Valentin Popa | Technical University of Iasi (original) (raw)

Papers by Valentin Popa

Memoirs of the Scientific Sections of the Romanian Academy, 2020

The paper presents some peculiar aspects of the life and scientific activity of acad. Cr.I.S., se... more The paper presents some peculiar aspects of the life and scientific activity of acad. Cr.I.S., seen through the eyes of his close collaborators.

Pulp Production and Processing, 2020

Cellulose Chemistry and Technology, 2005

Natural polymers are characterized by three main properties: multifunctionality, biodegradability... more Natural polymers are characterized by three main properties: multifunctionality, biodegradability and biocompatibility, which are essential for various applications that should comply with the environment. Due to the hugeavailability of the phytomass sources resulted from photosynthesis, there are several possibilities to achieve some complex composite systems based on the utilization of natural/synthetic polymer mixtures. On the other hand, it is known that hydrophilic lignocellulosic materials and hydrophobic synthetic polymers are incompatible. The compatibility between the two kinds of polymers could be achieved by modification of either the hydrophilic natural polymer or of the synthetic one. The paper discusses the results on the modification of hardwood flour chemicals by reactions with epichlorohydrin and steroyl chloride, for the introduction of modified flour into the composite materials. The modified products were characterized by FTIR spectroscopy, thermodifferential ana...

Phenolic extracts of bilberry: they protect lipid from oxidation in in vitro simulated digestion ... more Phenolic extracts of bilberry: they protect lipid from oxidation in in vitro simulated digestion conditions. ICP 2016 - XXVIIIth International Conference on Polyphenols

Pulp Production and Processing, 2020

The excellence of university is a problem which is disputed and discussed at world level. But is ... more The excellence of university is a problem which is disputed and discussed at world level. But is very clear that the performances of university in the education and research activities are determined by the quality of the management To obtain good results a manager position has to be occupied by competition based on strategic plan with very concrete objectives which have to be assumed by entire community without interest of some groups that can result in democratic election.

Environmental Engineering and Management Journal, 2002

The present paper focused on the effect of unmodified and modified lignins and copper ions on the... more The present paper focused on the effect of unmodified and modified lignins and copper ions on the interaction between birch veneer and some biocides. The aim of the present study was to modify commercial lignins (Protobind 1000, Protobind 2000, Protobind 3000) by the hydroxymethylation reaction in an alkaline medium and to describe the lignin derivatives by chemical, spectral (H NMR) and thermal analyses (TG). The studies revealed some functional changes, which are correlated with both the different reactivity of lignins and the reaction conditions. Also, lignin derivatives were observed by thermal analysis, which allowed establishing a correlation between the modification degree and the thermal stability. Treatments with unmodified and hydroxymethylated lignins were applied to birch veneer strips by immersing them in copper chloride solutions. The lignin products were dissolved in 0.1 N ammonia solution of 5% concentration. The biostability of the treated veneer was tested by buryi...

A comparative study of oxidative degradation with S 2 O 8 2 - /Ag + and Fenton systems was perfor... more A comparative study of oxidative degradation with S 2 O 8 2 - /Ag + and Fenton systems was performed on a series of ammonium lignosulphonate (ALS) solutions of different concentrations (0.079 - 3.785 mg/mL - 1 ), by means ofcyclic voltametry. These oxidized solutions have a complex composition and are susceptible of mutual interferences. However, cyclic voltametry can give only an overall view and estimation of such redox processes. The obtained voltammograms are quite different, as a function of the oxidants selected, and of the preliminary results (UV-VIS spectrophotometry, conductibility and turbidity data, total amount of hydroxylated aromatic compounds) obtained.

In this study, the adsorption of Cu(II) ions from aqueous solutions onto wheat straw lignin was i... more In this study, the adsorption of Cu(II) ions from aqueous solutions onto wheat straw lignin was investigated. The experiments were performed in a batch system, at room temperature (20 ± 0.5 °C), and the copper ions analysis was done after equilibrium was attained. Different experimental parameters (initial solution pH, sorbent dose, initial Cu(II) concentration and contact time) were varied in order to establish the optimum conditions for copper removal using wheat straw lignin. The experimental results were fitted using the Langmuir, Freundlich and Sips isotherm models, and the characteristic adsorption parameters were determined. Experimental data were also tested using two kinetic models: the pseudo-first-order Lagergren model and the pseudo-second-order Ho model. Based on these models, the kinetic parameters (rate constant and equilibrium adsorption capacity) for Cu(II) adsorption on lignin were calculated.

