Waste management in zinc promoted allylation of aldehyde

Abstract

By using an efficient, sustainable and green procedure, the waste zinc material in Zn(0) promoted Grignard–Barbier type allylation of aldehydes has been successfully utilized as a reusable material for the adsorption of various dyes and also converted into the corresponding hexagonal wurtzite phase of ZnO. The need for aqueous NH₄Cl was justified by experimental and theoretical evidence, which suggests that the probable coordination of H₂O or NH₃ to the Zn center in both the intermediate and transition states is responsible for a lower activation energy and consecutively higher yield of products in both the cases. The conversion of the corresponding Zn(0) to its hydroxide or ZnO was studied by XRD analysis, which showed the facile conversion of Zn(OH)₂ to its corresponding ZnO after calcination of the sample at 300 °C. The reported method is a cost-effective chemical route for producing the ZnO nanomaterial at the gram level. The as-obtained zinc waste from allylation reaction shows an excellent ability as a reusable material for the adsorption of Congo red, methyl red and methylene blue and is expected to be useful in many other applications. The easy synthesis, effortless separation, efficient recycling and good adsorption capability of the waste zinc nanomaterial toward various dye molecules make it a competent candidate for wastewater treatment.