Linear and crosslinked Polyurethanes based catalysts for reduction of methylene blue.

The large amount of synthetic dyes in effluents is a serious concern to be addressed. The chemical reduction is one of the potential way to resolve this problem. In this study, linear and crosslinked polyurethanes i.e. LPUR & CLPUR were synthesized from toluene diisocyanate (TDI), polyethylene glycol (PEG;1000g/mole) and tetraethylenepentamine (TEPA). The structure and morphology of synthesized materials were examined by FTIR, SEM and BET. The CLPUR was found stable in aqueous system with 0.80g/cm3 density and 16.4998m2 g-1 surface area. These materials were applied for the reduction of methylene blue in presence of NaBH4 . Both, polymers catalyzed the process and showed 100% reduction in 16 and 28mins., respectively, while, the reduction rate was significantly low in absence of these materials, even after 120mins. Furthermore, negligible adsorption was observed with only 7% removal of dye. The best reduction rates were observed at low concentration of dye, increasing concentration of NaBH4 and with more dosage of polymeric catalyst. The kinetic study of process followed zero order kinetics. It was hence concluded that both synthesized polymers played a catalytic role in reduction process. However, stability in aqueous system and better efficiency in reduction process endorsed CLPUR as an optimal choice for further studies.