8 Search Results

Digester-equipped municipal wastewater facilities generate recycle streams with high nutrient loads that increase energy consumption and can cause environmental pollution. The reduction of these loads through electrochemical nutrient recovery (ENR) could enhance the food–energy–water nexus by producing fertilizer (struvite). This study investigated the recovery process through a 1 year sampling of recycle streams and the implementation of nutrient recovery. Time series analyses showed that P (as orthophosphate) concentration was time-variant in digester effluent streams, while N (as ammonia) concentration was time-variant in only the aerobic system. Furthermore, these two nutrient concentrations did not correlate in any of the recycle streams.more » Subsequent multivariate screening analyses identified anode type, NH₄⁺ concentration, cathodic potential, P concentration, and temperature as most significant for ENR. Finally, the optimum conditions of cathodic potential, anode area-to-volume ratio, and temperature applied to a real recycle stream resulted in 95% P recovery with 0.03 kWh/kg P. This energy consumption is significantly lower than process energy for conventional P fertilizers (1.1 kWh/kg P) and chemical recovery processes at scale (1.7–12.9 kWh/kg P). Overall, this study recommended specific process controls for nutrient recovery, expanded the variables evaluated for ENR, and demonstrated the ability to significantly impact energy demand associated with P-based fertilizers.« less

Phosphorus (P) is an essential macronutrient for agriculture, yet global reliance on finite phosphorite reserves raises concerns about long-term food and nutrient security. Struvite (MgNH₄PO₄·6H₂O), a mineral recovered from municipal wastewater, represents a sustainable and circular source of P, but uncertainty remains regarding its nutrient availability relative to conventional fertilizers. This study evaluated the fertilizer value and environmental safety of electrochemically recovered struvite (RecoP) in comparison with diammonium phosphate (DAP), triple superphosphate (TSP), and rock phosphate (RockP). Nutrient availability, potential contaminant concentrations, and soil P and nitrogen (N) dynamics were assessed using standardized chemical analyses and an 8-week incubation experimentmore » across three soils with contrasting soil types. RecoP contained 14.7% citrate-soluble P, significantly greater than RockP and comparable to DAP and TSP. Across all soils, RecoP increased both readily available and moderately labile P pools (p < 0.01), matching the performance of conventional fast-release fertilizers. Despite containing approximately half the total of DAP, RecoP stimulated nitrification rates that were 2.2 times greater than the control and exceeded those of TSP, suggesting that fertilizer-derived N bioavailability, rather than total N loading, governed microbial N transformation responses. Concentrations of potentially toxic elements in RecoP were consistently well below US Environmental Protection Agency regulatory limits thresholds. Collectively, these results indicate that RecoP functions as a readily available source of both P and N, comparable to widely used conventional fertilizers, while meeting environmental safety standards. RecoP therefore represents a viable component of sustainable nutrient management strategies that support P recycling and agricultural productivity.« less

Electrochemical nutrient recovery systems rely on stable electrode materials capable of operating in chemically complex wastewater environments. We investigated corrosion resistance and interfacial electrochemical behavior of 316 stainless steel (SS316) in a synthetic wastewater matrix representative of centrate streams, a key knowledge gap in electrochemical phosphorus recovery. A comprehensive suite of electrochemical techniques (chronoamperometry, cyclic voltammetry, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS)) and surface characterization methods (scanning electron microscopy, X-ray diffraction) were employed. Results revealed that wastewater containing typical ionic constituents (such as PO43-, NH4+, and divalent cations) exhibited enhanced cathodic activity and the formation of a more stable,more » protective surface film on SS316 that mitigated chloride-induced corrosion. In contrast, SS316 in the NaCl solution showed significant susceptibility to passive layer breakdown and localized corrosion. Time-resolved EIS further confirmed improved interfacial stability and restricted charge transfer in WW over time, in stark contrast to the progressive passive layer degradation in NaCl. Surface analyses corroborated these findings, showing limited surface attack in WW compared to distinct localized corrosion features in NaCl. These findings indicate that competing ionic species in WW effectively mitigate chloride aggressiveness, enhance SS316 stability, and demonstrate improved electrode longevity and reliability for sustainable wastewater-based electrochemical phosphorus recovery applications.« less

Developing alternative, industrially viable ethylene production routes has received important research attention. One chemical pathway of interest is the oxidative dehydrogenation (ODH) of ethane, although issues such as product selectivity, combustion hazards, and oxidizer supply have hindered the practical scale-up of this technology. The presented work describes the use of a solid oxide fuel cell (SOFC) platform employing lanthanum-strontium-iron oxide perovskite (La_1-xSr_xFeO_3-δ, or LSFx) electrocatalysts to perform electrochemical-ODH (e-ODH), a process design that has the potential to address the challenges of ODH implementation. The effects of La and Sr stoichiometry, operating temperature, and current density are reported. The highest performancemore » was observed using a La:Sr ratio of 0.50 (LSF0.50) at 750 °C and a current density of 0.50 A·cm^–2, achieving an ethane conversion of 18.7 ± 0.3%, ethylene selectivity of 91.4 ± 1.9%, and ethylene yield of 17.1 ± 0.1%. These results demonstrate several potential advantages for utilizing a SOFC platform to perform e-ODH of ethane to ethylene.« less

Here, this study reports the catalytic activity of transition metal electrocatalysts (Co, Ni, and Cu) incorporated into Gd_0.1Ce_0.9O_1.95 (GDC10) cathodes for the electroreduction of CO₂ in solid oxide electrolyzer cells (SOECs). CO₂ electroreduction performance of cells having porous and non-infiltrated GDC10 cathodes was compared with the performance of cells containing transition metal electrocatalysts infiltrated into porous GDC10 cathodes at 750, 800, and 850°C. Results showed that cells with Co infiltrated cathodes had the best catalytic activity towards CO₂ electroreduction. Furthermore, these cells displayed good stability towards CO electroreduction, having a faradaic efficiency value close to 100% with insignificant voltage increasemore » when tested for 48h at 750 and 850°C under the current densities of 0.2, and 0.4Acm^-2, respectively.« less

CO₂ conversion to CO via solid oxide electrolysis provides a potentially efficient method for converting CO₂ into an industrially relevant product. A solid oxide electrolysis cell with (La_0.80Sr_0.20)_0.95MnO_3-δ (LSM) as the CO₂ reduction cathode, yttrium stabilized zirconia (YSZ) as electrolyte, and nickel as the H₂ oxidation anode was operated 800 °C and 850 °C. Thermogravimetric analysis of the LSM material showed no catalyst oxidation at operating temperatures allowing for CO₂ electrolysis without reducing safe gas. In addition, no cathode material mass gain was observed in the presence of CO suggesting little to no carbon deposition occurred above 750 °C. Themore » formation rates of CO for the cell reached 1.15 mL∙min-1∙ cm^-2 for an applied current of 150 mA∙cm^-2 achieving a faradaic efficiency of 100 %. Furthermore, the cell displayed good stability in the short-term CO₂ electrolysis test with a nominal voltage drop of 4 mV h^-1 for 10 h at 850°C. This study shows the feasibility of operating a solid oxide CO₂ electrolysis cell for CO production with H₂ at the anode to reduce endothermic process load.« less