Ingunda Sperberga, Polina Spela, Maris Rundans and Andris Cimmers
Materials were synthesized from illite based clay from Latvia by chemical and thermal activation using both NaOH and KOH solutions (4−6 M). Compressive strength and apparent porosity were measured. Effect of concentration of both solutions on the mechanical properties of the material was investigated by means of infrared spectroscopy (IR). Compressive strength data showed that alternative building materials could be obtained via alkaline activation.
Ruta Svinka, Visvaldis Svinka, Inga Pudze and Marite Damberga
Two different Quaternary clays from deposits Slucenieki and Prometejs were used for production of porous ceramic pellets. 3 wt % of sawdust additive was used to increase porosity of the obtained ceramic. Porosity and surface area of pellets was determined by mercury porosimetry. pH values after water immersion of fired pellets were determined using a pH meter. Pellets produced from both clays after sintering at similar temperatures had different pore size distribution and different sorption properties. Sorption properties were determined for a molecular substance (iodine) and anionic organic substance (methyl orange dye).
Olita Medne, Rita Serzane and Liga Berzina-Cimdina
This paper focuses on alternative daily cover materials intended for use in solid municipal waste landfills. Currently available and proposed cover materials are described by type. The functional contribution of cover components was considered. Special attention was given to alternative daily cover materials in form of sprayable slurries or emulsions. Using the obtained data, conclusions were drawn concerning the most promising components and compositions of sprayable alternative daily covers. Particularly promising components of sprayable daily covers for the use in local environment (Latvia) are clays, which are found in abundance in local mineral deposits.
Olga Muter, Baiba Limane, Silvija Strikauska and Maris Klavins
The aim of this work was to compare the effect of 1 % and 5 % humic substances (HS) on the growth of bean, wheat, rape and cress, as well as microbial activity (respiration, enzyme activity) in sandy loam soil spiked with a complex contamination, derived from municipal waste. The results of 23 days pot vegetation experiment demonstrated the stimulating effect of HS on the plant growth and soil microbial activity.
Gaida Sedmale, Inga Raubiska, Aija Krumina and Alexey Hmelov
This study focuses on the influence of illite clay on changes of ZrO2 modifications after sintering and consolidation of mullite-ZrO2 ceramics with or without Y2O3 additive.
It was found that mullite-ZrO2 ceramics both with 4.5 % Y2O3 additive or without it in presence of illite clay tend to have increased densification and compression strength after sintering. Presence of illite clay also promotes change of ZrO2 monoclinic phase to tetragonal phase and the presence of Y2O3 promotes change to ZrO2 cubic phase.
Two sialon compositions (Y0,33Si10,5Al1,5O0,5N15,5 and Y0,5Si9,5Al2,5O1,0N15,0) were used to determine the effect of starting components on densification and properties of sialon materials. Plasma synthesized nanopowders (Si3N4, AlN, Al2O3, Y2O3 and 73 wt% Si3N4-27 wt%AlN nanocomposite) were used for the investigation. Materials were sintered using traditional or spark plasma sintering methods. Sintering temperature was reduced significantly, if Si3N4-AlN nanocomposite was used as one of the components. The increased amount of asialon phase and higher hardness were characteristic to materials obtained from individual Si3N4, AlN, Al2O3, Y2O3 components.
Signe Žvagiņa, Zaiga Petriņa, Vizma Nikolajeva and Anita Lielpētere
Rhizobium leguminosarum biovar viciae is a bacterium, which can establish nodules on roots of legumes. Rhizobial inoculants are used in agriculture as bio-fertilizers. Peat, clay powder and three kinds of expanded clay were tested for the immobilization of bacteria. The results showed that carrier material influences the success of immobilization and that storage temperature influences the survival. The best results were achieved with maintenance of bacteria in a suspension and immobilization on peat. We recommend storage of rhizobial products at a temperature of −18 °C or 4 °C.
Daiga Pipira, Juris Kostjukovs and Ģirts Stinkulis
Siliciclastic deposits of the Burtnieki Formation and the Amata Formation in Latvia contain carbonate inclusions in places. Morphological peculiarities and mineral composition indicate that these carbonates represent dolocretes formed during subaerial exposure events in Devonian Burtnieki and Amata times. Dolocretes show nodular and veiny structure, circumgranular cracks, and other features of brecciation, but massive dolocretes also have been found in the Amata Formation. These features indicate that the dolocretes formed under the influence of both groundwater activity and pedogenic processes. These dolocretes were formed during episodes of subaerial exposure in repeated processes of drying and wetting either due to fluctuations of the groundwater table or climate change from semi-arid to semi-humid.
Silvija Strikauska, Andrejs Berzins, Lauris Arbidans, Agnese Kukela, Olga Muter and Maris Klavins
Contaminated microfibre cloths (80 % polyester and 20 % polyamide) which were previously used in waterless car cleaning process were treated in ultrasonic bath. Efficiency of water, ethanol, 2-propanol and ethylene glycol as liquid phase for ultrasonic treatment was compared. Chemical oxygen demand (COD), concentration of surfactants and total nitrogen in the extract were tested after 0 min, 10 min, 30 min and 60 min ultrasonic (US) exposure (42 kHz). In all cases the COD values gradually increased in a time dependent manner from 6 % to 35 % with ethanol, from 17 % to 37 % with ethyleneglycol and from 17 % to 33 % with 2-propanol at 10 to 60 min US mode, respectively.
In this report the obtaining and properties of hightemperature porous ceramic materials using local carbonate clays and quartz sand resources was studied. Materials with two different porosities were obtained by using different synthesis temperatures. The test results show that these materials contain cordierite as their main crystalline phase. The porosity directly influences the compressive strength and it is greatly reduced when overall porosity increases. The CTE of obtained materials is low − about 3-10−6 1/°C.