There is a great need to understand calcium scaling in black liquor evaporators and to reduce the... more There is a great need to understand calcium scaling in black liquor evaporators and to reduce the possibilty for scaling. However, it is still largely unknown how calcium is bound to organic compounds in black liquors. The main goal of this work has been to study the possibility to determine different Ca species in black liquor by using an all-solid-state Ca2+-ISE (Ion selective electrode). The Ca2+-ISE's where constructed by drop casting a Ca2+ selective cocktail on a conducting polymer film (PEDOT), which was electropolymerized on a glassy carbon rod in PVC body. These Ca2+-ISE's showed fast and reproducible response for free Ca2+ ions in diluted black liquors. The speciation studies was done by using Ca2+-ISE's to measure the free Ca2+ ions in black liquors during potentiometric titrations with a complexing agent (EDTA). The titration results were evaluated by using the method of linear titration curves. This method enabled simultaneous determination of both the free ...
Desorption of metal ions from oxygen-bleached hardwood and softwood kraft pulps by different chel... more Desorption of metal ions from oxygen-bleached hardwood and softwood kraft pulps by different chelation treatments were studied. The main focus was on desorption of manganese, iron, and magnesium ions, but also on desorption of some other common metal ions. The metal ion concentrations were determined by the DCP-AES and ICP-MS techniques. Acid treatments with nitric and oxalic acids removed manganese and magnesium very effectively and partially iron as well. Some potential complexing agents such as triethanolamine (TEA), citric acid, oxalic acid, and formic acid were also tested. By using the concept of side reaction coefficients, a comparison of the chelating strengths between different chelating agents can be made. TEA is a strong chelant for iron and did remove part of iron at pH 10. The effect of chemical reduction simultaneously with EDTA was studied by using sodium borohydride, sodium dithionite, and sodium bisulfite as reducing agents. The reducing environment improved desorpt...
The binding of metal ions to unbleached softwood pulp from a Finnish pulp mill was studied using ... more The binding of metal ions to unbleached softwood pulp from a Finnish pulp mill was studied using a column chromatographic method. The ion exchange mainly takes place by complexation, where divalent metal ions are coordinated to functional groups in the pulp phase. The following affinity order was obtained by combining the results from different sorption experiments: Pb(2+) >> Cu(2+) >> Cd(2+) > Zn(2+) > Ni(2+) > Ba(2+) > sr(2+) approximate to mn(2+) approximate to ca(2+) > mg(2+) >> Rb(+) > K(+) > Na(+) > Li(+) Rather large differences were observed in the binding strength (to pulp) for the divalent metal ions: lead, copper, cadmium, zinc and nickel. The differences in affinities within the alkali and alkaline earth metal groups were much smaller. The operating capacities in the sorption experiments were determined by acid-base titrations of the released hydrogen ions in the metal ion loading step and by measuring the concentration of metal ...
Chelation of unbleached and oxygen bleached hardwood and softwood kraft pulps with EDTA was studi... more Chelation of unbleached and oxygen bleached hardwood and softwood kraft pulps with EDTA was studied. The main focus was on the desorption of magnesium, manganese, and iron due to their impact in TCF-bleaching. Desorption of other metal ions present were also studied in order to get an over-all estimation of the metal ion concentrations and their desorption during chelation. By using the concept of side reaction coefficients, an estimation of the chelating strength of EDTA at different pH can be made. Metal ion concentrations were determined by DCP-AES and ICP-MS techniques. Mn, Zn, and Cd were the metal ions that could almost completely be chelated with EDTA. Most of the metal ions were found to be desorbed from the pulps at low pH values by ion exchange with hydrogen ions. With EDTA chelation 50 to 70% of the iron was desorbed. By EDTA chelation the highest Mg/Mn concentration ratios were obtained in the pH range 4 to 6. For oxygen-bleached softwood pulp the ratio was over 7000. Ou...
