Ecological Structure Activity Relationships Research Articles

Core-shell magnetic CFO@COF composites toward peroxymonosulfate activation for degradation of sulfamethoxazole from aqueous solution: A comparative study and mechanistic consideration

A core-shell covalent organic framework encapsulated Co1.2Fe1.8O4 magnetic particles (CFO@COF) was designed and prepared successfully to activate peroxymonosulfate (PMS) for sulfamethoxazole (SMX) degradation. It displays amazing catalytic reactivity since the unique interior structure and synergistic effect between COF shell and CFO core, reaching 99.8% removal of SMX (10 mg/L) within 30 min and 90.8% TOC removal. The synergy between bimetals vests high reactivity to CFO core. And the outer COF shell can stabilize the CFO core under intricate reaction conditions to restrain the leaching of Co ions (decreased from 0.75 to 0.25 mg/L). Further investigation compared the activation mechanism in two different system, CFO/PMS system and CFO@COF/PMS system. The result showed that the radical mechanism controlled by SO4⋅- guided the SMX degradation in CFO/PMS system whereas the 1O2 played a pivotal role in CFO@COF/PMS system called non-radical leading. The influences of various factors on degradation experiments and SMX degradation pathway were also studied. Most importantly, risk assessment in CFO@COF/PMS/SMX system was estimated via “ecological structure activity relationships”. In most case, the toxicities of intermediates were lower than the initial samples, which confirmed the effectiveness of CFO@COF/PMS/SMX system in the reduction of toxicity of SMX.

Insight into the synergy between rice shell biochar particle electrodes and peroxymonosulfate in a three-dimensional electrochemical reactor for norfloxacin degradation

In this study, rice shell biochar (RSB) has been employed as particle electrode in a three-dimensional electro-activation of peroxymonosulfate (3D-PMS) process. According to the experimental results, an outstanding degradation of norfloxacin (NOR) was successfully achieved in the 3D-PMS process. As compared with other processes, the three-dimensional electrode process and PMS oxidation have an obvious synergistic effect. An increase in PMS decomposition was observed due to electrochemical activation and heterogeneous catalysis of RSB. It was found that 87 % of NOR could be degraded in 120 min under optimal conditions of RSB 5 g L−1, NOR 10 mg L−1, PMS 10 mM, and 18 mA cm−2. Some trapping experiments and ESR analyses determine that SO4·-, OH, and 1O2 are all involved in the 3D-PMS process, while 1O2 is dominant ROS for NOR degradation. Furthermore, possible degradation pathways of NOR were investigated and the toxicity of intermediates was analyzed using ecological structure activity relationships (ECOSAR). After RSB was reused for 5 times, Raman spectrum, SEM, BET and FTIR results indicated that surface defects and physical structure were maintained in the 3D-PMS process. Lastly, the practical application of the 3D-PMS process is discussed in detail. Other contaminants, including ATZ, CBZ, SMX, and SMP were also tested in the 3D-PMS process. Based on the above findings, the 3D-PMS process was efficient and sustainable for various pollutants degradation in water.

Insights into the removal of chloramphenicol by electrochemical reduction on Pd/NiFe-MOF/foam-Ni electrode: Performance and mechanism

To effectively improve the particle dispersion of the catalytic metal and catalytic activity of the palladium electrode, a new type of efficient Pd/NiFe-MOF/foam-Ni composite electrode was prepared. The results showed that the reaction rate constant of chloramphenicol (CAP) by Pd/NiFe-MOF/foam-Ni was three times that of Pd/foam-Ni. X-ray absorption fine structure (XAFS) results showed that palladium on Pd/NiFe-MOF/foam-Ni had a lower oxidation state than that on Pd/foam-Ni. The Pd nanoparticles were uniformly dispersed on the composite electrode and had a small particle size. The electrode had good resistance to sulfites and the electrocatalytic activity was hardly affected in the presence of Cl-, NO3-, HCO3-, CO32- and Ca2+ in wastewater. Besides, the introduction of nickel-iron bimetallic organic framework (NiFe-MOF) increased the electron density of Pd, improved the dispersion and electrochemical active surface area (ECSA) of Pd. The reaction pathway of CAP was proposed, and the ecotoxicity of CAP and its products was evaluated by the Ecological Structure Activity Relationships (ECOSAR) model. Combined experimental data and density functional theory (DFT) analysis enable us to propose the hydrodechlorination mechanism of CAP on the Pd/NiFe-MOF/foam-Ni electrode. The Pd/NiFe-MOF/foam-Ni composite electrode has good application prospects in the treatment of organic pollutants in wastewater and other environmental remediation applications.

