UV/Sodium percarbonate for bisphenol A treatment in water: Impact of water quality parameters on the formation of reactive radicals

Combination of magnetite and sodium percarbonate to enhance acetate-enriched short-chain fatty acids production during sludge anaerobic fermentation

Large amounts of waste activated sludge are generated daily worldwide, posing significant environmental challenges. Anaerobic fermentation is a promising method for sludge disposal, but it has two technical bottlenecks: the availability of short-chain fatty acids (SCFAs)-producing substrates and SCFAs consumption by methanogenesis. This study proposes a pretreatment strategy combining sodium percarbonate (SPC) and magnetite (Fe3O4) to address these issues. Under optimized conditions (20 mg Fe3O4/g TSS and 15 mg SPC/g TSS), SCFAs production increased to 3244.10 ± 216.31 mg COD/L, about 3.06 times the control (1057.29 ± 35.06 mg COD/L) and surpassing reported treatments. The combined pretreatment enhanced the disruption of extracellular polymeric substances, increased the release of biodegradable matters, improved acidogenesis enzyme activities, and inhibited methanogenesis. Additionally, it increased NH4+-N release in favor of the recovery of phosphorus from sludge residual. This study demonstrates an efficient pretreatment for high SCFAs production and resource recovery from WAS.

Degradation of emerging contaminants in synthetic hydrolyzed urine by UV/peracetic acid: Free radical chemistry, and toxicity analysis

The ecological impact of emerging contaminants (ECs) in aquatic environments has raised concerns, particularly with regards to urine as a significant source of such contaminants in wastewater. The current investigation used the UV/Peracetic Acid (UV/PAA) processes, an innovative advanced oxidation technology, to effectively separate two emerging pollutants from urine at its source, namely, ciprofloxacin (CIP) and bisphenol A(BPA). The research findings demonstrate that the presence of the majority of characteristic ions has minimal impact on the degradation of ECs. However, in synthetic hydrolyzed urine, only NH4+ inhibits the degradation of two types of ECs, with a more pronounced effect observed on CIP degradation compared to BPA.The impact of halogen ions, specifically Cl- and I-, on the degradation of CIP in synthetic hydrolyzed urine was a complex phenomenon. When these two halogen ions are present individually, the generation of reactive halogen species (RHS) within the system enhances the degradation of CIP. However, when both types of ions coexist, the formation of diatomic radical species partially inhibits degradation. In terms of BPA degradation, while the production of reactive chlorine species (RCS) to some extent hinders the reaction rate, the generation of reactive iodine species (RIS) promotes the overall process. CIP undergoes fragmentation of the piperazine and quinoline rings, decarboxylation, defluorination reactions, as well as substitution reactions, leading to the formation of products with simplified structures. The degradation of BPA occurs gradually through hydroxyl and halogen substitution as well as isopropyl cleavage. The preliminary toxicity analysis confirmed that the presence of halogen ions in urine resulted in the formation of halogenated products in two types of ECs, albeit with an overall reduction in toxicity. The UV/PAA processes was considered to be an effective and relatively safe approach for the separation of ECs in urine.

A systematic review on percarbonate-based advanced oxidation processes in wastewater remediation: From theoretical understandings to practical applications

