Insights into Electrochemical Dehalogenation by Non-Noble Metal Single-Atom Cobalt with High Efficiency and Low Energy Consumption.

It is critical to discover a non-noble metal catalyst with high catalytic activity capable of replacing palladium in electrochemical reduction. In this work, a highly efficient single-atom Co-N/C catalyst was synthesized with metal-organic frameworks (MOFs) as a precursor for electrochemical dehalogenation. X-ray absorption spectroscopy (XAS) revealed that Co-N/C exhibited a Co-N4 configuration, which had more active sites and a faster charge-transfer rate and thus enabled the efficient removal of florfenicol (FLO) at a wide pH, achieving a rate constant 3.5 and 2.1 times that of N/C and commercial Pd/C, respectively. The defluorination and dechlorination efficiencies were 67.6 and 95.6%, respectively, with extremely low Co leaching (6 µg L-1), low energy consumption (22.7 kWh kg-1), and high turnover frequency (TOF) (0.0350 min-1), demonstrating excellent dehalogenation performance. Spiking experiments and density functional theory (DFT) verified that Co-N4 was the active site and had the lowest energy barrier for forming atomic hydrogen (H*) (ΔGH*). Capture experiments, electron paramagnetic resonance (EPR), electrochemical tests, and in situ Fourier transform infrared (FTIR) proved that H* and direct electron transfer were responsible for dehalogenation. Toxicity assessment indicated that FLO toxicity decreased significantly after dehalogenation. This work develops a non-noble metal catalyst with broad application prospects in electrocatalytic dehalogenation.

Electro-enhanced activation of peroxymonosulfate by a novel perovskite-Ti4O7 composite anode with ultra-high efficiency and low energy consumption: The generation and dominant role of singlet oxygen.

Traditional free radicals-dominated electrochemical advanced oxidation processes (EAOPs) and sulfate radical-based advanced oxidation processes (SR-AOPs) are limited by pH dependence and weak reusability, respectively. To overcome these shortcomings, electro-enhanced activation of peroxymonosulfate (PMS) on a novel perovskite-Ti4O7 composite anode (E-PTi-PMS system) was proposed. It achieved an ultra-efficient removal rate (k = 0.467 min-1) of carbamazepine (CBZ), approximately 36 and 8 times of the E-PTi and PTi-PMS systems. Singlet oxygen (1O2) played a dominant role in the E-PTi-PMS system and transformed from SO4•-, O2•-, •OH and oxygen vacancy (Vo••). The electric field expedited the decomposition and utilization of PMS, promoting the generation of radicals and expanding the formation pathway of 1O2. The E-PTi-PMS system presented superiorities over wide pH (3-10) and less dosage of PMS (1 mM), expanding the pH adaptability and reducing the cost of EAOPs. Simultaneously, the excellent reusability (30 cycles) solved the bottleneck of recycling catalysts in SR-AOPs via an ultra-low energy (0.025 kWh/m3-log). This work provides a promising alternative towards high-efficiency and low-cost treatment of polluted waters.

An efficient Fe2+ assisted UV/electrogenerated-chlorine process for carbamazepine degradation: The role of Fe(IV).

To improve the performance and solve the restrictions of UV/chlorine process (e.g., the narrow pH application range and high disinfection by-products (DBPs) formation), a Fe2+ assisted advanced oxidation process with electrochemically generated chlorine (UV/E-Cl/Fe2+) was proposed for carbamazepine (CBZ) degradation, which eliminated CBZ (5 mg/L) within 4 min under the optimal conditions. Compared with UV/electro-generated chlorine (UV/E-Cl) and anodic oxidation-chlorination/Fe2+ (AO-Cl/Fe2+) processes, the apparent first-order kinetics constant in UV/E-Cl/Fe2+ increased by 2.56 and 3.18 times respectively, and the energy consumption was lower (1.15 kWh/m3-log). Simultaneously, the pH application range could be expanded to 9, and DBPs formed in this process were 17.1% less than those in UV/E-Cl. Through quenching tests, electron paramagnetic resonance (EPR) experiments, measurement of •OH concentration, quantification of methyl phenyl sulfoxide (PMSO) and benzosulfone (PMSO2) and processes comparison, possible CBZ degradation pathways and mechanism of UV/E-Cl/Fe2+ were proposed, in which Fe(IV) played the dominant role in the early stage, while the production of radicals (i.e., •OH and Cl•) was enhanced with the increase of chlorine generation, accelerating the CBZ removal. Furthermore, this process demonstrated wide application prospect in treating various contaminants and real wastewaters. In conclusion, this study offers an effective and energy-efficient method for organic pollutants degradation.

