Materials Science and Applied Chemistry

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Authors: Anna Andersone, Alexandr Arshanitsa, Valentins Solodovniks, Valdis Kampars
Abstract: Debarking is an essential part in the technology of round timber processing. The volume of bark going to waste annually is millions of cubic metres, therefore the use of bark as an underexploited renewable source is of increasing importance. Pelletization is one of the recognized methods for increasing the bulk and energy densities of plant biomass, and respectively improving its value as a fuel. Plant biomass pellets are the only solid fuel that have a global constantly growing market. In this work the bark obtained after softwood trees debarking for the pulp manufacture was studied in terms of fuel pellets production feasibility. The fuel characteristics, including elemental composition, ash content, calorific values and other parameters required for fuel pellets standards were determined. The laboratory flat die pellet mill KAHL 14-175 was applied for pelletizing study. The study showed that using floatation process for purification / fractionation of bark batch under study, 86% of bark residue become suitable for obtaining of fuel granules quality of which meet the demand of EN 14961-2B European standard for non-industrial and industrial fuel pellets.
Authors: Agnese Stunda-Zujeva, Imants Kreicbergs, Olita Medne
Abstract: Biological treatment of municipal and industrial wastewater becomes more common in EU countries. As a result, the amount of wastewater sludge increases. The political and economic situation in world is requiring new methods for recovery of non-renewable mineral resources. Sludge is great secondary source of many elements. The aim of this research is to summarize available techniques for sustainable utilization of industrial sludge and recovery of critical raw minerals (CRMs). The most common sustainable method is using treated sludge as fertilizer in agriculture due to high content of P, N, C and microelements. However, this method has many restrictions, e.g. it can contain toxic substances or lack of appropriate land. Thermal sludge treatment methods like pyrolysis have developed crucially in last decade and pyrolysis units for sludge treatment are commercially available now. Pyrolysis becomes the most sustainable method due to recovery of CRMs and better energy recovery comparing to incineration.
Authors: Kristaps Māliņš, Valdis Kampars, Ruta Kampare, Zane Sustere, Alina Arenta
Abstract: Interesterification of vegetable oils is one of the methods which have been considered for biodiesel production. Average yield of fatty acid methyl esters (FAME)/triacetin (TA) containing product mixture obtained under developed optimal rapeseed oil (RO) interesterification reaction conditions reached 117.2%. Treatment of FAME/TA mixture with three different commercial ion exchange resins (Amberlyst-A26 (OH-), Amberlyst-15 (H+), Lewatit GF 202 (Na+)) and water was investigated to improve fuel properties or extract FAME and TA as two separate marketable products. Fuel properties of obtained product mixtures were relatively close to biodiesel obtained from RO by transesterification reaction with methanol. The highest influence on chemical composition of product mixture showed water as treatment agent. Water can be successfully used as extraction agent for separation of TA and other glycerol (G) acetates from fatty acid moiety containing compounds. Two separate product mixtures were obtained after treatment of FAME/TA containing mixture with water. G (~5 wt.%), DAG (~33 wt%) and TA (~61 wt.%) mixture extracted with water using developed method has high potential for application in different industrial areas. Rest of product mixture with high content of FAME (~77 wt.%) could be used as renewable fuel for diesel engine exploitation.
Authors: Agnese Stunda-Zujeva, Kristīne Ruģele
Abstract: Microalgae-cianobacteria Arthrospira (trade name Spirulina) are cultivated worldwide due to its nutritional and therapeutic qualities. The aim of this review is to summary production parameters affecting quality of Arthrospira. The biochemical composition of microalgae foodstuff is mostly determined by growing conditions, e.g. growth media, light intensity, temperature as well as drying method and conditions. This review showed that prospective directions for optimization of costs to cultivate Arthrospira indoors are: effective use of light, e.g., using effective artificial light sources like light emitting diodes (LED) in color with regards to necessary component in Arthrospira; mixotropic growth using growth media from food processing by-product/waste; and selection of Arthrospira strain according to available temperature. Common methods of algae drying for food and nutraceuticals are solar drying, convective drying, spray drying, lyophilization. The drying method and regime can greatly affect the amount of biologically active compounds and organoleptic quality.
