Abatement of some commercial fungicide content from model dispersions by a new thiourea-graft-polyethyleneimine derivative

Abstract

A new derivative of polyethyleneimine (PEI) with 9% degree of substitution of its primary and secondary amino groups with thiourea moieties (TU9-PEI) has been synthesized and investigated as flocculant in model suspensions of commercial fungicide formulations Dithane M45, Melody Compact 49 WG, Cabrio®Top, and their mixtures. The structure of TU9-PEI, obtained by an aqueous one-pot strategy involving formaldehyde mediated coupling of PEI and TU, was confirmed by FTIR and 1H NMR spectroscopy as well as the streaming potential measurements. The settling time, polymer dose, and fungicide type and concentration were the parameters used for assessing the flocculation ability of the new polycation sample. The UV-Vis spectroscopy measurements revealed a good removal efficiency of TU9-PEI for all of the fungicides investigated, between 88 and 94%. Slightly higher removal percent was found for greater fungicide concentrations. The charge neutralization was indicated by zeta potential measurements (values close to zero recorded at the optimum polymer dose) as the main mechanism which contributed to the Dithane and Cabrio®Top particle removal and a combined effect of the TU9-PEI/fungicide particle electrostatic attractions and hydrogen bonds between both the amine and thiourea groups of the polycation chains and the hydroxyl ones on the copper oxychloride particles (negative values) in case of the Melody Compact 49 WG particle separation. Particle size and surface morphology analysis data gave supplementary evidences regarding the TU9-PEI ability to separate the fungicides investigated from simulated wastewater.