Display omitted
•A Fenton-like reaction was proposed as an effective sludge dewatering process.•Uniform design was used to optimize this sludge dewatering process.•The mechanism for the enhanced ...dewatering performance was elucidated.
The presence of high moisture content in sewage sludge aggravates the disposal costs and restricts its application. Sewage sludge is traditionally conditioned by dosing organic/inorganic chemicals. However, after the treatment, the moisture content and inorganic solid mass remain to be a high level. In this work, a Fenton-like dewatering process, i.e., a combination of sulfuric acid, hydrogen peroxide and ferric sulfate, was developed. Uniform design was used to optimize the composite conditions, and the effects of Fenton-like treatment on sludge dewatering were examined. The results show that, after the treatment of the Fenton-like reaction, the moisture content of sludge cake and the dry solid mass decreased from 80.0% to 66.1% and from 12.9 to 10.6g/L, respectively. The mechanism for the enhanced dewatering performance was explored, and the degradation of abundant extracellular polymeric substances, the lysis of the sludge cells, and the release of bound water and typical metals within the sludge flocs were found to be mainly responsible for the enhanced dewatering performance. In addition, a surface thermodynamic analysis with the extended DLVO theory shows that the higher hydrophobicity and the less stable sludge flocs also contributed to the decrease in moisture content. Our results confirm that such a Fenton-like treatment exhibited excellent performance in enhancing sludge dewatering and metal leaching and is a promising pretreatment approach for sludge disposal.
Extracellular polymeric substances (EPS) are known to crucially affect the properties and performance of activated sludge, but the detailed influential mechanisms and the pertinence to specific ...compositional, structural properties of EPS are still elusive. Such knowledge gaps have severely limited our ability in optimizing biological wastewater treatment processes, for which long-term robust and efficient sludge performance remains one of the main bottlenecks. Here, we overview the new knowledge on the molecular structure of sludge EPS gained over the past few years and discuss the future challenges and opportunities for further advancing EPS study and engineering. The structural and functional features of several macromolecules in sludge EPS and their important structural roles in granular sludge are analyzed in detail. The EPS–pollutant interactions and environment-dependent regulation machinery on EPS production are deciphered. Lastly, the remaining knowledge gaps are identified, and the future research needs that may lead to molecular-level understanding and precise engineering of sludge EPS are highlighted.
Global warming, environmental pollution, and an energy shortage in the current fossil fuel society may cause a severe ecological crisis. Storage and conversion of renewable, dispersive and ...non-perennial energy from the sun, wind, geothermal sources, water, or biomass could be a promising option to relieve this crisis. Carbon materials could be the most versatile platform materials applied in the field of modern energy storage and conversion. Conventional carbon materials produced from coal and petrochemical products are usually energy intensive or involve harsh synthetic conditions. It is highly desired to develop effective methods to produce carbon materials from renewable resources that have high performance and limited environmental impacts. In this regard, biochar, a bio-carbon with abundant surface functional groups and easily tuned porosity produced from biomass, may be a promising candidate as a sustainable carbon material. Recent studies have demonstrated that biochar-based materials show great application potential in energy storage and conversion because of their easily tuned surface chemistry and porosity. In this review, recent advances in the applications of biochar-based materials in various energy storage and conversion fields, including hydrogen storage and production, oxygen electrocatalysts, emerging fuel cell technology, supercapacitors, and lithium/sodium ion batteries, are summarized, highlighting the mechanisms and open questions in current energy applications. Finally, contemporary challenges and perspectives on how biochar-based materials will develop and, in particular, the fields in which the use of biochar-based materials could be expanded are discussed throughout the review. This review demonstrates significant potential for energy applications of biochar-based materials, and it is expected to inspire new discoveries to promote practical applications of biochar-based materials in more energy storage and conversion fields.
Biochar, a bio-carbon with abundant surface functional groups and easily tuned porosity produced from biomass, shows great application potential in energy storage and conversion. In this review, recent advances in the applications of biochar-based materials in various energy storage and conversion fields are summarized, highlighting the mechanisms and open questions in current energy applications.
