Degradation Of Sulfadiazine Research Articles

Electrospun Nanofiber Dopped with TiO2 and Carbon Quantum Dots for the Photocatalytic Degradation of Antibiotics.

Novel photocatalysts were synthesized through the association of carbon quantum dots (CQDs) with commercial (P25) titanium dioxide (TiO2) by sonication. The resulting TiO2/CQDs composite was then incorporated into the polyamide 66 (PA66) biopolymer nanofibers using the electrospinning technique, considering a composite nanoparticles-to-polymer ratio of 1:2 in the electrospinning precursor solution. The produced nanofibers presented suitable morphology and were tested for the photocatalytic degradation under simulated solar radiation of 10 mg L-1 of amoxicillin (AMX) and sulfadiazine (SDZ), in phosphate buffer solution (pH 8.06) and river water, using 1.5 g L-1 of photocatalyst. The presence of the photocatalyst increased the removal of AMX in phosphate buffer solution by 30 times, reducing the AMX degradation half-life time from 62 ± 1 h (without catalyst) to 1.98 ± 0.06 h. Moreover, SDZ degradation half-life time in phosphate buffer solution was reduced from 5.4 ± 0.1 h (without catalyst) to 1.87 ± 0.05 h in the presence of the photocatalyst. Furthermore, the PA66/TiO2/CQDs were also efficient in river water samples and maintained their performance in at least three cycles of SDZ photodegradation in river water. The presented results evidence that the produced photocatalyst can be a promising and sustainable solution for antibiotics' efficient removal from water.

Activation of persulfate by MOF-derived MnFeOx to efficiently degrade sulfadiazine: Synergistic effects from free radicals and singlet oxygen

In this study, a facile hydrothermal approach was used to synthesize the MOFs materials [Mn-doped MIL-101(Fe)]. These materials were subsequently subjected to high temperature annealing process via calcination to generate the MOFs derivatives (MnFeOx). The synthesized materials were utilized for the removal of sulfadiazine (SDZ) removal through activated peroxymonosulfate (PMS). At the optimum Mn doping, the removal ratio of SDZ could reach 98.9 % (at natural pH) within 20 min. In addition, the study investigated the influence of PMS dosage, catalyst dosage, initial pH, various inorganic anions, and humic acid (HA) on the degradation of SDZ. The activation processes of both free and non-free radicals in the MnFeOx/PMS system were examined by free radical quenching experiments and electron paramagnetic resonance (EPR) techniques. The analysis of the degradation products of SDZ was conducted by using high performance liquid chromatography-mass spectrometry (HPLC-MS), and the breakdown pathways of SDZ in the MnFeOx/PMS system were proposed.

Insight in sulfadiazine degradation by peroxymonosulfate activated by polydopamine-derived nitrogen-doped carbon supported CoFe2O4: Co leaching inhibition and degradation enhancement

Heterogeneous catalyst-mediated sulfate radical-based advanced oxidation processes (SR-AOPs) showed excellent performance during antibiotics degradation. Spinel was a promising catalyst for SR-AOPs, but the secondary contamination due to metal ions leaching needed to be addressed. And the destruction of catalyst structure could lead to the reduction of catalytic activity and the difficulty of recovery. Thus, a novel nitrogen-doped carbon (NC)-supported CoFe2O4 (CoFe2O4@NC) was synthesized as the activator of PMS for sulfadiazine (SDZ) degradation under low Co leaching conditions. The consequences indicated that the CoFe2O4@NC/PMS system exhibited higher PMS decomposition efficiency and reaction stoichiometry efficiency than the bare CoFe2O4/PMS systems (CoFe2O4-180 and CoFe2O4-800), which in turn demonstrated a better SDZ removal performance. Under the condition of CoFe2O4@NC dosage 0.1 g/L, PMS concentration 0.5 mM, solution pH 6.8 and temperature 25°C, SDZ (20 mg/L) was almost completely degraded within 60 min. XPS analysis showed that the NC not only protected and stabilized CoFe2O4, but also provided additional active sites for PMS activation. During SDZ degradation, SO4•−, HO•, •O2− and 1O2 were involved in the reaction, among which SO4• and HO• made the main contribution. Meanwhile, CoFe2O4@NC could be recovered by magnetic separation, and showed great stability (Co leaching 0.852 mg/L) and reusability. In the fifth cycle experiment, 85.02 % SDZ degradation was obtained. Based on the detected intermediates (12 intermediates were identified) and DFT calculations, possible degradation pathways for SDZ in CoFe2O4@NC/PMS were proposed. The condensed dual descriptor indicated that the N7, N11, and C15 atoms on SDZ molecule were the main sites of electrophilic attack, which was consistent with the detected intermediates. The degradation of SDZ involved hydroxylation of NH2, cleavage of S−N and extrusion of SO2. This study explored the improvements made in NC support material to catalytic performance and resistance to dissolution of spinel, providing new insights for subsequent researches.

