Recovery of phenolic compounds from residual table olive fermentation brines by nanofiltration at different operating conditions

Nanofiltration membrane process has been investigated for the recovery of phenolic compounds from residual pickle industries, such as residual table olive fermentation brines. Two polyamide membranes were considered: NF245 and NF270 (DOW Chemical). Tests were performed varying the transmembrane pressure (TMP) and crossflow velocity (CFV) from 5 to 15 bar and from 0.5 to 1.5 m·s −1 , respectively. The NF245 membrane provided a better separation between organic matter and phenolic compounds. With this membrane, the largest phenolic compounds/chemical oxygen demand (COD) ratio in the permeate stream (0.195 mg ty eq/mg O 2 ) was obtained at the following operating conditions: CFV of 1.5 m·s −1 and a TMP of 15 bar. Under these conditions the permeate flux was 31.9 L·h −1 ·m −2 , while the elimination of turbidity was complete and color reduction was close to 91 %. The salts rejection, COD and phenolic compounds were 25 %, 64.7 % and 35.2 %, respectively. The pH of the permeate samples did not vary respect to the feed solutions. Furthermore, the values of permeate flux were compared to the predictions from the Kedem-Spiegler model. The permeate flux reduction in comparison with pure water flux was mainly caused by the osmotic pressure gradient. Moreover, NF270 membrane suffered greater membrane fouling than NF245 membrane.