A combo technology of autotrophic and heterotrophic denitrification processes for groundwater treatment

In this study,a sequential process (heterotrophic up-flow column and completely mixed membrane bioreactors) was proposed combining advantages of the both processes.The system was operated for 249 days with simulated and real groundwater for nitrate removal at concentrations varying from 25 to 145 mg·L-1 NO3-N.The contribution of heterotrophic process to total nitrate removal in the system was controlled by dozing the ethanol considering the nitrate concentration.By this way,sulfur based autotrophic denitrification rate was decreased and the effluent sulfate concentrations were controlled.The alkalinity requirement in the autotrophic process was produced in the heterotrophic reactor,and the system was operated without alkalinity supplementation.Throughout the study,the chemical oxygen demand in the heterotrophic reactor effluent was (23.7 ± 22) mg·L-1 and it was further decreased to(7.5 ± 7.2) mg·L-1 in the system effluent,corresponding to a 70％ reduction.In the last period of the study,the real groundwater containing 145 mg·L-1 NO3-N was completely removed.Membrane was operated without chemical washing in the first 114 days.Between days 115-249 weekly chemical washing was required.     

Synthesis and Characterization of PEG-Sr Hexaferrite by Sol–Gel Conversion

Sr-M-type hexagonal ferrites have been prepared via a sol?Cgel route, and the effects of addition of different molecular weight polyethylene glycol (PEG) into the sol solutions on the static magnetic properties and particle morphology have been studied. Crystalline phases of the samples were determined by XRD analysis. FT-IR and TG analyses were used to prove the presence of PEG on SrFe₁₂O₁₉. The results showed that adding PEG with different molecular weight into the sol solutions affected the formation mechanism of SrFe₁₂O₁₉. Sr-M precursors prepared by various PEG types show different magnetic behaviors after pre-calcination at 150?^°C. This discrepancy is explained by the formation of a different phase during the synthesis of SrM particles.     

Filtering of satellite images in geological lineament analyses: An application to a fault zone in Central Turkey

Lineament extraction and analysis is one of the routines in mapping large areas using remotely-sensed data, most of which is the satellite images. In this study, we aimed to test different lineament extraction techniques including single band, multiband enhancements and spatial domain filtering techniques. A fast algorithm has been developed for time and cost limited surveys in an area with known dominant and/or any selected orientation of lineaments. During the study for single band analysis, histogram equalization and stretching, for multiband, Principal Components Analysis (PCA) and for spatial domain filtering Prewitt and Sobel filters are utilized. Furthermore, we have developed a new algorithm which consists of a combination of large smoothing filters and gradient filters, in order to get rid of the artificial lineaments which are out of interest and to determine discontinuous and/or closely spaced regional lineaments. The results are as follows; the number of lineaments and their total lengths are 218 285.3 km using the single band; 255 343.9 km in multiband enhancements, and 347644.9 km in the combination of spatial domain filtering including our algorithm. The 59.17 per cent increase in the number of lineaments and the 126.04 per cent increase in the total lengths indicate that a combination of spatial domain filters is the most cost-time efficient algorithm in lineament analyses.     

Effect of Fuel on the Synthesis and Properties of Poly(methyl methacrylate) Modified SrFe12O19 Nanoparticles

Nanosized strontium hexaferrite (SrFe₁₂O₁₉) has been synthesized by citrate, urea, oxalic, and glycine precursor via a sol-gel route with poly(methyl methacrylate) (PMMA) as a templating agent. Crystal structure, morphology, and magnetic properties of as-synthesized nanoparticles were characterized by XRD, SEM, FT-IR, and VSM techniques. The formation of strontium hexaferrite and its crystallite size in presence of different fuels were compared. The influence of different fuels was reflected on the phase purity, morphology of the final powders as well as the magnetic properties. Magnetic measurements revealed that samples prepared by citric acid and glycine as fuel have high specific saturation magnetization and moderate coercivity, while urea and oxalic acid fuels resulted in low phase purity, and thus inferior magnetic properties.     

Effect of Synthesis and Sintering Conditions on the Thermoelectric Properties of n-Doped Mg2Si

Magnesium silicide (Mg₂Si)-based alloys are promising candidates for thermoelectric (TE) energy conversion in the middle–high temperature range. The detrimental effect of the presence of MgO on the TE properties of Mg₂Si based materials is widely known. For this reason, the conditions used for synthesis and sintering were optimized to limit oxygen contamination. The effect of Bi doping on the TE performance of dense Mg₂Si materials was also investigated. Synthesis was performed by ball milling in an inert atmosphere starting from commercial Mg₂Si powder and Bi powder. The samples were consolidated, by spark plasma sintering, to a density >95%. The morphology, and the composition and crystal structure of samples were characterized by field-emission scanning electronic microscopy and x-ray diffraction, respectively. Moreover, determination of Seebeck coefficients and measurement of electrical and thermal conductivity were performed for all the samples. Mg₂Si with 0.1 mol% Bi doping had a ZT value of 0.81, indicative of the potential of this method for fabrication of n-type bulk material with good TE performance.     

Synthesis,conductivity and dielectric characterization of salicylic acid–Fe3O4 nanocomposite

We report on the synthesis of water dispersible salicylic acid –Fe₃O₄ nanocomposites via a co-precipitation route by using Fe(III) and Fe(II) chloride salts, and salicylic acid. Crystalline phase was identified as Fe₃O₄ and the crystallite size was obtained as 13 ± 6 nm from X-ray line profile fitting. As compared to the particle size of 20 nm obtained from TEM analysis these particles show polycrystalline nature. The capping of salicylic acid around Fe₃O₄ nanoparticles was confirmed by FTIR spectroscopy, the interaction being via bridging oxygens of the carboxylate and the nanoparticle surface. ac and dc conductivity measurements performed on the nanocomposite revealed semiconductor characteristics and varying trends with temperature due to reorganization of the nanocomposite. Permittivity measurements showed increasing dielectric constant with increasing temperature as expected from semiconductors. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled in the nanocomposite.