Effects of hydrothermal pretreatment on sulfadiazine degradation during two-stage anaerobic digestion of pig manure

Antibiotics in animal manure pose significant risks to the environment and health. While anaerobic digestion (AD) is commonly used for pig manure treatment, its efficiency in antibiotic removal has been considerably limited. This study investigated the impact of hydrothermal pretreatment (HTP) on sulfadiazine (SDZ) removal in a two-stage AD system. Results indicated that the HTP process reduced SDZ concentration by 40.61%. Furthermore, the SDZ removal efficiency of the AD system coupling HTP increased from 50.90% to 65.04% compared to the untreated system. Biogas yield was also improved by 26.17% while maintaining system stability. Changes induced by HTP in the microbial communities revealed that Firmicutes, Bacteroidetes, Caldatribacteriota, and Proteobacteria emerged as the primary bacterial phyla. Following HTP, the relative abundance of Prevotella, which exhibited a strong negative correlation with SDZ concentration, increased significantly by 25-fold in the acidogenic stage. Proteiniphilum, Syntrophomonas and Sedimentibacter showed notable increases in the methanogenic stage after HTP. The N-heterocyclic metabolism carried out by Prevotella might have been the predominant SDZ degradation pathway in the acidogenic stage, while the benzene ring metabolism and hydroxylation by the Proteiniphilum emerged as the primary degradation pathways in the methanogenic stages. Furthermore, biodegradation intermediates were proven to be less toxic than SDZ itself, indicating that the HTP-enhanced two-stage AD process could be a viable way to lower the environmental risks associated with SDZ. The findings from this study provide valuable insights for removing SDZ from the environment via two-stage AD.

Preparation of printing and dyeing sludge biochar/macromolecule polymer microsphere as a non-sacrificial persulfate activator with excellent reusability and reduced heavy metals leaching

Biochar-based environmental functional materials offer a promising approach for the resourceful utilization of printing and dyeing sludge (PADS). However, pollutant desorption and heavy metal leaching pose potential environmental risks. In this study, we developed a novel PADS biochar (PADSBC) macromolecule polymer microsphere with outstanding reusability and stability. This microsphere effectively activated peroxymonosulfate (PMS) for the degradation of sulfadiazine (SDZ) while significantly reducing heavy metal leaching compared with PADSBC. The SDZ removal efficiency was not influenced by the type of macromolecule polymers (calcium alginate (CA), cellulose nanofibers (CNF), and polyvinyl alcohol (PVA)) incorporated into PADSBC. In the CA-PADSBC800 microsphere/PMS system, 97 % of SDZ was removed within 40 min, primarily through 1O2-induced oxidative degradation (62 %) and adsorption by CA-PADSBC800 (29 %). Additionally, CA-PADSBC800 prevented SDZ desorption for over five consecutive cycles, while PADSBC800 exhibited 25 % desorption. The presence of HCO3- and humic acids slightly delayed SDZ removal, while Cl- slightly accelerated it. Doping CA, CNF, and CA + CNF into PADSBC800 reduced the leaching of Cu and Cr by over 90 %, and Ni by over 80 %, under both experimental conditions and simulated surface water and landfill leachate situations. The excellent performance of the PADSBC-macromolecule polymer microspheres was attributed to the presence of carboxyl, hydroxyl, and C = O functional groups.

