The development of sorbents that can be added to the soil to immobilize pollutants is an area of great interest because of its growing demand. We intend to get biosorbents by interaction of two natural clays (SWy and CTI) and a synthetic hydrotalcite (HT) and its calcination product (HT500) with the washing water of a natural agro-residue from the olive oil production process. Those biosorbents try to emulate the organo-mineral complexes that can be found or formed in soil, for their use to increase the retention and decrease the mobility of organic pollutants in soils. This process of interaction was previously checked to be beneficial by itself to remove the soluble organic matter (SOM) of the olive mill waste and its toxicity for plants, which represents an additional environmental advantage.

Four biosorbents were prepared and the adsorption of diverse contaminants (three herbicides:diuron, terbuthylazine and terbutryn and an organic pollutant: dibenzofuran) was measured. The in situ formation of those biosorbents was tested by previously mixing the clays with the soil,and thereafter the contaminant is added in solution of olive mill waste SOM. The tested biosorbents produced an increase in the adsorption of contaminants (5-95%) relative to the initial materials (2-17%), especially for highly hydrophobic compounds (dibenzofuran and terbutryn). The higher adsorption increase was found for the smectite SWy, because of its ability to form interlayer organo-mineral complex with SOM, which enlarges the pollutant adsorbing surface. Previous soil amendment with clays and subsequent addition of the pollutant in the SOM solution shows the formation of these biosorbents in situ, with an increase in the retention of terbutryn (from 30 to 75%) and dibenzofuran (from 40 to 60%) in the soil, and again SWy showing the higher retention increase.

Acknowledgements: AGR-P07-03077, AGR-P11-07400andAGR-264 Andalusian(ERDF-ESF EU programs) and RECUPERA 2020MICINN-CSIC Contract.