Ruta Švinka

Sorption of Inorganic Substances on the Porous Latvian Clay Ceramic

Devonian clay of Liepa deposit (district of Cesis) and Quaternary clay of Laza deposit (district of Aizpute) was investigated. Pellets were fired at four different temperatures of 700, 800, 900, and 1050 °C. Porosity and surface area of pellets was determined by mercury porosimetry. The pH values after water immersion of fired pellets was determined with a pHmeter. The sorption ability of molecular substance (iodine) and ionic substances (ammonia and dichromate) were determined by titrimetric methods. The best sorption ability was found for iodine molecules. The entire amount of iodine in the water suspension was absorbed in two weeks, and the sorption ability reached 12.5 mg/g for samples fired at 700 and 800 °C temperature for the Liepa clay and 13.0 mg/g for the Laza clay. The sorption ability of these clay pellets for ammonia was lower and amounted to 3.0 and 2.5 mg/g, respectively. The sorption ability for dichromate ion was even less - only 0.6 mg/g for pellets of both clays. The investigated fired porous clay granules exhibited distinct sorption properties towards water-soluble ionic and molecular substances, which depended more on the firing temperature of granules and less on the source of clay. Porainai mālu keramikai raksturīgā specifiskā dažādu savienojumu sorbcijas spēja ļauj to izmantot ūdens attīrīšanas procesos. Sorbcijas selektivitāte vairāk ir atkarīga no mālu apdedzināšanas temperatūras un no adsorbāta īpašībām nekā no apdedzināmo mālu tipa. Lielākā sorbcijas spēja ir 700 un 800 oC temperatūrā apdedzinātām devona (Liepa) un kvartāra (Laža) mālu granulām. Molekulāro savienojumu sorbcijas spēja ir lielāka nekā jonogēno savienojumu. Keramiskos granulu sorbcijas spēju ietekmē ūdenī iegremdētu granulu pH, izmainot savienojumu tieksmi saistīties uz granulu virsmas un spēju iekļūt materiāla porās. It sevišķi tas attiecināms uz jonogēniem savienojumiem.

Porous Clay Ceramic for Environmental Technologies

In the present work porous clay ceramic pellets (porosity ≤ 30 %) are investigated for the wastewater purification technologies. Calcareous and non-calcareous illite containing clays with different content of fine clay fraction (particle size ≤ 0.005 mm) are used. Sawdust in amount of 3 wt% for the increasing of porosity and surface area is used. Non-calcareous clays are also used for the production of ceramic materials with porosity ≥ 50 %. Pores are formed in result of chemical reaction in clay suspension of aluminium paste with water. After sintering of dry samples the sorption ability of covalent (iodine) and ionic (ammonia) compounds are determined. Sorption ability depends on many factors such as chemical composition of clay, sintering temperature, pore size distribution in the ceramic materials, surface area, pH of water after immersion of pellets and adsorbable substances.

Floating Ceramics vs. Floating Oils: Search for Appropriate Conditions

Abstract Ceramic granules fabricated from Quaternary clay at 1200°C were tested for their flotation ability in a water model system containing silicone oil. The presence of oil in the liquid phase improved flotation of granules, probably due to sorption of oil by ceramics. Coating of granules with SiO2 resulted in decreased flotation ability, irrespectively of the presence of oil. Granules were shown to be appropriate for bacterial colonization.

Clay Ceramic Pellets for Water Treatment / Mālu keramikas granulas ūdens apstrādei

