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[Display omitted] By introducing a minute quantity of phytate ammonium into the conventional dilute zinc sulfate electrolyte, a static physical barrier is established by the phytic anion. Simultaneously, a dynamic electrostatic shield layer collaborates, yielding superior electrochemical performance. This addition facilitates an accelerated de-solvation process, effectively suppressing the so-called "tip effect" and mitigating dendrite growth. • Developed facile and effective additives for aqueous zinc-ion batteries. • Utilized both cation and anion for a multi-functional additive. • Physical barrier and dynamic electrostatic-field shield layer enhance performance. • Realized a dual protection mechanism for high performance. Corrosion and the formation of by-products resulting from parasitic side reactions, as well as random dendrite growth, pose significant challenges for aqueous zinc-ion batteries (AZIBs). In this study, phytate ammonium is introduced into the traditional dilute Zinc sulfate electrolyte as a multi-functional additive. Leveraging the inherent zincophilic nature of the phytic anion, a protective layer is formed on the surface of the zinc anode. This layer can effectively manipulate the deposition process, mitigate parasitic reactions, and reduce the accumulation of detrimental by-products. Additionally, the competitive deposition between dissociated ammonium ions and Zn2+ promotes uniform deposition, thereby alleviating dendrite growth. Consequently, the modified electrolyte with a lower volume addition exhibits superior performance. The zinc symmetric battery demonstrates much more reversible plating/stripping, sustaining over 2000 h at 5 mA cm−2 and 1 mA h cm−2. A high average deposition/stripping efficiency of 99.83 % is achieved, indicating the significant boosting effect and practical potential of our strategy for high-performance aqueous zinc-ion batteries. [ABSTRACT FROM AUTHOR]

• Bipolar membrane ED was used for nutrient recovery from AD dewatering sidestream. • Concentrated acid and base streams containing separated nutrients were produced. • Ammonia was recovered using a produced acid solution by membrane stripping. • Phosphate was recovery as struvite or hydroxyapatite by chemical precipitation. • Nutrient recovery was achieved with minimized chemical and energy inputs. Anaerobic digestion (AD) offers an efficient means for treating sludge generated in wastewater treatment plants (WWTPs), but nutrient-rich AD dewatering sidestream contributes as much as 30 % of the overall nutrient loading of WWTPs. Several electrochemical approaches are being developed as a sidestream treatment strategy to prevent return of nutrients to WWTP headworks and recover them for fertilizer production. One such method is to produce acids and bases, essential chemicals necessary to facilitate nutrient recovery, using bipolar membrane electrodialysis (BMED). In this study we show simultaneous separation of nutrients and production of acid/base streams with an additional consideration for increasing the concentration of ammonium and phosphate in the final product stream by systematically altering compartment flow rates and hence the retention time of each stream. Using a three-compartment BMED system with a synthetic sidestream containing 50 mM NH 3 -N and 2 mM PO 4 -P, we achieved up to 80 % ammonia removal (via a cation exchange membrane) and up to 60 % phosphate removal (via an anion exchange membrane) at a productivity of 34.2 L m−2 h−1. Separated ammonia was recovered (>90 %) in a subsequent membrane contactor (MC) that was fed with acid and base streams produced by the BMED unit. A phosphate recovery > 80 % was achieved by chemical precipitation (CP). In a combined BMED-MC-CP process, the concentrated final product contained 333.9 mM NH 3 -N and 3.1 mM PO 4 -P with an energy consumption of 8.9 kWh kg−1 N recovered. These results illustrate that the BMED-based treatment train is a promising strategy for nutrient recovery from AD dewatering sidestream. [ABSTRACT FROM AUTHOR]