Uv-activated Ni ions as electron donors for in-situ generation of tunable oxygen vacancies on the surface of Bi2O2CO3 with improving photocatalytic activity for sulfadiazine degradation

Uv-activated Ni ions as electron donors for in-situ generation of tunable oxygen vacancies on the surface of Bi2O2CO3 with improving photocatalytic activity for sulfadiazine degradation

Peroxymonosulfate promoted dioxygen activation with Mn(II)-nitrilotriacetic acid complexes for sulfadiazine degradation

In the field of peroxymonosulfate (PMS) activation technology, there is a pressing need to reduce PMS consumption and enhance its utilization rate. The present study demonstrates that the introduction of dissolved oxygen (DO) into the Mn(II)-nitrilotriacetic acid (NTA)-activated PMS system significantly enhances the degradation efficiency of sulfadiazine and increases the PMS utilization rate from approximately 15.0 to 41.3 %. Mechanistic analysis reveals that the Mn(II)-NTA/PMS system generates sulfate radicals as well as intermediate valent manganese species in the absence of DO; while in the presence of DO, Mn(II) is oxidized to Mn(III) by dioxygen to form superoxide anions and Mn(III), which can be further oxidized by PMS to higher valence states such as Mn(V) and Mn(VII). Consequently, the production of free radicals decreases while intermediate valent manganese species become more abundant. Additionally, O2•− can also reduce both Mn(VII) and Mn(IV) back to their lower oxidation state (Mn(II)). The cooperative interactions between these active species enhance the efficiency of catalytic cycles of manganese species. Moreover, the influence of multiple factors, the degradation products, and their associated toxicity assessment were investigated. Overall, this research provides valuable insights into the design of highly efficient PMS and DO activation systems.

Influence of carbon content and irradiation modes on the antibiotic removal from water using VIS-activated TiO2/expanded graphite composite photocatalysts

TiO2/expanded graphite (TiO2/EG) composite films were applied to water treatment for sulfadiazine (SDZ) degradation in a continuous flat plate photochemical reactor. The films were synthesized by sol-gel method and deposited on borosilicate glass by airbrush spray coating technique, forming a TiO2/C heterojunction. Increasing the amount of carbon promoted more efficient photocatalytic removal of SDZ under simulated sunlight, which increased from 9.1% in the absence of carbon to 49.8% for the material containing 7.5% C. From the formation of the TiO2/C heterojunction, morphological modifications, changes in the electronic structure and reduction of the band gap energy were observed. Type-II heterojunction formation was observed. Foreground and background irradiation modes were investigated, and a possible photocatalytic mechanism was proposed. TiO2/7.5 %-EG exhibited the best photocatalytic performance, with the possibility of reuse. The films showed good reusability in the SDZ degradation over 4 photocatalytic cycles. The influence of irradiation modes and the role of oxidizing species were discussed. The results showed that TiO2/EG hybrid films are a promising alternative for practical photocatalytic applications under sunlight.

Synthesis of nano-silver decorated β-Bi2O3/Bi2O2CO3 heterojunction using Bi-MOF precursor: Precisely controllable structure and enhanced photocatalytic activity for sulfadiazine degradation

