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Electrochemical nitrate reduction reaction (NO3RR) offers a route to balanced nitrogen cycle and sustainable ammonia production. However, unsatisfied performance in neutral media arising from competitive hydrogen evolution reaction and inefficient hydrogenation impede the further applications of NO3RR. Herein, the rational design of RuNi alloy nanostructures is reported. Benefited from the synergism effect between Ru and Ni, Ru20Ni80 alloy exhibits a high NH3 Faradaic efficiency of 98.02% at −0.35 V (vs reversible hydrogen electrode (RHE)) and a large NH3 yield rate of 27.88 mg mgcat−1 h−1 at −0.65 V (vs RHE). Importantly, the atomic scale cooperation between Ru and Ni active sites endows RuNi alloy a close‐to‐unity NH3 selectivity via HNO* pathway. Theoretical calculations have revealed that the interactions between Ru and Ni optimize the electronic structures of Ru20Ni80 alloy, where Ru sites with enhanced electroactivity improve the generation of active hydrogens and more electron‐rich Ni sites facilitate the reduction of nitrate. Accordingly, the adsorption strengths of key intermediates become stronger and the energy barriers of NO3RR are reduced to guarantee efficient NO3RR. Furthermore, a flow‐type reactor coupled with coprecipitation is established to achieve continuous NH3 generation and recovery as struvite. [ABSTRACT FROM AUTHOR]

Water pollution is a major concern due to its detrimental effects on the environment and public health. The particular danger of inorganic pollutants arises from their persistent toxicity and inability to biodegrade. Recently, electrocoagulation (EC) has been demonstrated as an alternative sustainable approach to purifying wastewater due to the increasingly strict pollution prevention rules. In particular, EC has been used to remove inorganic pollutants, such as Cr, Zn, Pb, or As. EC has emerged as a sustainable tool for resource recovery of some inorganic pollutants such as N and P that, when recovered, have value as plant nutrients and are critical in a circular economy. These recovered materials can be obtained from diverse agricultural drainage water and recycled as fertilizers. In this work, a state-of-the-art technique is reviewed describing the advances in contaminant removal and nutrient recovery using EC through an in-depth discussion of the factors influencing the contaminant removal process, including operating pH, time, power, and concentration. Furthermore, limitations of the EC technology are reviewed, including the high-power consumption, fast deterioration of the sacrificial electrodes, and the types of contaminants that could not be efficiently removed. Finally, new emerging constructs in EC process optimization parameters are presented. [ABSTRACT FROM AUTHOR]

Steam stripping of ammonia from ammonia-rich wastewater (5000–20,000 mg/L) was conducted in a continuous-flow rotating packed bed (RPB) at a pH of 11. This study aimed to elucidate the influence of key operational parameters, including the steam-to-liquid ratio, rotational speed (ω), initial ammonia concentration, steam inlet temperature (TSi), and liquid inlet temperature (TLi), on critical performance metrics such as the ammonia removal efficiency (ARE), the volumetric liquid mass transfer coefficient (KLa), and the concentration of the recovered ammonia solution (CR). The findings revealed that a CR of 22.88 wt.% was achieved under the optimal conditions of a steam-to-liquid ratio of 0.175 kg/kg, an initial concentration of 20,000 mg/L, a TSi of 120 °C, and a TLi of 70 °C. Key experimental factors, including the initial ammonia concentration, TSi, and TLi, significantly impacted the achievement of higher ARE and CR values. The KLa values exhibited a decrease with the increase in the steam-to-liquid ratio, while they increased with ω. However, the KLa remained relatively consistent with ω values within the range of 600 to 1200 rpm. In comparison with prior studies, steam stripping of ammonia exhibits a higher ARE than air stripping with RPB and a higher CR than conventional stripping methods. Moreover, RPB requires a smaller size to achieve equivalent ARE compared to conventional stripping apparatuses. Thus, the steam stripping process with RPB equipment emerges as a suitable method for ammonia recovery from ammonia-rich wastewater. [ABSTRACT FROM AUTHOR]

Wastewater treatment plants play a vital role in resource recovery, particularly through biogas production, a key renewable energy source. Beyond biogas, the digestate from anaerobic digestion is rich in nutrients like ammonia. This study explored the feasibility of recovering ammonia from sewage sludge digestate using air stripping. The process was modeled using Aspen Plus® software, utilizing real data from As-Samra WWTP in Jordan. Various operational parameters, such as digestate feed flow, air flow rate, temperature, and pressure, were analyzed to optimize ammonia recovery. The results showed that with a feed flow rate between 10,000 and 30,000 kg/hr, ammonia recovery reached 85%, with production exceeding 100 kg/hr, where the effect of the flow rate appears mostly at elevated feeding temperatures. Increased air flow rates significantly boosted recovery, achieving 90% efficiency at 60 °C with 50,000 kg/h as air flow. Flashing pressure peaked at 1.5 bar, with 85% efficiency at 95 °C, while higher pressures yielded diminishing returns, stabilizing production around 106 kg/hr. The NaOH feed rate also influenced output, rising from 100 kg/hr at a 50 kg/hr feed rate to 107 kg/hr at 750 kg/hr, with recovery efficiency exceeding 85%. The economic analysis showed that the project had a payback period of 6.07 years, reflecting a reasonable recovery of the initial investment. The net present value was 122,924 USD over 15 years, with 8% amortization rate, indicating that the project created value beyond the initial cost. The internal rate of return was 14.23%, surpassing the discount rate and highlighting the project's financial attractiveness.

The electrochemical nitrate reduction reaction (NO3RR) is able to convert nitrate (NO3−) into reusable ammonia (NH3), offering a green treatment and resource utilization strategy of nitrate wastewater and ammonia synthesis. The conversion of NO3− to NH3 undergoes water dissociation to generate active hydrogen atoms and nitrogen‐containing intermediates hydrogenation tandemly. The two relay processes compete for the same active sites, especially under pH‐neutral condition, resulting in the suboptimal efficiency and selectivity in the electrosynthesis of NH3 from NO3−. Herein, we constructed a Cu1‐Fe dual‐site catalyst by anchoring Cu single atoms on amorphous iron oxide shell of nanoscale zero‐valent iron (nZVI) for the electrochemical NO3RR, achieving an impressive NO3− removal efficiency of 94.8 % and NH3 selectivity of 99.2 % under neutral pH and nitrate concentration of 50 mg L−1 NO3−−N conditions, greatly surpassing the performance of nZVI counterpart. This superior performance can be attributed to the synergistic effect of enhanced NO3− adsorption on Fe sites and strengthened water activation on single‐atom Cu sites, decreasing the energy barrier for the rate‐determining step of *NO‐to‐*NOH. This work develops a novel strategy of fabricating dual‐site catalysts to enhance the electrosynthesis of NH3 from NO3−, and presents an environmentally sustainable approach for neutral nitrate wastewater treatment. [ABSTRACT FROM AUTHOR]