Authors: Valdis Kampars, Sintija Zīriņa, Agija Stanke, Modris Roze
Abstract: In this study SBA-15 based catalysts loaded with copper oxide were synthesized, characterised and investigated in fast catalytic pyrolysis of rapeseed oil using catalyst mixing method. Results of catalyst characterisation showed that all synthesised samples are mesoporous silica with uniform hexagonal shape cylindrical pores with space group P6mm and average pore size of 6 nm. Supported CuO did not influence the uniform hexagonal shape; however surface area and pore diameter decreased with increasing CuO loading. Investigation of fast pyrolysis of rapeseed oil shows that supporting with CuO suppresses the deoxygenation in form of H2O, CO and CO2 =regardless of the amount of CuO. At the same time supported CuO increased the content of oxygenates in the pyrolysis products = linearly to the CuO amount till 6-8% m/m of CuO. Further scale up the CuO content lowered the yield of oxygenates.
Authors: Anete Boroduske, Ilva Nakurte, Nils Rostoks
Abstract: Accumulating scientific evidence suggests that medicinal plant-associated microbiota has a significant role in biosynthesis of pharmacologically relevant compounds. Suppression of S. nigra microbiota by an antibiotic treatment leads to a decreased emission of volatile terpenoids from S. nigra flowers and an altered metabolome of a host plant. However, it is not known if suppression of microbiota also affects an abundance of health promoting compounds and pharmacologically relevant properties of S. nigra. The present study reveals, that suppression of phyllospheric microbiota by an antibiotic treatment affects total phenolic content (TPC), anti-radical activity (ARA) and total flavonol content (Flav) of wild S. nigra flowers. Significance analysis of metabolites (SAM) performed using ultra high performance liquid chromatography-time of flight-masspectrometry (UHPLC-TOF-MS) based metabolomics data identifies pharmacologically relevant flavonols as metabolites discriminating between antibiotic treated and control flowers of S. nigra. Reported results substantiate need for a research investigating an effect of microbiota suppression on a biological activity of S. nigra flowers.
Authors: Daniela Godiņa, Aigars Paze, Janis Rizhikovs, Kristaps Stankus, Inguss Virsis, Ilva Nakurte
Abstract: The literature survey summarizes information about birch outer bark phytochemical composition and details major components: betulin, betulinic acid, lupeol and ursolic acid. In the practical part of research birch outer bark major component stability against chemical and physical degradation was tested; total phenolic content and the antiradical activity of the degraded and nondegraded ethanolic extracts was studied using UV/VIS spectroscopy; the phytochemical composition of the birch outer bark ethanolic extract was investigated by HPLC-TOF/MS. The study of stability experiments has been carried out, which found that birch outer bark ethanolic extract compounds can be exposed to thermal and humidity degradation as well as exposure to β radiation, as extractants do not decompose in these degradation conditions. Acid or base degradation and oxidative degradation lead to partial degradation of the extracts. This kind of study for birch outer bark extract is not described and will serve as a basis for determining the expiry date of the extract containing cosmetic products and food additives, the choice of the required product packaging and storage conditions.
Authors: Elina Sile, Valdis Kampars, Zane Sustere
Abstract: Two catalytic systems (CH3OK/CH3OH and CH3OK/tert-BuOH) were tested to estimate competitive interesterification-transesterification processes of rapeseed oil with methyl acetate. Catalyst completely dissolves in methanol, while in tert-butanol suspension was obtained. With CH3OK/CH3OH catalytic system high FAME content was obtained (86 wt%), but triacetin content was negligible and without FAME mostly transesterification products of oil and triacetin were observed (up to 94 wt% of all products). When CH3OK/tert-BuOH catalytic system was used, only interesterification of oil proceeded, nevertheless the composition of product complicated the interesterification of triacetin with tert-butanol.
Authors: Sarmīte Janceva, Liga Lauberte, Jegor Akishin, Alexandr Arshanitsa, Tatiana Dizhbite, Galina Telysheva
Abstract: Optimization of extraction conditions of the proanthocyanidins (PAC) and PAC-rich extract (PACE) from bark of alder species (Alnus incana and Alnus glutinosa) were performed varying solvents (ethanol, distilled water), extraction methods (conventional and microwave assisted extraction), extraction temperature (20–120 °C) and extraction times (5–60 minutes). The optimal extraction conditions established in the work provide 87 % PAC transition from the bark of alder species to hydrophilic extracts. On the basis of the extraction results, the technological scheme of PAC and PACE isolation from grey alder bark with focus on biorefinery was developed.
Authors: Lauma Laipniece, Valdis Kampars
Abstract: We have synthesized polyester type dendrimers containing azobenzene chromophore in the core and trityl groups at the periphery using divergent growth strategy up to 3rd generation. We analyzed dendrimer samples using NMR, HPLC, TG, DSC and UV-Vis techniques. We found out that functionalization of dendrimer periphery is not complete. Dendrimers with trityl groups at the periphery have glass transition temperatures in the range 73-87 °C.

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