ACS ES&T engineering最新文献

Phosphate removal plays a pivotal role in alleviating eutrophication and maintaining water quality. Cerium (Ce) demonstrates considerable promise in phosphate removal, attributed to its strong affinity for phosphate ions. This study provides a dual utilization strategy for synthesizing Fe₂O₃- and CeCO₃OH-decorated hydrophilic porous biochar (Fe/Ce@HPBC), designed for phosphate recovery from eutrophic waters and followed by its application as a slow-release phosphate fertilizer. Fe/Ce@HPBC possessed excellent phosphate adsorption quantity, achieving a maximum uptake of 203.88 mg/g in accordance with the Sips model. Furthermore, the slow-release experiment demonstrated that Fe/Ce@HPBC used as a fertilizer after phosphate recovery could sustainably release 39.8% of its phosphate content within 28 days. Fe/Ce@HPBC-P could also significantly increase the effective phosphorus content of soil by 65.51% and promote the phosphorus uptake of maize seedlings by 70.36%. Mechanistic investigation revealed that the outstanding phosphate adsorption by Fe/Ce@HPBC was attributed to the formation of inner-sphere complexation through ligand exchange between phosphate and Ce(HCO₃)²⁺/Ce–OH, in addition to electrostatic attraction caused by enhanced surface protonation. Overall, this study contributes to the advancement of phosphate recovery techniques and promotes the development of sustainable agriculture by presenting an effective strategy for mitigating eutrophication.

Thiosulfate-assisted anaerobic fermentation (AF) effectively converts waste activated sludge into high-value products (e.g., short-chain fatty acids (SCFAs)). However, the roles of thiosulfate in organics transformation, electron transfer, and microbial interactions within AF systems are not fully understood, especially under long-term operations. In this study, an 88 day long-term experiment was conducted to address this knowledge gap. The results indicated an average SCFA yield of 3625.1 mg COD/L and an acetate proportion of 49.4% with a thiosulfate dosage of 600 mg S/L. Model organic degradation tests revealed that thiosulfate functioned as an electron acceptor, facilitating NAD⁺/NADH transformation, stimulating the expression of protein complexes like cytochrome c to enhance electron transport, and lowering thermodynamic barriers of propionate and butyrate to acetate (ΔG1_propionate = −335.0 kJ/mol; ΔG2_butyrate = −113.8 kJ/mol). Molecular ecological networks analysis showed that thiosulfate strengthened cooperative relationships among biomarkers of hydrolytic bacteria (i.e., Proteiniphilum, UBA5851), acidogenic bacteria (i.e., UBA4179), and sulfur reducers (i.e., JAEUSI01). Functional gene analysis using random forest confirmed that thiosulfate upregulated the expression of key genes (e.g., 2-oxoacid ferredoxin oxidoreductase) associated with electron transfer and acidogenic metabolism. This study deepens our understanding of thiosulfate, facilitating electron transfer and strengthening microbial cooperation within AF systems.

Promoting humification during composting is of pivotal significance for converting organic waste to value-added fertilizer. Traditional composting additives for enhanced humification commonly suffer from low efficiency and a large dosage. Herein, we presented a novel and effective technique with great application potential to promote humification during composting via simple addition of trace MnFe₂O₄, behind which the essential mechanism was interpreted from both chemical and biological perspectives. Results indicated that with an economical dosage of MnFe₂O₄ (0.02 wt %), the content of humic acid (HA) and humification index (HI) were increased by 15.2 and 18.7% in comparison with the control group, respectively. The chemical mechanism steering such enhanced humification was revealed through analysis of precursor substances evolution and HA structural characterization. Specifically, MnFe₂O₄ addition catalyzed the polyphenol-Maillard reaction, leading to rapid oxidation and subsequent polymerization of the precursor substances. Meanwhile, analysis of diversity and evolution of microbial communities as well as activities of laccase and peroxidase demonstrated that MnFe₂O₄ addition increased the relative abundance of laccase/peroxidase-producing bacteria and thus elevated the enzymatic activities of laccase/peroxidase, which played crucial roles in catalyzing polyphenol-Maillard reaction and humification. This study demonstrates that MnFe₂O₄ could serve as a promising composting additive to promote humification and thereby produce value-added composts.

