Characteristics of ozone decomposition inside ceramic membrane pores as nano-reactors

Abstract

The characteristics of ozone decomposition inside the nano-pores of ceramic membranes were identified according to nano-reactor configuration. Three types of ceramic membranes with a pore size of 50 nm were tested with compositions of Al2O3, MnO2/Al2O3 (4%) and CeO2/Al2O3 (4%) respectively. The results showed that the specific decomposition rate of ozone inside membrane pores was 428 times higher than that in pure water outside the pores. The influences of pH values or H2O2 dosages on ozone decomposition in bulk water can be explained on the basis of chain reactions or hydroxyl-radical mechanism; however, these did not work for the behaviours inside the nano-pores of membranes. The extents of the influences of NO3−, SO42− and Ca2+ were even opposite inside to outside the nano-pores of membranes. A unique configuration of nano-reactors within the ceramic membranes tested was proposed based on zeta potentials and water molecule-clusters. Inner charge layer and highly ordered water clusters might play critical roles for the reaction processes inside the nano-reactors.

In-Situ H2O2 Cleaning for Fouling Control of Manganese-Doped Ceramic Membrane through Confined Catalytic Oxidation Inside Membrane

“…Thus, the oxidation efficiency of organic foulants by generated ROS would be significantly improved if the reaction space were restricted far below the diffusion length scale of ROS. This phenomenon was reported in previous studies as a spatial confinement effect [20,19].…”

“…Confined spaces in membrane pores could achieve catalytic performances that are orders of magnitude faster than those obtained in the bulk phase [19]. We found that the ozone decomposition rate inside the membrane pores was about 428 times faster than that in the bulk phase, which was confirmed as a confinement effect of nano-scale membrane pores [20]. Similarly, it is believed that the confinement effect toward catalytic decomposition of H 2 O 2 within membrane pores could also promote the oxidation of foulants and enhance the cleaning efficiency.…”

Ceramic membrane based hybrid process for the upgrade of rural water treatment plants: A pilot study

“…The color is mainly derived from the decomposition of natural humic substances, and it is normally caused by the presence of unsaturated organic moieties conjugated in the compounds (Rice, Robson, Miller, & Hill, 1981). UF alone has a limited removal efficiency for those organic substances (Fan et al, 2015). Ozone is particularly reactive with unsaturated groups, cleaving the conjugation by oxidation.…”

“…Moreover, ozonation is combined with ceramic ultrafiltration in this study and ozone is added directly into membrane tank. A previous study has proven that part of the ozone can enter into the membrane nano‐pores and undergo much higher reaction efficiency than that in the bulk solution (Fan & Zhang, 2013; Qiao et al., 2008; Zhu, Fan, Tao, Wei, & Zhang, 2014). Besides, these trace PPCPs of ng/L concentrations are usually challenging for conventional AOPs and GAC adsorptions.…”

“…The concentrations of manganese ions are determined according to standard method GB/T5750.6-2006 with an ammonium persulfate spectrophotometry (722N). Geosmin (GSM) and 2-methylisoborneol (2-MIB) are detected with the method of head space solid-phase microextraction, gas chromatography and mass spectrometry (HSPME-GC/MS, Agilent GC 6890N) as reported in literatures (Fan et al, 2015). Thirty-seven kinds of PPCPs are measured by solid-phase extraction coupled with high-performance liquid chromatography and mass spectrometry/mass spectrometry (SPE-HPLC/MS/MS) as reported (Zhang et al, 2020).…”