In view of water eutrophication, global energy crisis and the carbon neutrality policies, the ammonia recovery from wastewater with high efficiency and low energy consumption is crucial for preserving the ecological environment and achieving sustainable development. Transmembrane electro-chemisorption (TMECS), which integrates transmembrane chemisorption with electrochemical systems to reduce the addition of chemicals and improve recovery efficiency, is a promising technology for ammonia recovery from wastewater. Accordingly, this paper first reviews the recent advances in TMECS for ammonia recovery from wastewater. In particular, the technology principles, including ammonia stripping by cathodic base, ammonia recovery by TMECS with authigenic acid and base, and ammonia recovery by membrane cathode with in situ cathodic base are elucidated. Couplings of TMECS with other electrochemical systems, including electrodialysis, flow-electrode capacitive deionization, and electrochemical precipitation, are further summarized and compared. Finally, the challenges and prospects of the TMECS technology are addressed. [ABSTRACT FROM AUTHOR]

Struvite crystallization can recover nitrogen and phosphorus simultaneously from various kinds of wastewaters as a slow-release fertilizer. However, the enhancement of the removal efficiency of NH4-N is challenging because the molar concentration of NH4-N is higher than that of PO4-P in many types of sewage including digested sludge filtrate. In this study, phosphorus eluate was recovered from sewage sludge incineration ash (SSA) and applied to the struvite crystallization process to increase the removal efficiency of NH4-N for the digested sludge filtrate. Under acidic conditions, a maximum of 98.4% of phosphorus was eluted from SSA; in alkaline conditions, a maximum of 51.2% was eluted; and in sequential elution conditions with (NaOH+H2SO4), a maximum of 98.0% was eluted. Jar tests were performed by injecting three types of eluates (H2SO4 1 N_elulate, NaOH 1 N_elulate, and (NaOH+H2SO4)_eluate), and PO4-P was stably removed (>86%) under all tested conditions. When the NaOH 1 N_eluate was injected, the NH4-N removal efficiency was highest at 84.4%, followed by 78.4% with the (NaOH+H2SO4)_eluate, and 58.7% with the H2SO4 1 N_eluate at the molar ratio of Mg:P:N of 1.5:1.5:1. In addition, the sequential jar tests were conducted by injecting both the NaOH 1 N_eluate and (NaOH+H2SO4)_eluate. In the pH range of 8.5–9.5, the PO4-P and NH4-N removal efficiencies reached 92.3–94.5% and 97.9–99.1%, respectively. X-ray diffraction analyses confirmed that the majority of the crystal phases were struvite forms. Therefore, the combined application of both the NaOH 1 N_eluate and (NaOH+H2SO4)_eluate was adequate to enhance not only the phosphorus recovery but also the removal efficiencies of PO4-P and NH4-N. SSA recovering PO4-P could be utilized as a new phosphorus source in the struvite crystallization process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Successful thermophilic composting of shrimp sludge through self-heating. • Clean nitrogen (ammonia) recovered used for high-value microalgae cultivation. • Shrimp sludge compost application as soil conditioner for enhanced mango growth. Due to the rapid growth of the aquaculture industry, large amounts of organic waste are released into nature and polluted the environment. Traditional organic waste treatment such as composting is a time-consuming process that retains the ammonia (NH 3) in the compost, and the compost produced has little economic value as organic fertilizer. Illegal direct discharge into the environment is therefore widespread. This study investigates the recovery of NH 3 through thermophilic composting of shrimp aquaculture sludge (SAS) and its application as a soil conditioner for the growth of mango plants. A maximum composting temperature of 57.10 °C was achieved through self-heating in a 200 L bench-scale reactor, resulting in NH 3 recovery of 224.04 mol/ton-ds after 14 days. The addition of calcium hydroxide and increased aeration have been shown to increase NH 3 volatilization. The recovered NH 3 up to 3 kg-N can be used as a source of clean nitrogen for high-value microalgae cultivation, with a theoretical yield of up to 34.85 kg-algae of microalgae biomass from 1 ton-ds of SAS composting. Despite the high salinity, SAS compost improved mango plant growth and disease resistance. These results highlight the potential of SAS compost as a sustainable source of clean nitrogen for microalgae cultivation and soil conditioner, contributing to a waste-free circular economy through nutrient recycling and sustainable agriculture. [ABSTRACT FROM AUTHOR]

Electrochemical process has been widely applied to eliminate recalcitrant contaminants (i.e., organic and nitrogenous compounds) in landfill leachate. This study aimed to evaluate the performance of a hybrid electro-oxidation-dialysis (EOD) system to minimize organic and nitrogenous compounds through a synergistic process of electrochemical oxidation (EO) and electrodialysis (ED) as well as the dissolved organic matter was characterized in terms of fluorescent component and molecular weight distribution. The EOD was carried out using boron-doped diamond (BDD) and Pt alternately. The results have shown that pH adjustment to acidic conditions is beneficial to EO. At optimal pH (pH 4), BDD-based EO is superior to removing COD and ${\rm NH}_4^ +$ NH 4 + up to around 56% and 64%, respectively. During EOD process, the lower current density at 20.83 mA cm−2 is preferred for the recovery of nitrogenous ions (i.e. ${\rm NH}_4^ +$ NH 4 + and ${\rm NO}_3^\ndash$ NO 3 – ), especially for BDD-EOD. In addition, the dominant humic acid-like (HAL) and soluble microbial products-like (SMPL) substances in the mature leachate are mostly degraded to smaller molecules from 105 Da to 103 Da in both EOD processes. Overall, BDD-EOD favours indirect oxidation and has a higher energy consumption efficiency than Pt-EOD induced by direct oxidation for simultaneous removal of organic and nitrogenous compounds. BDD-EOD requires a lower total operation cost of around $2.33/m3 compared to Pt-EOD. It is concluded that the hybrid BDD-EOD process is technically feasible as a powerful pre-treatment approach to mature landfill leachate for refractory organics degradation and nitrogenous nutrients recovery. [ABSTRACT FROM AUTHOR]

Selective electrochemical reduction of nitrate (NO3-) into ammonia (NH_3) is critical for environmental remediation and resource recovery. This review comprehensively summarizes the recent advances in electrochemical conversion of NO3- into NH_3. Mechanisms of NO3- reduction are discussed. The conversion of NO3- into NO_2 and formation of N—H is the key for achieving high selectivity of NH3. The technologies and strategies for enhancing the performance of electrode are summarized and compared. The crystal structure, morphology and charge density of materials are the key factors affecting the properties of electrode materials. The influence of electrochemical reactor on NO3- conversion and NH_3 formation is described. The core of electrolytic cell is to avoid anode interference and in-situ realize NH_3 separation and recovery. With these facts, it is proposed that the strategies for NO3- electrochemical selective reduction synthesis of NH_3 are the development of low-cost, stable, and efficient electrode materials and electrochemical synthesis and in-situ separation of NH_3 reactor. Besides, the long-term large-scale research on the electrochemical synthesis of NH_3 from actual NO3- wastewater is critical for promoting the industrialization of this technology.

