Peroxymonosulfate activation by Fe-N-S co-doped tremella-like carbocatalyst for degradation of bisphenol A: Synergistic effect of pyridine N, Fe-Nx, thiophene S

MnO/MnS nanoparticles encapsulated in Lycopodium spores derived nitrogen-doped porous carbon as a cost-effective peroxymonosulfate activator for pollutant decontamination: Insight into the mechanism of electron transfer-dominated non-radical pathway

The rational design and exploitation of cost-effective and robust catalysts for peroxymonosulfate (PMS) activation is of great significance. Herein, MnO/MnS nanoparticles encapsulated in Nitrogen-doped porous carbon skeleton (abbreviated as MnO/MnS@NPC) were first constructed through an easy two-step of impregnation along with subsequent pyrolysis technique and utilized to activate PMS for the elimination and mineralization of tetracycline (TC). Benefiting from the strong coupling of transition metal Mn with carbon-based material, the co-doping of heteroatom N and S, the enhanced electrical conductivity, and the hierarchical porous microarchitecture, the obtained MnO/MnS@NPC composite has been expected to present superior PMS activation capacity and pollutant elimination efficiency to its benchmark NPC and MnO@NPC, with 92.5 % degradation rate of TC within 60 min. Comprehensive investigations, involving quenching experiments, electron paramagnetic resonance (EPR) studies, in situ Raman identification, and electrochemical tests, jointly indicated that the non-radical pathways including electron-transfer, single oxygen (1O2) and the high-valent Mn-oxo species, especially the electron transfer process (ETP) from TC molecule to the metastable MnO/MnS@NPC-PMS* complex were dominantly responsible for PMS activation and further decomposition of TC, which greatly enhanced the selective removal of TC and the anti-interference capacity of the PMS system. Furthermore, the possible TC degradation routes were predicted by Density Functional Theory (DFT) calculation and the toxicity of degradation intermediates were also analyzed by toxicity assessment software. In addition, the heterogeneous catalyst displayed outstanding stability and reusability owing to the shield effect of NPC framework to MnO/MnS nanoparticles. Overall, this work proposed a prospective strategy for rationally designing and exploring heterogeneous PMS activator towards wastewater purification.

Precise fabrication of biochar nanosheets through CoAl-layered double hydroxide template-oriented effect for water decontamination via peroxymonosulfate activation

Fabrication of high catalytic activity, cost-efficient and eco-friendly carbon-based materials for water decontamination still possessed huge challenges. From this, in this research, the unique biochar nanosheets (FABN) were prepared from Fructus Aurantii residues by using CoAl-layered double hydroxide as template-oriented materials. Subsequently, the as-prepared FABN were employed as the peroxymonosulfate (PMS) activator to degrade tetracycline, a probe antibiotic contaminant in wastewater, achieving excellent catalytic degradation rate (0.67195 min-1) in optimal FABN/PMS system through the synergistic effect of radical and non-radical pathways. Characterization results and mechanism analysis demonstrated that high sp2/sp3 carbon ratio, abundant graphitic N, oxidized N, oxygen-containing functional groups (C=O and O-C=O) as well as large specific surface area were significant factors for PMS trigger. Moreover, the FABN/PMS system exhibited good catalytic activity towards various antibiotic contaminants (such as, oxytetracycline, chlortetracycline hydrochloride, ciprofloxacin and minocycline hydrochloride) and possessed beneficial adaptability to interference, including humic acid, ubiquitous inorganic anions, pH and various actual natural water samples. Finally, the possible catalytic degradation mechanism and catalytic degradation pathways were proposed and the related biological toxicological experiments were performed through the cultivation of wheat seeds and ECOSAR predictive model, respectively. Overall, this work not only provided novel insights into the fabrication of biochar nanosheets green catalysts, but also offered technical support for the decontamination of the wastewater containing various antibiotic contaminants.

