Peroxydisulfate Research Articles

Co single atoms anchored on straw biochar as an efficient peroxydisulfate activator for ultrafast removal of antibiotics

The removal efficiency of antibiotics decreases at low temperature, which is an urgent problem to be solved in cold regions. This study prepared a low-cost single atom catalyst (SAC) from straw biochar, which can rapidly degrade antibiotics at different temperatures by activating peroxydisulfate (PDS). Co SA/CN-900 + PDS system can degrade 100% of tetracycline hydrochloride (TCH, 10 mg/L) in 6 min. The high concentration of TCH (25 mg/L) was degraded by 96.3% in 10 min at 4 °C. The system was also tested in simulated wastewater and showed a good removal efficiency. TCH was primarily degraded by 1O2 and direct electron transfer pathway. Electrochemical experiments and density functional theory (DFT) calculations showed that CoN4 improved the electron transfer capacity of biochar and thus enhanced the oxidation capacity of Co SA/CN-900 + PDS complex. This work optimizes the application of agricultural waste biochar and provides a design strategy of efficient heterogenous Co SACs to degrade antibiotics in cold regions.

Effects of various persulfate oxidation pretreatments on enzymatic saccharification efficiency of sugarcane bagasse biomass and the related mechanism

This study explored the impact of different persulfate pretreatments on the substrate characteristics and enzymatic sugar yield of sugarcane bagasse (SCB) and the related mechanisms. We analyzed the biomass composition, physicochemical properties of SCB, enzymatic saccharification efficiency, pure commercial cellulose and lignin degradation dynamics, and ·OH and SO4∙ − generation properties under different persulfate pretreatments. The results revealed that potassium peroxymonosulfate (2KHSO5·KHSO4·K2SO4, PPMS) pretreatment had a significant effect on SCB. Under the optimal pretreatment conditions, SCB pretreated with PPMS showed a reducing sugar yield of 67.98%, a sugar conversion rate of 90.29%, and a lignin removal rate of 87.49%, which were about 2–3 folds those under pretreatment with peroxydisulfate (PDS) including sodium persulfate (Na2S2O8, SPS) and ammonium persulfate ((NH4)2S2O8, APS). PPMS had higher selectivity for lignin degradation and stronger free radical generation ability than PDS, which may be the main contributor to its superior pretreatment performance.

Interaction of Persulfate and Hydroxylamine Produces Highly Reactive Species in Aqueous Systems

Activation of persulfate is a hot topic in environmental remediation via generating reactive species such as SO4•– and 1O2. This study investigated the activation of peroxydisulfate (PDS) by HA with respect to the formation mechanisms of reactive species and their roles in contaminant transformation. SO4•–, HO•, and reactive nitrogen species (RNS, e.g., •NO, •NO2, and NH2O•) were proved to be predominant reactive species in the HA/PDS system by electron paramagnetic resonance analysis and radical scavenging tests. The reaction stoichiometric ratio of HA to PDS was about 0.63, involving two major steps: HA initially reacted with PDS to generate SO4•– and NH2O•, and NH2O• further reacted with PDS to form SO4•– and HNO. Ultimately, N2O was the major product of HA via the dimerization of HNO. •NO was formed via the reactions of HNO with O2 and HO•, and •NO2 could be formed via the reaction of SO4•– and NO2–. In the HA/PDS system, SO4•– and HO• primarily contributed to the degradation kinetic of carbamazepine, while RNS also played important roles in the transformation pathways of carbamazepine, resulting in the formation of nitroso compounds. As pH increased from 2 to 7, the removal rate of carbamazepine was highest at pH 3–4 (66–69% at 60 min), which is mainly due to NH2OH showing higher activation efficiency for PDS but faster consumption for SO4•– and HO• compared to NH3OH+. This study broadens the understanding of peroxide activation by HA and demonstrates the important roles of formed RNS in contaminant transformation.

