In this study, the recovery of gallium (Ga) and aluminum (Al) from the by-product of Bayer process, the electrofilter dust of a calcination plant, was studied. Factorial leaching tests were also designed based on the results of the preliminary tests. Effects of factors and their interactions on the extraction of Ga and Al were demonstrated using Analysis of Variance of the findings. In the factorial design, nitric acid (HNO3) leaching tests up to 43.4% Ga and 35.2% Al were leached from the electrofilter dust. The addition of oxalic acid (H2C2O4) significantly enhanced the sulphuric acid (H2SO4) leaching of the dust with up to 48.3% Ga and 39.6% Al extractions.