A high-temperature pH measuring system was developed, calibrated, and validated for measuring pH ... more A high-temperature pH measuring system was developed, calibrated, and validated for measuring pH during hot-water extraction of hemicelluloses from wood. The aim was to measure in-line pH during extraction in order to control the extraction pH. An yttria-stabilized Zr/ZrO 2 electrode was used for measuring the potential. Phthalate and phosphate buffers were used to calibrate the system at 160, 170, and 180 • C. Also, different buffer concentrations were tested for stability. Tap water and different salt solutions were tested to investigate the system response to pure water and water solutions. Calibration curves were acquired from the calibration results and Nernst equation was used to calculate the in-line pH during wood extractions. The setup showed stable and reliable potential readings during both calibration tests and wood extractions. The in-line pH was found to be 0.35 pH units higher than when measured at room temperature with a conventional pH meter.
ABSTRACT Sorption of metal ions from aqueous solutions to birch wood and spruce heartwood and sap... more ABSTRACT Sorption of metal ions from aqueous solutions to birch wood and spruce heartwood and sapwood has been studied. Functional groups in wood were determined by acid-base titrations. The sorption of metal ions to wood of the different tree species was investigated by a column chromatographic technique. The mechanism of sorption is mainly ion exchange by complexation of metal ions to the functional groups, e. g. carboxyl groups and phenolic hydroxyl groups, in the wood phase. By combination of the sorption experiments with four different metal ion mixtures, the following affinity order was established for spruce sapwood particles: Fe3+>> Pb2+>> Cu2+>> Fe2+>Cd2+>Zn2+>Ni2+>Mn2+>= Ca2+>= Sr2+>= Ba2+>> Mg2+>> K+>> Na+approximate to Li+. For all three types of stemwood studied, the affinity orders were almost the same. The ion exchange properties of wood were comparable to those of a weakly acid cation exchanger. The affinity order obtained for the synthetic resin was quite similar to the order given above for wood. The metal sorption properties of wood materials imply that they could be a potential material for removal of metal ions from aqueous solutions.
The concentrations and protonation constants of the functional groups like carboxyl and phenolic ... more The concentrations and protonation constants of the functional groups like carboxyl and phenolic hydroxyl groups in spruce bark were determined by a potentiometric acid-base titration method. The non-cellulosic carbohydrates in spruce bark were also characterized by acid methanolysis and GC, including determination of the uronic acid units, which are the key units involved in metal sorption. Sorption of metal ions to bark takes place by ion exchange, mainly by complexation to these functional groups. The sorption equilibrium time, studied by using a batch method, was approximately 5 min. The metal sorption capacity of spruce bark and the affinity order of metal ions were studied with four different metal ion mixtures using a column chromatographic method. Because a method of competition was used, concentration of metal ions adsorbed to bark depends on the metal ions present in the mixtures studied. In the sorption experiments with same metal ion mixtures, inner bark of spruce exhibited higher sorption capacity than outer bark. By combination of the results from several experiments, the following affinity order was obtained Fe 3?
A new type of all-solid-state reference electrode was designed and characterized. The electrodes ... more A new type of all-solid-state reference electrode was designed and characterized. The electrodes are based on a polymer/inorganic salt composite and a silver/silver chloride reference element. A rigorous testing procedure was used to reveal the possible influence of pH, solution composition, as well as the concentration and mobility of ions. The tests demonstrated the insensitivity of the electrodes to the matrix effects, excellent stability of the potential readings, and significantly reduced leakage of inorganic salt. In the performed tests the composite reference electrodes were on a par with or better than the high-quality commercial reference electrodes. The reference electrodes described here are of analytical quality allowing for continuous, prolonged, and intensive usage.
