Comparing the efficacy of various methods for sulfate radical generation for antibiotics degradation in synthetic wastewater: degradation mechanism, kinetics study, and toxicity assessment

Constructing an orderly electron transport channel on boron regulated biomass carbon fiber for selective ROS generation and water decontamination

Antibiotic pollution has raised widely attention due to the difficult biodegradation and lasting toxicity to public health, metal-free material based heterogeneous catalysis is a highly-promise and eco-friendly technology for organics elimination. Herein, boron doped biomass carbon fiber (B-CF) was synthesized to construct orderly electron transport channels for enhancing catalytic performance and deeply purifying organics polluted water. Integrating systematical quenching experiments and EPR detection, O2·- and 1O2 are found to be dominating reactive oxygen species (ROS) for norfloxacin (NOR) degradation rather than ∙OH or SO4∙-. Adsorption, catalytic degradation in pristine CF/peroxodisulfate (PDS) and B-CF/PDS systems, electrochemical tests, and theory calculations were compared and the results suggested B-CF surface can trigger intense electron transfer via simultaneous activating NOR and PDS, and electrons transferred from NOR to B-CF-PDS compound, resulting in selective and remarkably enhanced ROS generation. Moreover, it was found that B-CF exhibited surprising adsorption capacity for NOR (834.4 mg g-1), and it can also remove SO42- from the solution through electrostatic attraction. This B-CF/PDS system is efficient within a wide operation pH from 3 to 11 and exhibits long lasting activity (> 274 h maintaining over 80% efficiency). This study unveils the highly selective formation of O2-· and 1O2 and solves the short lifetime of catalysts in persulfate-based catalysis, which provides feasible technology for advanced water purification.

Peroxydisulfate Activation by Carbon Materials for the Degradation of the Herbicide Ametryn in Waters

Brazil, the largest global sugar cane producer, utilizes approximately 10 million hectares for cultivation. However, the increased use of agrochemicals in this industry raises concerns about environmental and human health impacts. Inclusively, ametryn (AMT), a pesticide intensively used in sugar cane plantations, has been detected in several water matrices at concerning levels, which evidences the urgent need for the development of technologies capable of removing this pesticide from the environment. This study investigated the removal efficiency of AMT from aquatic environments via oxidation promoted by persulfate (PS) activation mediated by carbon-based materials, such as graphene, carbon nanotubes, and activated carbon. Granular activated carbon (GAC) emerged as the most suitable material due to its clear catalytic role. A central composite design was used to evaluate and optimize the factors influencing AMT degradation and mineralization, revealing that the initial PS concentration and GAC dosage strongly impact the degradation rate and organic carbon removal in different directions. GAC was submitted to surface functionalization with N- and O-precursors to investigate how this impacts PS activation, and positive enhancements were noted with the latter, with a mineralization degree 9% superior. Experiments with real water matrices evidence the impact of other water constituents on the degradation rate of the target pollutant (k'300), which was reduced by half when performed in groundwater. Notwithstanding, the system still demonstrated a consistent capacity to remove organic content, ranging from 60 to 50% TOCremoval, regardless of the water matrix, indicating that the system might be effective in real contamination scenarios. This research highlights the potential of GAC and its modified version for remediation of AMT-contaminated water remediation.

Degradation of Ampicillin with antibiotic activity removal using persulfate and submersible UVC LED: Kinetics, mechanism, electrical energy and cost analysis