Abstract 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). Porainas keramikas granulas ieguva no diviem atšķirīgiem kvartāra māliem: liesiem Šļūcenieku un trekniem Prometeja atradnes māliem. Abi māli atšķiras gan ar karbonātu saturu (CaO saturs, attiecīgi, 11,18 % un 5,95 %), gan ar dažādu mālu frakcijas saturu (attiecīgi, 46,0 % un 84,9 %). Granulu porainības palielināšanai mālam pievienoja 3 masas% koksnes skaidu (Ø ≤ 2 mm) un granulas ar diametru 5 mm veidoja no plastiskas masas ar ekstrūzijas paņēmienu. No Prometeja māliem izgatavoja divu veidu granulas - otrā veida granulu veidošanas masai pievienoja arī 2 masas% glicerīna. Granulas apdedzināja 800 °C, 900 °C, 1000 °C un 1100 °C temperatūrā. Granulu sorbcijas spēju noteica attiecībā uz jodu, kas ir molekulārs savienojums ar kovalentu saiti, un attiecībā uz anjonu tipa krāsvielu (metiloranžu), kurā starp katjonu un anjonu pastāv jonu saite. Pastāvēja atšķirība abu mālu sorbcijas spējās gan no granulu īpašību viedokļa, gan no atšķirīgo vielu sorbcijas rakstura. Šļūcenieku mālu granulu porainība bija lielāka, salīdzinot ar tādā pašā temperatūrā apdedzinātām Prometeja mālu granulām. Sorbējot vielas ar kovalentu nepolāru saiti, sorbcija bija fizikāla, t.i., sorbcijas spēja bija atkarīga no poru izmēriem un virsmas laukuma. Tāpēc Šļūcenieku mālu keramikas granulu sorbcijas spēja attiecībā uz jodu bija lielāka un notika ievērojami īsākā laikā, salīdzinot ar Prometeja mālu granulām. Attiecībā uz savienojumu sorbciju, kuros pastāv jonu saite, svarīga nozīme bija absorbcijas vides pH un daļiņu zeta potenciālam, t.i., virsmas lādiņam, bet porainība, poru izmēri un virsmas laukums mazāk ietekmēja šādu vielu absorbciju. Granulām, kuru veidošanas procesā mālu masai pievienoja arī glicerīnu, konstatēts vidēji liels zeta potenciāls (23-34, atkarībā no apdedzināšanas temperatūras), kas arī ietekmēja sorbciju savienojumos ar jonu saiti. Tomēr Prometeja mālu gadījumā metiloranža sorbcija bija maza un nepārsniedz 6 % no šķīdumā esošā metiloranža daudzuma salīdzinot ar metiloranža sorbciju uz Šļūcenieku mālu granulām, kas bija 40-60 %.

Influence of Metal Oxides Additives on the Porous Mullite Ceramics

The porous mullite ceramics doped with such metal oxides as ZrO2, WO3 and MgO in quantity of 5 wt% were prepared by slip casting method. The mullite phase was the main and dominant phase of ZrO2-, WO3- and MgO-doped samples, which were sintered at the temperatures of 1650°C, 1500°C, respectively. The ZrO2, WO3 and MgO had the positive effect on the increase of porosity and decrease of thermal conductivity of porous mullite ceramics and the degree of this effect was in the order of ZrO2

Anisotropy of Compressive Strength in Porous Alumina Ceramics

Anisotropy of the compressive strength was investigated in porous alumina based ceramics produced by slip casting method. Aluminium paste was used as pore former similarly as in the aerated concrete technology. Materials were sintered at 1650°C and 1750°C. The apparent porosity of the investigated materials was in the range of 54±1% to 60±2%. The compressive strength of the samples in the directions parallel and perpendicular to the sample expansion direction was in the range from 3.8±0.3 to 13.0±1.1 MPa and from 6.4±1.3 to 27.0±1.1 MPa, respectively. The mechanical anisotropy was related with the flattening of the introduced pores. The level of mechanical anisotropy was affected by the initial composition of the slurry and sintering temperature.