A high content of iron (Fe) within paddy ecosystems can poison rice plants or increase the risk of migration from rice fields to pollute adjacent rivers and streams. Here, we found that paddy field periphytic biofilms, ubiquitous microbial aggregates that grow on the soil surface, function as potential in situ biointerceptors via Fe accumulation. This is because periphytic biofilms were discovered, according to a spatiotemporal distribution field survey, to have a high capacity for Fe accumulation. The Fe contents in the paddy field periphytic biofilms ranged from 12.40 to 50.60 g/kg at spatial distribution and from 18.24 to 56.53 g/kg at temporal distribution, revealing significant spatiotemporal patterns consistent with the Fe concentration in soils. Extracellular polymeric substance-dominated abiotic accumulation may be a key mechanism that accounts for no less than 30–46% of the Fe accumulation in periphytic biofilms. Periphytic biofilms that accumulate Fe hold potential in intercepting their migration from paddy soil to adjacent ecosystems, thus alleviating Fe poisoning in rice plants as well as minimizing pollution in the adjoining fields. Our findings suggest that the application of periphytic biofilms is a promising engineering measure for alleviating the negative effects of excessive Fe in paddy fields.

Supported amine-based CO₂ capture materials are promising direct air capture (DAC) sorbents due to their high CO₂ uptake capacity, tolerance to varied humidities, and acceptable energy requirements for sorbent regeneration. For the large-scale deployment of supported amine adsorbents for DAC, support materials must be cost-effective and readily available on a large scale. In this study, amine-impregnated Mg_xAl-CO₃ layered double hydroxides (LDHs) and Mg_xAl-O mixed metal oxides (MMOs) that can be produced with commercially available, earth-abundant chemicals are prepared, and their DAC performance is evaluated under a wide range of temperature (−20 to 25 °C) and humidity (0–85% RH) conditions. Although the 30 wt % poly(ethylenimine) (PEI)-impregnated LDHs and MMOs show moderate 400 ppm CO₂ uptakes (≤1 mmol/g) under dry conditions, impressive adsorption capacities are observed under humid conditions (70% RH) at −20 (3.2 mmol/g) and 25 °C (2.0 mmol/g). Furthermore, the sorbent materials demonstrate promising regenerability during 10 humid DAC cycles at a 25 °C adsorption temperature with a <10% decrease in working capacity. However, a dramatic decrease in working capacity (∼40%) is observed after 10 humid DAC cycles at cold temperatures (−20 °C) due to reduced CO₂ capture kinetics, attributed to amine redistribution. Overall, this study demonstrates the complex behavior that can be observed for an adsorbent over widely varying humidity and temperature conditions, reinforcing the notion that practical adsorbents must be carefully selected for operation in specific climatic zones.

Membrane wetting is a prominent challenge in the practical applications of membrane distillation (MD). In this study, we hypothesize that increasing the hydraulic pressure on the distillate side (P_d) can mitigate membrane wetting, an operation mode we refer to as pressurizing distillate membrane distillation (PDMD). To implement PDMD, an accurate measurement of the liquid entry pressure (LEP) of the membrane with the feed solution is essential. However, the conventional LEP measurement method struggles with solutions containing amphiphilic agents. Herein, we develop an impedance-based LEP measurement method and validate it by measuring the LEPs of a commercial poly(tetrafluoroethylene) (PTFE) membrane with ethanol–water mixtures. Further, we demonstrate that this method can accurately measure the LEPs of the PTFE membrane with solutions containing sodium dodecyl sulfate (i.e., a representative amphiphilic agent) by capturing the subtle changes of the feed solutions within the membrane. Additionally, we show that PDMD can effectively mitigate membrane wetting induced by various wetting agents, as the elevated P_d results in a transmembrane hydraulic pressure lower than the LEP of the membrane. Overall, our study provides an effective wetting mitigation approach that can be easily applied in practical MD and membrane contactor applications.