Cellulose Chemistry and Technology, 1991

Cellulose Chemistry and Technology, 1987

Synthese sur le potentiel et la technologie de conversion de la biomasse en produits energetiques... more Synthese sur le potentiel et la technologie de conversion de la biomasse en produits energetiques ou chimiques

The paper manufacture has a long tradition on the Romanian territory. The Romanian school of pulp... more The paper manufacture has a long tradition on the Romanian territory. The Romanian school of pulp and paper was founded in the Polytechnic Institute of Iași in 1949 and here it is alone place in Romania where the chemical engineers are prepared as specialists in this field. This paper presents main achievements obtained during the years in the education and research activities, recognized at national and international levels. Among them, it worth mentioning, along with education and scientific results the international symposia in the chemistry and technology of cellulose (14) and the foundation of peer reviewed international journal "Cellulose Chemistry and Technology" (1966). At present, the production of pulp and paper is among the very few industries corresponding to the principles of sustainable development and which can be integrated in an industrial complex based on biorefining for full valorization of biomass resources. Therefore, in the next future Romanian school of pulp and paper could be developed toward approach the education and research in the inter-and trans-disciplinary fields.

Plant growth and development are influenced by various exogenous and endogenous factors. In this ... more Plant growth and development are influenced by various exogenous and endogenous factors. In this context, a group of substances of particular interest are polyphenols. Considering the information presented in the literature data and the results obtained by our working group to date, our objective has been to study the influence of some polyphenolic extracts on the mitotic division. The investigated material comes from the seeds of maize, untreated (control) and treated with spruce bark polyphenolic extract (SBPE), hemp shives polyphenolic extract (HSPE) in different concentration. It was found that using SBPE or HSPE with lower concentration, the frequency of cells in mitosis was higher than in the control. At higher concentrations of the extracts, there were a higher number of cells with chromosomal aberrations. In the treatment variants, significant proportions had an ana-telophase (A-T) with bridges, delayed chromosomes and complex aberrations such as: A-T + bridges + late and/or...

Cellulose Chemistry and Technology, 1990

The wood suffers biodegradation processes in the environment under the biological agents’ action,... more The wood suffers biodegradation processes in the environment under the biological agents’ action, influenced by environmental factors and storage or usage conditions after treatment. Depending on their structure, wood chemical constituents will be degraded in the following order: hemicelluloses, cellulose and lignin [1-3]. Lignin represents the resistant component to biological attack and also grants mechanical resistance to the wood. Its wide use in various fields and its relatively low stability to the action of environmental factors requires the use of chemical compounds for protection against biological agents attack. Currently, for wood protection are used toxic products for microorganisms and insects that are also environmentally incompatible. Chemical protective aqueous agents are known whose efficiency is due to the presence of copper. Part of the copper ions is fixed in the wood substratum by hydroxyl or carboxylic ionized groups in the wood at high pH. Considering lignin’s...

Polyphenols are a widespread group of secondary metabolites found in woody species, including sof... more Polyphenols are a widespread group of secondary metabolites found in woody species, including softwood. Higher amounts of these bioactive compounds occurring in bark, heartwood, roots, branch bases and wound tissues and have a number of important roles to play in viticulture and ecology, including UV protection, disease resistance, pollination, color, and defense against predation in plants, plant growth regulation and bioremediation. The use of synthetic chelates has been strongly criticized because of excessive amount of metals solubilized, associated with risk of groundwater contamination through metal leaching. This study evaluate the possibility of using natural bioactive compounds, characteristic to grape seeds extracts, in phytoextraction as an alternative to synthetic chelators. The results obtained shown an improving trend in the bioaccumulation process of heavy metals into the rape plant. It may be properly mentioned that grape seeds natural polyphenolic extract present an...

