Determination of azine and triphenyl methane dye in wastewater using polyurethane foam functionalized with tannic acid

A simple and sensitive spectrophotometric method for the determination of azine (neutral red) and triphenyl methane (rosaniline) dye has been developed using tannic acid-polyurethane foam (TPF). TPF was prepared by coupling a polyhydroxypolyurethane foam matrix with tannic acid. TPF was characterized using a combination of analytical methods including IR and NMR spectroscopy, elemental analysis, density and pHZPC. The qualitative and quantitative determination of dyes is based on its sorption on the surface of the TPF. The sorption behavior of dye onto the TPF was investigated by batch and dynamic processes. The maximum sorption of neutral red and rosaniline was in the pH range of 7-9. The kinetics of sorption of the dye by the TPF was found to be fast with average values of half-life of sorption of 1.2 min. The equilibrium process was well described by the Freundlich isotherm model. The visual detection limit of dye in aqueous solution is 0.1 μg mL^-1. The Sandell’s sensitivity is 0.26 ng cm^-2 with molar absorptivity 1.3 × 10⁶ L mol^-1 cm^-1. The average sorption capacity of TPF and the recovery of dyes were 0.47 mmol g^-1 and 96.4 % (RSD ~ 1.5%, n=7). The method has been applied to various wastewater samples.