The recent interest in the utilisation of agricultural fibres has promoted research into their po... more The recent interest in the utilisation of agricultural fibres has promoted research into their potential as raw materials for the pulp and paper industry. In the current study, we report on the effect of biological pretreatment of wheat straw by Streptomyces cyaneus on the performance of the handsheets produced from the treated pulps. The pre-treatment of wheat straw with S. cyaneus had a positive effect on both the burst and tear indexes of the pulps but had a negative impact on tensile index. No significant variation in permeability and in folding endurance was observed. Manipulation of handsheets from wheat straw through biological treatment may therefore result in improved quality traits.
Additional file 5. Obtained films from cellulase control Ck (a) and Cmix (b) pretreatments after ... more Additional file 5. Obtained films from cellulase control Ck (a) and Cmix (b) pretreatments after mechanical fibrillation.
Additional file 4. Z potential values of the samples obtained after mechanical fibrillation. R (i... more Additional file 4. Z potential values of the samples obtained after mechanical fibrillation. R (initial refined pulp), Ck (control treatment), C9 (Cel9B), Cmix (cellulase mixture consisting in Fibercare and Celluclast), S (LPMO), SCmix (LPMO and Cmix) and L_Tempo (Laccase_Tempo treatment).
Additional file 3. FTIR spectra of obtained films from control treatment (Ck) and Laccase_Tempo t... more Additional file 3. FTIR spectra of obtained films from control treatment (Ck) and Laccase_Tempo treatment (L_Tempo). TCI was calculated from the ratio of the absorptions at 1372 and 2900 cm−1. The peak detected at 1750 cm−1 with L_Tempo correspond to the COOH groups.
Additional file 2. Effect of the hydrolytic (a) and oxidative and Cmix (b) enzymatic pretreatment... more Additional file 2. Effect of the hydrolytic (a) and oxidative and Cmix (b) enzymatic pretreatments on fibre length distribution. The confidence interval of the length fibre distribution was less than 2% in all cases.
Additional file 1. TLC analysis of sugars released during enzymatic treatments performed at 50 °C... more Additional file 1. TLC analysis of sugars released during enzymatic treatments performed at 50 °C, pH 5, during 18 h with 10 U g−1 odp of enzyme (in the case of Cmix the enzymatic dose was 20 U g−1 odp). C9 (Cel9B), C50 (Sertec20 cellulase), CF (Fibercare cellulase), Cll (Celluclast cellulase), Cmix (cellulase mixture consisting in Fibercare and Celluclast). M) size markers of glucose (G), cellobiose (G2), cellotriose (G3), cellotetraose (G4) and cellopentaose (G5).
Background: The increasing interest in replacing petroleum-based products by more sustainable mat... more Background: The increasing interest in replacing petroleum-based products by more sustainable materials in the packaging sector gives relevance to cellulose as a biodegradable natural resource. Moreover, its properties can be modified physically, chemically or biotechnologically in order to obtain new bioproducts. Refined cotton linters with high cellulose content were treated with hydrolytic (cellulases) and oxidative (LPMO and Laccase_Tempo) enzymes to evaluate their effect on fibre properties and in improving mechanical fibrillation. Results: Cellulases released cellooligosaccharides, reducing fibre length and partially degrading cellulose. They also improved mechanical fibrillation yielding up to 18% of nanofibrillated cellulose (NFC). LPMO introduced a slight amount of COOH groups in cellulose fibres, releasing cellobionic acid to the effluents. The action of cellulases was improved after LPMO treatment; however, the COOH groups created disappeared from fibres. After mechanical fibrillation of LPMO-cellulase-treated cotton linters a 23% yield of NFC was obtained. Laccase_Tempo treatment also introduced COOH groups in cellulose fibres from cotton, yielding 10% of NFC. Degree of polymerization was reduced by Laccase_Tempo, while LPMO treatment did not significantly affect it but produced a higher reduction in fibre length. The combined treatment with LPMO and cellulase provided films with higher transparency (86%), crystallinity (92%), smoothness and improved barrier properties to air and water than films casted from non-treated linters and from commercial NFC. Conclusions: The combined enzymatic treatment with LPMO and cellulases boosted mechanical fibrillation of cotton linters, improving the NFC production and providing bioproducts with high transparency and high barrier properties.
