Copper, nickel and zinc removal by peanut hulls: batch and column studies in mono, tri-component systems and with real effluent

The main goal of this research study was the removal of Cu(II), Ni(II) and Zn(II) from aqueous
solutions using peanut hulls. This work was mainly focused on the following aspects: chemical
characterization of the biosorbent, kinetic studies, study of the pH influence in mono-component
systems, equilibrium isotherms and column studies, both in mono and tri-component systems, and
with a real industrial effluent from the electroplating industry.
The chemical characterization of peanut hulls showed a high cellulose (44.8%) and lignin (36.1%)
content, which favours biosorption of metal cations.
The kinetic studies performed indicate that most of the sorption occurs in the first 30 min for all
systems. In general, a pseudo-second order kinetics was followed, both in mono and tri-component
systems. The equilibrium isotherms were better described by Freundlich model in all systems.
Peanut hulls showed higher affinity for copper than for nickel and zinc when they are both present.
The pH value between 5 and 6 was the most favourable for all systems.
The sorbent capacity in column was 0.028 and 0.025 mmol g-1 for copper, respectively in mono and
tri-component systems. A decrease of capacity for copper (50%) was observed when dealing with
the real effluent. The Yoon-Nelson, Thomas and Yan’s models were fitted to the experimental data,
being the latter the best fit.