Percarbonate encompasses sodium percarbonate (SPC) and composite in-situ generated peroxymonocarbonate (PMC). SPC emerges as a promising alternative to hydrogen peroxide (H2O2), hailed for its superior transportation safety, stability, cost-effectiveness, and eco-friendliness, thereby becoming a staple in advanced oxidation processes for mitigating water pollution. Yet, scholarly literature scarcely explores the deployment of percarbonate-AOPs in eradicating organic contaminants from aquatic systems. Consequently, this review endeavors to demystify the formation mechanisms and challenges associated with reactive oxygen species (ROS) in percarbonate-AOPs, alongside highlighting directions for future inquiry and development. The genesis of ROS encompasses the in situ chemical oxidation of activated SPC (including iron-based activation, discharge plasma, ozone activation, photon activation, and metal-free materials activation) and composite in situ chemical oxidation via PMC (namely, H2O2/NaHCO3/Na2CO3, peroxymonosulfate/NaHCO3/Na2CO3 systems). Moreover, the ROS generated by percarbonate-AOPs, such as •OH, O2•-, CO3•-, HO2•-, 1O2, and HCO4-, can work individually or synergistically to disintegrate target pollutants. Concurrently, this review systematically addresses conceivable obstacles posing percarbonate-AOPs in real-world application from the angle of environmental conditions (pH, temperature, coexisting substances), and potential ecological toxicity. Considering the outlined challenges and advantages, we posit future research directions to amplify the applicability and efficacy of percarbonate-AOPs in tangible settings. It is anticipated that the insights provided in this review will catalyze the progression of percarbonate-AOPs in water purification endeavors and bridge the existing knowledge void.

Synergistic activation of peroxymonosulfate by 3D CoNiO2/Co core-shell structure biochar catalyst for sulfamethoxazole degradation

In this study, a 3D CoNiO2/Co core-shell structure biochar catalyst derived from walnut shell was synthesized by hydrothermal and ion etching methods. The prepared BC@CoNi-600 catalyst exhibited exceptional peroxymonosulfate (PMS) activation. The system achieved 100 % degradation of sulfamethoxazole (SMX). The reactive oxygen species in the BC@CoNi-600/PMS system included SO4-, OH, and O2-. Density functional theory calculations explored the synergistic effects between nickel-cobalt bimetallic and carbon matrix during PMS activation. The unique 3D core-shell structure of BC@CoNi-600 features an outer nickel-cobalt bimetallic layer with exceptional PMS adsorption capacity, while protecting the zero-valence Co of the inner layer from oxidation. Based on the experimental-data, machine learning modeling mechanism, and information theory, a nonlinear modeling method was proposed. This study utilizes a machine learning approach to investigate the degradation of SMX in complex aquatic environments. This study synthesized a novel biochar-based catalyst for activated PMS and provided unique insights into its environmental applications.

Electron cycling mechanism in Fe/Mn DSAzyme accelerates BPA degradation and nanoenzyme regeneration

Peroxidase-like (POD-like) as a kind of new Fenton-like catalyst can effectively activate H2O2 to degrade organic pollutants in water, but improving the catalytic activity and stability of POD-like remains a challenging task. Here, we synthesized a novel dual single-atom nanoenzyme (DSAzyme) FeMn/N-CNTs with Fe-N4 and Mn-N4 bimetallic single-atom active centers by mimicking the active centers of natural enzymes and taking advantage of the synergistic effect between the dual metals. FeMn/N-CNTs DSAzyme showed significantly enhanced POD-like activity compared to monometallic-loaded Fe/N-CNTs and Mn/N-CNTs. Within the FeMn/N-CNTs/H2O2 system, bisphenol A (BPA) could be removed 100 % within 20 min. DFT calculations show that Mn-N4 in FeMn/N-CNTs can readily adsorb negatively charged BPA molecules and capture electrons. Meanwhile, Fe-N4 sites can easily adsorb H2O2 molecules, leading to their activation and splitting into strongly oxidizing hydroxyl radicals (·OH). Throughout this process, electrons are continuously recycled in BPA → Mn-N4 → Fe-N4 → H2O2, effectively promoting the regeneration of Fe2+. Practical studies on wastewater and cycling experiments have demonstrated the great potential of this method for remediating water environments.

