Anal Lett, 1993

ABSTRACT A problem arises when determining the decision and detection limits in a series of resul... more ABSTRACT A problem arises when determining the decision and detection limits in a series of results where the variance of the error distribution of the analytical signals around their expectation is not a constant when applying a method proposed by Hubaux and Vos. In this paper an approach is proposed to overcome this difficulty, that involves the use of a transform method to convert heteroscedastic data to homoscedastic data so that the limit of detection can be obtained by projection of the confidence band about the linear regression. This approach is applied to the case of a gravimetric determination of sulphate ion in the 1 – 5 mgL SO4 range. The results obtained from this approach are compared from others obtained previously.

Research paper thumbnail of Limit of detection and limit of identification for straight-line calibration curves

Peer Reviewed Postprint (published version)

Research paper thumbnail of Mineralization of Hetero BI-Functional Reactive Dye in Aqueous solution by Fenton and Photo-Fenton Reactions

Environmental Technology, 2015

This study focused on the advanced oxidation of the hetero bi-functional reactive dye Sumifix Sup... more This study focused on the advanced oxidation of the hetero bi-functional reactive dye Sumifix Supra Yellow 3RF (CI Reactive Yellow 145) using dark Fenton and photo-Fenton conditions in a lab-scale experiment. A 2(3) factorial design was used to evaluate the effects of the three key factors: temperature, Fe(II) and H2O2 concentrations, for a dye concentration of 250 mg L(-1) with chemical oxygen demand (COD) of 172 mg L(-1) O2 at pH = 3. The response function was the COD reduction. This methodology lets us find the effects and interactions of the studied variables and their roles in the efficiency of the treatment process. In the optimization, the correlation coefficients for the model (R(2)) were 0.948 and 0.965 for Fenton and photo-Fenton treatments, respectively. Under optimized reaction conditions: pH = 3, temperature = 298 K, [H2O2] = 11.765 mM and [Fe(II)] = 1.075 mM; 60 min of treatment resulted in a 79% and 92.2% decrease in COD, for the dye taken as the model organic compound, after Fenton and photo-Fenton treatments, respectively.

Research paper thumbnail of Fenton and photo-Fenton oxidation of textile effluents

Water Research, 2002

The simultaneous use of Fenton reagent and irradiation for the treatment of textile wastewaters g... more The simultaneous use of Fenton reagent and irradiation for the treatment of textile wastewaters generated during a hydrogen peroxide bleaching process is investigated. The experimental conditions tested during this study provide the simultaneous occurrence of Fenton, Fenton-like and photo-Fenton reactions. The batch experimental results are assessed in terms of total organic carbon reduction. Identification of some of the chemical constituents of the effluent was performed by means of GC-MS. Other pollution related features of the initial effluent-like COD and color were also measured. The main parameters that govern the complex reactive system, i.e., light intensity, temperature, pH, Fe(II) and H 2 O 2 initial concentrations have been studied. Concentrations of Fe(II) between 0 and 400 ppm, and H 2 O 2 between 0 and 10,000 ppm were used. Temperatures above 251C and up to 701C show a beneficial effect on organic load reduction. A set of experiments was conducted under different light sources with the aim to ensure the efficiency of using solar light irradiation. The combination of Fenton, Fenton-like and photon-Fenton reactions has been proved to be highly effective for the treatment of such a type of wastewaters, and several advantages for the technique application arise from the study. r

Research paper thumbnail of Use of the blank test for detecting threshold effects in the indirect spectrophotometric determination of sulfate ions in tap water

Research paper thumbnail of Study of the coprecipitation of calcium, potassium, sodium and chloride with barium sulfate using atomic spectrometry and visible spectrophotometry

The Analyst, 1993

ABSTRACT Sulfate ions at the 50 and 250 mg l–1 SO42– levels are precipitated gravimetrically as B... more ABSTRACT Sulfate ions at the 50 and 250 mg l–1 SO42– levels are precipitated gravimetrically as BaSO4 from 200 ml samples using a large excess of BaCl2. Atomic absorption or emission spectrometry and visible spectrophotometry are applied to ten pairs of BaSO4 precipitates obtained from each of two concentration levels of standard Na2SO4 solution with or without 4 g of the cation being studied, to determine the Na, K, Ca and Cl ions present as impurities, after dissolution of the BaSO4 precipitates with hot, concentrated H2SO4. The experimental results, Δexp, are compared with the theoretical values, Δcalc, calculated from a model that assumes that all the anion precipitates as BaCl2 and all the cation as the sulfate of the respective cation. Good agreement with the model is found for the cations studied.

