ACS ES&T engineering最新文献

The synergistic effect of multiple reactive oxygen species (ROS) facilitates the degradation and mineralization of recalcitrant contaminants. However, bottlenecks include the rational design of single-atom catalysts with multiple active sites to produce multiple ROS in heterogeneous catalytic ozonation (HCO) processes and the detailed interpretation of the generation mechanisms. In this study, we prepared a dual single-atom Mn–(N_x–C)–Ce catalyst with dual active sites via a simple and scalable one-pot method in which atomically dispersed active Mn–N₄ and Ce–N₄ sites synergistically promoted the generation of ^•OH. Moreover, density functional theory calculations and molecular dynamics simulations elucidated that Mn–N₄ sites on the catalyst surface preferred to generate ^•OH and ^•OH_ad, while Ce–N₄ sites preferred to generate other ROS (O₂^•–, ¹O₂, and *O_ad). The three main degradation pathways of N,N-diethyl-3-methylbenzamide (DEET) further revealed the synergistic effects of multiple ROS. Due to the ability for generation of multiple ROS, the Mn–(N_x–C)–Ce catalyst exhibited superior activity and excellent stability for the degradation of DEET and bezafibrate as well as advanced treatments of municipal sewage and coking wastewater. This study paves a new avenue for rationally designing a highly efficient and stabilized catalyst for ozone and provides an insight into the synergistic effect of Mn–Ce dual active sites in the HCO process.

This study assesses the potential of electrodialysis (ED), traditionally applied to demineralize brackish waters, for the emergent challenge of hypersaline desalination. The analysis reveals that the desalination performance of hypersaline ED is determined by two intrinsic membrane trade-offs─ion conductivity–charge selectivity and ion conductivity–water resistivity─and a process trade-off between energy consumption and concentrate volume reduction. The charge selectivity and ion–water selectivity of ion-exchange membranes (IEMs), which are both influenced by the structural property of water uptake, are principal factors affecting membrane-level performance, whereas the operating current density simultaneously impacts the module-level metrics of specific energy consumption and water recovery yield. With current commercial IEMs, the energy costs of ED can be competitive with prevailing thermally driven evaporative processes for the desalination of hypersaline streams < ≈100,000 ppm TDS (equivalent to ≈1.5 M NaCl). To enable energy-efficient ED for higher salinities, membranes capable of suppressing the detrimental effect of water permeation need to be developed. This can be attained by polymeric IEMs with low water per fixed charge site or through material innovation beyond the charged polymers of conventional IEMs.

Heterojunctioning anatase (A) and rutile (R) TiO₂ is considered a benchmark strategy for high photocatalytic activity. In this study, we synthesized heterojunctions of anatase (A) and bronze (B) TiO₂ via hydrothermal and annealing processes using low-cost commercial A-TiO₂. The as-synthesized AB-TiO₂ shows remarkable activity for toluene mineralization and a strong tolerance to deactivation. The activity and durability of AB-TiO₂ far exceed those of A-, R-, B-, and AR-TiO₂, which are bare and even Pt-deposited (a total of 10 TiO₂ samples). AB-TiO₂ exhibits highly active {001} facets for the generation of hydroxyl radicals and oxygen vacancies beneficial for O₂ adsorption. Transient absorption and time-resolved photoluminescence spectroscopies reveal the characteristic lifetimes of electrons and holes. Density functional theory calculations demonstrate facile charge separation and identify the catalytically active surface for oxidation as the anatase surface in AB-TiO₂. The observed high activity and durability are analyzed in terms of photochemical and catalytic factors.

Low-temperature thermal degradation of PCDD/Fs in incineration fly ash (IFA) has attracted widespread attention with the advantages of low energy consumption and high efficiency. However, in the process of industrialization, the inevitable O₂ leakage in the system has always been a technical bottleneck. Based on the characteristics of IFA and the mechanism of PCDD/F regeneration, this study first proposes a dual-strategy LTTD of predechlorination and reduction atmosphere-keeping. Predechlorination removes soluble chlorine and soluble metals while hydrolyzing CaClOH in IFA into Ca(OH)₂ to accelerate the detoxication of PCDD/Fs, and deep reduction atmosphere-keeping is created by introducing activated carbon to inhibit the possible PCDD/F regeneration. Compared with typical LTTD, synergistic application of dual-strategy LTTD can obtain 99.4 and 97.4% detoxification efficiencies of PCDD/Fs in the presence of 1 and 2% O₂, respectively. Based on the identification of congener distribution and density functional theory calculations, the dechlorination mechanism of acid chloride group-containing PCDD/F intermediates with the participation of CO and Ca(OH)₂ was proposed. Finally, the reproducibility of dual-strategy LTTD after optimization of working parameters was well verified and the proposed dual strategies are expected to provide a new direction for the industrialization of LTTD.

Chlorophenols (CPs) pose significant risks to human health due to their toxicity and carcinogenic properties. The direct oxidative breakdown of CPs can produce even more harmful byproducts, resulting in secondary pollution. There is a pressing need for a technology capable of both reducing and oxidizing CPs for their removal. For this research, we utilized commercially accessible organic polymer fluorinated ethylene propylene (FEP) as a catalyst, activated through ultrasound to kickstart a contact-electro-catalysis process to degrade pentachlorophenol (PCP). A proposed mechanism is presented for the reduction and oxidative breakdown of PCP relying on contact electrification-induced electron transfer that creates reactive species. Experimental findings demonstrate that PCP can be completely degraded with only 1.0 mg of FEP. Experiments on identifying and quenching reactive oxygen species indicate that ^•O₂⁻, ^•OH, and ¹O₂ play a role in the degradation process. The degradation of PCP involves four pathways: direct dechlorination, hydroxylation dechlorination, oxidation, and polymerization. Toxicity assessment reveals that the dechlorination process notably decreases the toxicity of intermediates. Furthermore, characterization and cycling experiments demonstrate the outstanding stability and recyclability of FEP, making it suitable for real environmental water applications. Ultrasound-driven contact-electro-catalysis system offers a straightforward, economical, and eco-friendly approach to degrade PCP. It offers valuable insights for potentially treating stubborn CPs effectively.