Tailoring the selective generation of oxidative organic radicals for toxic-by-product-free water decontamination

Peracetic acid (PAA) is emerging as a versatile agent for generating long-lived and selectively oxidative organic radicals (R-O•). Currently, the conventional transition metal-based activation strategies still suffer from metal ion leaching, undesirable by-products formation, and uncontrolled reactive species production. To address these challenges, we present a method employing BiOI with a unique electron structure as a PAA activator, thereby predominantly generating CH3C(O)O• radicals. The specificity of CH3C(O)O• generation ensured the superior performance of the BiOI/PAA system across a wide pH range (2.0 to 11.0), even in the presence of complex interfering substances such as humic acids, chloride ions, bicarbonate ions, and real-world water matrices. Unlike conventional catalytic oxidative methods, the BiOI/PAA system degrades sulfonamides without producing any toxic by-products. Our findings demonstrate the advantages of CH3C(O)O• in water decontamination and pave the way for the development of eco-friendly water decontaminations based on organic peroxides.

Peracetic acid activated by nickel cobaltite as effective oxidizing agent for BPA and its analogues degradation

The presented research concerns the use of nickel cobaltite nanoparticles (NiCo2O4 NPs) for the heterogeneous activation of peracetic acid and application of NiCo2O4-PAA system for degradation 10 organic micropollutants from the group of bisphenols. The bisphenols removal (initial concentration 1 μM) process was optimized by selecting the appropriate process conditions. The optimal amount of catalyst (115 mg/L), peracetic acid (PAA) concentration (7 mM) and pH (7) were determined using response surface analysis in the Design of Experiment. Then, NiCo2O4 NPs were used to check the possibility of reuse in subsequent oxidation cycles. The work also attempts to explain the mechanism of oxidation of the studied micropollutants. The participation of the sorption process on the catalyst was excluded and based on the experiments with radical scavengers it can be concluded that the oxidation proceeds in a radical pathway, mainly with participation of O2•- radicals. Experiments conducted in real water matrices exhibit low impact on degradation efficiency. Toxicity tests with green alga Acutodesmus obliquus and aquatic plant Lemna minor showed that post-reaction mixture influenced growth and the content of photosynthetic pigments in concentration dependent manner.

Chemical-free vacuum ultraviolet irradiation as ultrafiltration membrane pretreatment technique: Performance, mechanisms and DBPs formation

Membrane fouling induced by natural organic matter (NOM) has seriously affected the further extensive application of ultrafiltration (UF). Herein, a simple, green and robust vacuum ultraviolet (VUV) technology was adopted as pretreatment before UF and ultraviolet (UV) technology was used for comparison. The results showed that control effect of VUV pretreatment on membrane fouling was better than that of UV pretreatment, as evidenced by the increase of normalized flux from 0.27 to 0.38 and 0.73 after 30 min UV or VUV pretreatment, respectively. This is related to the fact that VUV pretreatment exhibited stronger NOM degradation ability than UV pretreatment owing to the formation of HO•. The steady-state concentration of HO• was calculated as 3.04 × 10-13 M and the cumulative exposure of HO• reached 5.52 × 10-10 M s after 30 min of VUV irradiation. And the second-order rate constant between NOM and HO• was determined as 1.36 × 104 L mg-1 s-1. Furthermore, fluorescence EEM could be applied to predict membrane fouling induced by humic-enriched water. Standard blocking and cake filtration were major fouling mechanisms. Moreover, extension of UV pretreatment time increased the disinfection by-products (DBPs) formation, the DBPs concentration was enhanced from 322.36 to 1187.80 μg/L after 210 min pretreatment. However, VUV pretreatment for 150 min reduced DBPs content to 282.57 μg/L, and DBPs content continued to decrease with the extension of pretreatment time, revealing that VUV pretreatment achieved effective control of DBPs. The variation trend of cytotoxicity and health risk of DBPs was similar to that of DBPs concentration. In summary, VUV pretreatment exhibited excellent effect on membrane fouling alleviation, NOM degradation and DBPs control under a certain pretreatment time.

