Treatment of refractory organics from membrane rejects using ozonation

The reject water or retentate generated from membrane application for recovery of water from tannery wastewater treatment contains certain refractory organics. These refractory organics are present in substantial quantity in the condensate of reject water also. Hence the treatment of rejects using conventional methods is rather difficult. In this paper, an attempt has been made to treat the reject water from the reverse osmosis (RO) and nano filtration (NF) operation on tannery wastewater using ozonation treatment technique. Ozonation studies on RO and NF rejects indicate that ozone dose of 80 and 100mg/min for 60 and 70 min contact time achieves 59 and 78% chemical oxygen demand (COD) reduction, respectively. The mass balance in ozone indicates the ozone consumption for RO and NF rejects varies from 2.4 to 3.4 and 2.8 to 4.5 g/g of COD removed respectively. The results suggest that ozonation of RO and NF rejects would significantly reduce the refractory organic pollutant loading into the environment from wastewater reuse facility.     

Effects of neutron irradiation on current gain and noise in siliconavalanche photodiodes

The authors report on an experimental study of the effects of fission neutron irradiation on a silicon avalanche photodiode, which is a photodetector that is often used as the front end of a receiver in a fiber-optic link. Measurements indicate that there is a degradation in the current gain and a decrease in the multiplication noise after irradiation. Some recovery is found to occur after three days. The device, however, continues to behave linearly after irradiation     

Separation of n-hexane/acetone mixtures by pervaporation using natural rubber membranes

Natural rubber (NR) membranes crosslinked by four different systems viz., conventional (CV), efficient (EV), dicumyl peroxide (DCP), and a mixture consisting of sulfur and peroxide (mixed), were employed for the separation of n-hexane/acetone mixtures of different compositions. The membranes exhibited preferential permeation toward n-hexane because of the closer solubility parameter values. The selectivity of the membranes depended on the nature and distribution of crosslinks between the macromolecular chains of the membrane but was independent on the thickness of the membrane. The effects of feed composition, cure time of the membranes, and the molecular size of the permeate on the permeation flux and selectivity were investigated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2597–2603, 1997     

Pervaporation of chlorinated hydrocarbon-acetone mixtures through poly(ethylene-co-vinyl acetate) membranes

Crosslinked and uncrosslinked ethylene-vinyl acetate copolymer membranes were prepared. The permeation characteristics in the pervaporation process were examined using carbon tetrachloride-acetone mixtures. Modified membranes exhibit carbon tetrachloride permselectivity, but unmodified membranes did not display the permselectivity of crosslinked polymer. Furthermore, membranes modified with dicumyl peroxide (DCP) showed a higher flux and selectivity than those of benzoyl peroxide (BP) modified ones. The effects of feed concentration, molecular size, and polarity of the permeating species on pervaporation were analyzed. The influence of crosslinking density of the membranes on pervaporation was also analyzed. The maximum separation and flux were found to be associated with an optimum amount of crosslinking agent in the membrane. A mixture of chloroform and acetone having a composition near the azeotropic region was also separated by the pervaporation technique. © 1996 John Wiley & Sons, Inc.     

Thermoluminescence properties of γ-irradiated KCaSO<Subscript>4</Subscript>Cl: X (X = Ce,Dy, Mn or Pb)

A new phosphor KCaSO₄Cl is very interesting for thermoluminescent properties. In this article, we present results concerning the main dosimetric properties of KCaSO₄Cl activated by Ce, Dy, Mn, and Pb at various concentrations. Polycrystalline KCaSO₄Cl: (Ce; Dy; Ce, Dy; Mn; Ce, Mn; Pb and Ce, Pb) phosphors prepared by solid state diffusion method have been studied for its thermoluminescence (TL) characteristics. The TL glow curves of γ-irradiated all KCaSO₄Cl samples show strong single glow peaks indicating that only one type of trap can be formed. The intensity of the TL glow peaks increases with increase of the γ-ray dose to the samples but the intensity of the TL glow peaks increases with decrease of the concentration of the dopent. The sensitivity of all the phosphors presented here are more than that of CaSO₄: Dy. The phosphors have a simple TL glow curve structure with a prominent peak at the lower temperature side. TL response, fading, reusability of the phosphors are also studied, and it is found that the phosphor is quite suitable for use in dosimetry of ionizing radiations.     

Nondegenerate solution of TE and TM modes in step-index fibers using power-series expansion method

The power-series expansion method has been used to compute the exact cutoff frequencies of TM modes in step-index fibers for various values of relative refractive index difference (Δ), ranging from 0.005 to 0.1. The difference between the propagation constants of TM and TE modes, intermodal delay between TM and TE modes, and their variation with respect to the relative refractive-index difference has also been calculated. Numerical results show that for a fiber withDelta = 0.005the intermodal delay between TM01and TE01modes is of the order of 1.5 ps/km at frequencies far away from cutoff, whereas it is of the order of 0.62 ns/km forDelta = 0.1.     

Eu3+ Doped Lithium Silicaborate Glasses for LED Application

Glass Physics and Chemistry - In the present study Eu2O3 doped Li2O–Si2O–B2O3 glasses (LSBE) were synthesized by the melt quench technique. The physical, thermal, and spectroscopic...     

Vinyl Monomers from Hydrogenated Sardine Oil - Their Preparation and Characterization

Preparation of vinyl monomers viz., acrylic, methacrylic, allyl and vinyl esters and vinyl ethers based on mixed fatty acids or alcohols derived from hydrogenated sardine oil is described. Their chromatographic behaviour both on direct and argenlated-TLC, were studied. The characterization of these products by spectroscopic techniques viz, IR and NMR is discussed.     

Electrical and optical properties of lithium borate glasses doped with Nd2O3

Glass series with general formula 25Li2O-(75-x)B2O3-xNd2O3 was prepared by conventional melt quench technique. Electrical and optical characterizations of these glasses were carried out. It was observed that conductivity of glasses decreased and activation energy increased with the addition of Nd2O3. The density and refractive index of the glasses increased while optical band gap and radiation length decreased due to structural changes.     

Enhancement in electrical conductivity of Li<Subscript>2</Subscript>O: B<Subscript>2</Subscript>O<Subscript>3</Subscript>: V<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

The study of electrical conductivity of 30Li₂O: (70 − x) B₂O₃: xV₂O₅ glass samples has been carried out. The results have been explained by dividing the temperature range into two regions. In region I, conductivity shows Arrhenius behaviour for all the samples. The conductivity increases with addition of V₂O₅. The results have been explained in the light of Anderson and Stuart Model. In region II, an anomalous enhancement in the conductivity is observed for all the samples up to certain temperature beyond which the conductivity decreases. The enhancement in the conductivity in the annealed glass sample has been attributed to nanocrystallization.