ABSTRACT A method based on column chromatography has been developed for determination of ion exch... more ABSTRACT A method based on column chromatography has been developed for determination of ion exchange (IE) constants for pairs of metal ions for different types of wood, pulp, and bark samples. Bark was found to have higher selectivity than wood and pulp for the metal ions studied. Of the 14 different metal ions studied, the toxic transition metal ions Pb, Cu, and Cd were most strongly bound to all the materials used in this work. The validity of the column method was tested by means of different mixtures of metal ions as the loading solution. The IE constants obtained by the column method showed a good agreement with those obtained by the batch method reported earlier by our group. The IE constants were also determined for synthetic cation exchanger (CE) based on weak and strong acid groups. The IE constants of most pairs of metal ions are highest for the weakly acidic CE followed by bark, wood, pulp, and strongly acidic CE.
ABSTRACT Chelation of thermomechanical pulp (TMP) was studied in this work. The desorption of Mn,... more ABSTRACT Chelation of thermomechanical pulp (TMP) was studied in this work. The desorption of Mn, Fe, and Mg due to their impact on peroxide bleaching was investigated. The desorption experiments were performed with EDTA, citric acid, oxalic acid, and formic acid as chelating agents at different pH. Chelation experiments with EDTA were carried out at pH 3-11. Sodium dithionite was used as the reducing agent in studying chelation with EDTA in a reducing environment. Mn was very effectively desorbed with EDTA from TMP at pH < 10 and the reducing environment further improved the removal of all the studied metal ions from TMP with EDTA. Citric acid also removed Mn effectively from TMP at pH 5. The thermodynamic stability constants of different metal chelates do not present the correct picture of how strongly the metal ions are bound by the chelating agents in different conditions. But by means of the side reaction coefficients (alpha(M(L))-coefficients) it is also theoretically possible to evaluate and compare the real binding strengths between the metal ions and different chelating agents at varying pH values and other solution conditions. In this study, a theory is given for the calculation of side reaction coefficients. Values of the alpha(M(L))-coefficients, for the pH range 0-14, are presented for EDTA, DTPA, and also for some other new potential environmentally friendly chelating agents.
A solid-contact Ca 2þ -selective electrode was used to study speciation of calcium in black liquo... more A solid-contact Ca 2þ -selective electrode was used to study speciation of calcium in black liquor. During extended time of operation the standard potential was found to change, but the sensitivity of the electrode, and the selectivity coefficients remained unchanged. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) measurements showed sodium sorption to the electrode membrane during the measurement in black liquor. Linearization of the complexometric titration curves were used to determine the concentrations of Ca 2þ , CaOH þ as well as weak and strong calcium complexes. With inductively coupled plasma optical emission spectrometry (ICP-OES), similar total calcium concentrations were obtained as by the EDTA titration.
Knowledge about how different metal ions are bound to pulp fibers is very important for optimal m... more Knowledge about how different metal ions are bound to pulp fibers is very important for optimal metal management in pulping processes. A column chromatographic method was used to assess the differences in affinity of 14 metal ions to untreated, alkali-treated and peroxide-bleached thermomechanical pulp (TMP). A method of competition between cations in the column chromatographic experiments was used in the sorption experiments, with an excess of each metal ion compared to the total capacity of the pulp studied. The method is very sensitive and even small differences in affinities can be detected. By combining the results from sorption experiments with four different metal ion mixtures the following order of affinity was obtained: Pb2+ ≫ Cu2+ ≫ Cd2+ > Zn2+ > Ni2+ > Ba2+ > Ca2+ > Mn2+ > Sr2+ > Mg2+ ≫ Rb+ ≈ K+ > Na+ > Li+. All three types of pulps showed the same affinity order. Lead and copper ions were clearly most strongly bound to the pulp fibers. Within the alkali and alkaline earth metal groups the differences in affinity were quite small. The sorption of metal ions to pulp fibers takes place mainly by complexation, where the divalent metal ions are coordinated to functional groups (acid groups) in the fiber phase. Protonation constants and concentrations of acid groups were determined by potentiometric titration. A model with two carboxyl groups and two phenolic hydroxyl groups satisfied best the experimental data. By treatment with alkali and peroxide new acid groups were created and the total binding capacity of hydrogen ions increased from 137 μeq/g for untreated pulp to 187 and 228 μeq/g for alkali-treated and peroxide-treated pulp, respectively.
