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.
Kinetic study of the biodegradation of glyphosate by indigenous soil bacterial isolates in presence of humic acid, Fe(III) and Cu(II) ions
Abstract The present study was executed to investigate the kinetics of the biodegradation of glyphosate in an aqueous medium. Three bacterial strains (Streptomyces sp., Bacillus subtilis, and Rhizobium leguminosarum) with excellent glyphosate-degrading capabilities were isolated from the agricultural soils and characterized on the basis of 16S ribosomal RNA (rRNA) gene sequencing methods. Biodegradation of glyphosate was performed with and without applications of metal ions [Fe(III) and Cu(II)] and humic acid (HA). In thirty days experiment, three strains were utilized 85-90% (with half life periods from 8.36 to 9.12 days) of glyphosate. Applications of Fe(III) and Cu(II) have inhibited the biodegradation to 70-80% (with half life periods from 10.03 to 11.15 days). In the presence of HA, biodegradation was inhibited significantly (57-70%) with half life periods from 12.54 to 13.09 days. Overall, glyphosate’s biodegradation inhibition order under different conditions was as HA > Cu(II) > Fe (III). UV-visible and mass spectrometric results indicated two concurrent pathways of degradation of glyphosate with major metabolites included glycine, aminomethylphosphonic acid (AMPA), sarcosine, glyoxylate, metaphosphoric acid and phosphate. Glyphosate breakdown by these three strains was achieved by the C-P lyase and the glyphosate oxidoreductase activity. Hence, these strains could be used as potential biological agents in the effective biodegradation campaign for other pesticide-contaminated sites.
Catalytic removal of tert-butyldimethylsilyl (TBS) ether by PVP-I
Abstract A mild, efficient and rapid protocol the deprotection of alcoholic TBDMS ethers using PVP-1 as catalyst in methanol, the procedure of deprotection of various TBDMS ethers were found to be very convenient, easy work-up, high yielding.