Prediction of zinc extraction from aqueous solution using iron oxide nanoparticles embedded formulation for tuning emulsion liquid membrane stability

The contamination of industrial wastewater with heavy metals poses a threat to both aquatic and human life. In this study, emulsion liquid membrane (ELM) as a great potential process was applied to remove and recover zinc (Zn) from industrial wastewater. However, the instability of ELM continues to hinder their commercialization. Consequently, this research focuses on studying the stability of water-in-oil-in-water (W/O/W) emulsion in ELM with the aid of nanoparticles in the formulation. The emulsion stability measurement based on volume and pH were applied. Additionally, a digital microscope with a camera is utilized to assess emulsion stability in terms of globule size. ELM formulation with incorporation of iron (III) oxide (Fe2O3) nanoparticles, and blended surfactant (Span 80 and Tween 80) were employed. The research investigates the optimal process parameters for W/ O/W emulsion stability. This includes varying parameters such as nanoparticle concentration (0-0.08 % w/v), treat ratio (1:3 - 1:7), agitation speed (200-600 rpm), and time (1 - 5 min). The W/O/W emulsion with the highest stability was achieved at Fe2O3 concentration of 0.04 % (w/v), a treat ratio of 1:3, agitation speed, and time of 300 rpm and 3 min, respectively. Under these stable conditions, Zn extraction was predicted by simulation using a mathematical boundary breakage model of the process. The effects of the treat ratio, concentrations of synergist carrier (D2EHPA and Cyanex 302), stripping agent (acidic thiourea), and external feed phase were examined. The result showed that almost 100 % of Zn was extracted within 3 min at a 1:3 treat ratio, 0.03 M synergist carrier, and 1.37 M acidic thiourea for 50 ppm Zn concentration in the feed phase. This research highlights the tremendous potential of nanoparticle presence in enhancing emulsion stability and improving Zn extraction.