Colza oil bleaching through optimized acid activation of bentonite. A comparative study

The acid activation of an Algerian bentonite was investigated using a factorial 33 experiment design in order to improve the bleaching capacity in the colza oil processing. Optimized acid treatment of this bentonite gave rise to an effective bleaching earth in colza oil treatment. The 80 °C temperature value was regarded as being convenient in this study. For this purpose, the effects at 80 °C of three key parameters were investigated, namely the effects of the acid concentration in aqueous solution, the contact time and the clay to acid (S/L) ratio upon the clay effectiveness, regarded as the response function to be prone to modeling, simulation and optimization. The results showed that the acid concentration displays a stronger individual effect, as compared to the other parameters. In optimal activation conditions (acid concentration 31%, contact time 10 h and solid to liquid ratio 320 g/L), the highest bleaching capacity was found to be 99%. Comparison of the bleaching capacity from our bentonite shows that similar performances require less acid activated bentonite than any other bentonite. The acid acid-activated bentonite displayed also even higher color and chlorophyll removal than both the Tonsil and Maghnia standards, for similar bleaching earth amounts. The recommended features for the colza oil were obtained using only 1 wt.% of acid-activated bentonite, as compared to the Tonsil and Maghnia standard (1.2–1.4 and 2 wt.%, respectively). The model adequacy was also verified through additional bleaching experiment within the fixed parameters ranges, and was discussed.