A fully bleached commercial acid dissolving pulp was treated with two endoglucanases, one obtaine... more A fully bleached commercial acid dissolving pulp was treated with two endoglucanases, one obtained from Paenibacillus barcinonensis (B) and the other one produced from Cerrena unicolor (F) with the intention to improve cellulose reactivity and processability in the viscose process. B cellulase was tested under 120 U/g odp (oven dry pulp) and the F cellulase under two conditions, 12U/g odp and 60 U/g odp. In addition, a purification stage, consisting in a cold caustic extraction (CCE) of 9% w/v NaOH, was applied before or after the enzymatic treatment in order to reduce the amount of hemicellulose and improve the action of enzymes. The treated pulps were evaluated in terms of brightness, viscosity, water retention value (WRV), fibre morphology, carbohydrate composition, Fock solubility and NMR. In general, results revealed that both endoglucanases improved cellulose reactivity, albeit in a different way; thus, B caused no scissions in the cellulose chain and no significant reduction in fibre length, whereas F strongly decreased viscosity, shortened fibre length and increased considerably the amount of fines. The result of applying two different doses of F cellulase was reflected on Fock solubility and fibre morphology. F60 treatment was found to give the highest value of Fock solubility and the biggest reduction of fibre length. The effect of both endoglucanases on Fock solubility was increased by introducing an earlier CCE stage. Finally, a CCE_B120 pulp with 3% of hemicellulose and 69% of Fock solubility was obtained.
Industrial & Engineering Chemistry Research, 2010
To obtain a more realistic appraisal of the potential efficiency of xylanases in the industrial b... more To obtain a more realistic appraisal of the potential efficiency of xylanases in the industrial bleaching, the influence of pH and the presence of black liquor (measured as COD) on the bleaching efficiency of two commercial xylanases was studied at high temperature. These pH's, CODs, and temperatures are close to those used in the storage tower of the B fiber line in Jacareí unit of Fibria (Brazil). The pulp samples obtained after each bleaching stage were analyzed for kappa number, brightness, viscosity, and hexenuronic acid content, and so were the effluents for COD, TOC, color, turbidity, and pH after the enzymatic stage. On the basis of the results, the xylanases were found to increase pulp brightness in the treatment involving the most unfavorable conditions (viz. high COD and pH). However, an initial COD above 9 kgO 2 t-1 and/or a pH higher than 9.5 detracted from their bleaching efficiency. The effect on the kappa number and hexenuronic acids content of the pulp was apparent immediately after the enzymatic stage, and the most marked increase in brightness was observed after the chlorine dioxide stage.
The environmental impact of enzyme bleaching stages applied to oxygen-delignified eucalypt kraft ... more The environmental impact of enzyme bleaching stages applied to oxygen-delignified eucalypt kraft pulp was assessed via the chemical oxygen demand (COD), color, absorbance spectrum, residual enzyme activity and Microtox toxicity of the effluents from a laccase-HBT (1-hydoxybenzotriazole) treatment. The influence of the laccase and HBT doses, and reaction time, on these effluent properties was also examined. The laccase dose was found to be the individual variable most strongly affecting COD, whereas the oxidized form of HBT was the main source of increased color and toxicity in the effluents. Moreover, it inactivated the enzyme. Oxidation of the mediator was very fast and essentially dependent on the laccase dose. Using the laccase-mediator treatment after a xylanase stage improved pulp properties without affecting effluent properties. This result holds great promise with a view to the industrial implementation of biobleaching sequences involving the two enzymes in the future.
Bleached cellulose with good end-properties (≈ 90% ISO brightness and 62% cellulose preservation)... more Bleached cellulose with good end-properties (≈ 90% ISO brightness and 62% cellulose preservation) was obtained by using a totally chlorine-free biobleaching process (TCF). Unbleached sulphite cellulose was treated with Trametes villosa laccase in combination with violuric acid. This enzymatic stage (L) was followed by a chelating stage (Q) and then by a hydrogen peroxide stage reinforced with pressurized oxygen (Po), resulting to an overall LQPo sequence. The use of violuric acid was dictated by the results of a preliminary study, where the bleaching efficiency of various natural (syringaldehyde and p-coumaric acid) and synthetic mediators (violuric acid and 1-hydroxybenzotriazole) were assessed. The outstanding results obtained with laccase-violuric acid system fulfil most of the characteristics of commercial dissolving pulp, totally acceptable for viscose manufacturing or CMC derivatives, with the added advantage that the enzymatic treatment saved 2h of reaction time and about 70% of hydrogen peroxide consumption, relative to a conventional sequence (Po).
