Comparison of the effects of three drying methods on lignin properties

In the last few years, a serious effort has been initiated to develop standard methods for lignin characterization at the national and international levels. Thus, several Canadian and ISO standards were recently developed. The current results were generated in an effort to assist the ISO/TC6 Committee come up with a reliable standard method for the measurement of the dry solids content of lignins. In particular, this work investigated the drying of lignin using three different drying methods: conduction oven drying (105 °C), vacuum oven drying at (60 °C), and freeze drying. Ten different lignins were used in this study including wet and air-dried softwood and hardwood kraft lignins in the acid and base forms from the industrial LignoForce™ process and hydrolysis lignin from the TMP-Bio™ process. The results showed that 7 h, 48 h and 24 h were sufficient to reach a constant solids content in the case of all lignins when oven drying, vacuum oven drying under negative pressure (150 mbar), and freeze drying (25 mT) were used, respectively. Kraft lignins in the base form showed higher sensitivity to degradation compared to lignins in the acid form. The total hydroxyl group content of air-dried and wet hardwood lignins in the base form decreased by more than 50 % after vacuum oven-drying for 71.5 h or oven-drying for 16 h compared to freeze-drying for 68 h. The decrease in the total hydroxyl groups was more pronounced (70 %) when the wet softwood lignin in the base form was dried in the oven compared to freeze drying for 68 h.

New approach to recycle and valorize the first filtrate of the LignoForce system™: Lignin extraction and its use in rigid lignin-based polyurethane foams

In this work, we report on the fractionation, recovery and characterization of softwood kraft lignin from the first filtrate of the LignoForce™ process. It is estimated that the lignin content in this stream could be >20-30 % of the lignin present initially in the black liquor. The use of a membrane filtration system was experimentally validated as an effective method for fractionating the first filtrate. Two membranes with different nominal molecular weight cut-offs (4000 and 250 Da) were tested. Higher lignin retention and recovery was obtained using the 250-Da membrane. This lignin (lignin_250) was found also to have a lower molecular weight and a tighter molecular weight distribution compared to the lignin obtained using the 4000-Da membrane (lignin_4000). The lignin_250 was characterized for it's hydroxyl group content and used to produce polyurethane (PU) foams. Up to 30 wt% petroleum-based polyol replacement by lignin_250, the resulting lignin-based PU (LBPU) foams presented the same thermal conductivity as the control (0.0303 W/m.K (control) vs 0.029 W/m.K (30 wt%)), as well as comparable mechanical (max stress: 145.8 kPa (control) vs 222.7 KPa (30 wt%), modulus 64.3 kPa (control) vs 75.1 (30 wt%)) and morphological properties to the petroleum polyol-based PU foams.

Analysis of Lignins Using 31P Benchtop NMR Spectroscopy: Quantitative Assessment of Substructures and Comparison to High-Field NMR

Lignin is quickly emerging as a biomass-derived source for the production of some crucial organic chemistry building blocks, typically obtained from unsustainable and non-renewable petroleum feedstocks. As a complex polymer, lignin characterization is often challenging, due to its random structure and multitudes of different repeating substructures. Over the last 20 years, advances in our understanding and processing of lignin, as well as important work on its characterization using 31P NMR, have led to numerous publications highlighting the many potential uses for this material. With the emergence of high-resolution benchtop NMR instruments, these types of analyses can now be accessed by many laboratories and industries that have historically not been able to take advantage of NMR due to cost or size constraints. Herein, we demonstrate that benchtop NMR is a viable technique for the 31P NMR analysis of lignin and compare our results to those obtained on a traditional high-field instrument.