Effects of wavelength on the treatment of contaminants of emerging concern by UV-assisted homogeneous advanced oxidation/reduction processes

Pollutants of emerging concern in aqueous environments present a significant threat to both the aquatic ecosystem and human health due to their rapid transfer. Among the various treatment approaches to remove those pollutants, UV-assisted advanced oxidation/reduction processes are considered competent and cost-effective. The treatment effectiveness is highly dependent on the wavelength of the UV irradiation used. This article systematically discusses the wavelength dependency of direct photolysis, UV/peroxides, UV/chlor(am)ine, UV/ClO2, UV/natural organic matter, UV/nitrate, and UV/sulfite on the transformation of contaminants. Altering wavelengths affects the photolysis of target pollutants, photo-decay of the oxidant/reductant, and quantum yields of reactive species generated in the processes, which significantly impact the degradation rates and formation of disinfection byproducts. In general, the degradation of contaminants is most efficient when using wavelengths that closely match the highest molar absorption coefficients of the target pollutants or the oxidizing/reducing agents, and the contribution of pollutant absorption is generally more significant. By matching the wavelength with the peak absorbance of target compounds and oxidants/reductants, researchers and engineers have the potential to optimize the UV wavelengths used in UV-AO/RPs to effectively remove pollutants and control the formation of disinfection byproducts.

A review of factors affecting the formation and roles of primary and secondary reactive species in UV254-based advanced treatment processes

The presence of organic micropollutants (OMPs) in water has been threatening human health and aquatic ecosystems worldwide. Ultraviolet-based advanced treatment processes (UV-ATPs) are one of the most effective and promising technologies to transform OMPs in water; therefore, an increasing number of emerging UV-ATPs are proposed. However, appropriate selection of UV-ATPs for practical applications is challenging because each UV-ATP generates different types and concentrations of reactive species (RSs) that may not be sufficient to degrade specific types of OMPs. Furthermore, the concentrations and types of RSs are highly influenced by anions and dissolved organic matter (DOM) coexisting in real waters, making systematic understandings of their interfering mechanisms difficult. To identify and address the knowledge gaps, this review provides a comparison of the generations and variations of various types of RSs in different UV-ATPs. These analyses not only prove the importance of water matrices on formation and consumption of primary and secondary RSs under different conditions, but also highlight the non-negligible roles of optical properties and reactivities of DOM and anions. For example, different UV-ATPs may be applicable to different target OMPs under different conditions; and the concentrations and roles of secondary RSs may outperform those of primary RSs in OMP degradation for real applications. With continuous progress and outstanding achievements in the UV-ATPs, it is hoped that the findings and conclusions of this review could facilitate further research and application of UV-ATPs.

Enhancing zerovalent iron-based Fenton-like chemistry by copper sulfide: Insight into the active sites for sustainable Fe(II) supply

Zerovalent iron (ZVI)-based Fenton-like processes have been widely applied in degrading organic contaminants. However, the surface oxyhydroxide passivation layer produced during the preparation and oxidation of ZVI hinders its dissolution and Fe(III)/Fe(II) cycling, and restricts the generation of reactive oxygen species (ROS). In this study, copper sulfide (CuS) was found to effectively enhance the degradation of diverse organic pollutants in the ZVI/H₂O₂ system. Moreover, the degradation performance for the actual industrial wastewater (i.e., dinitrodiazophenol wastewater) in the ZVI/H₂O₂ system was impressively improved by 41% with CuS addition, and the COD removal efficiency could reach 97% after 2 h of treatment. Mechanism investigation revealed that the introduction of CuS accelerated the sustainable supply of Fe(II) in the ZVI/H₂O₂ system. Specifically, Cu(I) and reductive sulfur species (i.e., S^2-, S₂^2-, S_n^2- and H₂S (aq)) from CuS directly induced efficient Fe(III)/Fe(II) cycling. The iron-copper synergistic effect between Cu(II) from CuS and ZVI expedited Fe(II) generation from ZVI dissolution and Fe(III) reduction by formed Cu(I). This study not only elucidates the promotion effects of CuS on ZVI dissolution and Fe(III)/Fe(II) cycling in ZVI-based Fenton-like processes, but also provides a sustainable and high-efficiency iron-based oxidation system for removal of organic contaminants.