In this study, a novel Ag/β-Bi2O3/Bi2O2CO3 nanocomposite was prepared by in-situ decomposition of a three-dimensional bismuth-trimesic acid complex (Bi–BTC) precursor at 300 ℃. The multilayered morphology and heterojunction structure of the prepared Ag/β-Bi2O3/Bi2O2CO3 nanocomposite were characterized by a series of technologies. The photocatalytic performance of Ag/β-Bi2O3/Bi2O2CO3 was evaluated by removal of sulfadiazine (SD) antibiotic from water under visible-light irradiation, and the degradation efficiency of SD was up to 96.8 % within 160 min. The superior catalytic activity of Ag/β-Bi2O3/Bi2O2CO3 is attributed to the p-n heterojunction structure constructed by β-Bi2O3 and Bi2O2CO3, as well as the surface plasmon resonance effect of nano-silver, which not only promoting the charge separation and transfer, but also increasing the hot electron density. Electron paramagnetic resonance (EPR) and active species trapping experiments indicated that ∙O2 and h+ play a major role in the oxidative degradation of sulfadiazine. The possible degradation pathway of sulfadiazine was identified, and the ecological toxicity of SD and its degradation intermediates was estimated using T.E.S.T. software. In addition, the as-prepared Ag/β-Bi2O3/Bi2O2CO3 showed excellent photo-corrosion resistance capacity and good reusability in photocatalytic degradation of SD.

Unlocking the potential of multifunctional and highly porous Ti3C2/TiO2@Bi2O3 – based MXene: Synergetic photocatalytic activation of peroxymonosulfate, hydrogen evolution and antimicrobial activity

A novel and efficient solar light responsive multi layered highly porous MXene-based Ti3C2/TiO2@Bi2O3 photocatalyst was synthesized by hydro/solvothermal technique. The optimized band gap (2.09 eV), high surface area (28.39 m2/g), schottky and p-n junctions remarkably enhanced the effectiveness of TTB20 in the solar region. The degradation of sulfadiazine (SDZ) by TTB20 under solar light was enhanced from 76.60 % to 97.40 % when coupled with 0.5 mM peroxymonosulfate (HSO5–) at an irradiation time of 30 min. The radical scavenging investigations indicated that SO4•−, O2•− and h+ are primarily engaged in photocatalytic activity. Moreover, the TTB20 sample showed promising activity against E-coli. In addition, the TTB20 sample displayed a remarkable 4.15-fold higher photocatalytic H2 evolution rate than the TTB0 sample. Thus, the present study suggests that TTB20/HSO5–/solar light is an auspicious approach for addressing environmental pollution, health issues and energy crises.

Visible light enhanced the degradation of sulfadiazine with persulfate activated by Cu2O@zeolite

ABSTRACT Cu2O/ZL-10 was successfully fabricated as a good activator of PDS and photo-catalyst. The physicochemical characteristics of the prepared Cu2O/ZL-10 were investigated. Cu2O/ZL-10 was employed to activate PDS for the sulfadiazine (SDZ) degradation under visible light irradiation. In the Vis/Cu2O/ZL-10/PDS system, 91.98% degradation rate of SDZ and 51.8% TOC removal after 180 min reaction were obtained. The SDZ degradation rate was improved significantly by the increase of the doping amount of Cu2O, PDS concentration and Cu2O/ZL-10 addition while it decreased with the growth initial pH. Moreover, the SDZ degradation rate descend by only 0.9% after five cycles uses of Cu2O/ZL-10. Quenching experiments and EPR spectra demonstrated that the dominant free radicals of •O2 –, SO4 •– and •OH were generated for the SDZ degradation. It demonstrated that Cu2O/ZL-10 was an effective and promising catalyst for the simultaneous activation of PDS and the utilization of visible light to generate active species and photo-induced electron, respectively.

Double template synthesis of N/S co-doped shrimp shell derived biochar for efficient sulfadiazine degradation: The role of non-radical pathway

In this work, waste shrimp shells were used to synthesize N/S-co-doped biochar nanomaterials (BC-NS) by simple hard template and soft template. Through the cooperative effect of adsorption and degradation, the BC-NS/PMS system could remove 100 % of SDZ within 30 min. The combination of soft and hard templates produces hierarchical porous structure and provides more reactive sites. The radical quenching tests and electron paramagnetic resonance measurements (EPR) illustrated that the non-radical 1O2 was the dominant reactive oxidative species (ROS) in the BC-NS/PMS system. By density functional theory (DFT) computation, it demonstrated that graphitic N and pyridinic N were the main reactive sites of BC-NS. Finally, intermediate products of SDZ have been identified and four possible pathways for the degradation of SDZ were proposed. Consequently, a novel synthesis strategy of metal-free biochar materials was proposed in this study, which broadened a new prospect for the application of metal-free biochar materials in SR-AOPs.

