ACS ES&T engineering最新文献

The extraction of valuable metals from spent Ni–Co–Mn oxide (NCM) cathodes typically encounters the use of strong acids or alkalis, often leading to secondary pollution. Herein, an environmentally friendly recovery route for the selective extraction of lithium (Li) by using sodium persulfate (Na₂S₂O₈) as the sole leaching agent was proposed. Under the optimized conditions, the leaching efficiency of Li achieved 98.02%, and the selective leaching efficiency of Li was 94.80%. Moreover, the lithium carbonate (Li₂CO₃) product was recovered from the Li-rich filtrate with a high purity of 99.5%. The mechanism of Li selective leaching was revealed by means of wet chemistry, kinetics, thermodynamics, and solid-phase analysis. During selective leaching, free radicals SO₄^•– and ^•OH, hydron ion (H⁺), and sodium ion (Na⁺) were generated by Na₂S₂O₈. These free radicals can increase the redox potential of the leaching system. Under these conditions, Co and Mn elements were both maintained in a high valence state and the cathode structure was collapsed, thus contributing to the leaching of Li. The proposed environmentally friendly recovery process of Li from spent NCM cathodes is promising for practical applications, offering significant economic benefits.

The ability of single-atom catalysts (SSCs) to degrade refractory organic pollutants in peroxymonosulfate (PMS)-based heterogeneous catalysis can be compromised due to less diversity in reactive species and unfavorable affinity with PMS. Herein, the as-prepared ternary atomic-scale site catalyst comprising single-atomic Fe/Ce sites and Fe cluster sites (Fe-Ce-BC-900) could completely remove concentrated 4-chlorophenol (4-CP, 40 mg L^–1) in aqueous solution within 30 min, 1.20–1.35 times more efficient than Fe SSCs or Ce SSCs. The reactive oxygen species (ROSs) could be highly diversified on the ternary atomic-scale sites because of the Janus mechanisms: the production of nonradicals (¹O₂) through PMS oxidation and the generation of radicals (SO₄^•– and •OH) via PMS reduction on the ternary catalytic sites, which accounted for oxidative degradation of concentrated 4-CP. Density functional theory (DFT) calculations indicated that the ternary catalytic sites enhanced the uneven charge distribution and down-regulated the d-band center of Fe-Ce-BC-900 as compared to Fe-BC-900 and Ce-BC-900 catalysts, thereby optimizing the adsorption energy of PMS molecules and promoting electron transfer between metal sites and adjacent oxygen atoms. This study provides valuable insights into the configuration of multicatalytic sites for detoxification of organic-contaminants-polluted wastewater.

Production of volatile fatty acids (VFAs) from organic wastes in anaerobic bioreactors can be increased if methanogenesis is inhibited. Pretreating bioreactor inocula at elevated temperatures slows methanogenesis in the short term, but over the long term, methanogenic activity often recovers. Here, we examined whether elevated temperatures or “heat shocks” (HSs) applied at the onset of CH₄ production can inhibit methanogenesis and increase VFA generation. The effects of multiple 15–30 min intermittent HSs at 50, 65, or 80 °C on mesophilic bioreactors compared to controls at 37 °C were studied. All HS temperatures significantly reduced CH₄ production (70–90%) without decreasing VFA production. After 135 days, total VFA concentrations in the HS treatments were around four times larger than the controls. The HSs led to appreciable shifts in the VFA profiles. Longer-chain VFAs, especially caproate, increased more than 6-fold in the 65 °C treated bioreactors. The microbial communities in the HS bioreactors were significantly different than the controls. The relative abundances of putative chain-elongating bacteria increased and those of syntrophic acetate-forming bacteria decreased when the HSs were applied. Our findings show that intermittent HSs may provide a chemical-free methanogen-specific strategy to improve the production of VFAs, especially longer-chain species.

Drinking water scarcity is a global challenge as groundwater and surface water availability diminishes. The atmosphere is an alternative freshwater reservoir that has universal availability and could be harvested as drinking water. In order to effectively perform atmospheric water harvesting (AWH), we need to (1) understand how different climate regions (e.g., arid, temperate, and tropical) drive the amount of water that can be harvested and (2) determine the cost to purchase, operate, and power AWH. This research pairs thermodynamics with techno-economic analysis to calculate the water productivity and cost breakdown of a representative condensation-based AWH unit with water treatment. We calculate the monthly and annual levelized cost of water from AWH as a function of climate and power source (grid electricity vs renewable energy from solar photovoltaics (PV)). In our modeled unit, AWH can provide 1744–2710 L/month in a tropical climate, 394–1983 L/month in a temperate climate, and 37–1470 L/month in an arid climate. The levelized cost of water of AWH powered by the electrical grid is $0.06/L in a tropical climate, $0.09/L in a temperate climate, and $0.17/L in an arid climate. If off-grid solar PV was purchased at the time of purchasing the AWH unit to power the AWH, the costs increase to $0.40/L in an arid climate, $0.17/L in a temperate climate, and $0.10/L in a tropical climate. However, if using existing solar PV there are potential cost reductions of 4.25–5-fold between purchasing and using existing solar PV, and 2–3-fold between using the electrical grid and existing solar PV, with the highest cost reductions occurring in the tropical climate. Using existing solar PV, the levelized cost of AWH is $0.09/L in an arid climate, $0.04/L in a temperate climate, and $0.02/L in a tropical climate.

Chemiluminescence (CL) is an attractive method for real-time quantification of toxic contaminants or intermediates generated during advanced oxidation processes due to its high sensitivity, low detection limit, and wide linear range. In this study, we present an unprecedented intrinsic CL phenomenon observed in an alkaline aqueous solution containing hydroquinone (HQ) and peroxydisulfate (PDS, S₂O₈^2–). Mechanistic investigations unveil a two-stage process for CL production: sulfate radical (SO₄^•–) generation and CL emission. Initially, the highly oxidizing SO₄^•– are formed via the decomposition of PDS by semiquinone radicals, originating from the comproportionation reaction of HQ with benzoquinone that is generated by the reaction of HQ with OH^– in the presence of dissolved oxygen. Subsequently, SO₄^•– promptly oxidizes the residual HQ to an excited-state light-emitting species, which returns to its ground-state, accompanied by a transient and intense light emission. Notably, HQ plays dual roles in the CL process by both participating in the generation of SO₄^•– and serving as the precursor of the light-emitting substrate. The proposed CL system is developed to quantify trace amounts of HQ and real-time monitor the degradation kinetics of phenols. These findings hold considerable significance in chemical analysis, intermediate identification, and advanced oxidation processes.

Extracellular electron transport (EET) is a biological process where microorganisms can donate electrons from the interior of their cells to external electron acceptors or act as electron acceptors to receive electrons from external sources and electrodes. This process often occurs in the surrounding environment or within biofilms, enabling the redox reactions essential for energy metabolism. This review evaluates the latest developments in electron transfer (EET) research in environmental biotechnology, showcasing its varied applications across bioelectrochemical systems (BES), including microbial fuel cells and microbial electrosynthesis for CO₂ upcycling, as well as its utilization in non-BES such as anaerobic digestion and bioleaching for useful resource recovery. The review emphasizes the interdisciplinary approach of EET research, merging microbiology, chemistry, environmental engineering, material science, and system control engineering. This paper provides insights into the performance optimization of EET and the outlook for future industrial and commercial applications. The review also explores the potential applications of EET to mitigate global and environmental challenges, offering innovative biotechnological solutions that pave the way for a sustainable circular bioeconomy.