Linda Li

Access to safe and reliable drinking water is a fundamental human right, yet remote Indigenous Homeland communities continue to face significant challenges achieving this basic standard. Across WA, health violations of Australian Drinking Water Guidelines for nitrate and uranium have been more frequent in recent years, having been linked to chronic kidney disease, diabetes, blue baby syndrome, and cancers. Furthermore, poor taste and appearance of drinking water drives a preference for unhealthy alternatives, and excessive hardness degrades infrastructure. These create a disproportionate health burden for First Nations peoples, as well as unnecessary social and economic strain. Aligning with recommended pathways to SDGs 6 and 10, and closing the gap for Indigenous Australians, this project works towards the development of a real-time, remote, water quality monitoring platform for application to remote Homeland communities.

Persulfate-assisted photocatalysis (PA-PC) has been considered as an efficient technique for wastewater treatment. However, regulating interfacial charge transfer and radical/non-radical active species in the reaction system is still a challenge. This study successfully decorated Co3O4 nanoparticles on BiOCl flower-like microspheres via a simple solution method, forming S-scheme Co3O4/BiOCl heterojunctions with enriched oxygen vacancies (OVs) for highly efficient PA-PC of tetracycline hydrochloride (TC). After exposure to 18-min visible light illumination in the presence of peroxydisulfate (PDS) (namely the BOC-5/PDS/Vis system), the optimized catalyst, BOC-5, reached a TC degradation of 92.3% and a total organic carbon (TOC) removal of 66.2%, outperforming many reported catalysts in the literature. Common anions (Cl−, CO32−, NO3−) and cations (Zn²⁺) showed negligible interference on the performance of BOC-5/PDS/Vis system, demonstrating its excellent anti-interference capability. Such system was also proven with a broad pH adaptability in the range of 3.0 – 11.0. Cycling tests confirmed the outstanding stability of BOC-5, while toxicity assessments revealed significantly reduced ecological toxicity of intermediates in comparison with TC. The construction of S-scheme Co3O4/BiOCl heterojunctions with intimate 0D/2D interfacial contact markedly promoted charge carrier separation efficiency. The photogenerated electron (e–) enabled the reduction of Co3+ to Co2+, accelerating the Co2+/Co3+ redox cycle to facilitate e– transfer for PDS activation. The OVs improved light absorption and induced generation of more superoxide radicals (•O2−) as the dominant active species. These along with singlet oxygen (1O2) boosted the degradation efficiency of TC. Our research presented efficient interfacial and defect engineering strategies for the design of heterojunctions aiming at antibiotic removal from wastewater through PA-PC.

Exfoliated La-doped g-C3N4, namely La(x%)-eCN-N (x = 0.1%– 10%), was prepared via in-situ La doping and thermal treatment. The photocatalytic activity of La(x%)-eCN-N was explored through the degradation of methyl orange (MO) under visible light and then optimized by varying the loading of La dopant. The optimised La(1%)-eCN-N displayed an enhanced photocatalytic performance over the bulk and exfoliated g-C3N4, and bulk La-doped g-C3N4. Meanwhile, the use of La(1%)-eCN-N was seen with a high photocatalytic efficiency towards MO removal when compared with La(1%)-eCN-C, La(1%)-eCN-T, and La(1%)-eCN-U, which were prepared via conventional chemical, thermal and ultrasonic exfoliation of the pre-formed bulk La-doped g-C3N4. The observed outstanding photocatalytic activity of La(1%)-eCN-N was explained by several favourable features. In particular, the thin nanosheets would permit swift migration and effective separation of photogenerated charge carriers. The nitrogen adsorption–desorption analysis revealed an increased surface area and porosity, which might expose more active sites on the photocatalyst surface to adsorption and subsequent photocatalytic removal of MO molecules. Moreover, La(1%)-eCN-N was proven with improved visible light absorption, enhanced charge carrier separation and reduced transfer resistance. Its activity, along with the crystal and chemical characteristics, was largely retained after five cycles of photocatalytic reaction, affirming its good reusability and stability for potential practical application. The key reactive oxidising species involved in the photocatalytic removal of MO using La(1%)-eCN-N was experimentally determined to be the superoxide radical.

