Membrane fouling behaviors in membrane Fenton process without acid-base agents controlled by current density for nanofiltration concentrate treatment

Abstract

Effective generation of H+ and OH− in the Fenton by electrodes is crucial for addressing the impact of acidity and alkalinity on the environment. In this study, electrolysis was coupled with membrane Fenton for nanofiltration concentrate treatment and membrane fouling behaviors were investigated. The effects of current density and dosage (H2O2 and Fe2+ ) were studied. According to the Box-Behnken design results, both current density and the dosages of H2O2 and Fe2+ positively influenced the removal of organic pollutants, with the former showing the most significant effect. Hydroxyl radical (•OH) oxidized the organic pollutants into intermediates, realizing a removal efficiency of 74.50 %. The anode oxidation and Fenton process effectively degraded fluorescent components, particularly humic acid-like substances. Ammonia nitrogen was degraded by active chlorine produced at the anode, with an average removal rate of 51.36 %. Additionally, an increase in current density enhanced ion exchange membrane fouling. Chemical composition analysis suggested that the membrane was primarily covered with hydroxide crystal substances. The ultrafiltration (UF) membrane analysis indicated that cake layer formation was responsible for the trans-membrane pressure (TMP) increase, and cake-complete was the primary mechanism contributing to UF membrane fouling. The membrane Fenton process without acid-base agents exhibits significant potential for contaminants removal from nanofiltration concentrate and is advantageous for cleaning membrane fouling.