Title

Sulfate radical based ceramic catalytic membranes for water treatments

Date of Award

2020

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Engineering

First Advisor

Professor Hongqi Sun

Second Advisor

Professor Lai-Chang Zhang

Abstract

The discharge of antibiotics into natural aquatic environment without proper treatments results in the propagation of antibiotics-resistant strains. Effective remediation technologies are therefore urged to remove those emerging contaminants from water. However, antibiotics are difficult to be degraded through a traditional biological treatment because they would deactivate the effective bacteria used in the process. Advanced oxidation processes (AOPs) using highly reactive oxygen species (ROS) such as hydroxyl radicals ( OH) and sulfate radicals (SO4 •− • ) have been widely employed as an efficient way for antibiotics degradation owing to the high oxidation ability, non-selectivity and low cost. However, the recovery of the suspended catalysts after use is the biggest obstacle for the wide application. Meantime, membrane separation has also been extensively applied as a promising wastewater treatment technology with the advantages of long-term operation, low energy consumption and high yield of production. The membrane fouling is, however, a critical issue restricting the widespread application of membrane. For addressing above-mentioned issues, with extensive technological and scientific endeavours, this PhD study focused on the development of novel integration technology of AOPs and membrane separation for antibiotics degradation. In this research, heterogeneous AOPs processes coupled with independent membrane separation unit for suspended catalysts recovery were studied. Moreover, metal oxide based-catalytic membrane for concurrent AOPs and membrane separation were investigated. Firstly, boron, nitrogen co-doped carbon nanotubes supported FeOOH (FeOOH@BNC) was synthesized for the degradation of sulfamethoxazole (SMX) by Fenton-like reaction. The as-synthesized FeOOH@BNC showed an excellent performance in SMX removal (Chapter 3). Secondly, boron, nitrogen co-doped nanotubes (BNC) were developed. The BNC nanotubes with a high specific area, abundant active sites, and controllable N–B–C structures demonstrated prominent peroxymonosulfate (PMS) activation ability towards 4-hydroxylbenzoic acid (HBA) degradation (Chapter 4). It was also found that both FeOOH@BNC and BNC suspended catalysts in the treated solution can be well recovered via membrane filtration (Chapter 3 and 4). Finally, two metal oxide-based catalytic ceramic membranes (Co3O4@CM and MnO2@CM) were prepared via a simple one-step ball-milling method with a high temperature sintering. The as-prepared Co3O4@CM and MnO2@CM composite catalytic membranes were characterized and tested for the degradation of aqueous HBA solution by SR-AOPs procedure. It was found that the composite membranes showed excellent HBA removal efficiencies, good reusability and high anti-fouling performances (Chapter 5 and 6). Mechanistic studies, e.g. materials chemistry, generation of reactive radicals, and degradation pathways, were also carried out. The developed catalysts, catalyst membranes, and the combined processes as well as the mechanistic studies are expected to provide significant contributions in terms of both technology and scientific knowledge to remediation of emerging contaminants.

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