Memoirs of the Scientific Sections of the Romanian Academy, 2020

The paper presents some peculiar aspects of the life and scientific activity of acad. Cr.I.S., se... more The paper presents some peculiar aspects of the life and scientific activity of acad. Cr.I.S., seen through the eyes of his close collaborators.

Pulp Production and Processing, 2020

Cellulose Chemistry and Technology, 2005

Natural polymers are characterized by three main properties: multifunctionality, biodegradability... more Natural polymers are characterized by three main properties: multifunctionality, biodegradability and biocompatibility, which are essential for various applications that should comply with the environment. Due to the hugeavailability of the phytomass sources resulted from photosynthesis, there are several possibilities to achieve some complex composite systems based on the utilization of natural/synthetic polymer mixtures. On the other hand, it is known that hydrophilic lignocellulosic materials and hydrophobic synthetic polymers are incompatible. The compatibility between the two kinds of polymers could be achieved by modification of either the hydrophilic natural polymer or of the synthetic one. The paper discusses the results on the modification of hardwood flour chemicals by reactions with epichlorohydrin and steroyl chloride, for the introduction of modified flour into the composite materials. The modified products were characterized by FTIR spectroscopy, thermodifferential ana...

Phenolic extracts of bilberry: they protect lipid from oxidation in in vitro simulated digestion ... more Phenolic extracts of bilberry: they protect lipid from oxidation in in vitro simulated digestion conditions. ICP 2016 - XXVIIIth International Conference on Polyphenols

Pulp Production and Processing, 2020

The excellence of university is a problem which is disputed and discussed at world level. But is ... more The excellence of university is a problem which is disputed and discussed at world level. But is very clear that the performances of university in the education and research activities are determined by the quality of the management To obtain good results a manager position has to be occupied by competition based on strategic plan with very concrete objectives which have to be assumed by entire community without interest of some groups that can result in democratic election.

Environmental Engineering and Management Journal, 2002

The present paper focused on the effect of unmodified and modified lignins and copper ions on the... more The present paper focused on the effect of unmodified and modified lignins and copper ions on the interaction between birch veneer and some biocides. The aim of the present study was to modify commercial lignins (Protobind 1000, Protobind 2000, Protobind 3000) by the hydroxymethylation reaction in an alkaline medium and to describe the lignin derivatives by chemical, spectral (H NMR) and thermal analyses (TG). The studies revealed some functional changes, which are correlated with both the different reactivity of lignins and the reaction conditions. Also, lignin derivatives were observed by thermal analysis, which allowed establishing a correlation between the modification degree and the thermal stability. Treatments with unmodified and hydroxymethylated lignins were applied to birch veneer strips by immersing them in copper chloride solutions. The lignin products were dissolved in 0.1 N ammonia solution of 5% concentration. The biostability of the treated veneer was tested by buryi...

A comparative study of oxidative degradation with S 2 O 8 2 - /Ag + and Fenton systems was perfor... more A comparative study of oxidative degradation with S 2 O 8 2 - /Ag + and Fenton systems was performed on a series of ammonium lignosulphonate (ALS) solutions of different concentrations (0.079 - 3.785 mg/mL - 1 ), by means ofcyclic voltametry. These oxidized solutions have a complex composition and are susceptible of mutual interferences. However, cyclic voltametry can give only an overall view and estimation of such redox processes. The obtained voltammograms are quite different, as a function of the oxidants selected, and of the preliminary results (UV-VIS spectrophotometry, conductibility and turbidity data, total amount of hydroxylated aromatic compounds) obtained.

In this study, the adsorption of Cu(II) ions from aqueous solutions onto wheat straw lignin was i... more In this study, the adsorption of Cu(II) ions from aqueous solutions onto wheat straw lignin was investigated. The experiments were performed in a batch system, at room temperature (20 ± 0.5 °C), and the copper ions analysis was done after equilibrium was attained. Different experimental parameters (initial solution pH, sorbent dose, initial Cu(II) concentration and contact time) were varied in order to establish the optimum conditions for copper removal using wheat straw lignin. The experimental results were fitted using the Langmuir, Freundlich and Sips isotherm models, and the characteristic adsorption parameters were determined. Experimental data were also tested using two kinetic models: the pseudo-first-order Lagergren model and the pseudo-second-order Ho model. Based on these models, the kinetic parameters (rate constant and equilibrium adsorption capacity) for Cu(II) adsorption on lignin were calculated.

