Revisit the Role of Salinity in Heterogeneous Catalytic Ozonation: The Trade-Off between Reaction Inhibition and Mass Transfer Enhancement

Unveiling the environmental sustainability of Ti4O7 electrified membrane for perfluorooctanoic acid removal

Emerging electrified membrane (EM) technology offers an efficient approach for decentralized water purification. However, EM currently faces the challenge of unknown environmental sustainability, which presents a critical knowledge gap impeding its scale-up implementation. In this work, we aim to explore the environmental impacts of EM technology via a "cradle-to-grave" life cycle assessment, benchmarked against sequential ultrafiltration-nanofiltration. Our study found that the current EM technology shows higher greenhouse gas (GHG) emissions (19.70 kgCO2e g-1) than ultrafiltration-nanofiltration (8.60 kgCO2e g-1) for micropollutants removal. Electro-filtration operation dominates the total environmental impacts of EM process, driven primarily by the supporting electrolyte and electricity consumption. Notably, transitioning to greener electrolytes at lower concentrations can reduce GHG emissions by up to 66%, while switching to low-carbon-grid electricity through renewable energy sources will achieve a 33% reduction. Overall, this work enhances understanding of the environmental impacts of EM technology, emphasizing electrolyte optimization and carbon-intensity-reduction of electricity as critical factors for its sustainable development.

Treatment of cationic red X-GRL in high-salt printing and dyeing wastewater by an electrocatalytic ozonation system: treatment efficiency and degradation mechanism

High salt concentrations in printing and dyeing wastewaters significantly influence pollutant removal. The function of the electrocatalytic ozonation (MgMn x O y -GAC/EP) system in removing pollutants from high-salt printing and dyeing wastewater was investigated. Under high NaCl concentration, the H2O2 yield in the electrochemical system was maintained at approximately 53 mg L-1. Under optimal treatment conditions, the degradation efficiency of cationic red X-GRL in the MgMn x O y -GAC/EP system reached 100% within 16 min, and the mineralization efficiency achieved 90.8% within 60 min. The specific energy consumption of the MgMn x O y -GAC/EP system was 0.027 kW h per gCOD. The SF of the MgMn x O y -GAC/EP system was 13.04, indicating that MgMn x O y -GAC, EO and O3 had a remarkable synergistic effect in the removal of cationic red X-GRL. The existence of ˙OH, ˙Cl, ˙O2 - and 1O2 in the MgMn x O y -GAC/EP system was demonstrated by quenching and electron paramagnetic resonance experiments. Based on these outcomes, the degradation mechanism of cationic red X-GRL in the MgMn x O y -GAC/EP system under high salt conditions was proposed, which was the action mechanism of multiple free radicals mainly dominated by ˙O2 - and 1O2. After repeated experiments, the MgMn x O y -GAC/EP system accomplished a COD removal efficiency of 84%, which signified its relatively high stability. The MgMn x O y -GAC/EP system achieved a COD removal efficiency of approximately 86% for diverse pollutants. Overall, this study revealed that the MgMn x O y -GAC/EP system has novel prospects for the treatment of organic pollutants in high-salt wastewater.

Ozonation and catalytic ozonation - Sources of error. What do we need to know?

Due to the increasing contamination of the environment, including water pollution by numerous emerging contaminants, there is a growing interest in advanced water purification/treatment processes. A technique of particular and growing interest over the years is ozonation in its broadest sense. It is a complex process, and its course, both in the version without and with the participation of a catalyst, depends on a number of factors that can affect its efficiency and the correct interpretation of the obtained results. The paper discusses the importance of the most relevant of these factors: ozone initiation and decomposition, proper catalyst preparation, potential sources enhancing the ozonation process (H2O2 and 1O2), the influence of commonly used buffers and natural water admixtures, and the importance of adsorption processes. The paper also explains how the structure of the ozonated compound can affect its oxidation efficiency and identifies the most common sources of errors having the influence on the interpretation of experimental data.

Systematic investigation and modeling prediction of virus inactivation by ozone in wastewater: Decoupling the matrix effects