Effects of Process Parameters on Hydrolytic Treatment of Black Liquor for the Production of Low-Molecular-Weight Depolymerized Kraft Lignin

The present research work aimed at hydrolytic treatment of kraft black liquor (KBL) at 200–300 °C for the production of low-molecular-weight depolymerized kraft lignin (DKL). Various process conditions such as reaction temperature, reaction time, initial kraft lignin (KL) substrate concentration, presence of a catalyst (NaOH), capping agent (phenol) or co-solvent (methanol) were evaluated. The research demonstrated effective depolymerization of KL in KBL at 250–300 °C with NaOH as a catalyst at a NaOH/lignin ratio of about 0.3 (w/w) using diluted KBL (with 9 wt. % KL). Treatment of the diluted KBL at 250 °C for 2 h with 5% addition of methanol co-solvent produced DKL with a weight-average molecular weight (M_w) of 2340 Da, at approx. 45 wt. % yield, and a solid residue at a yield of ≤1 wt. %. A longer reaction time favored the process by reducing the M_w of the DKL products. Adding a capping agent (phenol) helped reduce repolymerization/condensation reactions thereby reducing the M_w of the DKL products, enhancing DKL yield and increasing the hydroxyl group content of the lignin. For the treatment of diluted KBL (with 9 wt. % KL) at 250 °C for 2 h, with 5% addition of methanol co-solvent in the presence of NaOH/lignin ≈ 0.3 (w/w), followed by acidification to recover the DKL, the overall mass balances for C, Na and S were measured to be approx. 74%, 90% and 77%, respectively. These results represent an important step towards developing a cost-effective approach for valorization of KBL for chemicals.

[The psychopathology of bilingual children in a sample of a Community Mental Health Center]

Thoughts and views of one's internal self can be materialized via verbal symbols. Therefore literal people can use these verbal symbols as a means of recording their ideas and experiences in order for them to be passed on and read by others. Evidently the abovementioned mental operations can be reflected in speech and language. It is not yet known whether bilingualism is the sum of two monolingual situations or whether they coexist. The way each language is organized is also not known, neither are the psychological operations that may influence the organization of each language, memory and the relationship with each language. During childhood and adolescence, language is a very important tool via which one communicates, materializes emotional behavior and organizes oneself. Linguistic development and identity formation both follow a parallel and connected line in view of the internal psychological organization. However, in the bilingual person, this relationship is influenced both by the two different cultural stimuli and by the two different linguistic stimuli (i.e. language). However, in the case where children grow up in a bilingual environment there are some particularities and special issues affecting these children. Under such circumstances, the accomplishment of the feeling of coherence and stability of the self becomes an even more difficult task for the child. Nowadays, in Greek reality, the phenomenon of bilingualism tends to be associated with economic immigration. In the sample used, five fourths of children consist of children coming from families of economic immigrants. The composition of the student population in Greece is characterized by linguistic and cultural polymorphism. The presence and existence of a large number of immigrants has changed the setting in Greece in many regions of the country and in turn, the composition of the school population. Any public school allover in Greece consists, among others, of children coming from families of economic immigrants, including thus a random number of children speaking different languages. Without doubt, immigration affects the immigrating person as much as it affects the new group. Also, immigration adjustment and formation depends on the pre-existing characteristics of the immigrants as much as it does on the characteristics of the welcoming society. Research dealing with the issues of economic immigrants in Greece are limited and mainly come from schools. The focus of interest is aimed firstly on the psychopathology that can be linked to the phenomenon of immigration and secondly on the social consequences of the phenomenon. The formation of psychopathology is associated with immigration and the importance of psychological trauma and its consequences. However, the association between the creation of psychopathology, which is formulated in childhood/adolescence, and the bilingual environment together with identity formation, is not yet clear. The aim of this paper was to study the effect of the dual language environment on psychopathology formation among children and adolescents as it appears in everyday clinical practice and as it has been recorded at the Child and Adolescent Mental Health Unit of the Community Mental Health Centre of Byron and Kaissariani, Psychiatric Hospital, Athens University. Data deriving from the database of the Community Mental Health Centre were extracted from the files of 62 bilingual children, aged 0 to 18 years, who had visited the CMHC of Byron and Kaissariani in the period 2000 to 2005. The data selected concerned the sex, age, maternal language, diagnosis and the existence of economic immigration. Means deriving from the sample of bilingual children were compared to the means of the rest of the sample. (Pearson chi,2 Fishers exact test) Based on the results, four fifths of the sample was composed of children belonging to families of economic immigrants. The occurrence of Pervasive Developmental Disorders was triple among the sample of bilingual children compared to the sample of monolingual children. Among school-aged children the majority of diagnoses concerned Specific Language, Movement and Learning Disorders. On the contrary, during adolescence, there was a two-fold increase of psychiatric illness among bilingual adolescents compared to monolingual adolescents with conduct disorders being more prominent among males and mood disorders more prominent among females. Based on the extent and importance of the influence of the dual linguistic environment on children and adolescents as well as on the originality of the new situation in Greek society, further exploration of this area is believed to be necessary.

