Optimization of Electrometal-Elektrowinning Cobalt Process from the Slag of Nickel Pig Iron (NPI)

Slag from the manufacturing of nickel pig iron (NPI) from laterite soil is still containing 823.7 ppm of cobalt. In this research, the separation process is carried out from slag NPI by using the Response Surface Method (RSM). This method is to determine the optimum conditional process of Electrometal Electrowinning (EMEW) and get an equation model to see the correlation between a variable and know the most significant interfactor interaction. This research was conducted using three parameters, consists of duration of operation, potential voltage, and variable of boric acid. The first step in electro-metal electrowinning is leach the slag using acetic acid, and then extracted in two steps by versatic acid 10 and then with cyanex 272. The organic phase from this extraction then stripped using 6 M sulphuric acid so obtained aqueous phase at pH 5.5 with the highest cobalt content. The best condition of electro-metal electrowinning is obtained at 4.5 V, 2 hours, and 0.5 M of boric acid with 45.8273% of cobalt recovery. Based on statistic analysis using software, time is an individual factor which gives the most significant influence to the percent of generating electrowinning, while the most significant interfactor interaction based on the sequential model sum of squares, lack of fit test, model statistic, and analysis of variance (ANOVA) analysis is a quadratic model with R2 of 0.9544.