Research paper thumbnail of Limit of detection in barium sulphate gravimetry for water analysis

The Analyst, 1985

ABSTRACT Sulphate ions in the 1–5 mg l–1 SO42– range can be determined gravimetrically in 200-ml ... more ABSTRACT Sulphate ions in the 1–5 mg l–1 SO42– range can be determined gravimetrically in 200-ml samples using a large excess of barium chloride. From ten determinations at each of three concentration levels of standard sodium sulphate solution, the analytical calibration function calculated by weighted least squares is xc(mg l–1 SO42– found)=(0.093 ± 0.064)+(1.008 ± 0.039)c(mg l–1 SO42– added) with 95% confidence intervals. The limit of detection is cL= 1 mg l–1 SO42–(k= 3). A systematic approach is suggested for determining the limit of detection, by considering the variance of both the blank and the calibration function.

Research paper thumbnail of Use of the correct blank test in the determination of COD and AOX in bleached kraft mill D stage effluents

The Analyst, 2001

A study of four types of blank, two of which (the placebo blank and the method blank) are amenabl... more A study of four types of blank, two of which (the placebo blank and the method blank) are amenable to direct measurements and the other two [the total Youden blank (TYB) and system blank] to extrapolation, revealed the need to use a correct blank test, the TYB, in order to eliminate the constant error component. The conclusions drawn here are demonstrated for the microcoulometric determination of adsorbable organic halogen (AOX), according to Scandinavian standard SCAN-W 9+89, and in the spectrophotometric determination of chemical oxygen demand (COD) following a closed reflux spectrophotometric method. These environmental analytical parameters (AOX and COD) were determined in two different bleached kraft mill effluents: one from stage D (100% ClO 2 ) of the bleaching sequence AOD of the elemental chlorine-free type and the other for the chlorination step, the first in the conventional sequence (D 20 C 80 )(E 0 )D 1 D 2 , applied to kraft pulp from Populus spp.

Research paper thumbnail of Environmental assessment of different solar driven advanced oxidation processes

Solar Energy, 2005

In this work a comparative environmental assessment of different advanced oxidation processes (AO... more In this work a comparative environmental assessment of different advanced oxidation processes (AOPÕs) is performed. Two energy scenarios have been considered according to the energy source used: solar energy and electricity (UVA lamp). A life cycle assessment (LCA) is carried out in order to quantify the environmental impacts of the AOPÕs. The treatments considered are heterogenous photocatalysis, photo-Fenton reactions, the coupling of heterogeneous photocatalysis and photo-Fenton, and heterogeneous photocatalysis in combination with hydrogen peroxide. These AOPÕs are applied to the treatment of kraft mill bleaching wastewaters. The system under study includes the production of the catalysts, reagents as well as the production of electricity; eight environmental impact categories are assessed for each AOP: global warming, ozone depletion, aquatic eutrophication, acidification, human toxicity, freshwater aquatic toxicity, photochemical ozone formation, and abiotic resource depletion. the results of the LCA show that the environmental impact of AOPÕs is caused mainly by the amount of electricity consumed, whereas the impact of producing the reagents and catalysts is comparatively low. For this reason, the solar energy scenario reduces the impact more than 90% for almost all AOPÕs and impact categories. None of the solar driven AOPÕs can be identified as the best in all impact categories, but heterogenous photocatalysis and photo-Fenton reactions obtain better results than the remaining treatments, since these treatments do not consume simultaneously both TiO 2 and H 2 O 2 , the chemicals with highest environmental burdens in the system.

Research paper thumbnail of Decolorization and mineralization of commercial reactive dyes under solar light assisted photo-Fenton conditions

Solar Energy, 2004

The degradation of different commercial reactive dyes: a monoreactive dye (Procion Red H-E7B), an... more The degradation of different commercial reactive dyes: a monoreactive dye (Procion Red H-E7B), an hetero-bireactive dye (Red Cibacron FN-R) and a Standard Trichromatic System, by using solar light assisted Fenton and photo-Fenton reaction is investigated. The reaction efficiencies have been compared with the ones obtained for the same system in the dark or under the assistance of an artificial light source. The use of solar light is clearly beneficial for the removal of color, aromatic compounds (UV 254 ), total organic carbon (TOC), and the increase of the BOD 5 /COD ratio. The possibility of a combined advanced oxidation process (AOP)/biological treatment based on the use of sunlight is suggested.

