Lead biosorption capability of two biosorbents of aquatic origin based on Box-Behnken design

Considering the importance of using biosorbents to remove metal ions from wastewater and aquatic ecosystems, in this study the potential of using scales of two fish species (rainbow trout; Oncorhynchus mykiss and Caspian kutum; Rutilus kutum) to reduce the concentration of lead in aquatic environments were evaluated based on Box-Behnken design. The effects of some important parameters (biosorbent dose, biosorbent size, contact time, temperature, initial concentration, pH and salinity) on the adsorption capacity of the biosorbents were also evaluated. Among the seven studied factors, the effect of initial concentration, pH and adsorbent dose on the concentration of lead adsorbed by the two adsorbents was significant (P<0.05), while temperature and adsorbent size had no significant effect on the adsorption of lead by the sorbents. The initial concentration was the most effective independent variable (with a positive effect). The maximum adsorption capacities of lead by the two adsorbents are comparable to those of other adsorbents of aquatic origin, evaluated by other researchers. The maximum adsorption capacity of lead by scales of rainbow trout was higher than Caspian kutum. The characteristics of the adsorbents before and after adsorption were analyzed by SEM, EDX, XRF and FTIR. The lead ion concentrations were measured using AAS. The SEM-EDX and XRF analyses clearly revealed the presence of lead ions on the surfaces of both biosorbents after the adsorption experiments. The FTIR results showed that the two sorbents are composed of different functional groups, which could possibly play a significant role in their lead uptake capacity.