In the present study, a series of La-doped g-C3N4 with Ag nanoparticles (NPs) decoration was synthesized via one-pot thermal pyrolysis and wet impregnation. As compared with the bulk g-C3N4 (BCN), La-modified g-C3N4 or Ag-modified g-C3N4, the optimal La-doped g-C3N4 with Ag NPs decoration (Ag-0.8/LaCN-1) showed improved methyl orange (MO) adsorptive capacity and higher photocatalytic activity, because of the synergistic effect of La doping and Ag NPs decoration. Adsorption kinetic and isotherm models were employed to study the adsorption mechanism. The best fit of the experimental data was obtained using the pseudo-second-order (PSO) kinetic model and the Redlich-Peterson isotherm model. It indicated that the MO adsorption using Ag-0.8/LaCN-1 was mainly governed by chemisorption; the process appeared to follow neither an ideal monolayer nor a multilayer but a hybrid mechanism. The MO adsorptive (30 min) removal and photocatalytic degradation (80 min) rate using Ag-0.8/LaCN-1 was seen at around 49.6 and 13.1 times that of BCN, respectively. At pH = 6, the good MO adsorption could be mainly the result of π – π interaction and complexation; whilst the good photocatalytic efficiency was ascribed to improved visible light absorption, charge carrier separation and transfer. Superoxide radicals and holes were proven as the main reactive species for the high MO photocatalytic degradation, by conducting the scavenger test and ESR analysis. The as-prepared Ag-0.8/LaCN-1 displayed good reusability with approximately a 3% loss in the total MO removal % after five consecutive runs of tests. Good stability was observed, recording only ca. 0.25% and 0.01% leaching of Ag and La dopants from Ag-0.8/LaCN-1, respectively, suggesting its robustness for practical use.

Defective tungsten oxides (WO3−x) with oxygen vacancies (OVs) are recognized for exceptional photocatalytic properties attributed to their unique electronic structures, abundant OVs, and local surface plasmon resonance effect. There has been a growing research interest in developing OV-rich WO3−x as efficient photocatalysts for applications in environmental remediation and energy conversion. This review covers various available approaches for synthesizing WO3−x, including hydrothermal, solvothermal, microwave, and template methods. It also focuses on recent progresses on several modification strategies, such as ion doping, metal deposition, morphology control, heterojunction construction, and single-atom engineering, for maximizing the photocatalytic efficiency of WO3−x. The correlation between photocatalytic activity, chemical compositions, morphological characteristics, and textural properties of catalysts is highlighted. The application of these WO3−x photocatalysts with improved performances in the fields of wastewater treatment, H2 evolution, CO2 reduction, N2 fixation, photoelectrochemical catalysis, and stability is discussed. Finally, prospects and challenges in the synthesis and application of WO3−x-based photocatalysts are outlined.

This study systematically studied the effects of Pr, Fe, and Na as representative rare earth, transition, and alkali metal dopants, respectively, on the photocatalytic activity of exfoliated graphitic carbon nitride (g-C 3 N 4). The doped exfoliated g-C 3 N 4 samples were prepared by integrating precursor ion intercalation into the pre-formed g-C 3 N 4 with thermal treatment. The as-prepared catalysts were examined for crystal, textural, chemical, optical, and photoelectrochemical properties to explore the correlation between dopants and photocatalytic activity of the resulting composites. The detailed analyses revealed that the Pr-doped g-C 3 N 4 exhibited superior photocatalytic activity in degrading methylene blue under visible light, achieving a ~96% removal in 40 min. This was not only better than the activity of g-C 3 N 4 , but also much higher than that of Na-doped g-C 3 N 4 or Fe-doped g-C 3 N 4. The kinetic rate constant using Pr-doped g-C 3 N 4 was 3.2, 5.1, and 2.0 times greater than that of the g-C 3 N 4 , Fe-doped g-C 3 N 4 , and Na-doped g-C 3 N 4 , respectively. The enhanced performance was attributed to its inherent characteristics after optimal tuning, including good surface area, improved porosity, enhanced visible light absorption, suitable electronic band structure, increased charge carrier density, promoted charge separation, and reduced charge transfer resistance. In addition, the optimized Pr(0.4)g-C 3 N 4 was used to study the photocatalytic removal of methylene blue in detail under conditions with different initial methylene blue concentrations, types of dyes, catalyst dosages, initial solution pH, counter ions, and water matrices. Our results demonstrated the high photocatalytic activity of Pr(0.4)g-C 3 N 4 under varying conditions, including in real wastewater media, which were collected from our local municipal wastewater treatment plant. The observed good reusability and stability after five cycles of photocatalytic degradation test further suggested a promising potential of Pr(0.4)g-C 3 N 4 for practical application in wastewater treatment.

For the first time, groundwater treatment sludge was integrated with g-C3N4 towards highly efficient and cost-effective visible-light-initiated catalysts for organic removal. The optimized sample of g-C3N4/GWS-M(2.5 %), which was synthesized using the sludge rich in Al and Fe, was explored with improved photocatalytic activity. Its photocatalytic performance was ∼6, 4, and 7 times that of g-C3N4 in terms of removal of methyl orange, cephalexin, and ketoprofen, respectively. The observed greater photocatalytic activity was attributed to its upgraded physicochemical properties, including specific surface area, porous structure, visible light absorption, charge separation and transfer. In particular, the co-existence of dominant Al and Fe dopants in g-C3N4/GWS-M(2.5 %) aided abstraction of photogenerated charge carriers. After photocatalytic reaction, only 0.02 % and 0.01 % loss of Al and Fe was observed from the catalyst, respectively. A superior organic removal (∼92 %) was still observed by using g-C3N4/GWS-M(2.5 %) with no change in its crystal and chemical structures at the 5th cycle of photocatalytic degradation. The primary reactive species responsible for the reaction were inferred to be the superoxide and singlet oxygen radicals.

