Sequential electron beam and bioflocculation for treatment of textile nanodyes

Nanodyes are a new class of hazardous materials that are used in textile coloring. Their small size, color, stability and high dispersion characteristics pose a huge threat if they are released in open water systems. The aim of the present study is to test electron beam irradiation, bioflocculation and their sequential use for nanodye removal. The nanodye was obtained from a factory and was characterized using UV-visible spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, dynamic light scattering, zeta potential and energy dispersive X-ray (EDX). The obtained results show that applying 7.5 kGy electron beam irradiation results in complete color removal in 10 min for 50 and 100 ppm nanodye, while at 200 and 400 ppm concentrations, the decolorization reaches 90% but leaving a residual brownish color. Adding 5 mg mL^-1 of Serratia marcescens N2 biosurfactant resulted in agglomeration of 80% dye removal for 400 ppm nanodye after 24 h. On the other hand, the use of sequential electron beam and bioflocculation led to an initial removal of 80% in 1 h. The residual dyes were tested for toxicity on normal dermal HFB4 cells. The toxicity result was 1.19% after electron beam treatment, while those for sequential treatment and bioflocculation were 6.28 and 6.9%, respectively. It can be concluded that electron beam technology provides fast and highly efficient nanodye removal, while biosurfactants offer a low-cost, eco-friendly approach with a chance for dye retrieval.