Stable and recyclable FeS-CMC-based peroxydisulfate activation for effective bisphenol A reduction: performance and mechanism

In this study, a novel material, iron sulfide modified by sodium carboxymethyl cellulose (FeS-CMC), was successfully synthetized for peroxydisulfate (PDS) activation to remove bisphenol A (BPA). Characterization results showed that FeS-CMC had more attachment sites for PDS activation due to its higher specific surface area. A stronger negative potential contributed to preventing nanoparticles from reuniting in the reaction and improving the interparticle electrostatic interactions of the materials. Fourier transform infrared spectrometer (FTIR) analysis of FeS-CMC suggested that the coordination of the ligand for combining sodium carboxymethyl cellulose (CMC) with FeS was monodentate. A total of 98.4% BPA was decomposed by the FeS-CMC/PDS system after 20 min under optimized conditions (pH = 3.60, [FeS-CMC] = 0.05 g/L and [PDS] = 0.88 mM). The isoelectric point (pHpzc) of FeS-CMC is 5.20, and FeS-CMC contributed to reducing BPA under acidic conditions but showed a negative effect under basic conditions. The presence of HCO3−, NO3− and HA inhibited BPA degradation by FeS-CMC/PDS, while excess Cl− accelerated the reaction. FeS-CMC exhibited excellent performance in oxidation resistance with a final removal degree of 95.0%, while FeS was only 20.0%. Furthermore, FeS-CMC showed excellent reusability and still reached 90.2% after triple reusability experiments. The study confirmed that the homogeneous reaction was the primary part of the system. Surface-bound Fe(II) and S (-II) were found to be the major electron donors during activation, and the reduction of S (-II) contributed to the cycle of Fe(III)/Fe(II). Sulfate radicals (SO4•−), hydroxyl radicals (•OH), superoxide radicals (O2•−) and singlet oxygen (1O2) were produced at the surface of FeS-CMC and accelerated the decomposition of BPA. This study offered a theoretical basis for improving the oxidation resistance and reusability of iron-based materials in the presence of advanced oxidation processes.

Magnetic MnFe2O4 nanoparticles anchored on sludge-derived biochar in activating peroxydisulfate for levofloxacin degradation: Mechanism, degradation pathways and cost analysis

The sludge-derived biochar (SBC) was prepared by a low-cost microwave pyrolysis process, and then MnFe2O4 nanoparticles were anchored onto the surface of SBC through a hydrothermal route to construct a magnetic MnFe2O4/SBC composite catalyst. As-obtained MnFe2O4/SBC catalysts were characterized by XRD, FT-IR, Raman, FE-SEM, BET surface area and XPS. The optimized MnFe2O4/SBC(1:3) catalyst showed a higher catalytic activity to activate peroxydisulfate (PDS) for levofloxacin (LVF) degradation than that of SBC, MnFe2O4 and reported magnetic composite catalysts. After 80 min of reaction, 79.5% of LVF in water (10 mg/L) was degraded by MnFe2O4/SBC(1:3) in the presence of PDS (1.5 g/L), and LVF degradation followed the pseudo-second-order kinetics. Calcium carbonate (CaCO3) in SBC participates in PDS activation. XPS analysis, oxidative species capture experiments, EPR and linear sweep voltammetry (LSV) tests confirmed that LVF degradation in MnFe2O4/SBC-PDS oxidation system was achieved through the non-radical (electron transfer, 1O2) and radical (SO4•−, ∙OH and O2•−) pathways, with the former playing a dominant role. The degradation routes of LVF were established based on the degradation intermediates. LVF removal efficiency from real water matrices was improved by means of increasing catalyst dosage and reaction temperature. Cost analysis indicates that MnFe2O4/SBC-PDS oxidation process is a cost-effective method to eliminate the antibiotics in water.