Effective water treatment to remove antibiotics and its activity from contaminated water is urgently needed to prevent antibiotic-resistant bacteria (ARB) emergence. In this study, we investigated degradation of Ampicillin (AMP), an extensively used β-lactam antibiotic, using submersible Ultraviolet C Light Emitting Diode (λmax = 276 nm) irradiation source, and Persulfate (UVC LED/PS system). Pseudo first order rate constant (kobs) for degradation of AMP (1 ppm) by UVC LED/PS system was determined to be 0.5133 min-1 (PS = 0.2 mM). kobs value at pH 2.5 (0.7259 min-1) was found to be higher than pH 6.5 (0.5133 min-1) and pH 12 (0.1745 min-1). kobs value for degradation of AMP in deionized water spiked with inorganic anions (Cl-=0.5369 min-1,SO42-=0.4545 min-1, NO3-=0.1526 min-1, HCO3-=0.0226 min-1), in real tap water (0.1182 min-1) and simulated ground water (0.0372 min-1) were presented. Radical scavenging experiment reveal involvement of sulfate radical anion and hydroxyl radical in UVC LED/PS system. EPR analysis confirms the generation of sulfate radical anion and hydroxyl radical. Importantly, 74% reduction of total organic carbon (TOC) occurred within 60 min of AMP treatment by UVC LED/PS system. Seven degradation by-products were identified by high resolution mass spectrometry, and degradation pathways were proposed. Antibacterial activity of AMP towards Bacillus subtilis and Staphylococcus aureus was completely removed after UVC LED/PS treatment. ECOSAR model predicted no very toxic degradation by-products generation by UVC LED/PS system. Electrical Energy per order (EEo) and cost of UVC LED/PS system were determined to be 0.9351 kW/m3/order and ₹ 7.91/m3 ($ 0.095/m3 or € 0.087/m3), respectively. Overall, this study highlights, UVC LED/PS system as energy efficient, low-cost, and its potential to emerge as sulfate radical anion based advanced oxidation process (AOP) to treat water with antibiotics.

Degradation of Various Organic Coatings via UV-Generated Sulfate Radicals

Degradation of organic coatings is essential for recycling valuable substrates. Despite the development of strategies for this purpose, the resulting degradations are typically constrained by the composition of the coating. This paper presents a simple strategy utilizing radicals induced by UV for the degradation of diverse organic coatings. The sulfate radicals, generated from UV-exposed ammonium persulfates, induce the degradation of various organic coatings, including layer-by-layer assembled coating composed of alginate and chitosan polymers as well as polydopamine coating. This strategy also facilitates the separation of two adhered substrates by degrading the adhesive polymer layer positioned between them. This novel approach enables the complete degradation of various organic coatings in aqueous conditions without imposing restrictions on their composition, leading to the recovery of the original surface properties of the substrate.

Mesostructured lead dioxide grown on titania nanotubes for diclofenac water removal through electrocatalytic and photoelectrocatalytic processes

Mesostructured PbO2/TiO2 materials were synthesized to perform electrocatalysis (as electrooxidation, EO) and photoelectrocatalysis for removing diclofenac (DCF), 15 ppm concentration in 0.1 M NaSO4 solutions, at different pH conditions (3.0, 6.0 and 9.0) by applying 30 mA cm-2. Titania nanotubes (TiO2NTs)-based materials were prepared to synthetize with a massive PbO2 deposit on this support to obtain TiO2NTs/PbO2 and a TiO2NTs:PbO2 material consisting in a dispersed PbO2 deposit on TiO2-NTs that allowed the formation of a heterostructured surface of combined composition (TiO2 and PbO2). Organics removal (DCF and byproducts) was monitored through UV-vis spectrophotometry and high-performance liquid chromatography (HPLC) during degradation tests. TiO2NTs/PbO2 electrode was tested in both processes, removing DCF at neutral and alkaline solution conditions in EO while an unimportant photoactivity was registered at this material. Conversely, TiO2NTs:PbO2 was used as electrocatalytic material in EO experiments, achieving more than 50% of DCF removal at pH 6.0 by applying 30 mA cm-2. Also, for first time, the synergic effect was investigated when it was exposed to UV irradiation in photoelectrocatalytic experiments, enhancing its efficacy (⁓more than 20%) to remove DCF from a solution with 15 ppm over performance removals achieved (56%) when EO was applied under similar conditions. Chemical Oxygen Demand (COD) analyses showed that significantly higher DCF degradation is reached under photoelectrocatalysis, since COD values decrease a 76% against a 42% decrease achieved with electrocatalysis. Scavenging experiments showed a significant participation on the pharmaceutical oxidation process through the generation of photoholes (h+), hydroxyl radicals and sulfate-based oxidants.