[Display omitted] • NH 3 recovery from thermophilic composting of organic sludge to culture microalgae. • Calcium hydroxide dosing accelerated ammonia volatilization. • Geobacillus as the dominant bacteria for enhancing NH 3 recovery. A modified outdoor large-scale nutrient recycling system was developed to compost organic sludge and aimed to recover clean nitrogen for the cultivation of high-value-added microalgae. This study investigated the effect of calcium hydroxide addition on enhancing NH 3 recovery in a pilot-scale reactor self-heated by metabolic heat of microorganisms during thermophilic composting of dewatered cow dung. 350 kg-ww of compost was prepared at the ratio of 5: 14: 1 (dewatered cowdung: rice husk: compost-seed) in a 4 m3 cylindrical rotary drum composting reactor for 14 days of aerated composting. High compost temperature up to 67 °C was observed from day 1 of composting, proving that thermophilic composting was achieved through the self-heating process. The temperature of compost increases as microbial activity increases and temperature decreases as organic matter decreases. The high CO 2 evolution rate on day 0–2 (0.02–0.08 mol/min) indicated that microorganisms are most active in degrading organic matter. The increasing conversion of carbon demonstrated that organic carbon was degraded by microbial activity and emitted as CO 2. The nitrogen mass balance revealed that adding calcium hydroxide to the compost and increasing the aeration rate on day 3 volatilized 9.83 % of the remaining ammonium ions in the compost, thereby improving the ammonia recovery. Moreover, Geobacillus was found to be the most dominant bacteria under elevated temperature that functions in the hydrolysis of non-dissolved nitrogen for better NH 3 recovery. The presented results show that by thermophilic composting 1 ton-ds of dewatered cowdung for NH 3 recovery, up to 11.54 kg-ds of microalgae can be produced. [ABSTRACT FROM AUTHOR]

A combined thermophilic anaerobic bioreactor of food waste and bioelectrodialysis system was used to recover volatile fatty acids and ammonia as renewable materials and also to remove the inhibitory effect of biohydrogen production byproducts. Different configurations of bioelectrodialysis system under various amounts of inlet food waste and external electrical currents were examined were investigated to find out the best conditions for system performance. When the two anion exchange membranes (AEM) were installed on the anode and cathode sides of separation chamber, 12 mL min-1 of mixed liquid was circulated between fermenter and separation chamber, while the external energy of 2.7 V and 0.2 M NaCl as electrolyte were used in the electrodialysis chambers. As long as the food waste with 70000 mg COD L-1 was used in the fermenter, the concertation of organic acids in the recovery chamber was the highest, 507.3 mg L-1 after 24th h. As a result, 0.63 L L-1 biohydrogen and 50 mL cathodic hydrogen were produced. When a cation exchange membrane was embedded on the cathode side of the separation chamber, the ammonia concertation in the recovery chamber was the highest, 518 mg L-1, at 36th h. At the same time, the chemical oxygen demand of the anode solution was decreased by about 3600 mg L-1. This sustainable and bioelectrical system can recover organic acids and ammonia, cathodic hydrogen production, while simultaneously increase biohydrogen production and efficient even when substrate concentration was higher. • A combined thermophilic anaerobic bioreactor of food waste and bioelectrodialysis system was used. • Volatile fatty acids and ammonia as valuables and biohydrogen production inhibitor were recovered. • When anion exchange membranes on the two sides of separation chamber were used, recovery was highest. • 507.3 mg L−1 acids were recovered and 0.63 L L−1 biohydrogen and 50 mL cathodic hydrogen were produced. • When a cation exchange membrane was used, 518 mg L−1 ammonia in the recovery chamber was recovered. [ABSTRACT FROM AUTHOR]

This study investigates the performance of hydrophobic membrane contactors (HMC) for the recovery of dissolved ammonia (NH3) from natural rubber processing (NRP) wastewater during short- and long-term operation. The results show that 90% recovery of total NH3 nitrogen can be achieved. In the short-term operations, the increases in the wastewater velocity and pH enhanced the NH3 desorption overall mass transfer coefficient (KOV), but the increase in the number of total solids in the wastewater reduced the KOV. The Wilson plot method confirmed the significance of the mass transfer resistance of the wastewater phase for NH3 desorption. The long-term operation revealed that the KOV was kept constant for 15 days and then declined owing to membrane fouling. Flushing using water (physical cleaning) could not restore the KOV to its initial value, but a series of chemical cleanings with 0.1M NaOH and 0.1 M HCl solution successfully recovered the KOV. The comparison of cleaning solutions in the foulant extraction's ability showed that 0.1 M NaOH was the most potent, followed by 0.1 M HCl and water. Fouling characterization using scanning electron microscopy and energy dispersive X-ray spectrometry (SEM/EDS) and the Fourier transform infrared spectroscopy revealed a cake layer covering the membrane surface, and the foulants consisted of organic compounds composed of proteins from natural rubber (NR) particles and inorganic salts. The hydrophobic interaction of the proteins covering the NR particles allowed the natural rubber particles to be deposited on the membrane surface, even without hydraulic pressure in HMC. The negative charge of the NR particles could also interact with ions, leading to the formation of inorganic components in the fouling cake layers. Two types of fouled membrane surfaces were identified via SEM/EDS: a smooth area, which consisted of N-atom from proteins, and a rugged area with small conglomerate particles in which no N-atoms were observed. [ABSTRACT FROM AUTHOR]

Membrane contactors are among the available technologies that allow a reduction in the amount of ammoniacal nitrogen released into the environment through a process called transmembrane chemical absorption (TMCA). This process can be operated with different substances acting as trapping solutions; however, strong inorganic acids have been studied the most. The purpose of this study was to demonstrate, at laboratory scale, the performance of citric acid as a capturing solution in TMCA processes for recovering ammonia as an organic fertilizer from anaerobic digestor reject water using membrane contactors in a liquid–liquid configuration and to compare it with the most studied solution, sulfuric acid. The experiments were carried out at 22 °C and 40 °C and with a feed water pH of 10 and 10.5. When the system was operated at pH 10, the rates of recovered ammonia from the feed solution obtained with citric acid were 10.7–16.5 percentage points (pp) lower compared to sulfuric acid, and at pH 10.5, the difference decreased to 5–10 pp. Under all tested conditions, the water vapor transport in the system was lower when using citric acid as the trapping solution, and at pH 10 and 40 °C, it was 5.7 times lower. When estimating the operational costs for scaling up the system, citric acid appears to be a better option than sulfuric acid as a trapping solution, but in both cases, the process was not profitable under the studied conditions.

Ammonia recovery from wastewater is crucial, yet technology of low carbon emission and high ammonia perm-selectivity against complex stream compositions is urgently needed. Herein, a membrane-based hybrid process of the Donnan dialysis–electrodialysis process (DD–ED) was proposed for sustainable and efficient ammonia recovery. In principle, DD removes the majority of ammonia in wastewater by exploring the concentration gradient of NH4+ and driven cation (Na+) across the cation exchange membrane, given industrial sodium salt as a driving chemical. An additional ED stage driven by solar energy realizes a further removal of ammonia, recovery of driven cation, and replenishment of OH− toward ammonia stripping. Our results demonstrated that the hybrid DD–ED process achieved ammonia removal efficiency >95%, driving cation (Na+) recovery efficiency >87.1% for synthetic streams, and reduced the OH− loss by up to 78% compared to a standalone DD case. Ammonia fluxes of 98.2 gN m−2 d−1 with the real anaerobic digestion effluent were observed using only solar energy input at 3.8 kWh kgN−1. With verified mass transfer modeling, reasonably controlled operation, and beneficial recovery performance, the hybrid process can be a promising candidate for future nutrient recovery from wastewater in a rural, remote area.