Effect of persulfate dosage on organic degradation using N-doped biochar: Reaction pathway and environmental implications

Persulfate-based advanced oxidation processes (PS-AOPs) catalyzed by carbon-based catalysts are promising for removing organic pollutants via radical/non-radical pathways. However, the activation efficiency of peroxymonosulfate (PMS) or peroxydisulfate (PDS) usage and the reaction mechanism remain insufficiently understood. In this study, the effects of PMS/PDS dosage on the degradation of bisphenol A (BPA, 10 mg/L) were evaluated using N-doped biochar (N-BC, 0.2 g/L) assisted PS-AOPs. The reaction pathways were comprehensively investigated through a combination of characterization techniques and molecular simulations. With low PS dosages (0.05 and 0.1 mM), the degradation rate constants (k obs $$ {k}_{obs} $$ ) were higher in N-BC/PDS (0.04 and 0.07 min-1) compared to N-BC/PMS (0.02 and 0.04 min-1), likely due to higher PDS utilization, which enhanced the contribution of the non-radical pathway. Interestingly, with higher PS dosages (0.5 and 1.5 mM), thek obs $$ {k}_{obs} $$ values were 0.16 min-1 and 0.18 min-1 in N-BC/PMS, respectively, significantly exceeding those determined in N-BC/PDS (0.11 and 0.11 min-1). This result stemmed from the greater adsorption capacity of N-BC for PMS compared to PDS, leading to increased formation of 1O2. The contribution of non-radical pathways for both PMS and PDS increased with higher PS dosage. The results highlighted that BPA degradation improved significantly with the increase in PMS dosage; meanwhile, BPA degradation was insensitive to PDS dosage. The optimal PMS dosage for BPA degradation was found to be 1.5 mM and 0.1 mM for PDS. This study offered valuable insights for optimizing PS-AOPs in environmental remediation, helping to guide the selection of appropriate oxidants and dosages for maximizing pollutant removal. PRACTITIONER POINTS: Effect of PMS/PDS dosage on BPA degradation by N-doped biochar was revealed. Contribution of dominated non-radical pathway increased as PMS/PDS dosage increased. The greater PDS utilization and non-radical pathway resulted in the higherk obs $$ {k}_{obs} $$ at low dosage. N-BC adsorbed more PMS than PDS, leading to an increase ink obs $$ {k}_{obs} $$ at high dosage.

Recent advances in catalyst design, performance, and challenges of metal-heteroatom-co-doped biochar as peroxymonosulfate activator for environmental remediation

The escalation of global water pollution due to emerging pollutants has gained significant attention. To address this issue, catalytic peroxymonosulfate (PMS) activation technology has emerged as a promising treatment approach for effectively decontaminating a wide range of pollutants. Recently, modified biochar has become an increasingly attractive as PMS activator. Metal-heteroatom-co-doped biochar (MH-BC) has emerged as a promising catalyst that can provide enhanced performance over heteroatom-doped and metal-doped biochar due to the synergism between metal and heteroatom in promoting PMS activation. Therefore, this review aims to discuss the fabrication pathways (i.e., internal vs external doping and pre-vs post-modification) and key parameters (i.e., source of precursors, synthesis methods, and synthesis conditions) affecting the performance of MH-BC as PMS activator. Subsequently, an overview of all the possible PMS activation pathways by MH-BC is provided. Subsequently, Also, the detection, identification, and quantification of several reactive species (such as, •OH, SO4•-, O2•-, 1O2, and high valent oxo species) generated in the catalytic PMS system by MH-BC are also evaluated. Lastly, the underlying challenges associated with poor stability, the lack of understanding regarding the interaction between metal and heteroatom during PMS activation and quantification of radicals in multi-ROS system are also deliberated.

A lignin-derived N-doped carbon-supported iron-based nanocomposite as high-efficiency oxygen reduction reaction electrocatalyst

Fuel cells are a promising renewable energy technology that depend heavily on noble metal Pt-based catalysts, particularly for the oxygen reduction reaction (ORR). The discovery of new, efficient non-precious metal ORR catalysts is critical for the continued development of cost-effective, high-performance fuel cells. The synthesized carbon material showed excellent electrocatalytic activity for the ORR, with half-wave potential (E1/2) and limiting current density (JL) of 0.88 V and 5.10 mA·cm-2 in alkaline electrolyte, respectively. The material has a Tafel slope of (65 mV dec-1), which is close to commercial Pt/C catalysts (60 mV dec-1). Moreover, the prepared materials exhibited excellent performance when assembled as cathodes for zinc-air batteries. The power density reached 110.02 mW cm-2 and the theoretical specific capacity was 801.21 mAh g-1, which was higher than that of the Pt/C catalyst (751.19 mAh g-1). In this study, with the assistance of Mg5(CO3)4(OH)2·4H2O, we introduce an innovative approach to synthesize advanced carbon materials, achieving precise control over the material's structure and properties. This research bridges a crucial gap in material science, with potential applications in renewable energy technologies, particularly in enhancing catalysts for fuel cells.