Insights into electrocatalytic oxidation of aqueous ampicillin: Degradation mechanism and potential toxicity from intermediates

The residual antibiotics in environmental media posed a serious threat to public health and the ecosystem. In this work, the electrocatalytic degradation of ampicillin (AMP) by carbon nanotubes/agarose/titanium (CNTs/AG/Ti) electrode was studied and several experimental factors were further optimized. The results showed that the electrocatalytic degradation of AMP was highly dependent on applied potential and CNTs dosage. Under the optimal conditions (5 mg/L AMP, pH 8, 8 V applied potential, and 7 wt% CNTs dosage), the maximum degradation efficiency achieved 96.7% within 30 min. In the degradation process, superoxide radicals (•O2-) and hydroxyl radicals (•OH) played dominant roles, and the possible electrocatalytic degradation pathways for AMP were also proposed from the identified intermediates. Based on the quantitative structure-activity relationship (QSAR) model, the potential acute and chronic toxicities were predicted by the ecological structure-activity relationships (ECOSAR) program, and the bioconcentration factors (BCFs), developmental toxicity, and Ames mutagenicity were further analyzed using the toxicity estimation software tool (TEST). The results revealed the potential toxicity of some intermediates was higher than that of the parent antibiotic. This study provided an eco-friendly electrocatalytic technology for antibiotic wastewater treatment and investigated the potential toxicity of intermediates during the degradation process.

Introduction of oxygen vacancy to manganese ferrite by Co substitution for enhanced peracetic acid activation and 1O2 dominated tetracycline hydrochloride degradation under microwave irradiation

High microwave-response cobalt-substituted manganese ferrite (CMFO-0.5) was successfully synthesized as a heterogeneous catalyst for efficient peracetic acid (PAA) activation and tetracycline hydrochloride (TCH) degradation with singlet oxygen (1O2) as the dominated reactive oxidized species (ROS). The removal efficiency of TCH could reach 98.16% within 6 min under microwave irradiation when the CMFO-0.5 was added at 20 mg/L. It's found that the Co substitution could produce the oxygen vacancies (OVs), improve the microwave (MW) absorbing performance and enhance the internal electron transfer efficiency of materials. The phenomenon why 1O2 as the dominated ROS rather than hydroxyl radical (•OH) and organic radicals (R-O•) would be explained by the following aspects: the oxygen adsorbed on the OVs can accept the electron transformed from PAA to form superoxide radical (•O2−), which will disproportionate to form 1O2; the energy generated by the non-thermal effect of MW can dissociate PAA to generate peroxy-group for 1O2 generation. Furthermore, the possible TCH degradation pathways were proposed based on DFT theory calculations and product identification, and the toxicity predictions of the degradation products were also performed by the Ecological Structure-Activity Relationship Model (ECOSAR) software. Additionally, the decrease of acute toxicity of treated TCH, excellent stability and strong resistance towards water matrix fully demonstrate the superiority of the proposed system for practical application in wastewater treatment.

Removal of bisphenol A and methylene blue through persulfate activation by calcinated α-MnO2 nanorods: effect of ultrasonic assistance and toxicity assessment.

This work investigates the efficacy of α-MnO2 nanorods for persulfate-mediated degradation of bisphenol A (BPA) and methylene blue (MB), in silent and ultrasonic-assisted systems. The conversion of α-MnO2 nanoparticle flakes to nanorods occurs upon calcination at a temperature of 400°C for 3h under the ramping conditions. The comparative characterization of nanomaterials pre- and post-calcination reveals better physical, chemical, and thermal properties of α-MnO2 nanorods. The impact of various operational parameters such as pH, dosage of nanorods, persulfate dose, selected contaminant concentration, ultrasound frequency and power, scavengers, and landfill leachate medium on the degradation of pollutants is also assessed. The ultrasonic assistance yields higher removal for both BPA and MB than the silent system. This may be attributed to the generation of more radicals as ultrasound activates persulfate. This can be due to acoustic cavitation, which leads to better solute dissociation and excited state. The results obtained through scavenger tests reveal that both OH• and SO4•- can contribute to degradation, but the role of SO4•- is found dominant. Significant removal of BPA and MB ((BPA)silent, 87.12%; (MB)silent, 96.54%; (BPA)ultrasonic, 88.75%; (MB)ultrasonic, 93.86%)) is observed in landfill leachate medium. The degradation pathway for pollutants is also proposed. The toxicity of pollutants and their degradation intermediates are evaluated using Ecological Structure Activity Relationships (ECOSAR) program. The results indicate reduced toxicity of BPA intermediates, while most MB degradation intermediates show higher toxicity. Therefore, it can be affirmed that removing pollutants does not ensure a completely non-toxic process. However, the study proposes a comprehensive toxicity evaluation and eliminating toxic intermediates for completely harmless wastewater treatment.

