Removal of methylene blue and methyl orange in polluted waters and food samples by green synthesized iron nanoparticles via UV-Vis spectrophotometry

In this research, a simple and rapid green synthesis was developed for the preparation of iron nanoparticles. The iron based nanoparticles were provided as nano-adsorbents for application of dispersive solid-liquid phase microextraction (DSLME) and simultaneous determination of azo dyes; methylene blue (MB) and methyl orange (MO) in wastewaters and food products. The release of azo dyes into the environment is a concern due to coloration of natural waters and due to the toxicity, mutagenicity and carcinogenicity of the azo dyes and their biotransformation products [1, 2]. In the first step of research, green tea extract was prepared by heating the dried leaves of green tea until boiling. After settling for 1.0 h, the extract was vacuum-filtered. Secondary, a solution of 0.10 M FeCl2•4H2O was added to green tea in 2:3 volume ratio. Following this, 1.0 M NaOH solution was added dropwise until the pH was adjusted to 6.0 and the formation of green tea coated nano particles (GTFe NPs) was marked by the appearance of intense black precipitate. The functionalized iron nanoparticles were then separated from aqueous media by solution evaporation on a hot plate, and then by drying the residue overnight in a fume-hood. The synthesized nano sorbent was used for extraction of analytes. The main factors influencing extraction such as; feed pH, adsorption time, aqueous feed volume, agitation speed, type of disperser solvent, ionic strength effect and the desorption conditions have been examined in detail. Under the optimized experimental conditions, linearity was observed in the range of 0.01–40 µg/mL for methylene blue, and two different ranges from 0.01-10 µg/mL and 10-35 µg/mL for methyl orange, with coefficient of determinations more than 0.991. The limits of detection were 0.003 and 0.004 µg/mL for methylene blue and methyl orange, respectively. The proposed procedure was successfully applied to the determination of analytes in food and wastewater samples with the satisfactory results.