Fiber crops constitute a good alternative to wood fiber for manufacturing pulp and paper. In fact... more Fiber crops constitute a good alternative to wood fiber for manufacturing pulp and paper. In fact, fiber plants like flax surpass wood fiber in some technical respects and also in the environmental benignity of their processing. In this work, flax fiber was subjected to environmentally friendly bleaching sequences in order to obtain a high-quality pulp. The totally chlorine-free sequences (TCF) used for this purpose (LE and LRE) included an enzyme treatment with laccase in the presence of HBT as mediator (L stage), an alkaline extraction (E stage) and a reductive treatment with NaBH 4 (R stage). The operating conditions for the L stage (laccase and HBT doses, reaction time and oxygen pressure) were optimised by using a sequential statistical plan to assess their influence on pulp properties after the E stage. Mathematical models accurately predicting brightness and kappa number in terms of the previous four variables were developed based on which the most influential factors were the laccase and HBT rates, and treatment time. By contrast, oxygen pressures of 0.2e0.6 MPa in the reactor had no effect on brightness or kappa number. The flax pulp obtained contained some oxidized cellulose that was partially degraded in the alkaline extraction step and reduced viscosity as a result. The viscosity loss associated with the presence of oxidized cellulose in the control and enzyme-treated pulp samples was efficiently recovered by using a reductive stage with sodium borohydride. Effluent was also analysed in order to assess the environmental impact of the process.
Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on ... more Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre-including this research content-immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
In this work, we studied the influence of the alkyl chain length in enzymaticallyoxidized gallate... more In this work, we studied the influence of the alkyl chain length in enzymaticallyoxidized gallates on the development of hydrophobicity on paper-based materials, and further correlated the obtained effect to the redox mechanism of the enzymatic treatment. Laccase (Lac) enzyme was used to oxidize various members of the gallate homologous series in the presence or not of lignosulfonates (SL) to produce several functionalization solutions (FS), which were subsequently applied to cellulosic substrates. The hydrophobicity of the substrates was then assessed by means of water drop test (WDT) and contact angle (WCA) measurements. Hydrophobicity peaked reaching WDT and WCA values around 5000 seconds and 130º respectively, and then
An oxygen delignified eucalyptus Kraft pulp was bleached in a totally chlorine-free (TCF) sequenc... more An oxygen delignified eucalyptus Kraft pulp was bleached in a totally chlorine-free (TCF) sequence using an ozone stage (Z) followed by a hydrogen peroxide stage (P). Ozone treatments were carried out at a laboratory scale with new automated equipment. The Z stage was modeled using a four-variable sequential statistical plan over the following ranges: 10–20 g o.d.p. mass pulp, 20–50
Ozone appears to be an effective choice for developing new totally chlorine free (TCF) sequences.... more Ozone appears to be an effective choice for developing new totally chlorine free (TCF) sequences. One of the goals of current research into the use of ozone as a pulp-bleaching agent is to increase the selectivity of the process. In this work, various reagents were used as additives in the ozone bleaching stage (Z) with a view to raising its selectivity. Overall 16 different reagents were used under variable conditions and various properties of the resulting pulp (Kappa number, viscosity and brightness), in addition to the Z stage selectivity and the P stage efficiency, were determined. Based on the results, the additives studied exert a favourable effect on the process (particularly oxalic acid). The performance of the reagents are analysed through the study of chain scission number (CS) in the cellulose chain.
