ABSTRACT
The idea of this work is to reduce the negative effect of ordinary Portland cement (OPC) manufacture on the environment by decreasing clinker production temperature and developing an alternative rankinite binder that hardens in the CO2 atmosphere. The common OPC raw materials, limestone and mica clay, if they contain a higher MgO content, have been found to be unsuitable for the synthesis of CO2-curing low-lime binders. X-ray diffraction analysis (ex-situ and in-situ in the temperature range of 25-1150 °C) showed that akermanite Ca2Mg(Si2O7) begins to form at a temperature of 900 °C. According to Rietveld refinement, the interlayer distances of the resulting curve are more accurately described by the compound, which contains intercalated Fe2+ and Al3+ ions and has the chemical formula Ca2(MgO0.495·FeO0.202·AlO0.303)·(FeO0.248·AlO·Si1.536·O7). Stoichiometric calculations showed that FeO and Al2O3 have replaced about half of the MgO content in the akermanite structure. All this means that only ~4 wt% MgO content in the raw materials determines that ~60 wt% calcium magnesium silicates are formed in the synthesis product. Moreover, it was found that the formed akermanite practically does not react with CO2. Within 24 h of interaction with 99.9 wt% of CO2 gas (15 bar), the intensity of the akermanite peaks does not practically change at 25 °C; no changes are observed at 45 °C, either, which means that the chemical reaction does not take place. As a result, the compressive strength of the samples compressed from the synthesized product and CEN Standard sand EN 196-1 (1:3), and hardened at 15 bar CO2, 45 °C for 24 h, was only 14.45 MPa, while the analogous samples made from OPC clinker obtained from the same raw materials yielded 67.5 MPa.
ABSTRACT
Disruption of Neisseria denitrificans cells by microfluidizer was optimized using a factorial experiments design. The pH, pretreatment time, cell concentration, NaCl, ethylenediamine tetraacetic acid (EDTA) and Triton X-100 concentrations showed significant impact on disruption process and the process was optimized using central composite design and response surface methodology (RSM). Investigation revealed optimum conditions: 90 min pretreatment at pH 9.0 containing 110 g L(-1) cells (dry cell weight), 50 mM NaCl, 10 mM EDTA, and 0.2% Triton X-100. At optimized conditions, the disruption rate increased twofold, up to 5.62 ± 0.27 × 10(-3) MPa(-a); meanwhile, yield of intracellular content was increased by 26%, with 1 g of cells resulting in 113.2 ± 8.2 mg proteins, 12.1 ± 0.7 mg nucleic acids, 21.0 ± 1.2 mg polysaccharides, 0.99 ± 0.08 kU glucose-6-phosphate dehydrogenase (G6PD), and 10,100 ± 110 kU restriction endonuclease NdeI endonuclease. Particle size distribution analysis revealed nearly twofold larger cell lysate particles with diameter of 120 nm. For optimal release of intracellular content, 9200 J/g of energy was needed (95% confidence), yielding 6900 J/g energy savings. Model equations generated from RSM on cell disruption of N. denitrificans were found adequate to determine significant factors and its interaction. The results showed that optimized combination of known pretreatment and disruption methods could considerably improve cell disruption efficiency.