The QCD36A 1-1 350 shows excellent photocatalytic activity for H 2 O 2 production under visible light irradiation. [Display omitted] • A quaternary ammonium cyclodextrin polymeric photocatalyst QCD36A 1-1 350 is successfully synthesized. • The quaternary ammonium group in the QCD36A 1-1 350 structure broadened the absorption of visible light. • The introduction of quaternary ammonium groups can facilitate efficient charge transfer, speed up the 2e- ORR process. • A photocatalytic H 2 O 2 yield of 2.51 mmol g−1h−1 was achieved in purified water without an electron donor or aeration. A photocatalytic system can be used to efficiently produce hydrogen peroxide (H 2 O 2) without introducing a sacrificial agent or oxygen (O 2). This system has practical application potential but remains challenging to implement. To increase the H 2 O 2 yield of this system, a quaternary ammonium cyclodextrin polymeric photocatalyst QCD36A 1-1 350 is successfully synthesized using quaternization modification and low-temperature polycondensation. The photocatalyst is used to produce H 2 O 2 from pure water and air by the one-step two electron oxygen reduction reaction. Under irradiation by visible light, QCD36A 1-1 350 produces a higher H 2 O 2 yield (of up to 2.51 mmol g−1h−1) than unquaternized polymers and reported metal-free catalysts under similar conditions. Experimental and theoretical studies clearly show that the introduction of quaternary ammonium groups can effectively broaden the visible light absorption of polymer catalysts, while increasing the hydrophilicity, charge transfer efficiency and surface stability. The practicability of efficient photocatalytic production of H 2 O 2 is realized by increasing the activity and selectivity of the polymer photocatalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • UDB and DB at different pyrolysis temperatures played contrasting roles. • DB800-amended group displayed superior nitrogen removal performance. • DB at lower pyrolysis temperature imposed suppression. • Properties of dissolved organic matter released by DB were tracked at molecular level. Biochar has attracted increasingly attention in the biological wastewater treatment owing to its unique environmental behavior. However, the differential effects of undissolved and dissolved fractions of biochar (hereafter named as UDB and DB, respectively) on the anaerobic ammonium oxidation (anammox) process remain unclear. The study evaluated the nitrogen removal performance of anammox system in response to UDB and DB prepared at different pyrolysis temperatures (300 °C, 550 °C and 800 °C). The DB800-amended group displayed superior nitrogen removal performance with the total nitrogen removal efficiency (TNRE) of 92.8 ± 1.4 %. Compared with CK, TNRE was changed by +5.0 % (UDB300), +0.4 % (UDB550) and −22.3 % (UDB800) for UDB-amended groups, and by −16.0 % (DB300), −9.4 % (DB550), and +9.2 % (DB800) for DB-amended groups, respectively. The differences were closely related to the physicochemical properties of UDB and DB. Particularly, dissolved organic matter released by DB were tracked at molecular level, which revealed that CHO occupied the highest proportion of 70.3 % and lignin-like and carboxylic rich alicyclic molecules were dominant in DB800. This study would facilitate the understanding of the differences between the nitrogen removal performance of UDB and DB-amended anammox, thus providing deeper insights for the comprehensive assessment of the impacts of biochar on the anammox process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Micro-oxygen combined with applied voltage promote total nitrogen removal. • Electrode regulates the spatial distribution of functional microorganisms. • Applied voltage regulates function gene abundance and enzyme activity. • Hydroxylamine oxidation peaks and up-regulation hao gene are demonstrated. Anodic ammonium oxidation catalyzed by microorganisms holds great potential as an effective anaerobic approach for ammonium and total nitrogen removal. However, the application of this approach is constrained by a low rate of ammonium oxidation, limiting the efficiency of total nitrogen removal. To overcome this limitation, a small amount of oxygen was introduced into a single-chamber microbial electrolysis cell to initiate the production of hydroxylamine through ammonium oxidation. Enhanced efficiency of overall nitrogen removal was obtained by the combined regulation of micro-oxygen and microbial electrode catalysis for ammonium oxidation and denitrification. According to the ammonium oxidation amount, the total oxidized nitrogen removal efficiency reached 67.87 ± 0.25 % and total nitrogen removal amount was 202.9 ± 0.5 mg/L, showing a high performance for treating high ammonium-contained wastewater. The oxidation peaks of hydroxylamine were determined at 0.43 V (vs. Ag/AgCl) for revealing the possible process of anodic hydroxylamine oxidation coupling to cathodic denitrification. In addition, microbial community analysis revealed that increasing the applied voltage regulated the abundance of nitrifying and denitrifying functional microbial communities both in the solution and on electrodes, and the key functional genes including hydroxylamine oxidation (hao), nitrate reduction (narG , narH , narI , napA , napB), nitrite reduce (nirK, nirS), and nitric oxide reduce (norB , norC), increased significantly at the applied voltage of 0.9 V, which accompanied by an obvious enhancement of enzyme activity compared to anaerobic and open circuit voltage. This work revealed the enhanced performance and mechanism on synergistic regulation by micro-oxygen and applied voltage for ammonium oxidation and denitrification, and provided new insights and feasible enhancing measures for treating high ammonium-nitrogen wastewater with low C/N ratio. