Statistical design of experiments as a tool for optimizing the batch conditions to Cr(VI) biosorption on Araucaria angustifolia wastes.

In order to reduce the total number of experiments for achieving the best conditions for Cr(VI) uptake using Araucaria angustifolia (named pinhão) wastes as a biosorbent, three statistical design of experiments were carried out. A full 2(4) factorial design with two blocks and two central points (20 experiments) was experimented (pH, initial metallic ion concentration-C(o), biosorbent concentration-X and time of contact-t), showing that all the factors were significant; besides, several interactions among the factors were also significant. These results led to the performance of a Box-Behnken surface analysis design with three factors (X, C(o) and t) and three central points and just one block (15 experiments).