NOPR Collection:

Numerical investigation of stratified flow-parallel reaction microchannel system: A deterministic approach

Tue, 01 Sep 2015 00:00:00 GMT

Title: Numerical investigation of stratified flow-parallel reaction microchannel system: A deterministic approach Authors: Antony, Rahul; Nandagopal, Giri M S; Rangabhashiyam, S; Anu, N; Selvaraju, N Abstract: A deterministic based analytical model has been developed to study the mass transfer characteristics between the reactants in a liquid- liquid parallel flow microchannel reactor. Since each phase is continuous and parallel to each other, the interface between the phases is well defined. Convection and diffusion mass transfer mechanisms with a third order reaction is considered for the design of single dimensional deterministic model. The model is developed by considering the transport phenomena of the system and solved with the help of pdepe solver in Matlab 7.6.0. The effects of residence time with various concentration profiles are discussed. The study reveals that the concentrations of desired and undesired products mainly depend on the flow velocity and concentration gradient of the reactants. The time required for the equilibrium is inversely proportional to the pseudo mass transfer coefficient of the system. Page(s): 258-263

Micellar effects on the complex formation reaction of copper (II) with ciprofloxacin

Tue, 01 Sep 2015 00:00:00 GMT

Title: Micellar effects on the complex formation reaction of copper (II) with ciprofloxacin Authors: Panda, Akshya Kumar; Bhattamisra, S D Abstract: Complex formation between Cu (II) and ciprofloxacin in aqueous micellar media has been reported. Conventional spectroscopic and pH-metric methods have been adopted to investigate the micellar effects. Both cationic (cetyltrimethylammonium bromide, CTAB and cetylpyridinium chloride, CPC) and anionic (sodiumdodecylsulphate, SDS) surfactants have been used in the investigation. Results indicate considerable micellar effects with SDS, while the effects of CTAB and CPC are marginal. Deprotonation of ciprofloxacin hydrochloride is hindered in aqueous SDS medium, but the complex formation between Cu (II) and ciprofloxacin is considerably enhanced. The Cu (II) ciprofloxacin complex in SDS medium absorbs at 657 nm. The absorbance – [SDS] profile exhibits double maxima, one below cmc and the other almost at the cmc of SDS. The results are explained in terms of pseudo-phase model whereby it is assumed that the complex formation reaction predominantly occurs on the negatively charged SDS micellar surface compared to the bulk aqueous phase. From the rate-[SDS] profile, binding constant of ciprofloxacin-SDS is found to be 20. Page(s): 253-257

Bio-chemical leaching of kaolinite-hematite-boehmite type bauxite ore

Tue, 01 Sep 2015 00:00:00 GMT

Title: Bio-chemical leaching of kaolinite-hematite-boehmite type bauxite ore Authors: Gurevich, Yu L; Teremova, M I; Bondarenko, G N; Kislan, S L; Abhilash Abstract: Low grade bauxites of Severo-Onezhsky and Sredne-Timansky deposits of Russia have been evaluated for their amenability towards bioleaching. Two microbial isolates of Bacillus genera have been isolated in Zak medium and enriched to conduct leaching experiments of bauxites. The bacteria are chosen due their specific ability to secrete exo-polysaachrides (EPS), which is believed to be very beneficial in dissolution-cum-flocculation of aluminosilicates. The microbes have been able to leach nearly 50% alumina and nearly 10-35% SiO₂ and Fe₂O₃. Chemical leaching experiments with citric and oxalic acids on bauxite leaching result in a maximum extraction of aluminum to be nearly 39% at elevated concentrations of leaching agents and 2-8 hours residence time. Page(s): 248-252

Influence of three selection pressures on aerobic granulation in sequencing batch reactor

Tue, 01 Sep 2015 00:00:00 GMT

Title: Influence of three selection pressures on aerobic granulation in sequencing batch reactor Authors: Bindhu, B K; Madhu, G Abstract: Aerobic granulation is a promising biotechnology for wastewater treatment. The formation and development of granules and the pollutant removal are closely associated with hydrodynamic shear force, settling time and volume exchange ratio (VER), which are proved to be the selection pressures. Three different values of shear force (2, 3 and 4 cm/s), settling time (3, 5 and 10 min) and VER (25, 50 and 75%) have been experimented in sequencing batch reactor (SBR) in seven trials for the optimal performance of aerobic granulation. Higher shear force could develop smaller and more compact granules with better settling behaviour, but chemical oxygen demand (COD) removal is not found to improve beyond a value of 97.9% for shear force above 3 cm/s. A settling time as low as 3 min could result in very good biomass growth and formation of granules with sludge volume index (SVI) as low as 23 ml/g. Aerobic granulation is not successful at a long settling time of 10 min. Higher the VER, the lower is the SVI and the more efficient is the COD removal. Page(s): 241-247