Synthesis, characterisation and application of ZnO-bentonite nanocomposite for preconcentration and spectrophotometric determination of trace amounts of bromocresol purple in water and wastewater samples

Abstract

ABSTRACTZnO nanocomposite was synthesised by immobilisation of ZnO nanoparticles on sodium bentonite surface and the prepared nanocomposite (nZnO-Bn) was used to remove, preconcentrate and to determine spectrophotometrically trace amounts of an anionic dye (bromocresol purple, BCP) in tap, Nile, sea and industrial water samples. nZnO-Bn was characterised via X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller (BET) technique. Factors effect on BCP removal as shaking time, solution pH, BCP initial concentration and temperature was explored in a batch mode. In addition, sorption kinetics, isotherms, thermodynamics, and reusability were studied. Pseudo-second-order kinetic model explained well the experimental results. Freundlich isotherm has been found to have a high correlation coefficient. The sorbed BCP was successfully desorbed using acetone and determined spectrophotometrically. The nZnO-Bn nanocomposite could be regenerated efficiently and recycled up to the fifth cycle with a removal efficiency of more than 83%. The proposed method for BCP determination provided a wide linear range from 15.63 to 2000 μg L−1 of BCP. Moreover, the recoveries of BCP from spiked water samples ranged from 90.34% to 100.12%, indicating the suitability of nZnO-Bn as an efficient sorbent for the removal and determination of BCP in real samples.