Directly recovering ammonia from waste streams is a sustainable approach for ammonia management since it saves energy from both the Haber-Bosch process, the major industrial method for ammonia synthesis, and wastewater treatment. Membrane distillation (MD), an evaporation-based membrane separation process, has been employed to recover ammonia from ammonia-rich wastewater due to the high volatility of ammonia. In this study, the photothermal effect is incorporated into MD to enhance the ammonia recovery from ammonia-rich wastewater. Carbon black particles are coated on the membrane surface to increase its absorption of solar irradiation at the solution-membrane interface and facilitate the ammonia transport across the membrane. We demonstrate that the system can recover ammonia at a maximum ammonia flux of 4.52 g-N·m−2·h−1 with a solar intensity of 1.7 kW·m−2. The estimated mass transfer coefficient of carbon black coated membrane is 2.67 × 10−2 m·h−1 with solar irradiation, enhanced by 30.8% when compared to that in a pristine membrane. We also confirm that the improvement of ammonia flux by photothermal effect is equivalent to heating the feed solution by 20–30 °C. Our study demonstrates a promising pathway for utilizing solar energy by photothermal effects to enhance MD for ammonia recovery from ammonia-rich wastewater.

Ammonia is a toxic and hazardous substance, as well as a valuable chemical. The gaseous ammonia are soluble in water, rendering some industrial wastewater contains high concentration of ammonia. These wastewater can be a direct source for the production of commercially concentrated ammonia solution via sweep gas membrane distillation (SGMD). Taking advantage of vapor-liquid equilibrium of ammonia-water binary system, ammonia can be recovered from these wastewater, and concentrated to several times higher concentration under optimized conditions. In this work, we have demonstrated the ammonia recovery by SGMD process, and comprehensively investigated the effect of different operation conditions on the SGMD performance. [ABSTRACT FROM AUTHOR]

The recovery of livestock manure, rich in nutrients, as fertilizer in agriculture, could pose the risk of an excessive load of nitrogen on the soil. Ammonia stripping is one of the available technologies for reducing the amount of nitrogen in the digestate obtained by the anaerobic digestion of manure. The study investigated the performance and energy consumption of a full-scale ammonia-stripping plant, equipped with a bubble reactor and working without the use of any alkaline reagent under semi-batch conditions. Stripping tests were conducted on the liquid fraction of the digestate, studying the current and optimized operative conditions of the plant. The main variables influencing the process were pH, temperature, airflow, and feed characteristics. In the experimental tests, the pH spontaneously increased to 10, without dosing basifying agents. Higher temperatures favoured the stripping process, the higher tested value being 68 °C. The airflow was kept equal to 15 Nm3 h−1 m−3digestate in the pre-stripping and to 60 Nm3 h−1 m−3digestate in the stripping reactors, during all tests. The energy requirement was completely satisfied by the CHP (combined heat and power) unit fed with the biogas produced by manure digestion. Results showed anaerobic digestion coupled with stripping to be a suitable solution for removing up to 81% of the ammonium with neither external energy input nor reagent dosage. [ABSTRACT FROM AUTHOR]

In response to escalating environmental challenges, innovative solutions for collaborative waste management and recycling have become imperative. The eco-friendly microbial electrochemical resource recovery system (EMERS) integrated microbial electrolysis cell and forward osmosis for CO 2 capture from flue gas, ammonia and water recovery from wastewater and utilization of industrial wastes. 75 ± 1.8 % of ammonia from wastewater was enriched in MEC's catholyte and 38 % of synchronous water recovery from wastewater was achieved by forward osmosis, realizing multi-cycle recycling of catholyte. The enriched ammonia and CO 2 were then recovered by 100 % and 62 % through thermal extraction. The salt brine exhibited high efficiency in ammonia and CO 2 absorption, exceeding 90 %, and yielded hydrated basic magnesium carbonate. Additionally, hydrogen, NH 4 Cl and various carbonate products were also obtained. The EMERS demonstrated a promising strategy for integrated utilization of wastewater, flue gas and industrial waste, achieving pollution and carbon emissions reduction along with resource recovery. [Display omitted] [ABSTRACT FROM AUTHOR]

Although dairy cow manure is an abundant feedstock of anaerobic digestion, pretreatment is needed to increase biogas production. This study introduced the vacuum stripping and absorption (VaSA) process for pretreatment of dairy cow manure, examined the efficacy of VaSA pretreatment on anaerobic digestion, and applied VaSA to digester effluent for ammonia recovery and pathogen reduction. Two 18-L mesophilic digesters were operated semi-continuously with VaSA-treated and raw dairy manure in parallel with two control digesters fed raw manure only. Pretreatment of dairy manure by VaSA for 2 h increased the dissolved fraction of volatile solids by 44.8–45.5 %. Consequently, the digesters receiving VaSA-pretreated and raw manure produced 17 % more biogas than the control digesters at the volatile solids loading rate of 1.8 g/L reactor /d. The pretreatment also improved digestate dewaterability, with time-to-filter and viscosity decreased by 8.5–14.5 %. Post-treatment of digestate by VaSA reduced fecal coliform to undetected. Ammonia mass transfer coefficients were similar in VaSA pretreatment of dairy manure and post-treatment of manure digestate (0.21–0.29 1/h). Post-treatment allows more digestate to be applied to nearby land at lower transportation costs and benefits recycling of digestate due to pathogen reduction. Overall, this mini-pilot study proved coupling anaerobic digestion and VaSA to be a profitable strategy to empower anaerobic digestion systems. [Display omitted] [ABSTRACT FROM AUTHOR]

The industrial production of synthetic fertilizers and the wide-scale combustion of fossil fuels have disrupted the global nitrogen cycle, necessitating a prudent shift towards sustainable nitrogen management. Traditional wastewater treatment methods primarily focus on nitrogen elimination rather than recovery in useable form, exacerbating resource depletion and environmental degradation. This review explores integrated technologies, including bio-electroconcentration cells (BEC), direct ammonia fuel cells (DAFC), solid oxide fuel cells (SOFC), and microbial fuel cells (MFC), for effective nutrient recovery in conjugation with energy recovery. Recovered nitrogen, primarily green ammonia, offers a carbon-free energy carrier for diverse applications, including applications in DAFC and SOFC. This review underscores the importance of synchronously retrieving ammonia from wastewater and efficiently diverting it for energy recovery using an integrated fuel cell approach. The key technical challenges and future perspectives are discussed, highlighting the potential of these integrated systems to advance sustainability and circular economy goals. [ABSTRACT FROM AUTHOR]