Occurrence, distribution, and ecological risk of bisphenol analogues in marine ecosystem of urbanized coast and estuary

Bisphenol analogues are prevalent globally because of rampant usage and imprecise processing techniques, prompting alerts about environmental and health hazards. The method employed in this study by solid phase extraction (SPE) and liquid chromatography-tandem quadrupole mass spectrometer (LC-MS/MS) for both quantification and qualitative analysis of the bisphenol compounds in the surface water samples. The coastal and estuarine surface water of Port Dickson and Lukut ranges from 1.32 ng/L to 1890.51 ng/L of bisphenol analogues. BPF mean concentration at 1143.88 ng/L is the highest, followed by BPA and BPS at 59.01 ng/L and 10.96 ng/L, respectively. Based on RQm for bisphenol analogues, the highest for BPF at 2.49 (RQ > 1, high risk), followed by BPS at 0.12 (0.1 < RQ < 1, medium risk) and BPA at 0.09 (0.1 < RQ < 1, medium risk). The presence and current risk of bisphenols analogues should alert the possible water quality degradation soon.

Photodegradation of oxytetracycline by UV-assisted persulfate and percarbonate processes: kinetics, influencing factors, anion effect, and radical species

In this study, the performance of ultraviolet (UV)-assisted persulfate (PS) and percarbonate (PC) oxidation processes in oxytetracycline (OTC) removal was investigated. UVC lamps were used for the photolysis process and the effect of operating parameters (initial pH, oxidant dose, initial OTC concentration, UV intensity) on OTC removal efficiency was determined. Control experiments were carried out at pH 5.5 and 32 W UV power for 60 min by adding a 4 mM oxidant with 10 mg/L initial OTC concentration. The OTC removal efficiency obtained as a result of only photolysis was 17.3% and the removal efficiency obtained by PS and PC oxidation alone was 18.3% and 12.7%, respectively. The OTC removal efficiencies increased in the combined processes and reached 58.1% and 69.9% for the UV-PS and UV-PC processes, respectively. The reaction rates of the processes were ranked as UV-PC > UV-PS > PS > UV > PC. In the UV-PS and UV-PC processes, the highest removal efficiencies were achieved at alkaline pH values. The OTC removal efficiency was increased with the increase in oxidant dose; however, the efficiency decreased after a certain dose due to the scavenging effect. The removal efficiency also increased as the initial OTC concentration decreased. The UV intensity had a positive effect on OTC removal efficiency. The effect of the water matrix on OTC removal efficiency was investigated while the dominant radical types were determined in UV-assisted processes. The EE/O values for the UV-PS and UV-PC processes were calculated as 211 kWh/m³ and 153 kWh/m³, respectively for 60 min of reaction time. Although similar removal efficiencies were obtained with both UV-assisted processes, the UV-PC process steps forward in terms of being a novel, environmentally friendly, more economic, and promising technology for OTC removal.

New combination of pulsed light and iron (II) for carbonate radical production to enhanced degradation of bisphenol A: Parameter optimization and degradation pathway

Bisphenol A(BPA) is a common industrial chemical with significant adverse impacts on Environment and human health. The present work evaluates the efficacy of pulsed light (PL) and Fe²⁺ ions in activation of sodium percarbonate (SPC) to produce hydroxyl (OH^•) and carbonate (CO₃^•-) radicals for efficient degradation of BPA. The effects of operational parameters such as solution pH, SPC and Fe²⁺ dose as well as the mixture composition were analyzed and the decomposition pathway of BPA proposed. The BPA was successfully degraded at the initial concentration of 15.0 mg/L and optimized conditions by the PL/Fe²⁺/SPC process (99.67 ± 0.29%). A rapid reduction in the degradation of BPA was observed with increasing pH due to OH^• radicals quenching and also the precipitation of Fe²⁺. Under the optimized conditions, degradation of BPA by PL/Fe²⁺/SPC process was five-times faster than the individual process. The quenching experiments revealed that radical and non-radical pathways on BPA degradation was accomplished with OH^•, CO₃^•-, O₂^•-, and ¹O_2, while OH^• and CO₃^•- radicals (as a dominant radicals) have the contributions of 80.23% and 8.30%, respectively. Based on the detected byproducts, ring cleavage can be considered as the main transformation mechanism of BPA by the PL/Fe²⁺/SPC process.