Highly efficient removal of bisphenol A by a novel Co-doped LaFeO3 perovskite/PMS system in salinity water.

Although it can effectively degrade refractory organic pollutants, advanced oxidation processes (AOPs) can be seriously interfered with the co-existing substance in salinity water. Herein, three-dimensional hierarchical cobalt-doped LaFeO3 perovskites (LaCo0.5Fe0.5O3) micron spheres composed of nano-rods were hydrothermally synthesized and applied to activate peroxymonosulfate (PMS) for degrading bisphenol A (BPA). Nearly 100% BPA was removed by LaCo0.5Fe0.5O3/PMS system in presence of more than 50 mM Cl- within only 2 min compared that of 30 min without Cl-, which was attributed to reactive chlorine species (RCS) including Cl• and HOCl with higher oxidation capacity. •OH and SO4•- produced by LaCo0.5Fe0.5O3 activating PMS played crucial roles as the source of RCS in LaCo0.5Fe0.5O3/Cl-/PMS system. The synergistic effect between ROS and RCS promoted by the enhanced oxygen vacancies and the efficient redox recycling of FeIII/FeII and CoIII/CoII. Other anions like SO42- and NO3- hardly affected the BPA degradation. BPA degradation efficiency was also improved either in a wide pH range or in the presence of natural organic matters in salty water. This work also demonstrated the potential application of FeCo bimetallic LaCo0.5Fe0.5O3 activating PMS system for degradation of BPA or other organic micropollutants in seawater system.

Insight into the characteristics and sorption behaviors of aged polystyrene microplastics through three type of accelerated oxidation processes.

Ageing process can significantly alter the structural properties, environmental behaviors and potential ecotoxicity of microplastics (MPs) in water. In this study, the structural properties of aged polystyrene (PS) MPs being exposed to UV/H2O, UV/H2O2 and UV/Cl2 artificially accelerated oxidation processes and related sorption behaviors of bisphenol A (BPA) on those virgin/aged PS were investigated. The surface oxidation and hydrophilicity of aged PS were significantly increased according to infrared spectroscopy (IR) and water contact angle (CA) measurements. The differential scanning calorimetric (DSC) and gel permeation chromatography (GPC) revealed apparent degradation of aged PS especially in their amorphous domain. Obviously deteriorative BPA sorption capacity on aged PS was observed compared with that of virgin PS. The sorption rates of BPA on aged PS were accelerated and sorption of BPA shifted from partition dominant mechanism on virgin PS to the adsorption dominant mechanism through being fitted with the dual-mode sorption model. Besides, ageing in UV/Cl2 system introduces C-Cl groups on the surface of PS which strengthen the combination with BPA through halogen bonding interaction. Salt and dissolved organic matters (DOM) in marine water may increase the BPA sorption on aged MPs due to enhanced polar interaction.

High selectivity and effectiveness for removal of tetracycline and its related drug resistance in food wastewater through schwertmannite/graphene oxide catalyzed photo-Fenton-like oxidation.

Selectively and effectively for removal of tetracycline (TC) and its related antibiotic resistance gene from food wastewater matrix with high-salt and high COD characteristics is highly desirable. In this work, novel schwertmannite/graphene oxide (SCH/GO) nanocomposites were synthesized through a facile oxidation-coprecipitation method. The SCH/GO nanocomposites were characterized by TEM, XRD, BET, PL, DRS, XPS and FTIR. In the presence of 1 mM H2O2, the SCH/GO catalyzed Fenton-like oxidation can thoroughly degrade TC under visible light irradiation, even under nature sunlight, whose second-order kinetic rate constant was about 15 times higher than that of pure SCH. SCH/GO was capable of highly selectively capturing and effectively degrading TC in the presence of similar concentration of Cl-, NO3-, SO42- and PO43- with that of food wastewater, even at organic matters concentration of 12.5 times than that of TC. At the same time, the removal of total organic carbon (TOC) and chemical oxygen demand (COD) in aforementioned food wastewater in SCH/GO+H2O2+Vis system reached 27.3 % and 34.5 % after 60 min, respectively. The inhibition zone experiments authenticated that the removal of drug resistance of bacteria by TC degradation intermediates can be achieved very well without producing secondary contamination in this system.