• Recovery of ammonia and acids from scrubber effluents via bipolar membrane electrodialysis (BPMED). • BPMED regenerates sulphuric, citric, and maleic acids from scrubber effluents. • 54 % decrease in energy consumption while regenerating organic acids vs sulphuric acid. • Evaluation of cation exchange membrane's conductivity and permselectivity in organic ammonium electrolytes. While air stripping combined with acid scrubbing remains a competitive technology for the removal and recovery of ammonia from wastewater streams, its use of strong acids is concerning. Organic acids offer promising alternatives to strong acids like sulphuric acid, but their application remains limited due to high cost. This study proposes an integration of air stripping and organic acid scrubbing with bipolar membrane electrodialysis (BPMED) to regenerate the organic acids. We compared the energy consumption and current efficiency of BPMED in recovering dissolved ammonia and regenerating sulphuric, citric, and maleic acids from synthetic scrubber effluents. Current efficiency was lower when regenerating sulphuric acid (22 %) compared to citric (47 %) and maleic acid (37 %), attributable to the competitive proton transport over ammonium across the cation exchange membrane. Organic salts functioned as buffers, reducing the concentration of free protons, resulting in higher ammonium removal efficiencies with citrate (75 %) and malate (68 %), compared to sulphate (29 %). Consequently, the energy consumption of the BPMED decreased by 54 % and 35 % while regenerating citric and maleic acids, respectively, compared to sulfuric acid. Membrane characterisation experiments showed that the electrical conductivity ranking, ammonium citrate > ammonium malate > ammonium sulphate, was mirrored by the energy consumption (kWh/kg-N recovered) ranking, ammonium sulphate (15.6) < ammonium malate (10.2) < ammonium citrate (7.2), while the permselectivity ranking, ammonium sulphate > ammonium citrate > ammonium malate, aligned with calculated charge densities. This work demonstrates the potential of combining organic acid scrubbers with BPMED for ammonium recovery from wastewater effluents with minimum chemical input. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Among the various technologies for the removal and recovery of chemicals from gaseous streams, the membrane condenser (MCo) is proposed and analyzed in this work. In particular, the case of MCo used for the recovery of ammonia at minimum energy consumption is reported. For reaching this aim, three different MCo configurations have been proposed and compared. They differ in the way cooling is achieved: in configuration 1, the feed is cooled via cooling water before entering the membrane module; in configuration 2, a cold sweeping gas cools the feed stream directly inside the membrane module; in configuration 3, the feed is first partially cooled via an external medium and then a sweeping gas is used for the final cooling of the stream. The achieved results indicate configuration 2, among the three different proposed schemes, the one allowing to minimize energy consumption while permitting good water and chemicals recovery.

Ammonium (NH4+) recirculation from the streams generated in the dehydration stage of the sludge generated in the anaerobic digestion of urban wastewater treatment plants (WWTPs), known as centrate or sidestream, produces a reduction in the efficiency of WWTPs. Given this scenario and the formulation that a WWTP should be considered a by-product generating facility (biofactory), solutions for ammonia/ammonium recovery are being promoted. These include a nitrogen source that reduces the need for ammonia production through the Haber–Bosch process. Therefore, the recovery of nutrients from urban cycles is a potential and promising line of research. In the case of nitrogen, this has been aimed at recovering NH4+ to produce high-quality fertilizers through membrane or ion exchange processes. However, these techniques usually require a pretreatment, which could include an ultrafiltration stage, to eliminate suspended solids and organic matter. In this case, the coagulation/flocculation (C/F) process is an economical alternative for this purpose. In this work, the sidestream from Vilanova i la Geltrú WWTP (Barcelona, Spain) was characterized to optimize a C/F process before being treated by other processes for ammonium recovery. The optimization was performed considering a bibliographic and experimental analysis of several operating parameters: coagulant and flocculant agents, mixing velocity, and operation time, among others. Then, the removal efficiency of control parameters such as turbidity, chemical oxygen demand (COD), and total suspended solids (TSS) was calculated. This optimization resulted in the use of 25 mg/L of ferric chloride (FeCl3) combined with 25 mg/L of a flocculant composed of silicon (SiO2 3%), aluminum (Al2SO4 64.5%), and iron salts (Fe2O3 32.5%), into a 1 min rapid mixing process at 200 rpm and a slow mixing for 30 min at 30 rpm, followed by a final 30 min settling process. The numerical and statistical results of the process optimization reached 91.5%, 59.1%, and 95.2% removal efficiency for turbidity, COD, and TSS, respectively. These efficiencies theoretically support the enhanced coagulation/flocculation process as a pretreatment for a higher NH4+ recovery rate, achieving 570.6 mgNH4+/L, and a reduction in the dimensioning or substitution of other membrane processes process due to its high TSS removal value. [ABSTRACT FROM AUTHOR]

The effects of temperature, pH, and gas-to-liquid-volume-ratio on ammonia recovery via gas–liquid stripping have been widely studied. However, there is a lack of a structured approach towards characterising the stripping process. Furthermore, limited information is available on the effect of the composition of the stripping gas on ammonia recovery. This study includes the application of a factorial design of experiments to ammonia stripping. The outcome is a mathematical relationship for ammonia recovery as a function of process conditions. The temperature was found to have the highest influence on ammonia recovery. With respect to the influence of the stripping gas, similar ammonia recoveries were reported when using air, CH4, and N2 (96, 92, and 95%, respectively). This was attributed to their similar influences on the pH of the digestate, and subsequently, on the free ammonia equilibrium. In addition, the presence of CO2 in the stripping gas had a critical effect on ammonia recovery due to its influence on the total ammonia equilibrium in the digestate. These results showed the possibility of using different stripping gases interchangeably to obtain similar ammonia recoveries, with a critical emphasis on their CO2 content. [ABSTRACT FROM AUTHOR]

The ammonia recovery from anaerobic digestion (AD) effluent offers a low cost and low carbon footprint strategy for N recovery. To enhance ammonia recovery performance, the aeration-assisted membrane contactor (MC) process was presented with aeration applied on the feed side. The ammonia recovery performance with different pH adjustment methods and operating parameters were tested. Results illustrated that a high ammonia mass transfer coefficient (K ov = 4.85 ×10−7 m/s) could be achieved in the aeration-assisted MC. With the increase in air flow rate from 0 L/min to 0.6 L/min, the K ov increased from 1.21 × 10−7 m/s to 4.85 × 10−7 m/s by about 300%, and the ammonia separation factor (S t) increased from 5.75 to 8.91 by about 55%. Additionally, the K ov increased sharply with the increase in feed temperature. Notably, the ammonia removal efficiency can reach 82% after 6-h experiment, which might be due to the large contact area of membrane contactor and the high mass transfer efficiency caused by the optimal conditions. The greenhouse gas (GHG) emission evaluation showed that compared with that of Haber-Bosch process (4.2 kg-CO 2 eq/kg-N), the GHG emission of aeration-assisted MC was 1.86 kg-CO 2 eq/kg-N under room temperature. The aeration-assisted MC can provide a high-efficient and low GHG-emission ammonia recovery process. • Aeration-assisted membrane contactor (MC) can enhance ammonia recovery performance. • High air flow rate on the feed side, high ammonia recovery performance. • Aeration-assisted MC provides a low carbon footprint pathway for ammonia recovery. [ABSTRACT FROM AUTHOR]