Spectrophotometric determination of di-butyl phosphate in PUREX solvent using peroxo disulfate as oxidizing agent

Spectrophotometric determination of di-butyl phosphate in PUREX solvent using peroxo disulfate as oxidizing agent

Multiaperture g-C3N4@SiO2 to activate peroxydisulfate via visible light for efficient Rhodamine B removal.

The sulfate radical-based advanced oxidation process (SR-AOPs) has been verified as a promising method tohandle the persistent organic compounds in water using peroxydisulfate (PDS) as oxidant. A Fenton-like process was constructed and showed great potential to remove organic pollutants using visible-light-assisted PDS activation. The g-C3N4@SiO2 was synthesized via thermo-polymerization, and characterized using powder X-ray diffraction (XRD), scanning electron microscope equipped with an energy-dispersive X-ray (SEM-EDX), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) method, photoluminescence (PL), transient photocurrent, and electrochemical impedance. Photocatalytic performance was demonstrated using the removal rate of Rhodamine B (RhB), and 96.08% RhB was removed from the solution within 50 min (10 mg/L in 200 mL, g-C3N4@SiO2 = 0.25 g/L, pH = 6.3, PDS = 1 mmol/L). The free radical capture experiment proved that HO•,h+,[Formula: see text] and [Formula: see text] were generated and removed RhB. The cyclic stability of g-C3N4@SiO2 has also been studied, and the result shows no noticeable difference in the six cycles. The system of visible-light-assisted PDS activation might provide a novel strategy for wastewater treatment and must be an environment-friendly catalyst.

Control of chemical and microbial pollutants in liquid-solid phases of sewer pipes by Fe(II)-activated persulfate: Performance and mechanism of simultaneous removal

Most of the problems such as odor and corrosion in sewage systems originate from the biochemical reactions of liquid and solid phases in the pipes. Suppressing the activity of microorganisms and biofilms in the sewers is conducive to maintaining the proper operation of the sewer system. This study verified the removal of microorganisms and sulfides from wastewater and the inhibition of biofilm activity by peroxodisulfate (PDS) with the activation of ferrous ions (Fe(II)). Fe(II)/PDS can achieve efficient microbial inactivation within a reaction time of 20 min after a single dosing (Up to 95% removal of planktonic bacteria in the liquid phase), and the sulfide reduction can be maintained for more than 5 days, providing the possibility of intermittent dosing. The sulfide concentration can be maintained below 4 mg/L by intermittent dosing (average dosing interval is 10 days) during the long-term operation of the reactor. Dissolved organic matter (DOM) changes in sewage predict biofilm destruction. Changes in the biofilm microscopic morphology, extracellular polymer substances (EPS) fraction, biofilm functional groups, and microbial community revealed the effects of Fe(II)/PDS on the solid–liquid phase material fraction and biofilm structure of the sewage pipeline. The mechanism of biofilm disruption was analyzed based on the identification of strongly oxidizing active species in the Fe(II)/PDS system. This study shows that it is feasible to develop an efficient and cost-effective sulfide and microbial control strategy using Fe(II) with PDS in sewage systems.

Efficient degradation of phosphonate via trace Cu(II) mediated activation of peroxymonosulfate

The phosphonates in wastewater have attracted much attention due to their potential risks to the aquatic environment, which is oxidized to orthophosphate (PO43−) is a vital step to achieve their removal. Advanced oxidation processes based on free radicals is usually crucial methods to remove phosphonates, which could be easily disturbed by water matrix. Herein, using 1-hydroxyethane1,1-diphosphonic acid (HEDP) as a model pollutant, a nonradical system was constructed via Cu(II)/PMS process. 82 % HEDP is degraded by trace Cu(II) (5 μM) mediated peroxymonosulfate (PMS) activation process within 60 min at pH = 7.0, which is much higher than that in Cu(Ⅱ)/peroxydisulfate (PDS) and Cu(Ⅱ)/H2O2 systems under identical conditions. The results of multiple experiments reveal that Cu(III) induing intramolecular electron transfer as the dominant reactive species makes responsible for the oxidation of HEDP in the Cu(II)/PMS process, whereas the role of hydroxyl radicals (HO•) and 1O2 is negligible. In addition, the presence of HCO3−, benzoic acid (BA) and phenol shows a negative effect on the oxidation of HEDP in the Cu(II)/PMS process. However, in the actual wastewater, the removal efficiency of HEDP in the Cu(II)/PMS process is much higher than that in other free radical processes (i.e., UV/H2O2, UV/PDS). This study provides a new idea for the removal of phosphonates from actual wastewater.