ABSTRACT The reference electrode is an indispensable part of an electrochemical measurement setup... more ABSTRACT The reference electrode is an indispensable part of an electrochemical measurement setup and its role is to establish a precise, stable, and reproducible potential which is independent of the sample composition [1]. Internal filling solution used in conventional reference electrodes causes many drawbacks and inconveniences [2]. There are several papers proposing alternative ways of eliminating the inner filling solutions. The reference electrodes proposed there are indeed interesting from the scientific point of view but they should be further developed to be of practical applicability. The classical reference electrodes have so far been superior in terms of continuous, prolonged, and intensive usage. A new type of all-solid-state reference electrodes based on a polymer/inorganic salt composite (SSC) was designed and characterized. Both a chemical polymerisation method [3] and an injection moulding method [4] were used for fabricating those novel electrodes. A rigorous testing procedure was used to reveal possible influence of pH, solution composition, as well as the concentrations and mobility of ions. The tests demonstrated the insensitivity of the electrodes to the matrix effects, excellent stability of the potential readings, and significantly reduced leakage of inorganic salt. It was shown that composite reference electrodes were on par or better in the performed tests than high-quality commercial reference electrodes. The SSC reference electrodes described here are of analytical quality allowing for continuous, prolonged, and intensive usage. References 1. G. Inzelt, A. Lewenstam, F. Scholz Handbook of reference elctrodes (2013) Springer, Berlin. 2. T. Blaz, J. Migdalski, A. Lewenstam, Analyst 130 (2005) 637-643. 3. Z. Mousavi, K. Granholm, T. Sokalski, A. Lewenstam, Analyst 138 (2013) 5216-5220. 4. K. Granholm, Z. Mousavi, T. Sokalski, Andrzej Lewenstam, J Solid State Electrochem DOI 10.1007/s10008-013-2294-x Acknowledgements The study was supported by the SalWe Research Program for IMO (Tekes -the Finnish Funding Agency for Technology and Innovation grant 648/10).
There is a great need to understand calcium scaling in black liquor evaporators and to reduce the... more There is a great need to understand calcium scaling in black liquor evaporators and to reduce the possibilty for scaling. However, it is still largely unknown how calcium is bound to organic compounds in black liquors. The main goal of this work has been to study the possibility to determine different Ca species in black liquor by using an all-solid-state Ca2+-ISE (Ion selective electrode). The Ca2+-ISE's where constructed by drop casting a Ca2+ selective cocktail on a conducting polymer film (PEDOT), which was electropolymerized on a glassy carbon rod in PVC body. These Ca2+-ISE's showed fast and reproducible response for free Ca2+ ions in diluted black liquors. The speciation studies was done by using Ca2+-ISE's to measure the free Ca2+ ions in black liquors during potentiometric titrations with a complexing agent (EDTA). The titration results were evaluated by using the method of linear titration curves. This method enabled simultaneous determination of both the free ...
Desorption of metal ions from oxygen-bleached hardwood and softwood kraft pulps by different chel... more Desorption of metal ions from oxygen-bleached hardwood and softwood kraft pulps by different chelation treatments were studied. The main focus was on desorption of manganese, iron, and magnesium ions, but also on desorption of some other common metal ions. The metal ion concentrations were determined by the DCP-AES and ICP-MS techniques. Acid treatments with nitric and oxalic acids removed manganese and magnesium very effectively and partially iron as well. Some potential complexing agents such as triethanolamine (TEA), citric acid, oxalic acid, and formic acid were also tested. By using the concept of side reaction coefficients, a comparison of the chelating strengths between different chelating agents can be made. TEA is a strong chelant for iron and did remove part of iron at pH 10. The effect of chemical reduction simultaneously with EDTA was studied by using sodium borohydride, sodium dithionite, and sodium bisulfite as reducing agents. The reducing environment improved desorpt...