Water disinfection is undoubtedly regarded as a critical step in ensuring the water safety for human consumption, and ozone is widely used as a highly effective disinfectant for the control of pathogenic microorganisms in water. Although the diminished ozone efficiencies in complex water matrices have been widely reported, the specific extent to which individual components of matrix act on the virus inactivation by ozone remains unclear, and effective methodologies to predict the comprehensive effects of various factors are needed. In this study, the decoupled impact of the intricate water matrix on the ozone inactivation of viruses was systematically investigated and assessed from a simulative perspective. The concept of "equivalent ozone depletion rate constant" (k') was introduced to quantify the influence of different species, and a kinetic model was developed based on the k' values for simulating the ozone inactivation processes in complex matrix. The mechanisms through which diverse species influenced the ozone inactivation effectiveness were identified: 1) competition effects (k' = 105∼107 M-1s-1), including organic matters and reductive ions (SO32-, NO2-, and I-), which were the most influential species inhibiting the virus inactivation; 2) shielding effects (k' = 103∼104 M-1s-1), including Ca2+, Mg2+, and kaolin; 3) insignificant effects (k' = 0∼1 M-1s-1), including Cl-, SO42-, NO3-, NH4+, and Br-; 4) promotion effects (k' = ∼-103 M-1s-1), including CO32- and HCO3-. Prediction of ozone disinfection efficiency and evaluation of species contribution under complex aquatic matrices were successfully realized utilizing the model. The systematic understanding and methodologies developed in this research provide a reliable framework for predicting ozone inactivation efficiency under complex matrix, and a potential tool for accurate disinfectant dosage determination and interfering factors control in actual wastewater treatment processes.

Catalytic ozonation of reverse osmosis concentrate from coking wastewater reuse by surface oxidation over Mn-Ce/γ-Al2O3: Effluent organic matter transformation and its catalytic mechanism

Degradation of organics in high-salinity wastewater is beneficial to meeting the requirement of zero liquid discharge for coking wastewater treatment. Creating efficient and stable performance catalysts for high-salinity wastewater treatment is vital in catalytic ozonation process. Compared with ozonation alone, Mn and Ce co-doped γ-Al2O3 could remarkably enhance activities of catalytic ozonation for chemical oxygen demand (COD) removal (38.9%) of brine derived from a two-stage reverse osmosis treatment. Experimental and theoretical calculation results indicate that introducing Mn could increase the active points of catalyst surface, and introducing Ce could optimize d-band electronic structures and promote the electron transport capacity, enhancing HO• bound to the catalyst surface ([HO•]ads) generation. [HO•]ads plays key roles for degrading the intermediates and transfer them into low molecular weight organics, and further decrease COD, molecular weights and number of organics in reverse osmosis concentrate. Under the same reaction conditions, the presence of Mn/γ-Al2O3 catalyst can reduce ΔO3/ΔCOD by at least 37.6% compared to ozonation alone. Furthermore, Mn-Ce/γ-Al2O3 catalytic ozonation can reduce the ΔO3/ΔCOD from 2.6 of Mn/γ-Al2O3 catalytic ozonation to 0.9 in the case of achieving similar COD removal. Catalytic ozonation has the potential to treat reverse osmosis concentrate derived from bio-treated coking wastewater reclamation.

Integrated model of ozone mass transfer and oxidation kinetic: Construction, solving and analysis

Ozone-based advanced oxidation process (O3-AOPs) is rapidly evolving, but the surge of emerging pollutants brings new challenges for ozone oxidation research. Herein, we proposed a state-of-the-art model for simultaneously analyzing both ozone mass transfer and oxidation kinetics during ozone oxidation of emerging organic contaminants. The numerical solution and graphical representations of the integrated model were utilized to analyze the dynamics of ozone and pollutant concentration. An in-depth analysis of the integrated model revealed that the reaction rate constants in this present study were higher than previously reported apparent reaction rate constants, and catalysts were not always necessary. Finally, we developed an installable mobile application (APP) that allowed the simulation of the dynamic process for ozone oxidizing organic pollutants in the laboratory, which offered theoretical support for the selection of experimental conditions. The results of model simulation not only provide scientific explanations for counter-intuitive experimental phenomena, but also optimized experimental conditions to enhance ozone utilization.

2D-Like Catalyst with a Micro-nanolinked Functional Surface for Water Purification

In water purification, the performance of heterogeneous advanced oxidation processes significantly relies upon the utilization of the catalyst's specific surface area (SSA). However, the presence of the structural "dead volume" and pore-size-induced diffusion-reaction trade-off limitation restricts the functioning of the SSA. Here, we reported an effective approach to make the best SSA by changing the traditional 3D spherule catalyst into a 2D-like form and creating an in situ micro-nanolinked structure. Thus, a 2D-like catalyst was obtained which was characterized by a mini "paddy field" surface, and it exhibited a sharply decreased dead volume, a highly available SSA and oriented flexibility. Given its paddy-field-like mass-transfer routine, the organic capture capability was 7.5-fold higher than that of the catalyst with mesopores only. Moreover, such a catalyst exhibited a record-high O3-to-·OH transition rate of 2.86 × 10-8 compared with reported millimetric catalysts (metal base), which contributed to a 6.12-fold higher total organic removal per catalyst mass than traditional 3D catalysts. The facile scale preparation, performance stability, and significant material savings with the 2D-like catalyst were also beneficial for practical applications. Our findings provide a unique and general approach for designing potential catalysts with excellent performance in water purification.