Derivation and characterization of secondary zinc oxide from rubber glove manufacturing wastewater via adsorption-desorption-precipitation route

Abstract

The demand for zinc oxide surged during the Covid-19 pandemic as gloves became a necessity in daily life. The washing-off of the zinc oxide used to activate crosslinking in glove latex, generates hazardous zinc-containing wastewater, which is conventionally treated by chemical precipitation using lime and caustic soda. This produces large volumes of hazardous sludge. This study aims to demonstrate removal and recovery of zinc from real wastewater via adsorption-desorption-chemical precipitation approach to produce utilizable secondary zinc oxide. A low-cost palm shell activated carbon was used to adsorb zinc from raw wastewater with 93% efficiency, straightforwardly reducing zinc concentration below 2 mg/L (discharge standard) within 45 min, at pH 7 and 60 °C. Subsequent desorption with 0.3 M HCl facilitated recovery of 63% of secondary zinc oxide from the desorption solutions via chemical precipitation and calcination path. Morphological analysis of the synthesized secondary zinc oxide confirmed high crystallinity of hexagonal wurtzite crystalline structure of typical spherical and nanorods particle shapes measuring 102 nm in size. Surface area comprised of considerable 59.02 m2/g, with pores volume and size of 0.1735 m3/g and 11.76 nm, respectively. This study demonstrated successful recovery of zinc ions from raw industrial wastewater to produce good quality secondary zinc oxide, creating opportunities for zinc recycling, reduction in consumption of chemicals and chemical sludge volume, steering way towards sustainable practices in rubber gloves manufacturing sector.