The use of nanovermiculite catalyst in the study of removal of the organic load and degradation of atrazine via ozone process in RPB reactor

Abstract

The main objective of this study is the degradation of a synthetic solution of atrazine by a modified vermiculite catalyzed ozonation, in a rotating packed bed (RPB) reactor. A 0.5?L RPB reactor was used to perform the experiments, using a Central Composite Design (CCD) response surface to construct the quadratic model based on the factors: pH, catalyst concentration and reactor rotation frequency. The response variable was the removal of the organic load measured in terms of Chemical Oxygen Demand (COD). After the complete quadratic model was constructed through the response surface, the COD degradation process had an optimal removal of 41% under the following conditions: pH 8.0, rotation of 1150?rpm and catalyst concentration 0.66?g L^?1.     

Salinity modulates biochemical and histopathological changes caused by silver nanoparticles in juvenile Persian sturgeon (Acipenser persicus)

Environmental Science and Pollution Research - The objective of this study was to evaluate the effect of salinity on the acute and sub-chronic toxicity of silver nanoparticles (AgNPs) in Persian...     

Environment-health link in a context of urban agricultures: studies of oral exposure to pollutants in order promote the human health

Environmental Science and Pollution Research -     

Attenuation potentials of royal jelly against hydroxyurea-induced infertility through inhibiting oxidation and release of pro-inflammatory cytokines in male rats

Environmental Science and Pollution Research - Hydroxyurea (HDU), a class of antineoplastic drugs, has a powerful efficacy in the treatment of several types of malignancies. However, it has...     

Activated carbon produced from waste coffee grounds for an effective removal of bisphenol-A in aqueous medium

Environmental Science and Pollution Research - Bisphenol-A is widely used chemical in industry and unfortunately often detected in natural waters. Considered as an emerging pollutant, bisphenol-A...     

Susceptibility of different yeast species to environmental toxic metals

The purpose of the study reported here was to investigate the relative resistance of yeast species to various metallic and metalloid ions, with a view to gaining more knowledge on this subject, as resistant species may become dominant in habitats contaminated with the relevant metals. Saccharomyces cerevisiae, Candida albicans and Candida tropicalis were grown in media containing different concentrations of mercury (as HgCl(2)), cadmium (as CdCl(2)), lead (as Pb(CH(3)COO)(2)), arsenic (as Na(2)HAsO(4)) and selenium (as Na(2)SeO(3)) for various intervals. Invariably, the two Candida species turned out to be more resistant to all the metals studied than S. cerevisiae. The metal showing the highest toxicity for these species was mercury, with cadmium being the second, lead, the third and arsenic and selenium being the least toxic elements. Strains showing resistance to mercury were isolated, even in the case of S. cerevisiae.     

The fate of endosulfan in aquatic ecosystems

Endosulfan, one of the major pesticides used in cotton-growing, is of environmental concern because of its toxicity to fish and its apparent persistence in the environment. This study examines the distribution and degradation pathways for endosulfan in an aquatic system and the processes by which it is removed. In the alkaline waters of the cotton region, hydrolysis is the dominant degradation process. By this mechanism alone, the expected half-lives for the alpha- and beta-endosulfan isomers were found to be 3.6 days and 1.7 days, respectively. Partitioning studies showed, however, that the major proportion of endosulfan would associate with the sediments (log Koc(alpha) 3.6 and log Koc(beta) 4.3). Field studies confirmed the presence of high concentrations in sediments. Microcosm experiments showed that loss of endosulfan was slower than predicted from hydrolysis rates. Models are presented to explain how desorption from sediment limits the loss of endosulfan from a system.     

Quantifying the sorption of organic chemicals on sediments

The use of a reference compound to quantify the sorption of nonpolar organic chemicals is proposed. This is because organic carbon normalized sorption coefficients (K_OC) do appear to be dependent on the type of sediment, and are thus not generally applicable to characterize the sorption properties of chemicals. Therefore, in this paper the hypothesis that nonpolar chemicals sorb in a constant ratio, independent of the sediment, has been investigated. Evidence for this hypothesis is shown with data from the literature. This enables one to compare sorption properties of nonpolar compounds on different sediments, if the differences between the sediments are normalized with a reference chemical rather than with the organic carbon content. Sediments with an organic carbon content of less than 0.1% seem to be unsuitable, because the compounds do not sorb mainly on the organic carbon, but also on other parts of the sediment. Sorption coefficients of compounds with aqueous solubilities in the μg per liter range or octan-1-ol water partition coefficients of more than 10⁵ are strongly influenced by the experimental techniques used. For these compounds the sorption coefficients measured by different techniques are less comparable. To enable comparison of sorption coefficients of hydrophobic chemicals, the use of a chlorobenzene as a reference compound in sorption experiments is suggested.     

Residues of phosphamidon in rice fields

Thirty-day-old seedlings of rice plants (IR-20 variety) from the nursery were transplanted into experimental plots and after 52 days were sprayed with phosphamidon (Dimecron 85% EC) at two dose-rates (0.38 kg a.i. ha(-1) and 0.76 kg a.i. ha(-1)). Residues of phosphamidon in the plant, soil and water were analysed by GLC, at various time intervals, and were found to decrease steadily up to 15 days. A second application of the pesticide was made on day 113 and grains harvested on day 138. The residue level in the plants was 0.12 microg g(-1) and in the grains 0.04 microg g(-1) with the high dose. This is slightly below the EPA prescribed tolerance level of 0.05 microg g(-1). The residues in both soil and water were very low, 24 h after spraying.