Research paper thumbnail of Pilot plant scale reactive dyes degradation by solar photo-Fenton and biological processes

Journal of Photochemistry and Photobiology A: Chemistry, 2008

Solar photo-Fenton reactions as a stand-alone process and as a pre-treatment of an aerobic biolog... more Solar photo-Fenton reactions as a stand-alone process and as a pre-treatment of an aerobic biological treatment for Procion Red H-E7B and Cibacron Red FN-R reactive dyes degradation have been carried out at pilot plant scale. Photo-Fenton oxidation was conducted using a Compound Parabolic Collector (CPC) solar photo-reactor and the biological treatment was carried out with an Immobilised Biomass Reactor (IBR). Artificial light photo-Fenton experiments carried out at laboratory scale have been taken as starting point. When applying photo-Fenton reaction as a single process, 10 mg L −1 Fe (II) and 250 mg L −1 H 2 O 2 for 250 mg L −1 Procion Red H-E7B treatment, and 20 mg L −1 Fe (II) and 500 mg L −1 H 2 O 2 for 250 mg L −1 Cibacron Red FN-R treatment closely reproduced the laboratory mineralisation results, with 82 and 86% Dissolved Organic Carbon (DOC) removal, respectively. Nevertheless, the use of sunlight with the CPC photo-reactor increased the degradation rates allowing the reduction of Fe (II) concentration from 10 to 2 mg L −1 (Procion Red H-E7B) and from 20 to 5 mg L −1 (Cibacron Red FN-R) without yield loses. Carboxylic acids, SO 4 2− , NH 4 + and NO 3 − generation was monitored along with dye mineralisation. Finally, in the combined photo-Fenton/biological system, reagents doses of 5 mg L −1 Fe (II) and 225 mg L −1 H 2 O 2 for Cibacron Red FN-R and 2 mg L −1 Fe (II) and 65 mg L −1 H 2 O 2 for Procion Red H-E7B were enough to generate biodegradable solutions that could be fed to the IBR, even improving bench-scale results.

Research paper thumbnail of Removal of organic contaminants in paper pulp treatment effluents by TiO2 photocatalyzed oxidation

Journal of Photochemistry and Photobiology A: Chemistry, 1997

ABSTRACT TiO2 slurries under UV light irradiation were used for the oxidation and removal of the ... more ABSTRACT TiO2 slurries under UV light irradiation were used for the oxidation and removal of the organic load of effluent from the bleaching of paper pulp. TOC was the main analytical parameter used to characterize the reaction progress, although COD, AOX and color also received periodic attention. Conditions such as the catalyst load, light intensity, pH, temperature, and concentration of O2 and organic matter were changed through several series of experiments in order to determine their effect. A zero order kinetics accounts for the observed variation of TOC with time during most of the reaction, the rate constant being 0.25–0.40 ppm min−1 at 25 °C. This behavior is explained in terms of a Langmuir–Hinshelwood rate equation in a highly substrate concentrated system.

Research paper thumbnail of Environmental assessment of different photo-Fenton approaches for commercial reactive dye removal

Journal of Hazardous Materials, 2006

Research paper thumbnail of The testing of several biological and chemical coupled treatments for Cibacron Red FN-R azo dye removal

Journal of Hazardous Materials, 2008

Several biological and chemical coupled treatments for Cibacron Red FN-R reactive azo dye degrada... more Several biological and chemical coupled treatments for Cibacron Red FN-R reactive azo dye degradation have been evaluated. Initially, a two-stage anaerobic-aerobic biotreatment has been assessed for different dye concentrations (250, 1250 and 3135 mg l(-1)). 92-97% decolourisation was attained during the anaerobic digestion operating in batch mode. However, no dissolved organic carbon (DOC) removal neither biogas production was observed during the process, indicating that no methanogenesis occurred. Additionally, according to Biotox and Zahn-Wellens assays, the anaerobically generated colourless solutions (presumably containing the resulting aromatic amines from azo bond cleavage) were found to be more toxic than the initial dye as well as aerobically non-biodegradable, thus impeding the anaerobic-aerobic biological treatment. In a second part, the use of an advanced oxidation process (AOP) like photo-Fenton or ozonation as a chemical post-treatments of the anaerobic process has been considered for the complete dye by-products mineralisation. The best results were obtained by means of ozonation at pH 10.5, achieving a global 83% mineralisation and giving place to a final harmless effluent. On the contrary, the tested photo-Fenton conditions were not efficient enough to complete oxidation.

