Electrochemical oxidation of benzene on boron-doped diamond electrodes

This work presents an electrochemical investigation of the benzene oxidation process in aqueous solution on boron-doped diamond (BDD) electrodes. Additionally, in order to determine the main products generated during the oxidation process, electrolysis and high performance liquid chromatography experiments were carried out. The complete degradation of this compound was performed aiming to a further application in waste water treatment. The cyclic voltammetry studies indicate that benzene is irreversibly oxidized in acid medium (H₂SO₄ 0.5 M) on the BDD electrode surface at 2.0 V versus Ag/AgCl in a diffusion controlled process. During the cycling, other products are generated, and a pair of peaks was observed that can be associated with the oxi-reduction of anyone of the following species: hydroquinone, benzoquinone, resorcinol or catechol. The electrolysis experiments were carried out at 2.4 and 2.5 V on the BDD electrode surface in a solution containing 1 × 10⁻² M of benzene (below the saturation concentration in aqueous solution), for 3 and 5 h, respectively. The main products measured were: hydroquinone, resorcinol, p-benzoquinone, catechol and phenol. The complete electrochemical benzene degradation was performed in the electrolysis experiments using a rotating BDD disc electrode (2.5 V for 5 h) and the main products detected were all measured at concentrations lower than 10⁻⁵ M in this condition. The boron-doped diamond electrode had proved to be a valuable tool for the electrochemical degradation of the benzene, a very stable chemical compound.     

Preliminary assessment of antimicrobial activity and acute toxicity of norfloxacin chlorination by-product mixture

Environmental Science and Pollution Research - Among drugs and personal care products, antibiotics arouse interest since they are widely used in human and veterinary medicine and can lead to the...     

Photocatalytic degradation of dyes in aqueous solution operating in a fluidised bed reactor.

This work reports a preliminary design of a new photochemical reactor and its application to photochemical degradation of two dyes, Crystal Violet and Azure B, operating in both batch and continuous processes. A novel kind of photocatalyst, consisting of ZnO immobilised in alginate gel beads, which is able to photodegrade organic dyes effectively, has been employed in the present study. When this photocatalyst, at a concentration of 1 g of ZnO per litre of alginate gel at 3%, was employed in batch process, almost total decolourisation of Crystal Violet in reaction times lower than 120 min was observed. Operating in continuous process at different residence times, it was possible to achieve a total decolourisation of both Crystal Violet and Azure B. Moreover, the total organic carbon content (TOC) was reduced to 90% in the former and to 52% in the latter. These results indicated that the photoreactor developed in the present work was able to degrade effectively dyes of different structures, revealing the non-specificity of the system.     

Estimation of the critical effect level for pollution prevention based on oyster embryonic development toxicity test: the search for reliability

In spite of the consideration that toxicity testing is a reduced approach to measure the effects of pollutants on ecosystems, the early-life-stage (ELS) tests have evident ecological relevance because they reflect the possible reproductive impairment of the natural populations. The procedure and validation of Crassostrea rhizophorae embryonic development test have shown that it meets the same precision as other U.S. EPA tests, where EC(50) is generally used as a toxicological endpoint. However, the recognition that EC(50) is not the best endpoint to assess contaminant effects led U.S. EPA to recently suggest EC(25) as an alternative to estimate xenobiotic effects for pollution prevention. To provide reliability to the toxicological test results on C. rhizophorae embryos, the present work aimed to establish the critical effect level for this test organism, based on its reaction to reference toxicants, by using the statistical method proposed by Norberg-King (Inhibition Concentration, version 2.0). Oyster embryos were exposed to graded series of reference toxicants (ZnSO(4) x 7H(2)O; AgNO(3); KCl; CdCl(2)H(2)O; phenol, 4-chlorophenol and dodecyl sodium sulphate). Based on the obtained results, the critical value for C. rhizophorae embryonic development test was estimated as EC(15). The present research enhances the emerging consensus that ELS tests data would be adequate for estimating the chronic safe concentrations of pollutants in the receiving waters. Based on recommended criteria and on the results of the present research, zinc sulphate and 4-chlorophenol have been pointed out, among the inorganic and organic compounds tested, as the best reference toxicants for C. rhizophorae ELS-test.     

Apert syndrome: what prenatal radiographic findings should prompt its consideration?

Apert syndrome was diagnosed in a newborn with typical facial and digital features whose only detected prenatal abnormality had been agenesis of the corpus callosum. This prompted a review of the central nervous system findings in all cases of Apert syndrome treated at the Craniofacial Center Boston Children's Hospital between 1978 and 2004. Two of 30 patients with Apert syndrome had prenatal identification of mild dilatation of the lateral cerebral ventricles and complete agenesis of the corpus callosum (ACC) documented with both ultrasound and MRI. Both had the common S252W mutation of FGFR2. Though cranial and orbital malformations typical of Apert were eventually seen in these fetuses in the third-trimester, even in retrospect, these were not detectable at mid second-trimester, ultrasound screening for congenital malformations. Hand malformations also went undetected in the second-trimester despite extensive imaging by experienced radiologists. We conclude that prenatal ultrasonographic identification of mild ventriculomegaly or ACC should stimulate a careful search for features of Apert syndrome and prompt follow-up imaging to look for bony abnormalities that have later onset. Prenatal molecular testing for Apert mutations should be considered in cases of mild ventriculomegaly and ACC. Copyright © 2006 John Wiley & Sons, Ltd.     

Deflector Designs for Fish Habitat Restoration

Paired current deflectors are structures that are installed on each bank of a river to locally reduce the width of the channel, thereby creating flow acceleration and promoting scouring. These instream habitat structures have been used extensively in restoration projects to create pool habitat for fish, but there are many discrepancies in deflector design recommendations in terms of orientation, height, and length. Our objectives were to (1) examine how the angle, height, and length of paired deflectors affect scour hole dimensions and potential for bank erosion; and (2) test the applicability to paired deflectors of existing equations for scour hole depth and volume. Three deflector angles (45°, 90°, and 135°), two deflector heights (with flow under and over the deflector height), and two lengths (reducing the width by 25% and 50%) were investigated using uniform sand in a laboratory flume. Results showed a 26–30% smaller scour depth resulting from 45° deflectors than from 90° deflectors and a 5–10% smaller scour depth for 135° deflectors compared to 90° deflectors. The volume of scour and the potential for bank erosion were greater when flow was under the height of the deflectors rather than overtopping and when the length of deflector was increased. When flow was under the deflector height, 135° deflectors had the highest amount of bank erosion; whereas during overtopping flow conditions, 90° deflectors had the greatest bank erosion potential. Values predicted by the model of Kuhnle and others were closest to observed scour depth and volume measurements. The assumption that upstream-oriented deflectors always generate the largest scour should be revised.