The binding of metal ions to unbleached softwood pulp from a Finnish pulp mill was studied using ... more The binding of metal ions to unbleached softwood pulp from a Finnish pulp mill was studied using a column chromatographic method. The ion exchange mainly takes place by complexation, where divalent metal ions are coordinated to functional groups in the pulp phase. The following affinity order was obtained by combining the results from different sorption experiments: Pb(2+) >> Cu(2+) >> Cd(2+) > Zn(2+) > Ni(2+) > Ba(2+) > sr(2+) approximate to mn(2+) approximate to ca(2+) > mg(2+) >> Rb(+) > K(+) > Na(+) > Li(+) Rather large differences were observed in the binding strength (to pulp) for the divalent metal ions: lead, copper, cadmium, zinc and nickel. The differences in affinities within the alkali and alkaline earth metal groups were much smaller. The operating capacities in the sorption experiments were determined by acid-base titrations of the released hydrogen ions in the metal ion loading step and by measuring the concentration of metal ...
Chelation of unbleached and oxygen bleached hardwood and softwood kraft pulps with EDTA was studi... more Chelation of unbleached and oxygen bleached hardwood and softwood kraft pulps with EDTA was studied. The main focus was on the desorption of magnesium, manganese, and iron due to their impact in TCF-bleaching. Desorption of other metal ions present were also studied in order to get an over-all estimation of the metal ion concentrations and their desorption during chelation. By using the concept of side reaction coefficients, an estimation of the chelating strength of EDTA at different pH can be made. Metal ion concentrations were determined by DCP-AES and ICP-MS techniques. Mn, Zn, and Cd were the metal ions that could almost completely be chelated with EDTA. Most of the metal ions were found to be desorbed from the pulps at low pH values by ion exchange with hydrogen ions. With EDTA chelation 50 to 70% of the iron was desorbed. By EDTA chelation the highest Mg/Mn concentration ratios were obtained in the pH range 4 to 6. For oxygen-bleached softwood pulp the ratio was over 7000. Ou...
A high-temperature pH measuring system was developed, calibrated, and validated for measuring pH ... more A high-temperature pH measuring system was developed, calibrated, and validated for measuring pH during hot-water extraction of hemicelluloses from wood. The aim was to measure in-line pH during extraction in order to control the extraction pH. An yttria-stabilized Zr/ZrO 2 electrode was used for measuring the potential. Phthalate and phosphate buffers were used to calibrate the system at 160, 170, and 180 • C. Also, different buffer concentrations were tested for stability. Tap water and different salt solutions were tested to investigate the system response to pure water and water solutions. Calibration curves were acquired from the calibration results and Nernst equation was used to calculate the in-line pH during wood extractions. The setup showed stable and reliable potential readings during both calibration tests and wood extractions. The in-line pH was found to be 0.35 pH units higher than when measured at room temperature with a conventional pH meter.
ABSTRACT Sorption of metal ions from aqueous solutions to birch wood and spruce heartwood and sap... more ABSTRACT Sorption of metal ions from aqueous solutions to birch wood and spruce heartwood and sapwood has been studied. Functional groups in wood were determined by acid-base titrations. The sorption of metal ions to wood of the different tree species was investigated by a column chromatographic technique. The mechanism of sorption is mainly ion exchange by complexation of metal ions to the functional groups, e. g. carboxyl groups and phenolic hydroxyl groups, in the wood phase. By combination of the sorption experiments with four different metal ion mixtures, the following affinity order was established for spruce sapwood particles: Fe3+>> Pb2+>> Cu2+>> Fe2+>Cd2+>Zn2+>Ni2+>Mn2+>= Ca2+>= Sr2+>= Ba2+>> Mg2+>> K+>> Na+approximate to Li+. For all three types of stemwood studied, the affinity orders were almost the same. The ion exchange properties of wood were comparable to those of a weakly acid cation exchanger. The affinity order obtained for the synthetic resin was quite similar to the order given above for wood. The metal sorption properties of wood materials imply that they could be a potential material for removal of metal ions from aqueous solutions.
