Process development for sodium permanganate production by waste management of industrial sludge of zinc oxide ores recovery plants: Experimental and simulation study

Abstract

Produced sludge in the hot refining stage of zinc oxide ores recovery plants contains huge amount of MnO2. Aspen Plus modeling assembled based on Taguchi experimental design has been utilized to study a new plan for sodium permanganate (NaMnO4) production from an industrial sludge containing MnO2. The optimized results by Taguchi approach has been applied as the initial data for the modeling and sensitivity analysis of process using Aspen Plus software. The influence of key operating factors such as acid concentration of electrolysis spent solution (CSE) in the range of 60−90 g/l, reaction temperature (TR) in the range of 70−100 °C, stirring speed of solution (S) in the range of 100−400 rpm, reactions time (τ) with value of 1−3 h, MnO2 content in the industrial sludge (WMnO2) with values of 10–30 %, solid to liquid ratio (S/L) with amounts of 1:1−1:4, additives amounts (WAdditives) with values of 5−20 wt.% and oxygen gases pressure (PO2) in the range of 1–2.5 at m have been studied on the production efficiency of NaMnO4. The optimum condition to maximize NaMnO4 production from the industrial sludge has been found as: CSE=80 g/L, TR = 100 °C, S=300 rpm, τ=2.0 h, WMnO2 = 8 wt.%, S/L ratio = 1:2, WAdditives = 20 wt.% and PO2 = 2.5 atm. The maximum NaMnO4 production during designed process at optimized condition was more than 70 %. Also, under optimum condition, zinc extraction efficiency and removal percentage of Fe2+, Co2+, Mn2+ impurities from the industrial sludge were more than 85 % and 95 %, respectively.