Fig. 3From: Optimization of chromium and tannic acid bioremediation by Aspergillus niveus using Plackett–Burman design and response surface methodologyThree dimensional plots of A. niveus. a Three-dimensional plot of residual Cr(VI) as a function of metal dose and glucose at constant tannic acid (2.75%) and NH4Cl (1 g/L). b Three-dimensional plot of residual Cr(VI) as a function of metal dose and tannic acid at constant glucose (0.5 g/L) and NH4Cl (1 g/L). c Three-dimensional plot of residual Cr(VI) as a function of NH4Cl and metal dose at constant glucose (0.5 g/L) and tannic acid (2.75%)Back to article page