Photosensitive Dye as an Ideal Peroxymonosulfate Activator for Efficient Self-Degradation: A Novel Idea of Using Waste to Treat Waste.

Commonly used peroxydisulfate (PS) or peroxymonosulfate (PMS) activation methods have been limited in their practical application due to certain drawbacks, such as high cost, high energy consumption and secondary pollution. In this study, a catalyst-free alizarin green (AG) self-activating PMS catalytic system was constructed based on photosensitization properties of dye, which ultimately achieved efficient degradation of the dye activator, also the target pollutant. Here, 52.5% of the 100 mL mixture of 10 mg/L AG decomposed within 60 min with 1 mM PMS under visible-light irradiation, thereby showing a strong pH adaptation. Mechanism of AG self-activating PMS was revealed that the photo-excited AG can effectively transfer photo-induced electrons to PMS for its activation, which generates reactive oxidizing species dominated by singlet oxygen (1O2), and supplemented by hydroxyl radical (•OH), superoxide radical (O2•-) and sulfate radical (SO4•-) to realize the efficient self-degradation of the dye pollutants. Moreover, such self-catalytic system operated well under natural sunlight irradiation, indicating the great application potential in the actual wastewater treatment. Herein, photosensitive dye acted as an ideal PMS activator realizing its efficient self-degradation, which provides a novel idea of "using waste to treat waste" for developing wastewater treatment process in a high-efficiency and low-consumption way.

Synthesis of acetic acid-modulated NH2-MIL-101(Fe) for advanced oxidation of rhodamine B from aqueous solution

A novel composite of acetic acid-modulated AC-NH2-MIL-101(Fe) was prepared by mild chemistry. The catalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Brunaure-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). Acetic acid can control the crystal size, so that the catalyst had a large specific surface area (99.35 m2·g−1) and pore size (0.13 cm3·g−1), the adsorption amount of Rhodamine B (RhB) up to 446.965 mg·g−1, after the addition of peroxydisulfate (PDS), the catalytic degradation efficiency of RhB was as high as 99.7%. Electronic paramagnetic resonance spectrometer (EPR) and quenching experiments showed that the catalytic process may involve radical (·OH, SO4-· and O2·-) and non-radical (1O2) processes, in which the contribution of 1O2 to degradation reached 63.55% and played a major role.

Peroxydisulfate activation by CuFe2S3 nanocrystal doped C/N catalyst for phenanthrene degradation: Experimental, mechanism, and density functional theory calculation

In Fenton-like reactions, metal-doped catalysts generally have high catalytic activity, but their active sites are always randomly distributed, yielding electron transfer mechanisms between orbitals are difficult to explain. Herein, a CuFe2S3-C/N catalyst was synthesized to activate peroxydisulfate (PDS) for phenanthrene (PHE) degradation. The periodic structure of CuFe2S3 nanocrystals embedded in the C/N skeleton facilitated the cooperation of Fe, Cu, and S, resulting in a more effective degradation of PHE [i.e., maximum degradation rate of up to 93.5% (Initial PHE concentration: 1 mg/L)]. A phenanthrene degradation pathway was then proposed, and the dominant reactive oxygen species were proven to be •OH, SO4•-, 1O2 and O2•-. This pathway was elucidated using density functional theory (DFT) methods, and the negative adsorption energy (-2.05 eV) of S2O82- corresponding to a spontaneous adsorption process. The CuFe2S3 surface stretched the O-O bond from 1.306 to 1.433 Å, and the loss of electrons from the 2p bonding orbital of O atoms led to a lower energy barrier for O-O bond cleavage. Additionally, the electrons were transferred from part of the 3d orbitals of Cu and Fe atoms to the 2p orbital of O atoms in S2O82- and the electron donating capacity of the Cu atom was 3–7 times higher than that of the Fe atom, indicating that the Cu atoms dominated the PDS activation. This study expands on approaches that can be used to modify metal-doped materials to degrade phenanthrene and it contributes towards a clearer understanding of electron transfer mechanisms underlying PDS activation.

