Microporous materials have been tested as absorbent of olive oil mill waste (OOMW) from a three-phase mill. The aim of the present study is to characterise and test the OOMW absorption capacity of fine-grained rocks. The materials tested were zeolite-rich tuff, clay and zeolite-rich tuff, opal-A-rich clayey rock and opal-CT and zeolite-rich clays. The samples were characterised and physico-chemically analysed. The samples exhibit significant differences of their physicochemical properties. Correlations indicated that the OOMW absorption capacity depended mainly on the cumulative volume of pores. Very small pores did not affect considerably the OOMW uptake in contrast to the bigger pores. The opal-CT and zeolite-rich clayey rock was the most efficient absorbent. It is concluded that the synergistic action of three structurally diverse, randomly ordered microporous components which rarely coexist in rocks naturally, results in high cumulative volume of pores and an increased absorption capacity.

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