The development of efficient adsorbent for removing excessive nutrients (e.g. phosphorous – P) and antibiotics (e.g. tetracycline hydrochloride – TC) from livestock wastewater is necessary but challenging in practical application. In this study, magnetic Zr-based metal-organic frameworks (Fe3O4/UiO-66) with interfacial Fe-O-Zr bonds were synthesized and then modified with ethylenediamine (EDA) functional groups. The resultant optimized composite, namely Fe3O4/UiO-66-N2, showed promising removal of P and TC from both single and binary solution systems. It exhibited the maximum P and TC adsorption capacities of 90.0 mg P/g and 72.3 mg/g in the single component solution, respectively. In the binary solution with an initial P concentration of 5 mg P/L, the coexistence of TC posed a slight inhibition effect on the P adsorption over Fe3O4/UiO-66-N2. However, the TC adsorption was increased by raising the initial P concentration in solution from 5 mg P/L to 20 mg P/L. The Fe3O4 nanoparticles and EDA functional groups were suggested jointly improving the adsorption capacities of P and TC, with the synergy factors of 1.1 and 1.8, respectively. The effects of reaction time, water medium, initial pH and coexisting ions on the adsorption were investigated in detail. The mechanisms governing the adsorption of phosphate included electrostatic attraction, hydrogen bonding, ligand exchange and complexation. Those contributing to the adsorption of TC included Lewis acid-base interaction and π-π electron-donor-acceptor interaction, in addition to electrostatic attraction, hydrogen bonding and complexation. This work designed novel functionalized magnetic MOF composite adsorbents targeting at efficient and simultaneous removal of P and TC from water, under the synergistic effect of the Fe3O4 nanoparticles and surface functional groups.
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•Fe3O4/UiO-66 were grafted with ethylenediamine (EDA) as efficient adsorbents.•The synergy of Fe3O4 and EDA enhanced the sorption capacity of P and TC.•The coexisting of P favored TC adsorption in binary solution.•The P sorption involve electrostatic attraction, H bonding, and ligand exchange.•π-π electron-donor-acceptor interaction contributes to the TC adsorption.

Graphitic carbon nitride (g-C 3 N 4) is a promising material for photocatalytic applications. However, it suffers from poor visible-light absorption and a high recombination rate of photogener-ated electron–hole pairs. Here, Co/La@g-C 3 N 4 with enhanced photocatalytic activity was prepared by co-doping Co and La into g-C 3 N 4 via a facile one-pot synthesis. Co/La@g-C 3 N 4 displayed better performance, achieving 94% tetracycline (TC) removal within 40 min, as compared with g-C 3 N 4 (BCN, 65%). It also demonstrated promising performance in degrading other pollutants, which was ~2–4-fold greater relative to BCN. The improved photocatalytic activity of Co/La@g-C 3 N 4 was associated with improved photogenerated charge separation, reduced charge transfer resistance, a built-in electric field arising from the p-n-p heterojunction, and the synergistic effect of ternary components for the separation and transfer of the photogenerated charge carriers. Superoxide radicals are suggested to be the most notable reactive species responsible for the photocatalytic reaction. Environmental factors, including the pollutant concentration, catalyst dosage, solution pH, inorganic salts, water matrices, and mixture with dyes, were considered in the photocatalytic reactions. Co/La@g-C 3 N 4 showed good reusability for five cycles of the photocatalytic degradation of TC. The facile one-pot co-doping of Co and La in g-C 3 N 4 formed a p-n-p heterojunction with boosted photocatalytic activity for the highly efficient removal of TC from various water matrices.

Metal sulfides (MSs) have been explored extensively as promising semiconductors for photocatalytic applications in pollutant degradation, CO2 reduction, and H2 production. However, pure MSs suffer from several drawbacks, especially rapid electron–hole recombination. The construction of S-scheme heterojunctions has been recommended as one of effective strategies to improve charge separation and transfer, as well as to retain high redox potential electrons and holes to participate in reaction. This paper reviewed recent advances on the construction of MS-based S-scheme heterojunctions with high photocatalytic performances. In particular, various design and construction approaches, including integration with other semiconductors, microstructure control, and interface modulation, were covered along with mechanisms governing the boosted photocatalytic performances. The challenges and prospects in the research about MS-based S-scheme heterojunctions were discussed finally, providing our insight on future research.