Degradation and transformation of sulfapyridine in Fe2+/peroxydisulfate: Kinetics, mechanism and potential products

Sulfapyridine (SPY) is extensively consumed in aquaculture and may cause environmental damages. The mechanism of radicals on the degradation of SPY was still unclear. In this study, Fe2+ was found to have a positive contribute on the conversion of sulfate radical (SO4−) to hydroxyl radical (OH) in the peroxydisulfate (PDS) system. Kinetic modeling demonstrated that the concentration of OH was depended on pH, and OH was the dominant radical in Fe2+/PDS system. The second-order rates of OH (1.03 × 1010 M−1 s−1) and SO4− (8.41 × 109 M−1 s−1) reacting with SPY clarified OH reacted with SPY faster than SO4−. Combining the transformation products (TPs) and quantum chemical calculation, the degradation pathways of SPY by SO4− and OH were proposed. The antibacterial activity test illuminated that the antibacterial activity of some TPs (TP3 and TP6) was relatively higher than their parent compound. The antibacterial activity of solution was difficult to be removed with the SPY degradation. These results illustrated that the Fe2+/PDS treatment need further improvement.

Biocrystal-encased manganese ferrite coupling with peroxydisulfate: Synergistic mechanism of adsorption and catalysis towards tetracycline removal

Biocrystal-encased manganese ferrite (BC@MnFe2O4), an adsorption/catalytic bifunctional catalyst, was synthesized for peroxydisulfate (PDS) activation and tetracycline (TC) removal. Under the optimal conditions (PDS 6.0 mM, pH 7.0, dosage 0.30 g L−1, and TC content 20.0 mg L−1), the TC removal efficiency reached 85.11% and maintained 79.07% after four cycles. Furthermore, inorganic anions (H2PO4− > HCO3− > NO3− > SO42− > Cl−) and natural organic matter (HA) inhibited TC elimination to varying degrees. Compared with the MnFe2O4 nanorods, BC@MnFe2O4 effectively alleviated the side effects caused by particle aggregation and reduced metal ion leaching. Adsorption kinetic and isotherm results exhibited that the adsorption process of TC on MnFe2O4 and BC@MnFe2O4 were better fitted with the pseudo-second-order and Langmuir models. The analyses of quenching experiment, electron paramagnetic resonance, and X-ray photoelectron spectroscopy demonstrated that Fe and Mn sites exposed on the BC@MnFe2O4 served as the catalytic centers for PDS activation, and OH, SO4−, and 1O2 were crucial reactive oxidant species contributing to the rapid TC degradation. Based on the determination of TC degradation intermediates, three possible degradation pathways were proposed, and TC was converted to small molecules via hydroxylation, demethylation, deamidation, dehydration, and other reactions. This study offers novel insights into the synergistic effect of adsorption and catalysis by inorganic-biological hybrid design, and gives inspiration for the construction of high-performance catalysts in organic wastewater treatment.