A new approach on visible light assisted oxygen doped g-C3N4/β-Bi2O3 direct Z-scheme heterojunction towards the degradation of bisphenol A: Degradation pathway, toxicity assessment, and continuous mode study

Graphitic carbon nitride (g-C3N4, G) was firstly doped with oxygen atom and then bismuth oxide nanoparticles (β-Bi2O3, B) were embedded into the modified G to enhance its photocatalytic activity. The photocatalytic performance of the as-prepared composite (β-Bi2O3/O-G, BOG) was evaluated towards bisphenol A (BPA) degradation under visible light irradiation in both batch and continuous-flow reactors. A series of catalyst characterization tests, including XRD, FTIR, FESEM, HRTEM, XPS, TGA, EDX, BET, DRS, PL, EIS, transient photocurrent, CV, and LSV, revealed the significant improvement in photocatalytic activity of G after oxygen doping and its combination with B. Under optimum conditions, 98.7% BPA and 76.8% total organic carbon (TOC) removals were achieved. A direct Z-scheme heterojunction system was described via a series of photochemical tests as well as the identified oxidizing reactive species. The visible light-assisted BOG system also exhibited excellent performance for purifying real BPA-laden water samples. Moreover, BOG composite showed noticeable reusability, implying its cost-effective potential for practical applications. The mechanistic degradation pathway of BPA was proposed based on the identified transformation products (TPs). Furthermore, the toxicity of TPs was evaluated by the Ecological Structure-Activity Relationships (ECOSAR) predictive model. This study gives a new point of view on as-prepared BOG composite potential with highly-efficient photocatalytic performance towards degradation of emerging refractory contaminants and treatment of contaminated effluents.

Efficient PPCPs degradation by self-assembly Ag/Ti3C2@BiPO4 activated peroxydisulfate with microwave irradiation: Enhanced adsorptive binding and radical generation

A hybrid nanocomposite (Ag/Ti3C2@BiPO4) synthesized by an electrostatic self-organizing method for peroxydisulfate (PDS) activation to degrade pharmaceuticals and personal care products (PPCPs) under microwave irradiation (MW) was developed. Degradation and mineralization efficiencies of 99.4 % and 71.5 % for bisphenol A at initial concentration of 20.0 mg/L in 5.0 min operation were achieved in the proposed system. Other kinds of PPCPs including ciprofloxacin, diclofenac, sulfamethoxazole, benzophenone-3 and diethyltoluamide could also be effectively degraded. The two-dimensional (2-D) layered Ti2C-based material Ti3C2 significantly facilitated charge transfer, the separation of electron-hole pairs and production of radicals. Additionally, Ti3C2 incorporation also provided more active species being involved in MW-assisted PDS activation. Density functional theory calculation confirmed that PDS was more easily adsorbed by Ag/Ti3C2@BiPO4 than Ag@BiPO4, favoring PDS activation to produce more radicals for PPCPs removal. Evidences from radical scavenger trials and electron paramagnetic resonance analysis collectively suggested that sulfate radicals and hydroxyl radicals contributed significantly to PPCPs degradation. The main degradation pathways of investigated PPCPs were also clarified with the detected intermediate products. Meanwhile, the eco-toxicity effect of intermediate products of PPCPs on fish, daphnid, and green algae calculated using ecological structure activity relationship software showed that they were much less harmful or not toxic. This work opens up a new perspective on the applications of MXene-based 2-D materials for fast and highly efficient catalytic activation of PDS to degrade PPCPs under MW irradiation.