Sulfadiazine degradation by Bjerkandera adusta DH0817 at low temperatures and its cold-adaptation mechanisms

The prolonged period of low temperatures in northern China poses a significant challenge to the bioremediation of antibiotic pollution. This study reports that a white-rot fungus Bjerkandera adusta DH0817, isolated from a poultry farm in Liaoning Province, can remove 60 % of SDZ within 20 days at 10°C and reduce the biotoxicity of SDZ. Six degradation pathways were proposed. SDZ biodegradation was primarily driven by cytochrome P450. Transcriptome analysis revealed that DH0817 upregulated genes associated with cell membrane, transcription factors and soluble sugars in response to low temperatures. Subsequently, genes associated with fatty acid, proteins and enzymes were upregulated to remove SDZ at low temperatures. This study provides valuable microbial resources and serves as a theoretical reference for addressing antibiotic pollution in livestock and poultry farms under low temperature conditions.

Efficient degradation of sulfadiazine by UV-triggered electron transfer on oxalic acid-functionalized corn straw biochar for activating peroxyacetic acid: Performance, mechanism, and theoretical calculation

A novel UV/oxalic acid functionalized corn straw biochar (OCBC)/peroxyacetic acid (PAA) system was built to degrade sulfadiazine from waters. 94.7 % of SDZ was removed within 30 min by UV/OCBC/PAA. The abundant surface functional groups and persistent free radicals (PFRs) on OCBC were responsible for these performances. Cyclic voltammetry (CV) and other characterization analysis revealed, under UV irradiation, the addition of OCBC served as electron donor, which might promote the reaction of electrons with PAA. The quenching and electron paramagnetic resonance (EPR) tests indicated that R-O•, 1O2 and •OH were generated. Theoretical calculations indicated sulfonamide bridge was vulnerable under the attacks of reactive species. In addition, high removal effect achieved by 5 reuse cycles and different real waters also suggested the sustainability of UV/OCBC/PAA. Overall, this study provided a feasible approach to remove SDZ with high mineralization efficiency, in addition to a potential strategy for resource utilization of corn straw.

Self-reinforced Synchronization of persulfate activation and photocatalysis by Tri-metal heterojunction catalyst for efficient degradation of Sulfadiazine

The outstanding performance of advanced oxidation processes based on self-generated active species in the decomposition of antibiotics has attracted widespread attention. Herein, a novel heterojunction flower-shaped microsphere Iron-based Hydroxide/Tungstate Antimony Oxide (FSW) composed of nanosheets with synchronous persulfate activation and photocatalytic properties were proposed to achieve efficient degradation of sulfadiazine (SDZ) by enhanced active oxidation species. Constructed FSW/PMS/vis system realized the improved removal of SDZ at pH 2–6, with a degradation efficiency of 96.6 % in just 6 min (electron transfer efficiency, 6.19 × 10–4 A/cm2; kinetic rate, 2-ORR). Investigation of density functional theory demonstrated the superiority of FSW catalysts (Eads = -1.63 eV), indicating that FSW can not only enhance the adsorption of PMS but also activate PMS to generate a large number of free radical ions, realizing rapid carrier movement and effective charge transfer, which highlights the application prospects of the system in eliminating antibiotics in environmental water bodies.