The concentrations and protonation constants of the functional groups like carboxyl and phenolic ... more The concentrations and protonation constants of the functional groups like carboxyl and phenolic hydroxyl groups in spruce bark were determined by a potentiometric acid-base titration method. The non-cellulosic carbohydrates in spruce bark were also characterized by acid methanolysis and GC, including determination of the uronic acid units, which are the key units involved in metal sorption. Sorption of metal ions to bark takes place by ion exchange, mainly by complexation to these functional groups. The sorption equilibrium time, studied by using a batch method, was approximately 5 min. The metal sorption capacity of spruce bark and the affinity order of metal ions were studied with four different metal ion mixtures using a column chromatographic method. Because a method of competition was used, concentration of metal ions adsorbed to bark depends on the metal ions present in the mixtures studied. In the sorption experiments with same metal ion mixtures, inner bark of spruce exhibited higher sorption capacity than outer bark. By combination of the results from several experiments, the following affinity order was obtained Fe 3?
A new type of all-solid-state reference electrode was designed and characterized. The electrodes ... more A new type of all-solid-state reference electrode was designed and characterized. The electrodes are based on a polymer/inorganic salt composite and a silver/silver chloride reference element. A rigorous testing procedure was used to reveal the possible influence of pH, solution composition, as well as the concentration and mobility of ions. The tests demonstrated the insensitivity of the electrodes to the matrix effects, excellent stability of the potential readings, and significantly reduced leakage of inorganic salt. In the performed tests the composite reference electrodes were on a par with or better than the high-quality commercial reference electrodes. The reference electrodes described here are of analytical quality allowing for continuous, prolonged, and intensive usage.
ABSTRACT A method based on column chromatography has been developed for determination of ion exch... more ABSTRACT A method based on column chromatography has been developed for determination of ion exchange (IE) constants for pairs of metal ions for different types of wood, pulp, and bark samples. Bark was found to have higher selectivity than wood and pulp for the metal ions studied. Of the 14 different metal ions studied, the toxic transition metal ions Pb, Cu, and Cd were most strongly bound to all the materials used in this work. The validity of the column method was tested by means of different mixtures of metal ions as the loading solution. The IE constants obtained by the column method showed a good agreement with those obtained by the batch method reported earlier by our group. The IE constants were also determined for synthetic cation exchanger (CE) based on weak and strong acid groups. The IE constants of most pairs of metal ions are highest for the weakly acidic CE followed by bark, wood, pulp, and strongly acidic CE.
ABSTRACT Chelation of thermomechanical pulp (TMP) was studied in this work. The desorption of Mn,... more ABSTRACT Chelation of thermomechanical pulp (TMP) was studied in this work. The desorption of Mn, Fe, and Mg due to their impact on peroxide bleaching was investigated. The desorption experiments were performed with EDTA, citric acid, oxalic acid, and formic acid as chelating agents at different pH. Chelation experiments with EDTA were carried out at pH 3-11. Sodium dithionite was used as the reducing agent in studying chelation with EDTA in a reducing environment. Mn was very effectively desorbed with EDTA from TMP at pH < 10 and the reducing environment further improved the removal of all the studied metal ions from TMP with EDTA. Citric acid also removed Mn effectively from TMP at pH 5. The thermodynamic stability constants of different metal chelates do not present the correct picture of how strongly the metal ions are bound by the chelating agents in different conditions. But by means of the side reaction coefficients (alpha(M(L))-coefficients) it is also theoretically possible to evaluate and compare the real binding strengths between the metal ions and different chelating agents at varying pH values and other solution conditions. In this study, a theory is given for the calculation of side reaction coefficients. Values of the alpha(M(L))-coefficients, for the pH range 0-14, are presented for EDTA, DTPA, and also for some other new potential environmentally friendly chelating agents.