An oxygen delignified eucalyptus Kraft pulp was bleached in a totally chlorine-free (TCF) sequenc... more An oxygen delignified eucalyptus Kraft pulp was bleached in a totally chlorine-free (TCF) sequence using an ozone stage (Z) followed by a hydrogen peroxide stage (P). Ozone treatments were carried out at a laboratory scale with new automated equipment. The Z stage was modeled using a four-variable sequential statistical plan over the following ranges: 10–20 g o.d.p. mass pulp, 20–50
The recent interest in the utilisation of agricultural fibres has promoted research into their po... more The recent interest in the utilisation of agricultural fibres has promoted research into their potential as raw materials for the pulp and paper industry. In the current study, we report on the effect of biological pretreatment of wheat straw by Streptomyces cyaneus on the performance of the handsheets produced from the treated pulps. The pre-treatment of wheat straw with S. cyaneus had a positive effect on both the burst and tear indexes of the pulps but had a negative impact on tensile index. No significant variation in permeability and in folding endurance was observed. Manipulation of handsheets from wheat straw through biological treatment may therefore result in improved quality traits.
Additional file 5. Obtained films from cellulase control Ck (a) and Cmix (b) pretreatments after ... more Additional file 5. Obtained films from cellulase control Ck (a) and Cmix (b) pretreatments after mechanical fibrillation.
Additional file 4. Z potential values of the samples obtained after mechanical fibrillation. R (i... more Additional file 4. Z potential values of the samples obtained after mechanical fibrillation. R (initial refined pulp), Ck (control treatment), C9 (Cel9B), Cmix (cellulase mixture consisting in Fibercare and Celluclast), S (LPMO), SCmix (LPMO and Cmix) and L_Tempo (Laccase_Tempo treatment).
Additional file 3. FTIR spectra of obtained films from control treatment (Ck) and Laccase_Tempo t... more Additional file 3. FTIR spectra of obtained films from control treatment (Ck) and Laccase_Tempo treatment (L_Tempo). TCI was calculated from the ratio of the absorptions at 1372 and 2900 cm−1. The peak detected at 1750 cm−1 with L_Tempo correspond to the COOH groups.
Additional file 2. Effect of the hydrolytic (a) and oxidative and Cmix (b) enzymatic pretreatment... more Additional file 2. Effect of the hydrolytic (a) and oxidative and Cmix (b) enzymatic pretreatments on fibre length distribution. The confidence interval of the length fibre distribution was less than 2% in all cases.
Additional file 1. TLC analysis of sugars released during enzymatic treatments performed at 50 °C... more Additional file 1. TLC analysis of sugars released during enzymatic treatments performed at 50 °C, pH 5, during 18 h with 10 U g−1 odp of enzyme (in the case of Cmix the enzymatic dose was 20 U g−1 odp). C9 (Cel9B), C50 (Sertec20 cellulase), CF (Fibercare cellulase), Cll (Celluclast cellulase), Cmix (cellulase mixture consisting in Fibercare and Celluclast). M) size markers of glucose (G), cellobiose (G2), cellotriose (G3), cellotetraose (G4) and cellopentaose (G5).
Background: The increasing interest in replacing petroleum-based products by more sustainable mat... more Background: The increasing interest in replacing petroleum-based products by more sustainable materials in the packaging sector gives relevance to cellulose as a biodegradable natural resource. Moreover, its properties can be modified physically, chemically or biotechnologically in order to obtain new bioproducts. Refined cotton linters with high cellulose content were treated with hydrolytic (cellulases) and oxidative (LPMO and Laccase_Tempo) enzymes to evaluate their effect on fibre properties and in improving mechanical fibrillation. Results: Cellulases released cellooligosaccharides, reducing fibre length and partially degrading cellulose. They also improved mechanical fibrillation yielding up to 18% of nanofibrillated cellulose (NFC). LPMO introduced a slight amount of COOH groups in cellulose fibres, releasing cellobionic acid to the effluents. The action of cellulases was improved after LPMO treatment; however, the COOH groups created disappeared from fibres. After mechanical fibrillation of LPMO-cellulase-treated cotton linters a 23% yield of NFC was obtained. Laccase_Tempo treatment also introduced COOH groups in cellulose fibres from cotton, yielding 10% of NFC. Degree of polymerization was reduced by Laccase_Tempo, while LPMO treatment did not significantly affect it but produced a higher reduction in fibre length. The combined treatment with LPMO and cellulase provided films with higher transparency (86%), crystallinity (92%), smoothness and improved barrier properties to air and water than films casted from non-treated linters and from commercial NFC. Conclusions: The combined enzymatic treatment with LPMO and cellulases boosted mechanical fibrillation of cotton linters, improving the NFC production and providing bioproducts with high transparency and high barrier properties.