Applications of Titanium Dioxide (TiO2) Nanoparticles in Photocatalysis

Titanium dioxide nanoparticles (TiO2 NPs) are conspicuously preferred as photocatalyst among the transition metal oxide nanoparticles. It exhibited in three polymorphisms of steady state rutile phase while brookite and anatase sustaining in metastable phase. The mixed phases of anatase phase and rarely found brookite phase mostly preferred for the photodegradation applications. The economically affordable along with nontoxic nature on top of excellent opto-electronics and catalytic properties of TiO2 NPs are eminently favorable for the photocatalytic degradation of chemically complex structured numerous organic and inorganic dyes, phenol and phenol-based derivatives, passive microplastics as well as suspended matters, non-biodegradable cytostatic drugs, acetaminophen, pharmaceutical organic waste compounds in addition to water pollutants. The photocatalytic capability of these NPs enhanced by upgrading the structural and morphological nature by opting different synthesis techniques as well preparing the nanocomposites of TiO2 incorporation with other metals. The hydrothermally prepared polymeric membranes of polyvinylidene with TiO2 NPs effectively (more than 90%) removed 17 α–ethinylestradiol from the contaminated water compared to Diclofenac under Uv irradiation. As it fronting the issue of electrostatic repulsion to all other membranes surface. The grafted membrane recorded highest degradation efficiency of 95.4% and best reusability of 90% saturated at fifth recycle for Methylene Blue azo dye compared with blending and dip coating membranes. The TiO2 modified ultrafiltration membranes of Polyvinylidene Fluoride with Dopamine illustrated the 92.6% photocatalytic degradation of Sulfadiazine which is most hazardous and highly resistant to biodegradation. 100% degradation of phenol derivative by TiO2 NPs hybrid polymeric films in visible light irradiation. The degradation efficiency of heterogenous photocatalyst Carbon–TiO2 contained anatase and brookite phased for Methylene Blue dye was 100% while for Rhodamine–B higher than 99% in solar and more than 78% in LED light irradiation. The recent trends for improvisation of photocatalytic ability of TiO2 NPs to enhance the quality of water and hence the mankind are elaborated.

PH-dependent mechanisms of sulfadiazine degradation by natural pyrite-driven heterogeneous Fenton-like reactions

The development of a natural pyrite/peroxymonosulfate (PMS) system for the removal of antibiotic contamination from water represented an economic and green sustainable strategy. Yet, a noteworthy knowledge gap remained considering the underlying reaction mechanism of the system, particularly in relation to its pH sensitivity. Herein, this paper investigated the impacts of critical reaction parameters and initial pH levels on the degradation of sulfadiazine (SDZ, 3 mg/L) in the pyrite/PMS system, and elucidated the pH dependence of the reaction mechanism. Results showed that under optimal conditions, SDZ could be completely degraded within 5 min at a broad pH range of 3.0–9.0, with a pseudo-first-order reaction rate of >1.0 min−1. The low or high PMS doses could lower degradation rates of SDZ through the decreased levels of active species, while the amount of pyrite was positively correlated with the removal rate of SDZ. The diminutive concentrations of anions exerted minor impacts on the decomposition of SDZ within the pyrite PMS system. Mechanistic results demonstrated that the augmentation of pH levels facilitated the transition from the non-radical to the radical pathway within the natural pyrite/PMS system, while concurrently amplifying the role of •OH in the degradation process of SDZ. This could be attributed to the change in interface electrostatic repulsion induced by pH fluctuations, as well as the mutual transformation between active species. The stable presence of the relative content of Fe(II) in the used pyrite was ensured owing to the reduced sulfur species acting as electron donors, providing the pyrite/PMS system excellent reusability. This paper sheds light on the mechanism regulation of efficient removal of organic pollutants through pyrite PMS systems, contributing to practical application.

Investigation into the synergistic roles of exposed crystal planes and S vacancies during the photo-Fenton degradation of sulfadiazine via pyrite with three different morphologies