Heterogeneous activation of persulfate by macroscopic nitrogen-doped graphene oxide cubes for the degradation of antibiotic contaminants in water

As a sustainable and green approach, carbocatalysis, a metal-free strategy, has shown exceptional results in advanced oxidation processes (AOPs). Nonetheless, the recovery of these catalysts has been a major shortcoming over the years. Herein, three-dimensional nitrogen-doped graphene macrostructures (3D-NGMs), in the form of macro cubes, were synthesised by a simple cross-linking and thermal annealing procedure, after which they were employed in the activation of peroxydisulfate (PS) for the degradation of sulfamethoxazole (SMX). The catalytic cubes were loaded with different amounts of nitrogen precursor to investigate the role of nitrogen configuration in the sp2 hybridised carbon network on AOPs. NGC3 cubes with optimum N-loading exhibited outstanding performance for SMX degradation owing to their optimum N/C ratio. Various reaction parameters were studied to optimise the catalytic system. Comprehensive studies on the radical generation were done and illustrated the dominance of the non-radical pathway leading to the proposal of a possible reaction mechanism for SMX. This study not only suggests the role of nitrogen doping on graphene macrostructures but also provides novel insights into macro catalysis to overcome the recovery challenges posed by nano catalysis.

N-doped biochar mediated peroxydisulfate activation for selective degradation of bisphenol A: The key role of potential difference-driven electron transfer mechanism

N-doped biochar has emerged as a promising material for peroxydisulfate (PDS) activation to degrade organic pollutants; however, its reaction mechanism remains elusive. In this study, we synthesized N-doped piggery biogas residue biochar (NBRBC) and investigated an NBRBC-mediated PDS activation system for contaminants degradation. The experimental results show that the NBRBC/PDS system exhibits superior activity for selective degradation of bisphenol A (BPA) via an electron transfer pathway (ETP) but does not work for the degradation of bisphenol S (BPS) and hexafluorobisphenol A (BPAF). Density functional theory (DFT) calculations indicate that the removal efficiencies of contaminants are highly related to the potential difference (EPD) between the highest occupied molecular orbitals (HOMOs) of contaminants and the lowest unoccupied molecular orbital (LUMO) of the NBRBC/PDS system (R2 = 0.9568). Contaminants with low EPD (e.g., BPA) were more easily degraded via ETP, while the oxidation of high EPD contaminants (e.g., BPS, BPAF) was inert to ETP. In addition, N-doping process endowed NBRBC with superior PDS activation activity by lowering the EHOMO−ELUMO gap of the NBRBC/PDS system, thereby accelerating electron transfer. Graphitic carbon, pyridinic N and graphitic N are regarded as the predominant active sites. Our NBRBC/PDS system also possessed resistance to the interference of water matrix and efficient mineralization capacity during BPA degradation. This work further clarified the in-depth mechanism of PDS activation over N-doped biochar catalysts, unraveled the mysterious selective degradation behavior of the NBRBC/PDS system toward BPA, and provides a novel perspective for developing a “fit-for-purpose” strategy for organic wastewater purification.

Conditioning fecal sludge of public toilets with coupled zero-valent iron and persulfate: Efficiency and mechanism

This study investigated the efficiency of fecal sludge conditioning using peroxydisulfate (PDS) activated by zero-valent iron (ZVI). For fecal sludge obtained from public toilets in a densely-populated rural area in China, the ZVI/PDS coupling greatly improved its dewaterability as well as the supernatant quality in terms of organic matter and nutrient contents. The capillary suction time (CST) and supernatant turbidity of fecal sludge can be reduced up to 97% and 73% respectively in 10 min by the combination of 0.15 g/g TS ZVI and 0.2 g/g TS PDS. Protein removal, especially for tightly and loosely bound extracellular-polymeric-substance (EPS), is more linearly correlated to CST reduction than polysaccharide removal. Fecal sludge dewatering was improved by the hybrid functions of radical oxidation and iron coagulation. The ZVI/PDS treatment produced larger and looser flocs, probably because 1) surface ionic and hydrophilic groups of fecal sludge were reduced, 2) surface charge was neutralized, and 3) secondary structures of EPS proteins were altered by the radicals. The excellent fecal sludge dewatering was related to strengthened particle hydrophobicity and reduced sludge viscosity and compressibility. The results highlight that the ZVI/PDS combination is potentially an effective conditioning approach for fecal sludge from public toilets.