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nature based redox materials can serve as electron acceptors and donors. • Complete nitrogen removal based on redox materials. • Emergence of a new pathway for anerobic ammonium oxidation. • Nature-based sustainable solutions for nitrogen management. Complete nitrogen removal depends on the requirement of oxygen as an electron acceptor and organics as electron donors. In the natural environment, these electron acceptors and donors regulate the nitrogen cycle in association with several nature-based processes, such as iron dependent (feammox), sulphur dependent (sulfammox), and nitrite dependent (annamox). These processes represent the latest discoveries in the nitrification part of the nitrogen cycle and provide the electron acceptors for anaerobic ammonium oxidation. Research findings on these processes suggest that a previously undescribed pathway is available for anaerobic ammonium oxidation, which can regulate the nitrogen cycle in natural environments. It has been shown that some redox active materials can serve simultaneously as electron acceptors and donors in the nitrogen cycle. This review provides comprehensive information of the known oxidative processes in the nitrogen cycle and highlights the emergence of a new pathway for anaerobic NH 4 + oxidation, which is dependent on insoluble redox active materials as electron donors and acceptors. This new pathway is not limited to anaerobic NH 4 + oxidation, but it also includes reductive pathways to nitrogen gas, and thus can lead to complete nitrogen removal from nitrogen environments. Recent developments and knowledge advancement in the nitrogen cycle open a new path for nature-based sustainable solutions for nitrogen management. This new knowledge can provide innovative and novel approaches for conventional NH 4 + removal processes. [ABSTRACT FROM AUTHOR]

• Biological nitrogen removal is a carbon source of wastewater treatment. • Nitrogen neutrality determines carbon neutrality of wastewater treatment. • Ammonium recovery is necessary for carbon–neutral wastewater treatment. • Nature inspired green approaches for ammonium recovery are highly desirable. • AnMBR coupled with microalgae can address the water-energy-resources nexus. With rapidly evolving global climate change, municipal wastewater treatment has been identified as a nonneglected carbon source contributing to about 1–2% of total carbon emissions worldwide. Given such a situation, the development of carbon–neutral municipal wastewater treatment process has become highly desirable and pressing. However, almost all wastewater ammonium is biologically converted to nitrogen gas in the present biological treatment processes of municipal wastewater, making ammonium recovery impossible. It is shown in this article that the current biological nitrogen removal (BNR) processes indeed are a significant carbon source, implying that nitrogen neutrality largely determines carbon neutrality of wastewater treatment. To tackle this challenge, ammonium recovery instead of BNR should be incorporated into future municipal wastewater treatment processes. Although several advanced bio/electrochemical approaches have recently been developed for ammonium recovery from municipal wastewater, their engineering and economic feasibility have not yet been determined. Instead, the nature-inspired green approach for recovery of wastewater ammonium should deserve more attention and effort. It is shown that an integrated anaerobic fixed-film membrane bioreactor-microalgae bacterial granular sludge process coupled with heat exchange can create a significant carbon sink, likely leading to carbon-negative municipal wastewater treatment. Consequently, it is reasonable to consider that the way forward is to explore a green-to-green engineering approach through harnessing the synergies among wastewater treatment, energy-heat-nutrients recovery, and carbon dioxide capture. