Adsorbent properties of olive mill wastes for chromate removal

The removal of chromate ions from aqueous solutions by adsorption onto two different olive mill waste materials was investigated using batch rate experiments. The solid material was obtained from olive mill wastes coming from two different extraction plants, two phase continuous, and discontinuous plant. The initial absence of chromium in the material was confirmed through scanning electron microscope equipped with Energy Dispersive X-ray analyzer. The adsorption analysis has demonstrated that both biomasses are able to adsorb chromate ions. An accurate analysis of polyphenols has highlighted that the presence of polyphenols does not interfere with the adsorption of chromate ions. A heterogeneous kinetics model provided the parameters of the adsorption kinetics within all the time ranges explored. For each biomass, a critical initial chromate concentration exists beyond which the adsorption process becomes independent of the initial chromate concentration. The results indicate that olive mill wastes may be reused as an adsorbent material for chromate ions removal by means of an ecologically friendly technology.