A look at how biochar is formed in the biomass pyrolysis process is offered. Research points toward a biochear-based sustainable platform carbon material.
Networked control systems (NCSs) are systems whose control loops are closed through communication networks such that both control signals and feedback signals can be exchanged among system components ...(sensors, controllers, actuators, and so on). NCSs have a broad range of applications in areas such as industrial control and signal processing. This survey provides an overview on the theoretical development of NCSs. In-depth analysis and discussion is made on sampled-data control, networked control, and event-triggered control. More specifically, existing research methods on NCSs are summarized. Furthermore, as an active research topic, network-based filtering is reviewed briefly. Finally, some challenging problems are presented to direct the future research.
The electrochemical oxygen evolution reaction (OER) is a core electrode reaction for the renewable production of high‐purity hydrogen, carbon‐based fuel, synthetic ammonia, etc. However, the sluggish ...kinetics of the OER result in a high overpotential and limit the widespread application of OER‐based technologies. Recent studies have shown that bimetallic‐based materials with the synergism of different metal components to regulate the adsorption and dissociation energy of intermediates are promising OER electrocatalyst candidates with a lower cost and energy consumption. In the past two decades, tremendous efforts have been devoted to developing OER applications of bimetallic‐based materials with a focus on compositions, phase, structure, etc., to highlight the synergism of different metal components. However, there is a lack of critical thinking and organized analysis of OER applications with bimetallic‐based materials. This review critically discusses the challenges of developing bimetallic‐based OER materials, summarizes the current optimization strategies to enhance both activity and stability, and highlights the state‐of‐the‐art electrocatalysts for OER. The relationship between the componential/structural features of bimetallic‐based materials and their electrocatalytic properties is presented to form comprehensive electronic and geometric modifications based on thorough analysis of the reported works and discuss future efforts to realize sustainable bimetallic‐based OER applications.
The impressive progress in the rational design of bimetals and bimetallic compounds toward oxygen evolution reaction (OER) is summarized. Based on the main advantages and challenges for the bimetallic‐based OER electrocatalysts, the optimization strategies are presented to modify the electronic structure and geometric construction to highlight the synergism characteristics, including compositional regulation, elemental doping, coordination adjustment, interfacial structure establishment, morphology control, and support interaction for achieving efficient OER performance.
•Main non-organic electron donors for low C/N wastewater denitrification are summarized.•Autotrophic denitrification processes for treating low C/N wastewater are highlighted.•Concerns about their ...potential adverse impacts in practical applications are discussed.•Combined denitrification processes for multi-contaminant removals are envisaged.
Denitrification with non-organic electron donors for treating low C/N ratio wastewater has attracted growing interests. Hydrogen, reduced sulfur compounds and ferrous ions are mainly used in autotrophic denitrification, holding promise for achieving practical applications. Recently, the development of autotrophic denitrification-based processes, such as bioelectrochemically-supported hydrogenotrophic denitrification and sulfur-/iron-based denitrification assisted multi-contaminant removal, provide opportunities for applying these processes in wastewater treatment. Exploration of the autotrophic denitrification process in terms of contaminant removal mechanism, interaction among functional microorganisms, and potential full-scale applications is thus of great importance. Here, an overview of the commonly used non-organic electron donors, e.g., hydrogen, reduced sulfur compounds and ferrous ions, in denitrification for treating low C/N ratio wastewater is provided. Also, the feasibility of applying the combined processes based on autotrophic denitrification with the compounds is discussed. Furthermore, challenges and future possibilities as well as concerns about the practical applications are envisaged in this review.
•Molecular spectroscopy is a key platform to characterize and monitor NOM.•Advances/innovations on spectroscopic studies of NOM are summarized.•Limitations of spectroscopic approaches for NOM ...interpretation are criticized.•Perspectives on spectroscopic developments in NOM-related topics are envisaged.
