Influence of salts and phenolic compounds on olive mill wastewater detoxification using superabsorbent polymers

For a selection of nine commercially available superabsorbent polymers, the absorption capacity was evaluated for the principal absorption-inhibition constituent of OMW, mineral salts and for phytotoxic-components, the phenolic compounds. A double exponential model was established for electrical conductivities ranging 4.2–25,000 μS cm−1. For solutions of phenolic compounds ranging 0–0.5 g l−1, a distribution coefficient near unit was achieved, while for OMW, the phenolic compounds were concentrated inside the gel as the distribution coefficient was 1.4. Correction of OMW pH towards neutrality was found to increase the absorption capacity by up to 35%. The phytotoxicity was assessed by the germination of Lepidium sativum. Inhibition in plant growth occurred for all OMW dilutions without superabsorbent polymers application. For 5% of OMW (COD 5 g l−1 and 200 ppm of phenolic compounds) immobilised in PNa2 (1 g l−1), plant growth was promoted being observed a 120% growth germination, thus indicating that olive mill wastewater detoxification occurred.