Interaction of Oily Water with Floating Porous Ceramic and Immobilized Microorganisms

Oily water was treated with porous ceramic granules and immobilized microorganisms. Floating granules with bulk density of 0.63-0.66 g cm-3 were used. The sorption of motor oil was investigated for dry and wetted granules. Respiration experiments showed that microorganisms immobilized on floating ceramic carrier and treated with oily water were influenced by agitation of liquid. The treatment of oily water with low salinity (1-9 g L-1) showed that oil removal efficiency decreased after increasing water salinity. Likewise, oil removal efficiency decreased from 12 to 9% per gram of ceramic carrier after increasing the spill of oil from 9 to 35 g per square meter. Porous granules with immobilized microorganisms can be used in cases with insignificant oil pollution or for pretreatment of wastewater before feeding it into a wastewater treatment plant.

Evaluation of Glyphosate Ecotoxicity and Biodegradability in the Municipal Wastewaters

Glyphosate (G) is a broad-spectrum systemic organophosphate herbicide being widely used to control weeds in agricultural fields and urban areas. Its safety for both human health and aquatic biomes is a subject of wide debate. This study was aimed at evaluating the removal efficiency and ecotoxicity of G based herbicide (GBH) Klinik® (Nufarm, Austria) added to the raw municipal wastewater (WW) in a lab-scale model column system. The effect of oxide ceramics as a filtering medium (treatment „B”), as well as activated sludge and nutrients (treatment „C”) was compared with the control columns, which contained only WW (treatment „A”). After 72h treatment of WW spiked with 100 mg/L G, the lowest G concentration was detected in the treatment „B”, i.e., 79.4±0.6 mg/L. Treatments „A” and „C” resulted in the remaining G concentrations of 83.3±3.8 and 89.6±3.7 mg/l, respectively. The second addition of 100 mg/L G to the columns followed by 72h incubation also showed the advantage of oxide ceramics. Most probably, this effect could be explained by coupled sorption and biodegradation processes. Experiments were accompanied by microbiological (colony forming units; biological oxygen demand) and ecotoxicological (Daphtoxkit F magna, MicroBioTests) testing. The results indicated that WW-derived microorganisms resist the presence of GBH in the tested concentration range of G, i.e., up to 300 mg/L. As for Daphnia magna, the 24-h EC50 for the GBH Klinik® under standard conditions and in raw WW was found to be 22 mg/L and 6 mg/L G, respectively.

Catalytic Pyrolysis of Wood by Presence of Clay Minerals

Devonian, and Quaternary clays of Latvia together with additive of sawdust after plastic moulding of pellets were used. Partial oxidation of sawdust and formation of active carbon after thermal shock at temperature 800°C were determined. The main clay mineral in all of clays was hydromica with some difference in the structure. Obtained materials with bulk density 1.1 g/cm3 as sorbent for different chemicals such as iodine and methylene blue was used. Dependence of sorption ability of pellets on the type of used clay (clay minerals) was determined. XRD for the determination of phase compositions, nitrogen absorption for the pore size distribution, SEM for the analysis of structure and nanoscale Zetasizer for the determination of surface charge were used.

Common and Different in Latvian Clay Minerals

Clays are materials consisting of clay minerals and non-clay minerals. Some applications allow to use raw clay others require to separate clay minerals from non-clay minerals. Clay mineral fraction is considered to be a nanofraction. Description and characterization of 3 different Latvian clay nanosized minerals from 3 different geological periods (clay Liepa from Devonian period, clay Vadakste from Triassic period and clay Apriki from Quaternary period) are summarized. The main mineral in these clays is illite, however the presence of kaolinite is observed and its quantity depends on geological period in which clays formed. Nanosized clay mineral particles were obtained using sedimentation method. Comparison of mineralogical composition, BET nitrogen adsorption, zeta potential, DTA/TG analysis and FTIR spectra is given. XRD phase analysis results were very close to each other and shows that mineral of illite is more than that of kaolinite. BET nitrogen adsorption data shows that clay minerals of Apriki has the highest specific surface area (81 m2/g), whereas clay minerals of Vadakste has it the lowest (43 m2/g). Zeta potential values for clay minerals Apriki, Liepa and Vadakste are-40.9 mV, -49.6 mV and-43.0 mV, respectively. DTA analysis and FTIR spectra show similar tendencies for all 3 clay minerals.