Research paper thumbnail of Degradation of Procion Red H-E7B reactive dye by coupling a photo-Fenton system with a sequencing batch reactor

Journal of Hazardous Materials, 2006

Research paper thumbnail of Bias-free results in the spectrophotometric determination of chemical oxygen demand in bleached textile mill effluents

Journal of Chemical Technology & Biotechnology, 2002

ABSTRACT A calibration methodology that enables validation of the analytical procedure used in th... more ABSTRACT A calibration methodology that enables validation of the analytical procedure used in those cases where no placebo or standard reference material is available is applied here. The total Youden blank is used to eliminate the constant error component, and analytical measurements in the presence of the matrix at two different levels of the test portion, in order to avoid its interactive interference, are made. Moreover, the results obtained in the determination of chemical oxygen demand following a closed reflux spectrophotometric method are compared with those obtained when a definitive analytical method is applied, in order to show the absence of direct interference from the matrix.© 2002 Society of Chemical Industry

Research paper thumbnail of Removal of organic contaminants in paper pulp effluents by AOPs: an economic study

Journal of Chemical Technology & Biotechnology, 2002

ABSTRACT The degradation of the organic content of a bleaching Kraft mill effluent was carried ou... more ABSTRACT The degradation of the organic content of a bleaching Kraft mill effluent was carried out using Advanced Oxidation Processes (AOPs). The study was focused on the identification of the AOP, or combination of AOPs, that showed the highest efficiency together with the lowest cost. Direct UV photolysis (UV), TiO2 assisted-photocatalysis (TiO2/UV), Fenton, Fenton-like, and photo-Fenton reactions (Fe(II)/H2O/UV), UV-assisted ozonation (O3/UV) and addition of Fe2+ and/or H2O2 to the TiO2/UV and the O3/UV systems, were used for the degradation of a conventional cellulose bleaching effluent. The effluent was characterized by the general parameters TOC, COD and color, and analyzed for chlorinated low molecular weight compounds using GC–MS. The costs of the systems per unit of TOC reduction were compared. Fenton, Fenton-like and photo-Fenton reactions achieved better levels of TOC degradation than photocatalysis and with lower cost's than photocatalytic treatments. Ozonation is an effective but rather expensive process. The use of UVA light, however, increased the effectiveness of ozonation with a significant decrease (>25%) in the operational cost.© 2002 Society of Chemical Industry

Research paper thumbnail of Treatment of bleaching Kraft mill effluents and polychlorinated phenolic compounds with ozonation

Journal of Chemical Technology & Biotechnology, 2002

ABSTRACT The effect of the simultaneous use of ozone, UVA or visible light, and small quantities ... more ABSTRACT The effect of the simultaneous use of ozone, UVA or visible light, and small quantities of Fe(II)/Fe(III) ions in solution on the degradation rate of the organic content of a bleaching Kraft mill effluent was investigated. The same treatment was applied to synthetic samples of polychlorinated phenolic compounds, because these are one of the main groups of compounds found in real bleaching Kraft mill effluents. In order to improve the treatment efficiency and to lower the cost of the process several other strategies were investigated. It was found that a previous irradiation of the wastewater or the synthetic sample in the absence of ozone significantly improves the rate of removal of organic pollutants during the subsequent ozonation step.© 2002 Society of Chemical Industry

Research paper thumbnail of Degradation Pathways of the Commercial Reactive Azo Dye Procion Red H-E7B under Solar-Assisted Photo-Fenton Reaction

Environmental Science & Technology, 2008

Reactive azo dye Procion Red H-E7B solutions have been submitted to solar-assisted photo-Fenton d... more Reactive azo dye Procion Red H-E7B solutions have been submitted to solar-assisted photo-Fenton degradation. The solution color quickly disappears, indicating a fast degradation of the azo group. Nevertheless, complete DOC removal was not accomplished, in accordance with the presence of resistant triazine rings at the end of the reaction. The intermediates generated along the reaction time have been identified and quantified. LC-(ESI)-TOF-MS analysis allowed the detection of 18 aromatic compounds of different size and complexity. Some of them shared the same accurate mass, and consequently, the same empirical formula, but appeared at different chromatographic retention times, evidencing their different molecular structures. Heteroatom oxidation products like NH 4 + , NO 3 -, Cl -, and SO 4 2have also been quantified and explanations of their release are proposed. Short chain carboxylic acids are also detected at long reaction times, as a previous step to complete dye mineralization. A link between the disappearance of the largest intermediate products and the increase of the solutions biodegradability has been established. Finally, taking into account all the findings of the present study and previous related works, the evolution from the original dye to the final products (triazine and CO 2 ) is proposed in a general reaction scheme.