Performance enhancement of ultrafiltration in apple juice clarification via low-pressure oxygen plasma: A comparative evaluation versus pre-flocculation treatment

The aim of this study was to improve ultrafiltration (UF) performance during clarification of raw apple juice through surface modification of commercial polysulfone membranes (US100) by low-pressure oxygen plasma treatment (LP-OPlsT). A Plasma power of 90 W and exposure time of 10 min were determined as the most effective parameters enabling an increase in the ΔGiwi value of the plain membrane from (−) 25 ± 2 mN m−1 to (+) 30 ± 1 mN m−1. Improved hydrophilicity achieved by LP-OPlsT remarkably enhanced the performance of US100 throughout the clarification of raw apple juice without the need of an additional pre-flocculation step. While Rfrev (86%) was the dominant resistance controlling the fouling during UF of raw apple juice through the plain membrane, the contribution of Rfrev to Rt decreased to 56% after pre-flocculation step. LP-OPlsT further decreased this ratio, up to 46%, confirming the charge repulsion between the modified membrane and the foulant particles.