Mechanistic insights into UV photolysis of carbamazepine and caffeine: Active species, reaction sites, and toxicity evolution

The pseudo-persistence of pharmaceutical and personal care products (PPCPs)in the aqueous environment may pose potential risks to human health and ecosystems. The UV disinfection in wastewater treatment plants is one of the essential processes before PPCPs enter the water environment, so it is crucial to elucidate the photolytic behavior and mechanism of PPCPs under UV radiation. In this work, carbamazepine (CBZ) and caffeine (CAF) were selected as typical pollutants to investigate the effect of water matrixes, humic acid, inorganic ions, and pH on the UV radiation performance. Hydroxyl radical (•OH) and singlet oxygen (1O2) were identified by quenching experiments and electron paramagnetic resonance (EPR) spectra as playing a dominant role in the degradation process. UPLC-TOF/MS was conducted to identify 13 and 14 possible intermediates of CBZ and CAF, respectively. Moreover, combining density functional theory (DFT) calculations (Frontier Molecular Orbital and Fukui index), hydroxylation, oxidation, and ring cleavage were proposed as the main degradation pathways of the contaminants, which occurred first at the C(7C), N(17 N) and O(18O) sites of CBZ and at the C(9C) site of CAF. The bio-acute toxicity experiment and the Ecological Structure-Activity Relationships (ECOSAR) program were performed to analyze and predict the toxicity of the intermediates of CBZ and CAF under UV radiation, respectively. The results showed that the acute toxicity of both solutions increased after UV radiation and followed with the combined toxicity. This work has great scientific value and practical environmental significance for evaluating the UV disinfection process and managing PPCPs in the aqueous environment.

Co single-atom confined in N-doped hollow carbon sphere with superb stability for rapid degradation of organic pollutants

Single-atom catalysts (SACs), which have great potential in the field of water environmental remediation. Development of highly efficient SACs with sufficient stability and excellent catalytic performance was highly desirable, yet remains a huge challenge. Herein, a CoSA/NHCS catalyst was prepared by confining Co single-atom into the N-doped Hollow Carbon Sphere (NHCS) to activate peroxymonosulfate (PMS) for removing bisphenol A (BPA). Experimental and density functional theory (DFT) studies show that the combination of Co-N4 active site and electron transfer mechanism could achieve rapid degradation of BPA (98 % within 1 min). The main active sites of BPA attacked by the electron transfer pathway were predicted by calculating BPA molecular orbitals and Fukui indices. The possible degradation intermediates of BPA were identified by LC-MS and demonstrated to be nontoxic using ecological structure activity relationship modeling (ECOSAR). In a flow-through device for BPA degradation reaction, no deactivation of the catalyst was seen after 60 h and still remained 90 % remove efficiency after 100 h, which further renders it promising for actual water environmental remediation.

Construction of microalgae-bacteria consortium to remove typical Neonicotinoids Imidacloprid and Thiacloprid from municipal wastewater: Difference of algae performance, removal effect and product toxicity

The studies on the removal of Neonicotinoids pesticides (NNIS) and their degradation products have attracted more and more attention. However, the simultaneous removal of pesticides and conventional pollutants remain inadequately understood. In this study, a green alga strain Scenedesmus sp. TXH was isolated from a wastewater treatment plant and the microalgae-bacteria system was constructed with municipal wastewater. The removal effect of consortium system on Imidacloprid (IMI)/Thiacloprid (THI) and conventional nutrients was employed. Results showed that Scenedesmus sp. TXH achieved 71.24 % and 9.71 % removal of IMI and THI in wastewater under 100 μmol m−2 s−1 of light intensity, much higher than the 55.54 % and 2.71 % without inoculating Scenedesmus sp. TXH. The removal efficiency of the two pollutants was obviously different, which may be attributed to the different functional groups of pollutants. Meanwhile, a much faster removal of conventional pollutants (TDN, TDP and sCOD) occurred in algae-wastewater group. Based on the identified products from mass spectrometer, the main reaction pathways were found and products have lower toxicity evaluated by Ecological Structure-Activity Relationship (ECOSAR) program. This study provided valuable information for the development of NNIS removal with microalgae, which could further enhance the feasibility of microalgae applications in removing NNIS and conventional pollutants.