In the realm of sewer management, precise machine learning simulations of physicobiochemical processes during sewage transport are essential yet are hindered by skewed distributions and data constraints. To address this issue, the present study introduces an innovative algorithm, the Automatic Synthetic Minority Over-Sampling Technique for Regression with Gaussian Noise (AutoSMOGN), designed to mitigate the adverse effects of skewed data set distributions. The findings reveal that the integration of the AutoSMOGN algorithm with ML models significantly enhances the precision of gaseous H₂S concentration predictions. Of these approaches, ensemble learning models demonstrated superior accuracy in forecasting gaseous H₂S concentrations within sewer environments, achieving the highest coefficient of determination (R²) of 0.80. Furthermore, the study validates the effectiveness of the AutoSMOGN algorithm in addressing skewed distribution, as evidenced by its acceptable predictive performance on a full-sequence data set (R² of 0.52) and when applied to multiple variables, yielding R² values of 0.88 for total nitrogen and 0.66 for total organic carbon, respectively. These results underscore the potential of the AutoSMOGN algorithm to significantly contribute to the development of new control and optimization strategies, thereby enhancing the maintenance and operational efficacy of sewer systems.

A hybrid modeling framework has been developed for electrodialysis (ED) and resin-wafer electrodeionization (EDI) in brackish water desalination, integrating compositional modeling with machine learning techniques. Initially, a physics-based compositional model is utilized to characterize the behavior of the unit. Synthetic data are then generated to train a machine learning-based surrogate model capable of handling multiple outputs. This model is further refined using a limited set of experimental data. The effectiveness of this approach is demonstrated by its ability to accurately predict experimental results, indicating an acceptable representation of the system’s behavior. Through an analysis of feature importance facilitated by the machine learning model, a nuanced understanding of the interaction between the chosen ion-exchange resin wafer type and ED/EDI operational parameters is obtained. Notably, it is found that the applied cell voltage has a predominant impact on both the separation efficiency and energy consumption. By employing multiobjective optimization techniques, experimental conditions that enable achieving 99% separation efficiency while keeping energy consumption below 1 kWh/kg are identified.

Electrocoagulation has attracted significant attention as an alternative to conventional chemical coagulation because it is capable of removing a wide range of contaminants and has several potential advantages. In contrast to most electrocoagulation research that has been performed with nonporous electrodes, in this study, we demonstrate energy-efficient iron electrocoagulation using porous electrodes. In batch operation, investigation of the external pore structures through optical microscopy suggested that a low porosity electrode with sparse connection between pores may lead to mechanical failure of the pore network during electrolysis, whereas a high porosity electrode is vulnerable to pore clogging. Electrodes with intermediate porosity, instead, only suffered a moderate surface deposition, leading to electrical energy savings of 21% and 36% in terms of electrocoagulant delivery and unit log virus reduction, respectively. Neutron computed tomography revealed the critical role of electrode porosity in utilizing the electrode's internal surface for electrodissolution and effective delivery of electrocoagulant to the bulk. Energy savings of up to 88% in short-term operation were obtained with porous electrodes in a continuous flow-through system. Further investigation on the impact of current density and porosity in long-term operation is desired as well as the capital cost of porous electrodes.

This study proposed a sustainable method for the concurrent recovery of metals from olivine minerals and carbon sequestration through carbon mineralization to address the challenges of climate change and critical mineral recovery for the renewable energy transition. It developed a comprehensive development in leaching processes, recovery of metals, and reagent recycling while assessing its economic benefits and environmental impact. Employing hydrometallurgical leaching, our approach facilitates the selective recovery of Ni²⁺ while converting Mg²⁺ into their carbonates. This approach is further refined through a stepwise technique that controls operating conditions to generate high-purity valuable products, enabling nearly 90% of Mg²⁺ and Ni²⁺ to be dissolved and converted to carbonates. This study evaluated various organic and inorganic acids for the leaching process, followed by Fe extraction and pH swing, to yield pure Fe salts and amorphous silica. Separately extracting iron from the solution significantly reduces the loss of valuable metals in subsequent stages by minimizing the coprecipitation of iron with silicon. A techno-economic assessment (TEA) was performed to evaluate the economic impact of removing iron before the solvent extraction of nickel. This analysis, based on mass balance flow comparisons, determined that the independent removal of iron is more profitable, resulting in the production of more and higher-value products. Ni²⁺ was selectively extracted from the leachate using Versatic 10, which forms a complex with nickel in the organic phase. The solution containing either a strong acid or a greener agent (i.e., gaseous CO₂) was effectively used to strip Ni²⁺ from the organic phase. Different polymorphs of Mg carbonates were produced under ambient conditions. The proposed process flow results in high-purity products suitable for use in various industries, which enhances the economy, facilitating the rapid adoption of this technology.