Kristīne Kalneniece, Andrejs Bērziņš, Zaiga Petriņa, Kristīne Ruģele, Elīna Salava, Kārlis Švirksts, Māra Grūbe, Vizma Nikolajeva and Olga Mutere
The aim of this study was to characterize the digestate from an activated sludge biogas reactor (IDARS) as an inoculum for enzymatic hydrolysis and biogas production from organic wastes. Aerobic and anaerobic bacteria are represented in IDARS with H’ index 3.1 and 2.5, respectively. IDARS stimulated the enzymatic hydrolysis of wood and leaves, preferably broadleaf tree species. The results demonstrated the potential of IDARS for improvement of the technological parameters for conversion of organic wastes into biogas.
Jūlija Karasa, Juris Kostjukovs and Solveiga Grinberga
Low cost, effective and water soluble organic coagulant is offered for the extraction of charged clay particles. Coagulation with KOHIDRAC results in simultaneous concentration and purification of the clay fraction. After treatment with KOHIDRAC the obtained clay samples were free of carbonates and feldspar. Moreover, the amount of quartz decreased significantly in finished samples. The proposed coagulant and the patented methodology can be successfully used as purification procedure or as pretreatment for qualitative and quantitative analysis of clay minerals. The possible structure of the active compound KOHIDRAC was investigated in this paper. Real applications of the coagulant were provided.
Ceramic water filters were prepared from different proportions of kaolin and soft wood and sintered at 900 °C, 950 °C, and 1000 °C. The flow rate, conductivity, pH of filtered water and removal efficiency (microbial, water hardness agent’s, nitrite and turbidity) were analysed. The ceramic filter with 15 % saw dust, 80 % clay and 5 % grog that was fired at temperature of 950 °C or 1000 °C showed the best removal efficiency. Statistical ANOVA tests showed a significant difference between ceramic filters with various compositions in their removal efficiencies.
Palusamy Suppuraj, Ganesamoorthy Thirunarayanan, Meenakshisundaram Swaminathan and Inbasekaran Muthuvel
Spinel ZnFe2O4 was developed successfully as a heterogeneous-Fenton catalyst for the degradation of Reactive Yellow 86 (RY 86) under UV light. The ZnFe2O4 was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) and UV-diffuse reflectance spectroscopy (UV-DRS). FE-SEM reveals that the some of the particles sizes are in the range from 10 nm to 50 nm. The photocatalytic performance of ZnFe2O4 was evaluated by degradation of RY 86 dye solution under UV light. The degradation rate was highly influenced by pH, initial concentrations of H2O2 and catalyst concentration. The results indicated that ZnFe2O4 could be used as a photocatalyst for treatment of industrial coloured wastewater. The catalyst was reused for five consecutive runs without significant change in its activity. Moreover, the antibacterial effects were investigated.
Agnese Stunda-Zujeva, Jana Vecstaudža, Guna Krieķe and Līga Bērziņa-Cimdiņa
There is a lack of studies on a wide composition range for calcium phosphate glasses containing transition elements, e.g. niobium. Addition of Nb2O5 increases mechanical and chemical strength of calcium phosphate glasses and glass ceramics.
Glass is formed in a wide range of compositions. CaO promotes batch melting. The oxidation state of niobium has important role in glass forming. Solid state reactions between P2O5 and Nb2O5 during batch melt change the oxidation state of niobium. Nb5+ in this system acts as an intermediate or conditional glass former (glass is yellow) while Nb4+ is a glass modifier (glass is blue). It is possible to obtain glass with Nb2O5 (Nb5+) content up to 70 mol%. The glass ceramics obtained by reheating powdered glass contained niobium in crystalline phases. The composition of crystalline phases depends on the phosphate amount.
A novel method for lead(II) removal from aqueous acidic solutions is presented. The method involves electrodialysis through bulk liquid membranes accompanied by electrodeposition of metal from the cathodic solution. Solutions of di(2-ethylhexyl)phosphoric acid with admixtures of tri-n-octylamine in 1,2-dichloroethane were used as the liquid membranes. The effects of the main electrodialysis parameters as well as of the composition of the liquid membranes and aqueous solutions on the lead(II) transport rate are studied. The optimal conditions are determined. A possibility of effective single-stage transfer of lead(II) through the liquid membrane into dilute solutions of perchloric, nitric and acetic acids is demonstrated. Dense and adherent lead electrodeposits are obtained from perchloric acid solutions. Maximum extraction degree of 93 % and electrodeposition degree of ~60 % are obtained during 5 h of electrodialysis.
Ženija Roja, Ingars Reinholds, Jānis Zicāns and Remo Merijs Meri
Radiation crosslinking of polyolefins has gained interest for the development of advanced heat-shrinkable materials. Propylene homopolymer (PP1), polypropylene-polyethylene block copolymers (PP2, PP3) and their mixtures with 3 wt.% of bisphenol A dimethacrylate (BPDMA) crosslinking agent were irradiated with 25–150 kGy of accelerated electrons and were compared for aforementioned purpose. The studied mechanical properties indicated increased elongation in the presence of BPDMA that was contributed to the crosslinked moieties of PP and the crosslinking agent. The shrinkage stresses were comparable to that of polyethylene based heat-shrinkable material.
A historical paint manufactory in Staicele, Latvia (1967), was using local resources – colour earth. Oil paint composition consisted of pigment, drying oil, varnish and siccative. It had two different tones that are obtained by using natural colour earth pigments: ochre and its burnt form (burnt umber). Pigment quality was analyzed using historical documents, modern pigment tests, and manufactory technology. Chemical composition, particle size, and pigment tone were determined, and the coating ability was calculated. A palette of oil paints based on the historical recipes for restoring Staicele oil paints was created. Properties of colour earth pigments were compared to specimens taken from the local source of iron that is located near the old paint factory. Results provide a historical and technological insight as well as insight in the properties of the basic paint composition.
The solid acidic nanocatalyst fly-ash:H3PO4 was prepared and characterized by FT-IR, SEM, EDS and TEM analysis. This catalyst was utilized for aldol condensation, coupling and cyclization reaction. The effect of catalytic activity of this fly-ash:H3PO4 nanocatalyst was studied with the obtained yield of products under solvent-free conditions. In this synthetic reaction the obtained yields were more than 95 %.
Svetlana Marija Goliškina, Dace Cīrule, Ērika Bizdēna and Māris Turks
5-Alkylamino derivatives of tetrazolo[1,5-a]quinazoline were obtained with high regioselectivity in the reaction of 5-azidotetrazolo[1,5-a]quinazoline (formally, 2,4-diazidoquinazoline) with long chain alkylamines. The obtained 5-aminoquinazoline derivatives were used in a copper catalyzed azide-alkyne 1,3-dipolar cycloaddition reaction to obtain series of 4-(alkylamino-2-(1,2,3-triazol-1-yl)quinazolines.