Screening of pesticides and emerging contaminants in eighteen Greek lakes by using target and non-target HRMS approaches: Occurrence and ecological risk assessment

Lakes, albeit ecosystems of vital importance, are insufficiently investigated with respect to the degradation of water quality due to the organic micropollutants load. As regards Greece, screening of lake waters is scarce and concerns a limited number of contaminants. However, understanding the occurrence of contaminants of emerging concern (CECs) and other micropollutants in lakes is essential to appraise their potential ecotoxicological effects. The aim of this study was to deploy a multiresidue screening approach based on liquid chromatography−high-resolution mass spectrometry (HRMS) to get a first snapshot for >470 target CECs, including pesticides, pharmaceuticals, personal care products (PPCPs), per- and polyfluoroalkyl substances (PFASs), as well as organophosphate flame retardants (OPFRs) in eighteen Greek lakes in Central, Northern and West Northern Greece. The omnipresent compounds were DEET (N,N-diethyl-meta-toluamide), caffeine and TCPP (tris (1-chloro-2-propyl) phosphate). Maximum concentrations varied among the different classes. DEET was detected at a maximum average concentration of >1000 ng/L in Lake Orestiada, while its mean concentration was estimated at 233 ng/L. The maximum total concentrations for pesticides, PPCPs, PFASs, and OPFRs were 5807, 2669, 33.1, and 1214 ng/L, respectively, indicating that Greek lakes are still threatened by the intense agricultural activity. Besides, HRMS enabled a non-target screening by exploiting the rich content of the full-scan raw data, allowing the ‘discovery’ of tentative candidates, such as surfactants, pharmaceuticals, and preservatives among others, without reference standards. The potential ecotoxicity was assessed by both the risk quotient method and ECOSAR (Ecological Structure Activity Relationships) revealing low risk for most of the compounds.

Investigations On the Fish Acute Toxicity of Fragrance Ingredients Involving Chinese Fish Species and Zebrafish Embryos.

While zebrafish (Danio rerio) have been accepted worldwide for evaluating chemical hazards to aquatic vertebrates, and in some countries it is mandated to generate fish toxicity data using native species, such as Chinese rare minnow (Gobiocypris rarus) in China. This represents an additional regulatory constraint that may cause redundant tests, additional animal uses, and higher costs. Previous studies showed that juvenile G. rarus was more sensitive than zebrafish juveniles and embryos to metals. To better understand the sensitivity of G. rarus to organic chemicals, we selected 29 fragrance ingredients belonging to various chemical classes and with differing physicochemical properties, for which good quality zebrafish acute toxicity data were available and tested them with juvenile G. rarus and embryo D. rerio using the Organisation of Economic Co-operation and Development test guidelines. Chemical toxicity distribution (CTD) and chemical ratio distribution (CRD) models were established to systematically compare the sensitivity between juveniles of G. rarus and D. rerio, as well as between D. rerio embryos and juveniles. The results of the CTD models showed that for tested chemicals, the sensitivity of juvenile G. rarus was similar to that of D. rerio juveniles and embryos. The CRD comparisons revealed that juvenile G. rarus was slightly less sensitive by a factor of ~2 than juvenile D. rerio to ingredients belonging to Verhaar class 3 and Ecological Structure Activity Relationship ester class, while comparable to other chemicals. These comparative experiments demonstrated that fish toxicity data with G. rarus can be submitted for use in chemical registrations outside China, which would avoid repeating animal tests using D. rerio. Meanwhile, the similar sensitivity of zebrafish juveniles and embryos to fragrance ingredients confirmed the suitability of replacing juveniles by zebrafish embryos. Environ Toxicol Chem 2022;41:2305-2317. © 2022 SETAC.

Highly efficient activation of peroxymonosulfate by Co, S co-doped bamboo biochar for sulfamethoxazole degradation: Insights into the role of S