A solid-contact Ca 2þ -selective electrode was used to study speciation of calcium in black liquo... more A solid-contact Ca 2þ -selective electrode was used to study speciation of calcium in black liquor. During extended time of operation the standard potential was found to change, but the sensitivity of the electrode, and the selectivity coefficients remained unchanged. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) measurements showed sodium sorption to the electrode membrane during the measurement in black liquor. Linearization of the complexometric titration curves were used to determine the concentrations of Ca 2þ , CaOH þ as well as weak and strong calcium complexes. With inductively coupled plasma optical emission spectrometry (ICP-OES), similar total calcium concentrations were obtained as by the EDTA titration.
Knowledge about how different metal ions are bound to pulp fibers is very important for optimal m... more Knowledge about how different metal ions are bound to pulp fibers is very important for optimal metal management in pulping processes. A column chromatographic method was used to assess the differences in affinity of 14 metal ions to untreated, alkali-treated and peroxide-bleached thermomechanical pulp (TMP). A method of competition between cations in the column chromatographic experiments was used in the sorption experiments, with an excess of each metal ion compared to the total capacity of the pulp studied. The method is very sensitive and even small differences in affinities can be detected. By combining the results from sorption experiments with four different metal ion mixtures the following order of affinity was obtained: Pb2+ ≫ Cu2+ ≫ Cd2+ > Zn2+ > Ni2+ > Ba2+ > Ca2+ > Mn2+ > Sr2+ > Mg2+ ≫ Rb+ ≈ K+ > Na+ > Li+. All three types of pulps showed the same affinity order. Lead and copper ions were clearly most strongly bound to the pulp fibers. Within the alkali and alkaline earth metal groups the differences in affinity were quite small. The sorption of metal ions to pulp fibers takes place mainly by complexation, where the divalent metal ions are coordinated to functional groups (acid groups) in the fiber phase. Protonation constants and concentrations of acid groups were determined by potentiometric titration. A model with two carboxyl groups and two phenolic hydroxyl groups satisfied best the experimental data. By treatment with alkali and peroxide new acid groups were created and the total binding capacity of hydrogen ions increased from 137 μeq/g for untreated pulp to 187 and 228 μeq/g for alkali-treated and peroxide-treated pulp, respectively.
ABSTRACT The reference electrode is an indispensable part of an electrochemical measurement setup... more ABSTRACT The reference electrode is an indispensable part of an electrochemical measurement setup and its role is to establish a precise, stable, and reproducible potential which is independent of the sample composition [1]. Internal filling solution used in conventional reference electrodes causes many drawbacks and inconveniences [2]. There are several papers proposing alternative ways of eliminating the inner filling solutions. The reference electrodes proposed there are indeed interesting from the scientific point of view but they should be further developed to be of practical applicability. The classical reference electrodes have so far been superior in terms of continuous, prolonged, and intensive usage. A new type of all-solid-state reference electrodes based on a polymer/inorganic salt composite (SSC) was designed and characterized. Both a chemical polymerisation method [3] and an injection moulding method [4] were used for fabricating those novel electrodes. A rigorous testing procedure was used to reveal possible influence of pH, solution composition, as well as the concentrations and mobility of ions. The tests demonstrated the insensitivity of the electrodes to the matrix effects, excellent stability of the potential readings, and significantly reduced leakage of inorganic salt. It was shown that composite reference electrodes were on par or better in the performed tests than high-quality commercial reference electrodes. The SSC reference electrodes described here are of analytical quality allowing for continuous, prolonged, and intensive usage. References 1. G. Inzelt, A. Lewenstam, F. Scholz Handbook of reference elctrodes (2013) Springer, Berlin. 2. T. Blaz, J. Migdalski, A. Lewenstam, Analyst 130 (2005) 637-643. 3. Z. Mousavi, K. Granholm, T. Sokalski, A. Lewenstam, Analyst 138 (2013) 5216-5220. 4. K. Granholm, Z. Mousavi, T. Sokalski, Andrzej Lewenstam, J Solid State Electrochem DOI 10.1007/s10008-013-2294-x Acknowledgements The study was supported by the SalWe Research Program for IMO (Tekes -the Finnish Funding Agency for Technology and Innovation grant 648/10).
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