Evaluating the anti-fouling performance of electrochemically active nickel based membrane

Abstract

Fouling is inevitable for membrane-based processes. To increase longevity of membranes, anti-fouling mechanisms are crucial. Current anti-fouling mechanisms are often chemical-intensive, expensive and are known to hinder the membrane matrix. This study examined the potential of electrified membranes to induce electro-repulsion and trigger specific electrochemical reactions to remove fouling. A series of experiments were conducted. In general, in all the experiments, electrochemical self-cleaning performance of the membrane was tested by applying different voltages across the membrane. 100 mM NaCl, 1g/L diatomaceous earth and Lake Water were used as foulant mediums for different experiments. As water flux recovery is a characteristic of anti-fouling, it was observed that with an increase in voltage, the water flux increased simultaneously. This observation can be related to the presence of reactive hydroxyl species and free chlorine present inside the membrane module responsible for the degradation of foulants from the membrane surface. For example, with diatomaceous earth as model foulant, the water increased from 9.2 ± 4.12 Kg/m2/h to 30.82 ± 3.92 Kg/m2/h when the voltage was stepped up from 0V to 2.5V. Severe membrane fouling was observed without any voltage. As continuous application of voltage increases energy consumption, intermittent self-cleaning was therefore performed when lake water was introduced as the feed solution. Experiments reveal higher water flux recovery with 10 minute intermittent self-cleaning at the end of 3 hours of membrane operation over a 12 hour period. State-of-the-art backwashing process was also investigated and compared with electrochemical cleaning and results suggest a 7% increase in water flux retention when the latter was used, around 93.25%. In all the cases, flux decline was observed as a consistent effect of fouling. To counteract this effect, Electrocoagulation was tested with the current setup. Compared to previous experiments, water flux increased by almost 25-30% and never declined to an absolute 0 kg/m2/h suggesting superior anti-fouling performance.