Recently, highly efficient activation of peroxymonosulfate (PMS) by S-doped cobalt-based catalysts are receiving increased attention. The effect of S is worth exploring since it has a great influence on PMS activation performance. In this work, dimethyl sulfoxide was adopted as an S source and loaded on bamboo biochar (BB) with Co to form CoS/BBC, which served as an efficient catalyst for PMS activation to degrade sulfamethoxazole (SMX). The experiment results showed that CoS/BBC exhibits an excellent catalytic activity and the SMX (20 mg/L) can be completely degraded under the attack of species of ·OH, SO4-·, 1O2 and electron transfer. The SMX degradation conformed to pseudo first-order kinetics with rate constant reaching 0.442 min−1 in 10 min under the optimal conditions (a catalyst dose of 0.02 g/L, a PMS dose of 0.3 g/L and an initial pH = 7.0). The electrochemical experiments and density functional theory (DFT) calculation revealed that the introduction of S can accelerate electron transfer and promote the decomposition of PMS while facilitating Co(III)/Co(II) redox cycling. Furthermore, liquid chromatograph-mass spectrometer (LC-MS) and ecological structure activity relationships (ECOSAR) proved that the degradation process of SMX in CoS/BBC/PMS system has low ecotoxicity and is harmless to the environment. This work provides a new strategy for enhancing electron transfer by S-doped metal materials and the synthesis of efficient catalysts for SMX removal.

Toxicity alleviation and metabolism enhancement of nonylphenol in green algae Dictyosphaerium sp. by NaHCO3

Nonylphenol (NP) toxicity limits the improvements in its algal remediation efficiency. This study comprehensively investigated the performance and mechanism of NaHCO3-driving effects on NP-exposed algae. The results showed that NaHCO3 enhanced algal resistance to NP and the corresponding EC50 values increased 1.31–4.25 times. Further, the toxicological effects of NP reduced with increasing pyrenoid volume and chlorophyll and carotenoids production, and decreasing cellular damage degree. Moreover, the concentration of extracellular polymeric substances was enhanced and more NP adsorption sites were formed. Consistently, RNA-seq demonstrated significant expression alterations in genes related to energy metabolism, cellular synthesis, photosynthesis, and carbon fixation. Besides, NP biodegradation rate was increased by 15.2 % and 11.1 % in the 1, and 4 mg/L NP treatments, respectively. Identification of degradation intermediates and their toxicity via Ecological Structure Activity Relationship program showed that NaHCO3 accelerated sequential α-C removal from NP in algae with faster generation of less toxic metabolites, namely, 4-ethylphenol, 4-cresol and 4-hydroxybenzoic acid. This study provides new insights into the role of NaHCO3 in toxicity alleviation and metabolism enhancement of NP in algae and can assist NP bioremediation efforts in aquatic environment.

In situ synthesis of flower-structured ZnO@YFC for the efficient piezocatalytic degradation of tetracycline wastewater: Degradation mechanism and toxicity evolution

Antibiotic wastewater has attracted significant attention in recent years. In this study, a novel biochar-based piezocatalyst with a nanoflower structure was synthesized using a method involving the in situ growth of ZnO on a Yang flocculant. The piezoelectric degradation rate of tetracycline was 89.07% after 20 min, and the first-order kinetic constant was 0.682 min−1. Density functional theory calculations showed that the high catalytic activity of ZnO@YCF resulted from its excellent electron transport ability. Radical quenching and electron paramagnetic resonance results showed that OH and O2− radicals were the main radicals involved in TC degradation, with contributions of 58.78% and 37.39%, respectively. A possible TC degradation pathway was proposed based on intermediate studies. Moreover, aquatic toxicity migration was evaluated during the TC degradation process using an ecological structure–activity relationship model. This study proposes a new concept and an efficient way to reuse biomass waste.

Degradation of metoprolol by UV/sulfite as an advanced oxidation or reduction process: The significant role of oxygen

The degradation of metoprolol (MTP) by the UV/sulfite with oxygen as an advanced reduction process (ARP) and that without oxygen as an advanced oxidation process (AOP) was comparatively studied herein. The degradation of MTP by both processes followed the first-order rate law with comparable reaction rate constants of 1.50×10−3sec−1 and 1.20×10−3sec−1, respectively. Scavenging experiments demonstrated that both eaq− and H• played a crucial role in MTP degradation by the UV/sulfite as an ARP, while SO4•− was the dominant oxidant in the UV/sulfite AOP. The degradation kinetics of MTP by the UV/sulfite as an ARP and AOP shared a similar pH dependence with a minimum rate obtained around pH 8. The results could be well explained by the pH impacts on the MTP speciation and sulfite species. Totally six transformation products (TPs) were identified from MTP degradation by the UV/sulfite ARP, and two additional ones were detected in the UV/sulfite AOP. The benzene ring and ether groups of MTP were proposed as the major reactive sites for both processes based on molecular orbital calculations by density functional theory (DFT). The similar degradation products of MTP by the UV/sulfite process as an ARP and AOP indicated that eaq−/H• and SO4•− might share similar reaction mechanisms, primarily including hydroxylation, dealkylation, and H abstraction. The toxicity of MTP solution treated by the UV/sulfite AOP was calculated to be higher than that in the ARP by the Ecological Structure Activity Relationships (ECOSAR) software, due to the accumulation of TPs with higher toxicity.