A fully bleached commercial acid dissolving pulp was treated with two endoglucanases, one obtaine... more A fully bleached commercial acid dissolving pulp was treated with two endoglucanases, one obtained from Paenibacillus barcinonensis (B) and the other one produced from Cerrena unicolor (F) with the intention to improve cellulose reactivity and processability in the viscose process. B cellulase was tested under 120 U/g odp (oven dry pulp) and the F cellulase under two conditions, 12U/g odp and 60 U/g odp. In addition, a purification stage, consisting in a cold caustic extraction (CCE) of 9% w/v NaOH, was applied before or after the enzymatic treatment in order to reduce the amount of hemicellulose and improve the action of enzymes. The treated pulps were evaluated in terms of brightness, viscosity, water retention value (WRV), fibre morphology, carbohydrate composition, Fock solubility and NMR. In general, results revealed that both endoglucanases improved cellulose reactivity, albeit in a different way; thus, B caused no scissions in the cellulose chain and no significant reduction in fibre length, whereas F strongly decreased viscosity, shortened fibre length and increased considerably the amount of fines. The result of applying two different doses of F cellulase was reflected on Fock solubility and fibre morphology. F60 treatment was found to give the highest value of Fock solubility and the biggest reduction of fibre length. The effect of both endoglucanases on Fock solubility was increased by introducing an earlier CCE stage. Finally, a CCE_B120 pulp with 3% of hemicellulose and 69% of Fock solubility was obtained.
Industrial & Engineering Chemistry Research, 2010
To obtain a more realistic appraisal of the potential efficiency of xylanases in the industrial b... more To obtain a more realistic appraisal of the potential efficiency of xylanases in the industrial bleaching, the influence of pH and the presence of black liquor (measured as COD) on the bleaching efficiency of two commercial xylanases was studied at high temperature. These pH's, CODs, and temperatures are close to those used in the storage tower of the B fiber line in Jacareí unit of Fibria (Brazil). The pulp samples obtained after each bleaching stage were analyzed for kappa number, brightness, viscosity, and hexenuronic acid content, and so were the effluents for COD, TOC, color, turbidity, and pH after the enzymatic stage. On the basis of the results, the xylanases were found to increase pulp brightness in the treatment involving the most unfavorable conditions (viz. high COD and pH). However, an initial COD above 9 kgO 2 t-1 and/or a pH higher than 9.5 detracted from their bleaching efficiency. The effect on the kappa number and hexenuronic acids content of the pulp was apparent immediately after the enzymatic stage, and the most marked increase in brightness was observed after the chlorine dioxide stage.
The environmental impact of enzyme bleaching stages applied to oxygen-delignified eucalypt kraft ... more The environmental impact of enzyme bleaching stages applied to oxygen-delignified eucalypt kraft pulp was assessed via the chemical oxygen demand (COD), color, absorbance spectrum, residual enzyme activity and Microtox toxicity of the effluents from a laccase-HBT (1-hydoxybenzotriazole) treatment. The influence of the laccase and HBT doses, and reaction time, on these effluent properties was also examined. The laccase dose was found to be the individual variable most strongly affecting COD, whereas the oxidized form of HBT was the main source of increased color and toxicity in the effluents. Moreover, it inactivated the enzyme. Oxidation of the mediator was very fast and essentially dependent on the laccase dose. Using the laccase-mediator treatment after a xylanase stage improved pulp properties without affecting effluent properties. This result holds great promise with a view to the industrial implementation of biobleaching sequences involving the two enzymes in the future.
Bleached cellulose with good end-properties (≈ 90% ISO brightness and 62% cellulose preservation)... more Bleached cellulose with good end-properties (≈ 90% ISO brightness and 62% cellulose preservation) was obtained by using a totally chlorine-free biobleaching process (TCF). Unbleached sulphite cellulose was treated with Trametes villosa laccase in combination with violuric acid. This enzymatic stage (L) was followed by a chelating stage (Q) and then by a hydrogen peroxide stage reinforced with pressurized oxygen (Po), resulting to an overall LQPo sequence. The use of violuric acid was dictated by the results of a preliminary study, where the bleaching efficiency of various natural (syringaldehyde and p-coumaric acid) and synthetic mediators (violuric acid and 1-hydroxybenzotriazole) were assessed. The outstanding results obtained with laccase-violuric acid system fulfil most of the characteristics of commercial dissolving pulp, totally acceptable for viscose manufacturing or CMC derivatives, with the added advantage that the enzymatic treatment saved 2h of reaction time and about 70% of hydrogen peroxide consumption, relative to a conventional sequence (Po).