• Novel physics-informed data-driven optimization for complex multi-physics problems. • Loss of physics laws added in the optimization solver to improve generalizability. • The new method requires fewer training samples than physics-informed neural networks. • The method applied successfully for performance optimization of a complex SGMD. The application of advanced machine learning algorithms such as deep learning is limited for the surrogate-based process optimization of complex multi-physics problems because high-quality experimental and numerical training samples required for deep-learning model training are expensive and scarce. To address this issue, in this study, a novel physics-informed process optimization (PIPO) framework was introduced. In the first step, surrogate models based on conventional neural networks (NN) were trained using a few available high-quality training samples. In the second step, the trained NN models were coupled to the process optimization solver in which the loss of physical laws was added to the optimizer's objective function to find optimal design points that satisfy the laws of physics. As a result, the generalization performance of the framework was greatly improved for design targets outside the training range of NN models. PIPO is substantially different from the physics-informed neural networks where the loss of physics is added to the loss function used during NN model training. The PIPO framework was used to optimize a sweeping gas membrane distillation (SGMD) module. Eight input design variables, including process and geometrical parameters, were optimized for different challenging targets to achieve the best SGMD performance in terms of ammonia recovery ratio and concentration. It was shown that for noticeably few training samples of 68 experiments, the proposed framework was able to achieve the optimization targets within a reasonable computational cost. The optimum designs were verified and analyzed in detail by high-resolution computational fluid dynamics models. [ABSTRACT FROM AUTHOR]

[Display omitted] • A system was first constructed to degrade organic pollutants in membrane distillation by activating PMS with γ-FeOOH@PVDF. • In-situ OCT verified the superior antifouling performance of γ-FeOOH@PVDF. • Self-cleaning mechanism of the γ-FeOOH@PVDF/PMS system was elucidated. • Quinone substances were involved in the Fe(Ⅲ)/Fe(Ⅱ) redox cycle preferentially. • Both free radical (SO 4 •-, O 2 •- and •OH) and non-free radical (1O 2) pathways participated in the degradation of TAP. The resolution of membrane fouling issues is crucial for the commercial application of membrane distillation (MD) ammonia recovery. The peroxymonosulfate-based advanced oxidation process (PMS-AOP) exhibited conspicuous degradation of organic pollutants, and in-situ coupling with the MD process could probably achieve desirable antifouling performance. In this research, a novel γ-FeOOH@PVDF catalytic membrane was fabricated by gas–liquid self-deposition method and fluorination treatment. The γ-FeOOH nanosheets arrayed on the substrate membrane endowed the catalytic membrane with superhydrophobicity. The MD ammonia recovery of the digestate achieved a high recovery rate (97.3%), and no membrane fouling or wetting phenomena were detected by real-time monitoring by optical coherence tomography (OCT). The batch degradation experiments of thiamphenicol (TAP) validated the γ-FeOOH@PVDF/PMS system with superior degradation performance and stability. The electron paramagnetic resonance (EPR) coordinated free radical quenching experiment determined the active substance (SO 4 •-, 1O 2 , O 2 •- and •OH) in the degradation process. In addition, the potential self-cleaning mechanism of the radical and non-radical pathways of γ-FeOOH@PVDF was elucidated via density functional theory (DFT) calculation. The quinone groups in the organic pollutants facilitated the redox of Fe(Ⅲ)/Fe(Ⅱ) and accelerated the activation of PMS. Hence, the catalytic membrane developed in this research provided a novel instructive strategy for membrane fouling control and also exhibited significant potential of coupling catalysis and membrane technology for water treatment. [ABSTRACT FROM AUTHOR]

Electrochemical nitrate reduction (NO 3 RR) is regarded as a potential technique for reducing nitrate (NO 3 -) pollution and promoting the synthesis of ammonia (NH 3) with greater value. However, NO 3 RR, restricted by weak NO 3 - adsorption and slow transfer of multiple electrons and protons, is still a challenge. In this study, we present a distinctive Cu(I)/Cu(II) oxide nanowire catalyst that can efficiently electro-reduce NO 3 - to NH 3 via dual function of Cu element. The pivotal mechanism: Cu(I) in Cu(I)/Cu(II) oxide is oxidized to Cu(II) by reacting with water molecules to produce active hydrogen (H*); the formed Cu(II) facilitate NO 3 - adsorption and then is reduced to Cu(I); the cycle of Cu(I)/Cu(II) pair strengthens the adsorption of NO 3 - and then achieves the transfer of multiple electrons and protons converting NO 3 - to NH 3. As results, the NH 3 yield rate of Cu(I)/Cu(II) oxide nanowire electrode was 495.8 µg h−1 cm−2, which is 3.3-fold, 5.0-fold, 2.9-fold up-higher than that of copper (Cu) foam electrode, Cu(I) oxide nanowire electrode, and Cu(II) oxide nanowire electrode, respectively. Additionally, the NH 3 selectivity of the Cu(I)/Cu(II) oxide nanowire electrode was 92.6 %, significantly surpassing the selectivity of the Cu foam electrode (27.2 %), Cu(I) foam nanowire electrode (38.0 %), and Cu(II) oxide nanowire electrode (51.8 %). Importantly, the Cu(I)/Cu(II) oxide nanowire electrode, with the characteristics of simple and large-scale preparation, and low cost, could be used in a large-scale reactor to efficiently recover NH 3 , maintaining a consistent yield rate of around 1000 μg h−1 cm−2. Hence, this work provides an effective method to eliminate NO 3 - pollution and generate higher-value NH 3 with a low-carbon technology. [Display omitted] [ABSTRACT FROM AUTHOR]

Massive and accumulated emissions of ammonium nitrogen are crucial pollutants, and ammonium nitrogen in wastewater is valuable resources to the production of fertilizer. Liquid-liquid hollow fiber membrane contactor (LL-HFMC) has been proven to apply in ammonia recovery with high separation efficiency, low cost and saving energy consumption. This review focused on three components of LL-HFMC, including membranes, feed and receiving solution, summarized the principles of LL-HFMC, effects and developments of hydrophobic hollow fiber membranes. Besides traditional hydrophobic hollow fiber membranes fabricated by PP, PVDF and PTFE three types of polymers, some novel membrane materials and modifications are utilized through casting, electrospinning and other methods, aiming at enhanced mechanical properties, chemical durability or hydrophobicity. The characteristic properties and compositions of feed and receiving solution were analyzed. In order to improve ammonia recovery efficiency and meet the requirements of near-zero discharge, it may become inevitable to realize ammonia recovery process by using liquid-liquid hollow fiber membrane contactor at low ammonium ion concentration, and it is necessary to optimize the process, prepare novel hydrophobic hollow fiber membranes with high ammonia selectivity, low water flux and good acid/alkaline resistance. The summary and comprehensive analysis in this review provides guiding fundaments and outlooks for researches and applications in the future. [Display omitted] • Liquid-liquid hollow fiber membrane contactor apply in ammonia recovery. • Preparation and modification of hollow fiber membranes were summarized. • Analysis of characteristic properties of feed and receiving solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alkali-driven DD for ammonia recovery was studied based on modelling. • Excellent performance was ascribed to fluctuated Donnan equilibrium constant. • Key parameters as ratio of driving cation and alkali to ammonia were identified. • 3.49 g CO 2 /g NH 4 + via coupling-driven was the lowest among three DD for N recovery. Recovery of ammonia from wastewater is of practical importance toward a sustainable society. To this end, concentration-driven Donnan dialysis (DD) is a promising recovery method especially for its simplicity and negligible energy consumption. Upon the traditional salt-driven DD, the conceptive alkali-driven DD significantly enhanced mass transfer and removal efficiency, yet their performance in terms of key process parameter were not deeply understood and further optimization remained unclear. Models for salt (NaCl) and alkali (NaOH)-driven DD processes were thus established and the ammonia transfer was theoretically investigated. The results showed that a fluctuated Donnan equilibrium constant was found responsible for the superior performance of alkali-driven DD (mass transfer accelerated by 90 % than control). Interestingly, there was an optimal ammonia recovery mode via adjusting ratios of alkali/ammonia and cation/ammonia, two key parameters governing the process efficiency, based on which the salt-alkali coupling-driven DD process was further proposed. It was verified that the coupling-driven DD process achieved the ammonia removal kinetic value of 0.1632 h−1 under insufficient alkali conditions (accounting for 50 % ammonia concentration in feed) with lowest CO 2 emissions of 3.49 kg CO 2 /kg NH 4 +. The descending overall efficiency of ammonia removal, following alkali-driven (0.2943 h−1) > coupling-driven (0.1632 h−1) > salt-driven (0.1228 h−1), was ascribed to the variations in the electrochemical potential of ions involved in the respective processes. In addition, the cost of chemical consumption for a coupling-driven DD process (3.99 $/kg NH 4 +) was close to that of a salt-driven process, but much lower than that of an alkali-driven process (14.81 $/kg NH 4 +). These finding insight the low-carbon and efficient recovery of ammonia from wastewater. [ABSTRACT FROM AUTHOR]