Natural organic matter (NOM) is ubiquitous in environment and plays a fundamental role in the geochemical cycling of elements. It is involved in a wide range of environmental processes and can significantly affect the environmental fates of exogenous contaminants. Understanding the properties and environmental behaviors of NOM is critical to advance water treatment technologies and environmental remediation strategies. NOM is composed of characteristic light-absorbing/emitting functional groups, which are the “identification card” of NOM and susceptive to ambient physiochemical changes. These groups and their variations can be captured through optical sensing. Therefore, spectroscopic techniques are elegant tools to track the sources, features, and environmental behaviors of NOM. In this work, the most recent advances in molecular spectroscopic techniques, including UV-Vis, fluorescence, infrared, and Raman spectroscopy, for the characterization, measurement, and monitoring of NOM are reviewed, and the state-of-the-art innovations are highlighted. Furthermore, the limitations of current spectroscopic approaches for the exploration of NOM-related environmental processesand how these weaknesses/drawbacks can be addressed are explored. Finally, suggestions and directions are proposed to advance the development of spectroscopic methods in analyzing and elucidating the properties and behaviors of NOM in natural and engineered environments.
Display omitted
The occurrence of microplastics (MPs) as emerging contaminants in the environment may cause changes in water or sediment characteristics, and further affect their biogeochemical cycles. Thus, ...insights into the interactions between dissolved organic matter (DOM) and MPs are essential for the assessment of environmental impacts of MPs in ecosystems. Integrating spectroscopic methods with chemometric analyses, this work explored the chemical and microstructural changes of DOM-MP complex to reveal the mechanism of DOM-MP interaction at a molecular level. MPs were found to interact with the aromatic structure of DOM via π-π conjugation, then be entrapped in the DOM polymers by the carboxyl groups and C=O bonds, constituting a highly conjugated co-polymer with increased electron density. This induced the fluorescence intensity increase in DOM. The interaction affinity of DOM-MP was highly dependent on the MP size and solution pH. This work offers a new insight into the impact of MP discharge on environment and may provide an analytical framework for evaluating MP hetero-aggregation and the roles of MPs in the transportation of other contaminants. Furthermore, the integrated methods used in this work exhibit potential applications in exploring the fragmentation processes of MPs and formation of secondary MPs under natural conditions.
Display omitted
•DOM is adhered onto MPs via π-π conjugation, carboxyl groups and C=O bonds.•MP-DOM constitutes a conjugated co-polymer with an elevated electron density.•Interaction between DOM and MP depends on MP size and solution pH.•The approach has a great potential in elucidating plastics fragmentation and secondary MPs formation.
The interaction mechanism between humic acid and polystyrene microplastics is explored and new insights into the impact of MP discharge on environment are provided.
Iron-assisted biological wastewater treatment processes have shown a promising potential in removing various types of contaminants. Synergistic effects between iron and microbes on the contaminant ...degradation make the role of iron beyond that of a nutritional necessity. Exploration of the synergistic mechanisms and the interactions between iron species and microbes and their metabolic products in bio‑iron systems is therefore of significant importance. Iron, including zero-valent iron, ferrous/ferric ions and iron minerals are all reported to be capable of enhancing specific contaminant removals. Although the main role of different iron species in stimulating biological process may differ between each other, their similar transformation pathways may bring us useful information about bio‑iron systems. In this paper, an overview of iron-assisted biological wastewater treatments, including anaerobic digestion, S and Cl reduction, N and P removal, heavy metal immobilization, aromatic and halogenated hydrocarbon compounds degradation, and sludge granulation is provided. Also, the potential synergistic effects between iron and microbes involved in these processes are explored. Furthermore, the main advantages, limitations, and challenges for the development of iron-assisted treatment processes are envisaged.
•Iron-assisted biological wastewater treatment processes are summarized.•Synergistic effects between iron and microbes in bio‑iron systems are highlighted.•Mechanisms behind the iron-enhanced bio-treatment are described.•Concerns on the full-scale application of iron-assisted bio-treatment are discussed.•Potential developments beyond iron-assisted bio-treatment are envisaged.
