Goen Ho

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.

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.

Biogas, consisting mainly of CO2 and CH4, offers a sustainable source of energy. However, this gaseous stream has been undervalued in wastewater treatment plants owing to its high CO2 content. Biogas upgrading by capturing CO2 broadens its utilisation as a substitute for natural gas. Although biogas upgrading is a widely studied topic, only up to 35% of produced raw biogas is upgraded in the world. To open avenues for development research on biogas upgrading, this paper reviews biogas as a component in global renewable energy production and upgrading technologies focusing on electrochemically driven CO2 capture systems. Recent progress in electrochemical CO2 separation including its energy requirement, CO2 recovery rate, and challenges for upscaling are critically explored. Electrochemical CO2 separation systems stand out for achieving the most affordable technology among the upgrading systems with a low net energy requirement of 0.25 kWh/kg CO2. However, its lower CO2 recovery rate compared to conventional technologies, which leads to high capital expenditure limits the commercialisation of this technology. In the last part of this review, the future perspectives to overcome the challenges associated with electrochemical CO2 capture are discussed.

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.

Graphitic carbon nitride (g-C3N4) is a widely studied visible-light-active photocatalyst for low cost, non-toxicity, and facile synthesis. Nonetheless, its photocatalytic efficiency is below par, due to fast recombination of charge carriers, low surface area, and insufficient visible light absorption. Thus, the research on the modification of g-C3N4 targeting at enhanced photocatalytic performance has attracted extensive interest. A considerable amount of review articles have been published on the modification of g-C3N4 for applications. However, limited effort has been specially contributed to providing an overview and comparison on available modification strategies for improved photocatalytic activity of g-C3N4-based catalysts in antibiotics removal. There has been no attempt on the comparison of photocatalytic performances in antibiotics removal between modified g-C3N4 and other known catalysts. To address these, our study reviewed strategies that have been reported to modify g-C3N4, including metal/non-metal doping, defect tuning, structural engineering, heterostructure formation, etc. as well as compared their performances for antibiotics removal. The heterostructure formation was the most widely studied and promising route to modify g-C3N4 with superior activity. As compared to other known photocatalysts, the heterojunction g-C3N4 showed competitive performances in degradation of selected antibiotics. Related mechanisms were discussed, and finally, we revealed current challenges in practical application.

The traditional electrochemical caustic soda recovery system uses the generated pH gradient across the ion exchange membrane for the regeneration of spent alkaline absorbent from CO 2 capture. This electrochemical CO 2 capture system releases the by-products H 2 and O 2 at the cathode and anode, respectively. Although effective for capturing CO 2 , the slow kinetics of the oxygen evolution reaction (OER) limit the energy efficiency of this technique. Hence, this study proposed and validated a hybrid electrochemical cell based on the H 2-cycling from the cathode to the anode to eliminate the reliance on anodic oxygen generation. The results show that our lab-scale prototype enabled effective spent caustic soda recovery with an electron utilisation efficiency of 90%, and a relative carbonate/bicarbonate diffusional flux of approximately 40%. The system also enabled the regeneration of spent alkaline absorbent with a minimum electrochemical energy input of 0.19 kWh/kg CO 2 at a CO 2 recovery rate of 0.7 mol/m 2 /h, accounting for 30% lower energy demand than a control system without H 2-recycling, making this technique a promising alternative to the conventional thermal regeneration technology.

This book provides a practical and technical focus on environmental engineering technologies and will serve engineers, designers, architects, and project developers that seek to successfully integrate them into urban, rural, and remote settlements. These professionals need to work closely together and understand the technologies to be utilized, therefore this book presents the technologies in an applied manner along with a brief discussion of the underpinning principles in order to ensure correct selection from the various options available and their successful integration into the project at hand, whether an individual building or an entire district.

Dr. Martin Anda is an environmental engineer with over 30 years’ experience in the energy efficiency, renewable energy, water recycling and built environment sectors. In 2007 he designed and launched the Environmental Engineering degree program at Murdoch University, which is now fully accredited by Engineers Australia. In the early 2010s Martin combined his academic role with work in industry and spent five years as Principal Engineer Sustainability at ENV Australia, leading a number of commercial consultancy projects including several large-scale water efficiency behavioural change programs for the Water Corporation. Today, Martin is Academic Chair and Senior Lecturer in Environmental Engineering at Murdoch University in Western Australia.

Emeritus Professor Goen Ho joined Murdoch University in 1976, and helped establish the Environmental Science program at the university, the first in Australia. Goen is a Fellow of the Institution of Engineers Australia and a Chartered Professional Engineer. He is a Fellow of the International Water Association and has been active in the Association (2000-04 Chair of Specialist Group of Small Water Systems, 2005-07 Co-chair of the Asia Pacific Regional Council, 2002-10 Member of Strategic Council). In 2011 he received the Vice Chancellor’s Excellence in Research Award for Distinguished and Sustained Achievement. He was Program Leader of Environmental Biotechnology at Murdoch University from 2011 to 2013. Goen retired as Professor of Environmental Engineering in July 2013 and was appointed Emeritus Professor.

Dr. Linda Li received her PhD degree in 2009 and then started her postdoctoral research in the Department of Chemical Engineering at Monash University. She joined Murdoch University as a lecturer in Environmental Engineering at the end of 2011. Her current research interests include the development of advanced materials and membranes for wastewater treatment.

With an extensive presence in the world of Industrial Symbiosis literature, the Kwinana industrial area in Perth, Western Australia is a powerhouse of integrated heavy industrial activity. From when its first entrant arrived in 1955, development has been strong, and now it presents a complex industrial cluster with a wide range of industrial enterprises present, ranging from several major industrial multi-product manufacturers to those filling niche markets. Formal reporting of its economic contribution has occurred periodically over 40 yr, with one of the features of this being a series of four earlier iterations, and in this paper, the fifth, of a schematic diagram that identifies the enterprises engaged in symbiotic relationships and the nature of the associated materials exchanged. While the earlier reports concentrated solely on the traditional materials exchanges, the present study (data collected in 2021) went beyond these to gather additional data on what the authors are proposing as additional dimensions of the traditional Industrial Symbiosis framework. Aspects of Kwinana's skilled workforce, its support industry base, and its overlying governance framework were studied to provide insights into what role they play in explaining why some industrial clusters appear to provide a supportive business environment, and why other clusters struggle to gain momentum. The new study identified that the novel posited dimensions of Industrial Symbiosis are interlinked at the precinct level, and that at the macro (societal) level, they combine to contribute to the effectiveness of the Circular Economy.