• We investigated the effect of ion exchange membrane (IEM) thickness on the BMED process for improving ammonia nitrogen removal and recovery. • The effect of the IEM thickness was evaluated by using three different thicknesses (<80 µm, 80–250 µm, and > 250 µm). • IEM thickness of 80–250 µm at 40 mA/cm2 is optimal for balanced BMED efficiency. • An optimal IEM thickness of 80–250 µm is suggested for achieving high removal and recovery with low energy consumption in the BMED process. Bipolar membrane electrodialysis (BMED) has emerged as an efficient and promising technology for the removal and recovery of ammonia nitrogen. Despite its potential, the optimization of BMED systems for enhanced performance and energy efficiency remains a critical challenge, particularly in the context of varying ion exchange membrane (IEM) thicknesses. Membranes with a thickness of < 80 µm have low resistance and are mainly used for processes requiring low energy consumption. Membranes with a thickness of 80–250 µm have moderate resistance and high ion selectivity and are widely used for electrodialysis applications. Membranes with a thickness of > 250 µm have higher ion selectivity than commercial membranes with a thickness of 80–250 µm and are suitable for processes that demand high purity. This study investigates the effect of IEM thickness ranging from 16–400 µm on BMED performance for ammonia nitrogen removal and recovery, and energy consumption. The BMED configuration comprising five cell triplets consisting of a cation exchange membrane, bipolar membrane, and anion exchange membrane was employed. The thickness of IEMs was divided into three categories: 16–17 µm (PCEM/ PAEM), 100–150 µm (CD100/AD100, InnoSep-C/InnoSep-A), and 380–400 µm (MC-3470/MA-3475). In membranes with a thickness of 100–150 µm, the ammonia nitrogen removal was exceptionally high at 99.2 %, with a recovery of 98.7 % (CD100/AD100: 100 µm) at a current density of 80 mA/cm2, and the system exhibited low specific energy consumption (SEC) of 8.87 kWh/kg-N (InnoSep-C/InnoSep-A: 150 µm) at a current density of 20 mA/cm2. However, when using the thinnest IEMs (PCEM: 16 µm, PAEM: 17 µm), an increase in total ammonia nitrogen loss (10.21–22.01 %) led to a reduction in ammonia nitrogen recovery. Conversely, when using the thickest IEMs (MC-3470: 380 µm, MA-3475: 400 µm), the SEC was extremely high (30.98–126.67 kWh/kg-N), making them unsuitable for the BMED process for ammonia nitrogen removal and recovery. Based on these experimental results, it is suggested to use an optimal thickness of IEM within the range of 80–250 µm in the BMED systems to achieve a balanced performance, maximizing ammonia nitrogen removal and recovery while minimizing the SEC. Consequently, the present study provides a comprehensive understanding of the effects of the IEM thicknesses on the BMED systems and could offer a practical perspective for optimizing the BMED stack with respect to improving the removal and recovery rate of ammonia nitrogen and reducing the energy consumption. [ABSTRACT FROM AUTHOR]

• Novel electrodialysis configuration for simultaneous TAN removal and recovery. • Monovalent selective cation-exchange membranes enhance TAN removal. • A 78% removal efficiency from real AD reject water can be achieved. • Total energy consumption achieved at 17.4 MJ·kgN−1 by the SEDR + BPC. The removal of ammonium and ammonia, represented as total ammoniacal nitrogen (TAN), from reject water through electro-dialysis (ED) and bipolar membrane electrodialysis (BPMED) encounters challenges such as organic fouling, NH 3 back-diffusion, and high energy consumption. The efficacy of electrodialysis reversal (EDR) combined with bipolar membrane electrodialysis using cation-exchange membranes (BPC) was assessed as a more practical configuration (EDR + BPC). Additionally, a novel configuration involving monovalent selective cation-exchange membranes (MSCEMs) in an EDR + BPC setup (SEDR + BPC) was investigated. Comparisons were made among BPMED, EDR + BPC, and SEDR + BPC under three load ratios (L N) of 0.8, 1, and 1.3 during continuous operation. The innovative SEDR + BPC configuration, with an L N of 0.8, exhibited the lowest energy consumption for transported TAN (E TAN) at 4.4 MJ·kgN−1 removal and achieved the highest TAN removal efficiency of 78 % with an L N of 1.3. In contrast to conventional BPMED, SEDR + BPC allowed for the recovery of potentially back-diffused NH 3 into the acid chamber, minimizing transport losses. Furthermore, scaling in the base chamber was reduced due to the contribution of MSCEMs when applying an L N of 0.8. The MSCEMs increased the molar ratio of TAN over (Mg2+ + Ca2+) in the concentrate and decreased it in the diluate. EDR + BPC and SEDR + BPC configurations exhibited stable and lower cell resistance throughout the operation compared to BPMED, attributed to their ability to generate higher concentration gradients. The results clearly demonstrated the feasibility of low-energy TAN removal from real reject water from sludge anaerobic digestion using the SEDR + BPC setup. [ABSTRACT FROM AUTHOR]