Decomplexation of Ni-EDTA by thermally activated persulfate: Efficiency and mechanism

The thermally activated persulfate (TAP) advanced oxidation process is a promising technology for treating complex heavy–metal wastewater because of its environmental friendliness and high efficiency. However, previous studies have not fully explored the potential mechanisms involved in removing complex heavy metals. Herein, we investigated the effects of temperature, initial pH, peroxydisulfate (PDS) dosage, and the initial concentration of Ni-EDTA on the removal of Ni-EDTA using TAP. Results showed that increasing the activation temperature and PDS dosage enhanced the removal rate of Ni-EDTA, whereas decreasing the pH and initial concentration of Ni-EDTA were more conducive to Ni-EDTA removal. In addition, the quenching experiment indicated that OH and SO4− were the main active species, with OH being the most important contributor in the Ni-EDTA removal process. The degradation mechanism of Ni-EDTA was also explored through ultra performance liquid chromatography–mass spectrometry (UPLC–MS) analysis and density functional theory (DFT) calculations. These showed that the TAP-based degradation of Ni-EDTA is a step-by-step decarboxylation process due to increased bond lengths of CN or NCCN bonds of Ni-EDTA, resulting in the destabilization of Ni-EDTA. Overall, this study provides unique insights into the degradation of complex heavy metals in industrial wastewater using TAP.

Activation of persulfate by blue algae biochar supported FeOX particles for tetracycline degradation: Performance and mechanism

Recent research has shown that iron modified biochar has high catalytic performance in peroxydisulfate (PDS) activation; however, the role of iron or complex biochar structure and reaction mechanisms remains unclear. With blue algae as a raw material, recyclable magnetic biochar modified with iron catalyst was produced in this study. Using a combination of electron spin resonance (ESR) and radicals scavenging experiments, it was determined that the TC degradation process included free and non-free radicals. It was accomplished in order to analyse the TC degradation mechanism comprehensively. Superoxide radicals (O2•−) derived from FeOX (zero-valent iron and iron oxide) and PDS played a dominant role by attacking adsorbed TC molecules. The results demonstrated that the modification of FeOX and the structural properties of biochar increased the production of O2•−, thereby accelerating the degradation rate of TC. CC, CO, O-CO, Fe-O functional groups and persistent free radicals (PFRs) promoted the activation of PDS. This non-free radical catalytic process was applicable over a broad pH range and has superior inorganic ion tolerance. This study aids in comprehending the mechanism of the activation and degradation of organic pollutants for PDS by biochar catalysts derived from blue algae. It provides a new method for the future utilization of blue algae resources.

Insights into molecular imprinting polydopamine in-situ activating peroxydisulfate for targeted removal of refractory organic pollutants: Overlooked N site

This study proposed a simple and green method to develop a molecular imprinting polymer for in-situ activating peroxydisulfate (PDS) without metal active sites and then targeted degrading pollutants. The molecularly imprinted polydopamine (MI-PDA) can selectively re-bonded target pollutant (sulfamethoxazole, SMX) by nitrogenous and oxygenated functional groups. On this basis, the N site of nitrogenous groups can efficiently in-situ activate PDS to generate singlet oxygen (1O2). The detailed mechanism is that PDS adsorbed on the electron-deficient N site of MI-PDA would transfer the electron to the N atom in MI-PDA, shorting the O-O bond length and resulting in the cleavage of S-O bond of PDS, which induced more 1O2 generation. Tow functions, selective enrichment and in-situ activation, endowed MI-PDA/PDS system with over 95% removal efficiency of SMX and 9.23-fold enhancement of degradation rate constants. This work provided novel insights into the selective removal of target pollutants in complicated water matrix.