Two-phase olive-oil washing wastewater treatment plus phenolic fraction recovery by novel ion exchange resins process modelling and optimization

•Phenols recovery from 2-phase olive-oil-washing wastewater and effluent purification.•Dowex21KXLT® and Dowex66® strong and weak-base resins key operating factors studied.•Optimal 114–146 gresin/L, 20–25 °C, pH0 6.5–8.2 and 4.7–7.1 and 60 vs. 25 min found.•Optimized Dowex 66® weak-base resin ensured best performance of 83.5% phenols uptake.•Feasible and sustainable compliance of the irrigation standards were achieved. This research was focused on the modelling and optimization of an environmentally friendly procedure to recover added-value polyphenols (TPhs) from two-phase olive-oil washing wastewaters (OOWW) by ion exchange (IE) resins and simultaneously permit the treatment of this effluent. The reason is the need of olive mills to evolve into a whole environmentally friendly conception to upgrade this ancestral industry, comprising the management of the by-produced effluents. Key operating factors of Dowex 21KXLT® strong-base and Dowex66® weak-base resins were studied, modelled and optimized by statistical multifactorial analysis. Optimal resin amount between 140 and 146 and 114–146 gresin/LOOWW, T from 20 to 25 °C, pH0 between 6.5 and 8.2 and 4.7–7.1 and 60 vs. 25 min contact time were determined for the strong-base and weak-base resins. Final phenols concentration uptake of 60.8% vs. 83.3% plus 55.8% vs. 53.7% COD removal supported major efficacy of the selected weak-base resin. In addition, the process could be directly driven with raw OOWW exiting the mills’ vertical centrifuges upon unmodified pH0 nor T. The high added-value concentrated pool of antioxidant phenols could render feasible the industrial scale-up, and the treated effluent could be now driven to biological treatment given the high removal of TPhs preventing biomass inhibition, or partially discharged.