Cellulose Chemistry and Technology, 1991

Cellulose Chemistry and Technology, 1987

Synthese sur le potentiel et la technologie de conversion de la biomasse en produits energetiques... more Synthese sur le potentiel et la technologie de conversion de la biomasse en produits energetiques ou chimiques

The paper manufacture has a long tradition on the Romanian territory. The Romanian school of pulp... more The paper manufacture has a long tradition on the Romanian territory. The Romanian school of pulp and paper was founded in the Polytechnic Institute of Iași in 1949 and here it is alone place in Romania where the chemical engineers are prepared as specialists in this field. This paper presents main achievements obtained during the years in the education and research activities, recognized at national and international levels. Among them, it worth mentioning, along with education and scientific results the international symposia in the chemistry and technology of cellulose (14) and the foundation of peer reviewed international journal "Cellulose Chemistry and Technology" (1966). At present, the production of pulp and paper is among the very few industries corresponding to the principles of sustainable development and which can be integrated in an industrial complex based on biorefining for full valorization of biomass resources. Therefore, in the next future Romanian school of pulp and paper could be developed toward approach the education and research in the inter-and trans-disciplinary fields.

Plant growth and development are influenced by various exogenous and endogenous factors. In this ... more Plant growth and development are influenced by various exogenous and endogenous factors. In this context, a group of substances of particular interest are polyphenols. Considering the information presented in the literature data and the results obtained by our working group to date, our objective has been to study the influence of some polyphenolic extracts on the mitotic division. The investigated material comes from the seeds of maize, untreated (control) and treated with spruce bark polyphenolic extract (SBPE), hemp shives polyphenolic extract (HSPE) in different concentration. It was found that using SBPE or HSPE with lower concentration, the frequency of cells in mitosis was higher than in the control. At higher concentrations of the extracts, there were a higher number of cells with chromosomal aberrations. In the treatment variants, significant proportions had an ana-telophase (A-T) with bridges, delayed chromosomes and complex aberrations such as: A-T + bridges + late and/or...

Cellulose Chemistry and Technology, 1990

The wood suffers biodegradation processes in the environment under the biological agents’ action,... more The wood suffers biodegradation processes in the environment under the biological agents’ action, influenced by environmental factors and storage or usage conditions after treatment. Depending on their structure, wood chemical constituents will be degraded in the following order: hemicelluloses, cellulose and lignin [1-3]. Lignin represents the resistant component to biological attack and also grants mechanical resistance to the wood. Its wide use in various fields and its relatively low stability to the action of environmental factors requires the use of chemical compounds for protection against biological agents attack. Currently, for wood protection are used toxic products for microorganisms and insects that are also environmentally incompatible. Chemical protective aqueous agents are known whose efficiency is due to the presence of copper. Part of the copper ions is fixed in the wood substratum by hydroxyl or carboxylic ionized groups in the wood at high pH. Considering lignin’s...

Polyphenols are a widespread group of secondary metabolites found in woody species, including sof... more Polyphenols are a widespread group of secondary metabolites found in woody species, including softwood. Higher amounts of these bioactive compounds occurring in bark, heartwood, roots, branch bases and wound tissues and have a number of important roles to play in viticulture and ecology, including UV protection, disease resistance, pollination, color, and defense against predation in plants, plant growth regulation and bioremediation. The use of synthetic chelates has been strongly criticized because of excessive amount of metals solubilized, associated with risk of groundwater contamination through metal leaching. This study evaluate the possibility of using natural bioactive compounds, characteristic to grape seeds extracts, in phytoextraction as an alternative to synthetic chelators. The results obtained shown an improving trend in the bioaccumulation process of heavy metals into the rape plant. It may be properly mentioned that grape seeds natural polyphenolic extract present an...