Application of factorial design to study of heavy metals biosorption by waste biomass from beverage distillery

A full factorial design leading to 20 sets of sorption runs was conducted to study the influence of four variables (bleaching earth and biomass concentrations, pH, and sorption time) on the iron, nickel, and chromium removal from stainless steel effluent using waste biomass from a beverage industry. Similar factor effects and interactions were found for each metal involved in this biosorption study, and the main factors were pH (positive effect) and biomass concentration (negative effect). Response surface methodology was adopted and an empirical linear polynomial model constructed on the basis of the specific uptake (mg of metal/g of biomass as dry weight) for each metal species. Under optimized process conditions (pH 4.0, biomass concentration of 2.0 g/L, absence of Celite), uptake values of 155 mg of Fe/g, 38 mg of Cr/g, and 0.4 mg of Ni/g were achieved after 3 h. This corresponded to a reduction in heavy metals concentration of approx 94% for Cr, 57% for Fe, and 25% for Ni.