Ammonia recovery from wastewater has positive environmental benefits, avoiding eutrophication and reducing production energy consumption, which is one of the most effective ways to manage nutrients in wastewater. Specifically, ammonia recovery by membrane distillation has been gradually adopted due to its excellent separation properties for volatile substances. However, the global optimization of direct contact membrane distillation (DCMD) operating parameters to maximize ammonia recovery efficiency (ARE) has not been attempted. In this work, three key operating factors affecting ammonia recovery, i.e., feed ammonia concentration, feed pH, and DCMD running time, were identified from eight factors, by a two-level Plackett-Burman Design (PBD). Subsequently, Box-Behnken design (BBD) under the response surface methodology (RSM) was used to model and optimize the significant operating parameters affecting the recovery of ammonia though DCMD identified by PBD and statistically verified by analysis of variance (ANOVA). Results showed that the model had a high coefficient of determination value (R2 = 0.99), and the interaction between NH 4 Cl concentration and feed pH had a significant effect on ARE. The optimal operating parameters of DCMD as follows: NH 4 Cl concentration of 0.46 g/L, feed pH of 10.6, DCMD running time of 11.3 h, and the maximum value of ARE was 98.46%. Under the optimized conditions, ARE reached up to 98.72%, which matched the predicted value and verified the validity and reliability of the model for the optimization of ammonia recovery by DCMD process. [Display omitted] • PBD was used to screen the important factors affecting ammonia recovery. • NH 4 Cl concentration, feed pH, and DCMD running time were identified as significant factors. • RSM was employed to optimize the operating parameters of DCMD. • Ammonia recovery efficiency was high to 98.72% under optimized conditions. • High feed pH promoted ammonia mass transfer but increased ammonia loss. [ABSTRACT FROM AUTHOR]

The present study continues the development and enhancement of a highly efficient unique hybrid technique—membrane-assisted gas absorption in designing the separation unit, which provides the improvement in mass-transfer of a target component during the ammonia capture process from a process loop of the Haber–Bosch technological route. In order to minimize the absorbent volume to membrane area ratio, the special separation cell was designed based on a combination of two types of hollow fiber membranes, dense gas separation membrane and porous pervaporation membrane. The separation performance tests were implemented under two sets of conditions, sweeping the bore (permeate) side of a cell with helium and hydrogen-nitrogen mix. For both cases, the membrane-assisted gas absorption cell demonstrated high separation efficiency, and the ammonia concentration in the permeate was never lower than 81 mol%; meanwhile, under the hydrogen-nitrogen bore sweep conditions, the ammonia concentration in the permeate reached 97.5 mol% in a single-step process. Nevertheless, there is a product purity–recovery rate trade-off, which is a typical issue for separation processes. [ABSTRACT FROM AUTHOR]

Among the various technologies for the removal and recovery of chemicals from gaseous streams, the membrane condenser (MCo) is proposed and analyzed in this work. In particular, the case of MCo used for the recovery of ammonia at minimum energy consumption is reported. For reaching this aim, three different MCo configurations have been proposed and compared. They differ in the way cooling is achieved: in configuration 1, the feed is cooled via cooling water before entering the membrane module; in configuration 2, a cold sweeping gas cools the feed stream directly inside the membrane module; in configuration 3, the feed is first partially cooled via an external medium and then a sweeping gas is used for the final cooling of the stream. The achieved results indicate configuration 2, among the three different proposed schemes, the one allowing to minimize energy consumption while permitting good water and chemicals recovery. [ABSTRACT FROM AUTHOR]

Traditional bioelectrochemical systems (BESs) coupled with stripping units for ammonia recovery suffer from an insufficient supply of electron acceptors due to the low solubility of oxygen. In this study, we proposed a novel strategy to efficiently transport the oxidizing equivalent provided at the stripping unit to the cathode by introducing a highly soluble electron mediator (EM) into the catholyte. To validate this strategy, we developed a new kind of iron complex system (tartrate-EDTA-Fe) as the EM. EDTA-Fe contributed to the redox property with a midpoint potential of −0.075 V (vs. standard hydrogen electrode, SHE) at pH 10, whereas tartrate acted as a stabilizer to avoid iron precipitation under alkaline conditions. At a ratio of the catholyte recirculation rate to the anolyte flow rate (RC-A) of 12, the NH4+-N recovery rate in the system with 50 mM tartrate-EDTA-Fe complex reached 6.9 ± 0.2 g N m−2 d−1, approximately 3.8 times higher than that in the non-EM control. With the help of the complex, our system showed an NH4+-N recovery performance comparable to that previously reported but with an extremely low RC-A (0.5 vs. 288). The strategy proposed here may guide the future of ammonia recovery BES scale-up because the introduction of an EM allows aeration to be performed only at the stripping unit instead of at every cathode, which is beneficial for the system design due to its simplicity and reliability.

The accumulation of nitrates in the environment causes serious health and environmental problems. The electrochemical nitrate reduction reaction (e-NO 3 RR) has received attention for its ability to convert nitrate to value-added ammonia with renewable energy. The key to effective catalytic efficiency is the choice of materials. Group VIII-based catalysts demonstrate great potential for application in e-NO 3 RR because of their high activity, low cost, and good electron transfer capability. This review summarizes the Group VIII catalysts, including monatomic, bimetallic, oxides, phosphides, and other composites. On this basis, strategies to enhance the intrinsic activity of the catalysts through coordination environment modulation, synergistic effects, defect engineering and hybridization are discussed. Meanwhile, the ammonia recovery process is summarized. Finally, the current research status in this field is prospected and summarized. This review aims to realize the large-scale application of nitrate electrocatalytic reduction in industrial wastewater.

The reduction and recovery of nitrogen (N) from anaerobically digested manure (digestate) is desirable to mitigate N-related emissions, mainly ammonia and nitrate, derived from digestate land application in nutrient-saturated zones. This work reports the results of a gas-permeable membrane (GPM) pilot-scale plant to recover ammonia from digestate in the framework of the EU project Ammonia Trapping. The total ammonia nitrogen (TAN) concentration in digestate was reduced by 34.2% on average (range 9.4-57.4%). The recovery of TAN in the trapping solution in the form of a (NH4)2SO4 solution averaged 55.3% of the removed TAN, with a TAN recovery rate of 16.2 g N m-2 d-1 (range between 14.5 and 21.0 g Nm-2 d-1). The TAN concentration in the trapping solution achieved a value of up to 35,000 mg N L-1. The frequent change of the trapping solution has been proven as an efficient strategy to improve the overall performance of the GPM technology. [ABSTRACT FROM AUTHOR]

The technology of gas-permeable tubular membranes (GPMs) is promising in reducing ammonia emissions from livestock manure, capturing NH3 in an acidic solution, and obtaining final products suitable for valorization as fertilizers, in line with the principles of the circular economy. This study aimed to evaluate the performance of several e-PTFE membrane systems with different configurations for the recovery of NH3 released from pig slurry. Ten different configurations were tested: only a submerged membrane, only a suspended membrane in the same chamber, only a suspended membrane in an annex chamber, a submerged membrane + a suspended membrane in the same chamber, and a submerged membrane + a suspended membrane in an annex chamber, considering in each case the scenarios without and with agitation and aeration of the slurry. In all tests, sulfuric acid (1N H2SO4) was used as the NH3 capture solution, which circulated at a flow rate of 2.1 L·h−1. The results showed that NH3-N removal rates ranged from 36–39% (for systems with a single submerged or suspended membrane without agitation or aeration of the slurry) to 70–72% for submerged + suspended GPM systems with agitation and aeration. In turn, NH3-N recovery rates were found to be between 44–54% (for systems with a single membrane suspended in an annex compartment) and 88–91% (for systems based on a single submerged membrane). However, when choosing a system for farm deployment, it is essential to consider not only the capture and recovery performance of the system, but also the investment and operating costs (ranging from 9.8 to 21.2 €/kg N recovered depending on the selected configuration). The overall assessment suggests that the simplest systems, based on a single membrane, may be the most recommendable.