Gravity-driven layered double hydroxide nanosheet membrane activated peroxymonosulfate system for micropollutant degradation

For the first time in this study, CoAl-layered double hydroxide nanosheet membrane (LDHm) with abundant active sites was fabricated for peroxymonosulfate (PMS) activation with the mindset to catalytically degrade micropollutants. Depending on the catalyst loading, the developed LDHm can be driven under gravity at a permeate flux of approximately 80 L/m2 h and 210 L/m2 h at LDH loading of 0.80 mg/cm2 and 0.08 mg/cm2, respectively. Notably, the LDHm (0.63 mg) exhibited excellent PMS activation efficiency as indicated by 87.8% removal of the probe chemical (ranitidine) at 0.2 mM PMS, which was higher than that (37–44%) achieved by conventional LDH (5–20 mg)/PMS (0.2 mM) system. In addition to efficient degradation of several micropollutants, LDHm/PMS performance was not inhibited by variation in solution pH (4−8) as well as during long-term (29 h) continuous-flow operation. SO4•− and 1O2 were identified as the primary reactive species in the LDHm/PMS system, while both [tbnd]Co and [tbnd]Al participated in PMS activation. This study offers a simple strategy for efficient removal of several micropollutants with significantly reduced catalyst leaching, which could be applied sustainably in water treatment.