Process optimization for the removal of sodium diclofenac from water using a green polymeric membrane

Abstract

New polymeric membranes for water treatment have been regularly developed and reported by the scientific community; however, process optimization based on the application purpose is necessary to achieve the best performance. In this work, a previously developed “green” polymeric membrane was employed to investigate the influence of process parameters on the removal of sodium diclofenac (DCF) from water. The “green” classification relies on the membrane components (poly(vinyl alcohol) – PVA, citric acid, glycerol, and green synthesized silver nanoparticles) and the mild conditions for its preparation. The parameters studied were the compaction and operational pressure (1.0 – 5.0 bar), feed temperature (10 – 25 °C), DCF concentration (0.002 – 0.010 g L−1), and feed pH (4.0 – 10.0). The results showed a positive influence of pressure on DCF removal (from 54 % to 75 %, within a range of 1.0–5.0 bar) due to the PVA structure densification, as well as the temperature (from 61 % to 82 %, within a range of 10–25 °C) because of the increased water affinity. The DCF concentration influenced the absorption of DCF into the membrane, reaching the maximum of 73 % of DCF removal at 0.007 – 0.010 g L−1. The feed pH determined the mechanism of removal but had a minor influence on the final performance (from 73 % of DCF removal at acidic pH to 77 % at alkaline conditions). The optimized conditions of 5 bar, 25 °C, 0.008 g L−1 DCF, and pH ∼5.75 promoted a permeability of 0.024 L m−2 h−1 bar−1 with 80 % DCF removal. This performance is comparable to that observed for commercial nanofiltration membranes but offers the advantage of a membrane fabricated and operated using a sustainable approach.