The synergistic effect of photocatalysis on pyrite (FeS2) Fenton process largely depends on its morphology. However, the relationship between morphology and performance remains unclear. The study aims to investigate how different morphologies FeS2 (cube, octahedron and sphere) affects the photo-Fenton degradation of sulfadiazine (SDZ) by considering crystal planes exposure and sulfur (S) vacancy. Results demonstrated octahedral FeS2 exhibited highest efficiency in photo-Fenton degradation (93.4 %) and mineralization (82.3 %) of SDZ. The synergistic effect of photocatalysis on Fenton process of octahedral FeS2 was particularly notable. The unique characteristics of octahedral morphology accelerated the Fe3+ to Fe2+ cycle and various active species generation (·OH, h+, ·O2– and ·SO4-). Specifically, the exposed crystal planes and S vacancies was the key reason influencing the photocatalytic synergy of FeS2. The octahedron with exposed crystal planes (200) exhibited strongest crystallographic energies, larger specific surface area with sharp corners and edges. These features improved adsorption performance and increased the release of Fe2+. Furthermore, the crystal planes narrowed the band gap of octahedral FeS2, facilitating the generation of more photo-generated carriers. The higher concentrations of S vacancies on octahedral FeS2 provided more active sites, reducing the band gap, and extending the carrier lifetime. Given the increasing demand for practical applications of the FeS2 photo-Fenton in pollutant treatment, this study establishes a solid theoretical foundation for the design and optimization of high-efficiency and low-cost catalysts.

Sulfadiazine degradation by hydroxyl radical and direct electron transfer pathways in the self-prepared boron doped diamond electrochemical process

Sulfonamide antibiotics are frequently detected in livestock wastewater, seriously harming the ecological environment and human health. Boron-doped diamond (BDD) electrochemical process has prominent potential in degrading organic pollutants from special industrial wastewater. In this work, the degradation efficiency and mechanism for sulfadiazine (SDZ) with the prepared BDD electrode were investigated. Scanning electron microscopy (SEM) and Raman spectroscopy revealed a 2 μm thick, compact, and crack-free BDD film on silicon. The BDD's oxygen evolution potential was 1.47 V. About 93.3 % of SDZ in the synthetic wastewater was removed under the conditions of a current density of 40 mA/cm2, electrode spacing of 20 mm, electrolyte concentration of 40 mM, and an initial pH of 8. Hydroxyl radical and direct electron transfer (DET) mainly contributed to SDZ degradation based on specific quencher tests and electrochemical analysis. The possible transformation pathways of SDZ were proposed according to the detected oxidation products and DFT calculation, mainly including amino hydroxylation, sulfur dioxide extrusion, and pyrimidine heterocyclic ring opening. Furthermore, the toxicity of intermediates products markedly weakened compared to that of SDZ. The presence of ion chloride could slightly improve the removal of SDZ, while bicarbonate and phosphate inhibited the SDZ degradation. In addition, the efficient removal of chemical oxygen demand and SDZ in the effluent of aerobic biological treatment effluent of actual livestock wastewater was confirmed. To sum up, BDD electrochemical oxidation is a viable approach for the advanced treatment of livestock wastewater.

Synthesis of N-doped porous biochar from chemical pollutant for efficient sulfadiazine degradation: Performance, mechanism and bio-toxicity assessment

Turning chemical wastes into valuable materials presently is a key challenge. Therefore, a facile method was employed upon synthesis of an N-doped porous biochar (NPBC) catalyst via pyrolysis of chemical pollutant (reactive red 2, RR2), urea, and NaHCO3. Using NaHCO3 activation, the NPBC/PMS system exhibited excellent catalytic efficiency for sulfadiazine (SDZ) degradation, which was attributed to the porous structure with abundant active species of graphitic C/N, C=O, –COOH, and C–S–C. Significantly, the NPBC displayed excellent environmental suitability, catalytic universality for the decomposition of common organic pollutants (i.e. bisphenol A, ciprofloxacin, tetracycline, and sulfamethoxazole) and catalytic recycling stability. In addition, free radical quenching and mechanism inspection demonstrated that 1O2 is the dominating reactive oxygen species (ROS) in the NPBC/PMS system. The most probable degradation pathway and mechanism are proposed. Finally, the biotoxicity of SDZ before and after degradation was evaluated by ECOSAR analysis and the germination tests of wheat seeds. This study not only provides a rational method for the facile synthesis of valuable materials from chemical pollutants, but also presents a direction for discovering metal-free catalysts with remarkable activity for water decontamination in the future.