Experimental Model for Cu(II) and Fe(III) Sorption from Synthetic Solutions Based on Maize Stalk

This study is based to a new concept, to use maize stalk for specific sorption and recovery of
Cu(II) and Fe(III) from synthetic solutions. Thus, the sorption properties of the biomass resulting from
the recycling of the maize stalk that reached maturity (autumn) were studied. In the first stage, the
sorption properties of the maize stalk were evaluated in batch system. Moreover, in terms of water
quality improvement several key parameters that influence the sorption equilibrium were evaluated.
The effect of contact time (0-120min) and cations initial concentration (investigated range: 0.05-0.4
mg/L) on biomaterial sorption capacity were assessed. Kinetic studies were performed taking into
consideration the initial concentration of metallic cation. The experimental data were analyzed based
on first order kinetic model, pseudo-second-kinetic model and Morris Webber kinetic model. The
kinetics of sorption was in accordance with the pseudo - second - kinetic model as the correlation
coefficients showed (R2=0.9940 for Cu(II) and R2=0.9999 for Fe(III)). Moreover the desorption study
was evaluated with hydrochloric acid and have detected to be 63% and 89% for Cu(II) and Fe(III)
when 4M HCl is used. The surface of the maize stalk loaded with Cu(II) and Fe(III) was characterized
by various specific techniques such as FTIR-ATR, SEM, and TG. Experimental results revealed that
cations sorption process takes place on the sorbent surface. The sorption rate of each metallic cation
is controlled by the formation of chemical bonds with surface polar groups. Their presence on biomass
structure, evidenced by FTIR-ATR analysis, explains the behavior of maize stalk as a weak ion
exchanger acid.