Effect of Fe (III) on acid degradation of methylparathion
A study was undertaken to determine the transformation kinetic of methylparathion (O, O, -dimethyl O-4 nitrophenylphosphorotioate) in the presence of Fe(III) between pH 2 and 7. The Fe(III) was not electroactive under the conditions used in this study, and polarographic signals were exhibited by methylparathion and main degradation product only. Data suggest that hydrolysis of methylparathion in an acid medium is catalyzed by Fe(III) and the pesticide did not degrade in this medium without this cation. Methylparathion degradation was observed at all the pHs studied and was independent of the predominant chemical form of Fe(III) in the aqueous medium. The reaction was first-order with pH-dependent rate constant (k) values ranging from 3.3 × 10− 3 h− 1 to 7.0 × 10− 3 h− 1. The k values increased as pH decreased, suggesting that Fe(III) acted as an electrophile in the reaction mechanism.
Efficient biodegradation of acephate by Pseudomonas pseudoalcaligenes PS-5 in the presence and absence of heavy metal ions [Cu(II) and Fe(III)], and humic acid
Abstract
The present study was intended to investigate the biodegradation of acephate in aqueous media in the presence and in the absence of metal ions [Fe(III) and Cu(II)], and humic acid (HA). Biodegradations were performed using Pseudomonas pseudoalcaligenes PS-5 (PS-5) isolated from the heavy metal polluted site. Biodegradations were monitored by UV–Visible, FTIR, and electron spray ionization–mass spectrometry (ESI–MS) analyses. ESI–MS analysis revealed that PS-5 degraded acephate to two metabolites showing intense ions at mass-to-charge ratios (m/z) 62 and 97. The observed kinetic was the pseudo-first order, and half-life periods (t1/2) were 2.79 d−1 (of PS-5 + acephate), 3.45 d−1 [of PS-5 + acephate + Fe(III)], 3.16 d−1 [of PS-5 + acephate + Cu(II)], and 5.54 d−1 (of PS-5 + acephate + HA). A significant decrease in degradation rate of acephate was noticed in the presence of HA, and the same was confirmed by UV–Visible and TGA analyses. Strong aggregation behavior of acephate with humic acid in aqueous media was the major cause behind the slow degradation rate of acephate . New results on acephate metabolism by strain PS-5 in the presence and in the absence of metal ions [Fe(III) and Cu(II)] and humic acid were obtained. Results confirmed that Pseudomonas pseudoalcaligenes strain PS-5 was capable of mineralization of the acephate without formation of toxic metabolite methamidophos. More significantly, the Pseudomonas pseudoalcaligenes strain PS-5 could be useful as potential biological agents in effective bioremediation campaign for multi-polluted environments.
Electrochemical Behavior of Methylparathion Under UV Irradiation
Abstract The electrochemical behavior of methylparathion under UV irradiation was monitored by polarography in an aqueous medium (pH 6.5) at 254 and 366 nm, and the effects of atmospheric oxygen and TiO2 on methylparathion were also looked at. Dissapearance of the methylparathion and appearance of two major electroactive degradation products were observed. The reaction rate constants for the process ranged from 3.55 × 10−5 to 5.69 × 10−5s−1, and the reaction showed pseudo-first-order kinetics. The methylparathion transformation did not depend on the experimental conditions. Spectroscopic and electrochemical data suggest the presence of p-nitrobenzoic acid as a common electroactive product.