Protein C-Terminal Tyrosine Conjugation via Recyclable Immobilized BmTYR

Protein modification plays an essential role in biological and pharmaceutical research. Due to the ordinary selectivity and inevitable damage to proteins of chemical synthetic methods, increased efforts were focused on biocatalysts which exhibited high regioselectivity and mild reaction conditions. However, separation of the biocatalysts and modified proteins remained a problem, especially when scaling up. Here, we developed a simple method for site-specific protein modification with a recyclable biocatalyst. The immobilizing tyrosinase (BmTYR) on magnetic beads can oxidize C-terminal tyrosine residues of the target protein to o-quinone, followed by the spontaneous addition of different nucleophiles (e.g., aniline derivatives), resulting in a C-terminal modified protein. Compared to the homogeneous biocatalytic system reported before, this heterogeneous system leads to an easier separation. Furthermore, the solid-phase biocatalyst can be regenerated during separation, providing reusability and lower costs.

Electrocatalytic hydrodechlorination system with antiscaling and anti-chlorine poisoning features for salt-laden wastewater treatment

The high salinity and coexistence of scaling ions (Ca²⁺, Mg²⁺, HCO₃^-) in wastewater challenge the efficacy and durability of palladium (Pd)-mediated electrocatalytic hydrodechlorination (EHDC) reaction for chlorinated organic pollutant detoxification, due to the accompanying Cl^- poisoning at Pd sites and scaling on electrode. In a concentrated NaCl solution (5.8 g L ^- 1) with Ca²⁺ (80.0 mg L ^- 1), Mg²⁺ (30.0 mg L ^- 1) and HCO₃^- (180.0 mg L ^- 1), the EHDC efficiency of Pd towards 2,4-dichlorophenol decreases significantly from 67.8% to 33.1% in 72.0 h of reaction, and the electrode is covered with layers of fluffy aragonite precipitate. Herein we demonstrate the inclusion of a commercial antiscalant 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) can prevent both scale formation and Cl^- poisoning, leading to an efficient and steady EHDC process. A mechanistic study reveals that the unique dual function of PBTC primarily originates from the bearing phosphonate and carboxyl groups. With the large affinity of these groups (especially the phosphonate group) for scaling cations and Pd, the PBTC can chelate and stabilize the scaling cations in water and replace Cl^- at Pd surface. It can also release protons, and trigger the formation of more electron-deficient Pd^δ+ species via PBTC-Pd binding, leading to an enhanced EHDC. This work provides effective solutions to the scaling/poisoning issues that commonly encountered in real wastewater and paves a solid road for EHDC application in pollution abatement.

Humic Acid Removal in Water via UV Activated Sodium Perborate Process

Humic acid (HA) has complex molecular structure and is capable of adsorption, ion exchange, and chelation with organic and inorganic pollutants in water bodies, worsening water quality and jeopardizing human health and ecological environment. How to effectively remove HA from water is one of the research focuses of this paper. In this study, the UV-activated sodium perborate (SPB) synergistic system (UV/SPB) was established to eliminate HA in water. The effects of initial HA concentration, SPB dose, and initial pH value on the HA elimination were determined, and the main mechanisms of the synergy and HA degradation were explored. The outcomes show that the HA elimination ratio by the sole UV and only SPB system were only 0.5% and 1.5%, respectively. The HA removal of UV/SPB reached 88.8%, which can remove HA more effectively than other systems. Free radical masking experiment proved that hydroxyl radical produced by SPB activation is the main active substance for HA removal. The results of UV-vis absorption spectrum, absorbance ratio, specific UV absorbance, and excitation–emission matrix spectroscopy verified that the UV/SPB system can effectively decompose and mineralize HA.