MOF-based photocatalytic degradation of the antibiotic lincomycin enhanced by hydrogen peroxide and persulfate: Kinetics, elucidation of transformation products and toxicity assessment

The metal–organic frameworks (MOF)-based photocatalytic treatment of lincomycin employing Basolite F300 as catalyst in the presence of two oxidants (H2O2, S2O82-) was investigated. Both processes led to the elimination of lincomycin within 120 min of treatment. The oxidant’s addition has an enhancing effect on the process, possibly from heterogeneous Fenton-type reactions. The concentration effect (0–300 mg/L) of the oxidants was explored, and the optimum amount achieving the highest degradation rate proved to be 100 mg/L for both oxidants. In total, 39 transformation products were identified out of which 24 are proposed for the first time, while the main transformation pathways were hydroxylation, S-oxidation, desulfurization, pyranose ring opening, and cleavage of the C-N bond. For an integrated evaluation of the process, toxicity measurements of the treated solution were performed by a bioassay using D.Magna. Toxicity was more pronounced in the first stages of treatment, implying synergistic effects between the formed intermediate transformation products (TPs), while notable toxicity reduction was achieved at the end of the process. Ecological structure-activity relationship (ECOSAR) predictions revealed the formation of many non-toxic TPs with hydroxylation being the key to the detoxification of the formed compounds.

Dendritic fibrous nanosilica-enhanced adsorption enables efficiently catalytic removal of 2,4-dichlorophenol from soil

Soil contaminated by 2,4-dichlorophenol (2,4-DCP) is a substantial environmental concern because it poses severe health hazards. Fenton and Fenton-like oxidation in the removal of 2,4-DCP in soil has attracted considerable attention but suffers from low efficiency due to strong adsorption of pollutants by soil. In this study, the non-toxic catalyst (DFNS-Fe2O3) was prepared by loading Fe2O3 on dendritic fibrous nanosilica (DFNS) for degradation of 2,4-DCP in soil. DFNS-Fe2O3 could rapidly remove 2,4-DCP within 120 min (98 %), and the removal rate maintained 70 % after 3 cycles of durability test. In addition, BPA, phenol and 2-CP could be efficiently degraded by DFNS-Fe2O3. •OH and •O2 were the main reactive oxygen species (ROS) in the reaction. It is speculated that 2,4-DCP degrades through hydroxylation, substitution process according to the GC-MS results. The toxicity of 2,4-DCP and intermediate products were observed by Ecological Structure Activity Relationships Predictive Model program (ECOSAR). This work paves an avenue for rational design of heterogeneous catalyst on DFNS and their applications in chlorophenol contaminated soil.

Electro-enhanced sulfamethoxazole degradation efficiency via carbon embedding iron growing on nickel foam cathode activating peroxymonosulfate: Mechanism and degradation pathway

The combination of peroxymonosulfate (PMS) activation by hetero-catalysis and electrolysis (EC) attracted incremental concerns as an efficient antibiotics degradation method. In this work, carbon embedding iron (C@Fe) catalysts growing on nickel foam (NF) composite cathode (C@Fe/NF) was prepared via in-situsolvothermal growth and carbonization method and used to activate PMS toward sulfamethoxazole (SMX) degradation. The EC-[C@Fe/NF(II)]-PMS system exhibited an excellent PMS activation, with 100% SMX removal efficiency achieving within 30 min. Reactive oxygen species (ROS) generation and their roles in SMX degradation were confirmed by quenching experiments and electron paramagnetic resonance. It was found that singlet oxygen (1O2) and surface-bound radicals were responsible for SMX degradation, and 1O2 contributed the most. Furthermore, the possible SMX degradation pathways were proposed on the base of the detected degradation intermediates and density functional theory (DFT) calculation. Toxicity changes were also assessed by the Ecological Structure Activity Relationships (ESAR). This work provides a practicable strategy for synergistically enhancing PMS activation efficiency and promoting antibiotics removal.