Liquid chromatographic retention behaviour and separation of chlorophenols on a β-cyclodextrin bonded-phase column. Part III. Diaromatic chlorophenols

The liquid chromatographic retention behaviour of 16 diaromatic phenols and chlorophenols (PCB metabolic analogues) on a β-cyclodextrin bonded-phase column was investigated with respect to mobile-phase composition, pH, temperature, and ionic strength. The mechanistic aspects of retention of these compounds on the β-cyclodextrin column were studied and compared to other reversed-phase columns. Comparison is also made to the liquid chromatographic retention behaviour and separation of monoaromatic chlorophenols on the same column. The size, shape, and spatial geometry of each substrate appears to affect retention and selectivity. Most of the evidence suggests that inclusion complex formation, which involves hydrophobic interactions with the interior of the cavity and/or van der Waals interactions of the chlorine substituents with the backbone of the cavity, provides the physical basis for the resolution of these positional isomers. Under certain chromatographic conditions, however, it appears that, for certain congeners, all or part of the molecule is excluded from the cyclodextrin cavity; in such cases a normal-phase or mixed chromatographic mechanism is postulated based on the interaction of the substrates with the secondary hydroxyls on the periphery of the cyclodextrin moieties. The gradient–elution separation of 14 out of 16 of this type of compound on a single chromatogram is also reported and discussed. Keywords: biphenylols, chlorobiphenylols, biphenyldiols, liquid chromatographic retention behaviour, gradient-elution separation, β-cyclodextrin bonded-phase column.

Liquid chromatographic retention behavior and separation of chlorophenols on a beta-cyclodextrin bonded-phase column, Part II. Monoaromatic chlorophenols: separation

The liquid chromatographic separation of 19 monoaromatic chlorophenols on a beta-cyclodextrin bonded-phase column is investigated in both an isocratic and a gradient elution mode. Even though the isocratic mode can be employed for the separation of the member components of each category of chlorophenols (e.g., mono-, di-, etc.), significant overlaps between the retention times of the various categories prevent the separation of all chlorophenols on a single chromatogram. Gradient elution can be used, however, for the separation of 15 of the 19 chlorophenol isomers. The unique features of gradient elution as applied to beta-cyclodextrin bonded-phase columns are discussed. The detection of chlorophenols with UV and electrochemical methods is also discussed and the two are compared.

Liquid chromatographic retention behavior and separation of chlorophenols on a beta-cyclodextrin bonded-phase column, Part I. Monoaromatic chlorophenols: retention behavior

The liquid chromatographic retention behavior of nineteen monoaromatic chlorophenols on a beta-cyclodextrin bonded-phase column is investigated with respect to mobile phase composition, pH, temperature, and ionic strength. The mechanistic aspects of retention of these compounds on the beta-cyclodextrin column are studied and compared to other reversed-phase columns. Most of the evidence suggests that the unique selectivity of this column is due to inclusion complex formation, which provides the physical basis for the resolution of positional isomers. Under certain chromatographic conditions, however, the more highly chlorinated congeners appear to be excluded from the cyclodextrin cavity; in such cases a normal-phase chromatographic mechanism is postulated, based on the interaction of the substrates with the secondary hydroxyls on the periphery of the cyclodextrin moieties.