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multiple mediators function as electron shuttles to promote anammox process; • The EET capability of anammox bacteria can be facilitated by external mediators; • The concurrent presence of mediators triggered the activation of essential enzymes; • The application perspective should focus on the EET-enhanced anammox optimization. The anaerobic ammonium oxidation (anammox) process, transforming ammonia into nitrogen gas in oxygen-free environments using nitrite as an electron acceptor, is increasingly recognized for its potential in treating ammonium-rich wastewater. A major challenge for widespread application of this technology is the limited presence of nitrite in most wastewaters. The intrinsic electroactivity of anammox bacteria implies that the introduction of exogenous additives through the extracellular electron transfer (EET) process could effectively stimulate ammonia oxidation even in the absence of nitrite. This comprehensive review consolidates various approaches to enhance EET-dependent anammox, including the utilization of carbonaceous materials, metal ions, and humic substances. Molecular mechanisms involved in enhancing nitrogen removal performance based on extracellular electron transfer capacity are expounded. The co-occurrence of electron acceptors and exogenous electron shuttles is proposed to increase the activity of c-type cytochromes (c -Cyts) and N-acyl-homoserine lactones (AHLs) in extracellular polymeric substances (EPS), as well as enzymes such as hydrazine synthase (HZS) and hydrazine dehydrogenase (HDH), leading to stable a nitrogen removal performance. This review presents novel insights into the engineering of the EET-enhanced anammox process, providing a theoretical framework for its advancement and optimization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxalate ions form a protective layer on zinc anode, inhibiting side reactions. • Oxalate ions alter solvation of zinc ions, replacing water molecules. • Oxalate ions promote Zn (0 0 2) crystal plane growth, optimizing deposition. • Ammonium ions shield zinc protrusions, suppressing tip effect. • Ammonium oxalate enhances cycle life in Zn-Zn cells and Zn-MnO 2 batteries. The natural reactivity of Zn metal in aqueous environments leads to surface deterioration and uncontrolled dendrite growth, posing challenges in the advancement of Zn-ion batteries. In this research, we introduce an environmentally friendly and cost-effective electrolyte additive, ammonium oxalate (AO), to significantly extend the cycle life of Zn-ion batteries with minimal usage. Oxalate ions within AO actively participate in the solvation of hydrated Zn ions and attach to the Zn anode surface prior to H 2 O molecules, creating a robust solid-electrolyte interface (SEI) layer. This SEI layer serves a dual purpose: it inhibits further reactions with H 2 O and restricts the two-dimensional movement of Zn ions, promoting the preferential growth of the (0 0 2) crystal plane. Consequently, Zn||Zn cells exhibit an impressive lifespan surpassing 1800 h (at 1 mA cm−2, 1 mAh cm−2), and Zn||Cu cells experience a tenfold increase in cycling life. Moreover, Zn||MnO 2 full cells, incorporating this low-cost and highly efficient inorganic additive, maintain an outstanding 80.84 % capacity retention after 1200 cycles at 1 A g−1. This breakthrough with AO offers a promising avenue for the practical implementation of Zn-ion batteries, emphasizing their cost-effectiveness and environmental sustainability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electro-oxidation of N-heterocycles produces N 2 , N H 3 / N H 4 + , N O 3 - , C O and C O 2. • N H 3 / N H 4 + and an apparent N 2 yield correlate linearly with carbon removal. • Both apparent N 2 and N O 3 - form directly from organic intermediates rather than N H 3 / N H 4 +. • Higher concentrations of parent compounds promote a higher apparent N 2 selectivity. • N O 3 - dominates when oxidation of carbon is mass transfer-limited or at basic pH. We report for the first time the carbon and nitrogen product distribution during the electrochemical oxidation (EO) of pyrazine and related N-heterocyclic compounds (NHCs) present in the hard-to-treat wastewater from a biofuel production process. The experimental study was carried out using a boron-doped diamond anode. Identified and quantified intermediate products included oxamic acid, formamide, oxalic acid, and formic acid. Analysis of the C and N yields as a function of the extent of carbon removal reveals the influence of the current- and mass transfer-control operating regimes on product distribution. Carbon monoxide, which was detected among the gaseous products, suggests a possible decarbonylation pathway in the current-controlled regime. An apparent nitrogen gas and ammonium yields correlated linearly with the carbon removal, while nitrate yields significantly increased in the mass transfer-controlled regime. Nitrate and apparent nitrogen gas appear to form directly from organic nitrogen intermediates, rather than from the ammonium that also forms in the process. The research gives new insights into the NHCs degradation pathways, product distribution, and final water composition as a function of operating regime in the EO of recalcitrant wastewater. [ABSTRACT FROM AUTHOR]