Use of Biochars from Olive OIL Mill Waste for Water Decontamination.

The objective of this work was to search for low cost materials to be used as sorbents of contaminants.  Biochar is the solid residual remaining after the thermo-chemical transformation of biomass. In this work, we obtained biochar from two residues from olive oil extraction known as “alperujo” (BCA) and “orujo” (BCO). Biochars were obtained by heating these residues at 550 ^oC 50 min.  In order to evaluate sorption capacity of the biochars, we selected different contaminants: three organic contaminants (OCs) and two heavy metals (HMs). The OCs were two pesticides (tebuconazole and MCPA) and a dioxin (dibenzofuran)  and the HMs selected were Cu And Zn. Removal of dibenzofuran from water reached 60 % of the initial concentration for both BCA and BCO, whereas in the case of tebuconazole BCA removed  only 20% of the initially applied fungicide and BCO  10 %. Sorption of the acidic herbicide MCPA by BCA and BCO was very low (< 5%), probably due to repulsion between MCPA and negatively charged surfaces. These results suggest that sorption of OCs to the studied biochars is related to their hydrophobicity. When compared to OCs, these biochars were more effective in sorption of HMs: BCA sorbed 90 % of the Cu and Zn present in water and BCO more than 70 % of both HMs. Sorption of HMs on biochars surface can be through polar bonds between carboxylate or carbonyl groups from biochars surfaces and the metals.

Acknowledgements: Grants P 11-07400 and AGR-264 by Junta de Andalucía, Contract RECUPERA 2020 MINECO-CSIC