Fiber crops constitute a good alternative to wood fiber for manufacturing pulp and paper. In fact... more Fiber crops constitute a good alternative to wood fiber for manufacturing pulp and paper. In fact, fiber plants like flax surpass wood fiber in some technical respects and also in the environmental benignity of their processing. In this work, flax fiber was subjected to environmentally friendly bleaching sequences in order to obtain a high-quality pulp. The totally chlorine-free sequences (TCF) used for this purpose (LE and LRE) included an enzyme treatment with laccase in the presence of HBT as mediator (L stage), an alkaline extraction (E stage) and a reductive treatment with NaBH 4 (R stage). The operating conditions for the L stage (laccase and HBT doses, reaction time and oxygen pressure) were optimised by using a sequential statistical plan to assess their influence on pulp properties after the E stage. Mathematical models accurately predicting brightness and kappa number in terms of the previous four variables were developed based on which the most influential factors were the laccase and HBT rates, and treatment time. By contrast, oxygen pressures of 0.2e0.6 MPa in the reactor had no effect on brightness or kappa number. The flax pulp obtained contained some oxidized cellulose that was partially degraded in the alkaline extraction step and reduced viscosity as a result. The viscosity loss associated with the presence of oxidized cellulose in the control and enzyme-treated pulp samples was efficiently recovered by using a reductive stage with sodium borohydride. Effluent was also analysed in order to assess the environmental impact of the process.
Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on ... more Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre-including this research content-immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
In this work, we studied the influence of the alkyl chain length in enzymaticallyoxidized gallate... more In this work, we studied the influence of the alkyl chain length in enzymaticallyoxidized gallates on the development of hydrophobicity on paper-based materials, and further correlated the obtained effect to the redox mechanism of the enzymatic treatment. Laccase (Lac) enzyme was used to oxidize various members of the gallate homologous series in the presence or not of lignosulfonates (SL) to produce several functionalization solutions (FS), which were subsequently applied to cellulosic substrates. The hydrophobicity of the substrates was then assessed by means of water drop test (WDT) and contact angle (WCA) measurements. Hydrophobicity peaked reaching WDT and WCA values around 5000 seconds and 130º respectively, and then
An oxygen delignified eucalyptus Kraft pulp was bleached in a totally chlorine-free (TCF) sequenc... more An oxygen delignified eucalyptus Kraft pulp was bleached in a totally chlorine-free (TCF) sequence using an ozone stage (Z) followed by a hydrogen peroxide stage (P). Ozone treatments were carried out at a laboratory scale with new automated equipment. The Z stage was modeled using a four-variable sequential statistical plan over the following ranges: 10–20 g o.d.p. mass pulp, 20–50
Ozone appears to be an effective choice for developing new totally chlorine free (TCF) sequences.... more Ozone appears to be an effective choice for developing new totally chlorine free (TCF) sequences. One of the goals of current research into the use of ozone as a pulp-bleaching agent is to increase the selectivity of the process. In this work, various reagents were used as additives in the ozone bleaching stage (Z) with a view to raising its selectivity. Overall 16 different reagents were used under variable conditions and various properties of the resulting pulp (Kappa number, viscosity and brightness), in addition to the Z stage selectivity and the P stage efficiency, were determined. Based on the results, the additives studied exert a favourable effect on the process (particularly oxalic acid). The performance of the reagents are analysed through the study of chain scission number (CS) in the cellulose chain.
An oxygen delignified eucalyptus Kraft pulp was bleached in a totally chlorine-free (TCF) sequenc... more An oxygen delignified eucalyptus Kraft pulp was bleached in a totally chlorine-free (TCF) sequence using an ozone stage (Z) followed by a hydrogen peroxide stage (P). Ozone treatments were carried out at a laboratory scale with new automated equipment. The Z stage was modeled using a four-variable sequential statistical plan over the following ranges: 10–20 g o.d.p. mass pulp, 20–50
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