Ozonation of CI Reactive Black 5 using rotating packed bed and stirred tank reactor

This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry     

The reduction of sulphur dioxide by carbon monoxide on a La0.5Sr0.5CoO3 catalyst

The semiconducting perovskite oxide, La_0.5Sr_0.5CoO₃, is a catalyst for the reduction of sulphur dioxide by carbon monoxide. Unlike aluminia-supported metal catalysts, La_0.5Sr_0.5CoO₃ tolerates high levels of oxygen in the gas stream if sufficient carbon monoxide is present to react with all the oxygen. Water vapour (2%) does not adversely affect the reaction; unwanted byproducts H₂S and COS are reduced for contact times less than 0.25 s. A computer model is used to predict equilibrium gas compositions for systems containing oxygen and water vapour. During the reaction the catalyst itself reacts with sulphur producing metal sulphides, possibly of simple cubic structure. The perovskite sulphides LaCoS₃ and La_0.5Sr_0.5CoS₃ are theoretically unstable.     

Reduction of Sulfur Dioxide on Perovskite Oxides

Reactions of sulfur dioxide on perovskite oxides have been investigated from two distinct standpoints. First sulfur dioxide is a poison for reactions of carbon monoxide, nitric oxide and hydrocarbons (1-11). How to mitigate this poisoning and how to regenerate the catalyst is therefore of importance when designing pollution abatement catalysts for motor cars. However the reaction between sulfur dioxide and carbon monoxide, catalyzed by perovskites, itself may provide an important route for the removal of a major pollutant (12-16).     

A rare and little known variant of hypospadias

Hypospadia is a congenital defect presenting as different variants of dysplasia of the distal urethra with ectopy of the urethral external orifice and distortion of the penis. A variant of hypospadia not yet described in Russian medical literature was observed in a newborn boy. He had normal penis and scrotum, but on the under-side of the penis there was a site of thin skin protruding as a resonance bag in urination. At the site of the thin skin the back urethral wall was absent with a cavity covered by the thin skin. In urination urine filled the cavity blowing up the skin above it to the form of the resonance bag. This variant of hypospadia was designated as segmental urethral hypoplasia.