Sono-enhanced degradation of dye pollutants with the use of H2O2 activated by Fe3O4 magnetic nanoparticles as peroxidase mimetic

Sonocatalytic degradation of tetracycline hydrochloride using SnO2 hollow-nanofiber decorated with UiO-66-NH2

In this study, a porous hollow nanofiber SnO2 was decorated with UiO-66-NH2 nanoparticles with straightforward solvothermal method and utilized for sonocatalytic degradation of tetracycline (TC) by ultrasonic irradiation (USI). The prepared materials were characterized using different techniques such as SEM, EDS, FTIR, XRD, BET, XPS, UV-DRS, EIS, and zeta potential. SnO2 PHNF/UiO-66-NH2 nanocomposite offered the highest apparent rate constant of 0.0397 min-1 which was 6.3 and 3.1 times higher than those obtained for SnO2 PHNF and UiO-66-NH2, respectively. The integration of nanocomposite components revealed the synergy factor of 1.58, which can be due to the created heterojunctions resulted in efficiently charge carriers separation and retaining high redox ability. The effects of different affecting parameters such as TC initial concentration, pH of the solution, catalyst dosage, trapping agents, and coexisting anions on the catalytic performance were examined. The inhibitory effects of anions were confirmed to be decreased in the sequence of Cl- > NO3- > SO42-, while the sonocatalytic efficiency of the nanocomposite improved considerably in the presence of humic acid and bicarbonate. Also, the excellent performance of the catalyst was preserved during six successive cycles, suggesting the high stability of the prepared catalyst. In addition, based on the scavenger analysis, the created O2·-, OH·, and holes were contributed to the TC degradation. In conclusion, the creation heterojunction is an impressive methodology for improving the sonocatalytic activity of a catalyst, and SnO2 PHNF/UiO-66-NH2 nanocomposite was introduced as a satisfactory catalyst in sonocatalytic degradation of organic contaminants.

Preparation and characterisation of alkali-activated blast furnace slag and Na-jarosite catalysts for catalytic wet peroxide oxidation of bisphenol A

In this study, cost-effective alkali-activated materials made from industrial side streams (blast furnace slag and Na-jarosite) were developed for catalytic applications. The catalytic activity of the prepared materials was examined in catalytic wet peroxide oxidation reactions of a bisphenol A in an aqueous solution. All materials prepared revealed porous structure and characterisation expressed the incorporation of iron to the material via ion exchange in the preparation step. Furthermore, the materials prepared exhibited high specific surface areas (over 200 m2/g) and were mainly mesoporous. Moderate bisphenol A removal percentages (35%-37%) were achieved with the prepared materials during 3 h of oxidation at pH 7-8 and 50°C. Moreover, the activity of catalysts remained after four consecutive cycles (between the cycles the catalysts were regenerated) and the specific surface areas decreased only slightly and no changes in the phase structures were observed. Thus, the prepared blast furnace slag and Na-jarosite-based catalysts exhibited high mechanical stability and showed good potential in the removal of bisphenol A from wastewater through catalytic wet peroxide oxidation.

Synthesis of magnetic layered double hydroxide (Fe3O4@CuCr-LDH) decorated with ZIF-8 for efficient sonocatalytic degradation of tetracycline

A series of Fe3O4@CuCr-LDH hybrids decorated with different amount of ZIF-8 (FLZ, 10-40 wt%) was prepared using simple methods and characterized with different techniques. The activity of the synthesized nanocomposites was investigated in the sonocatalytic degradation of tetracycline (TC) antibiotic from wastewater. When the content of ZIF-8 in the nanocomposite structure was 20 wt%, the FLZ-20 sonocatalyst exhibited the high performance in the sonocatalytic removal of TC. At optimum conditions (0.7 g/L catalyst dosage, pH of 7, 50 mg/L initial concentration of antibiotic, and 15 min sonication time) of the sonocatalytic removal of TC approached to 91.4% under ultrasonic irradiation (USI) using FLZ-20. This efficiency was much higher than those of obtained results by Fe3O4@CuCr-LDH and pristine ZIF-8. The formed ●OH and ●O2- exhibited the major roles in the sonocatalytic TC degradation process. The excellent performance of FLZ-20 can be attributed to the heterojunctions created between composite components, which could improve the electron transfer ability and effectively separate e-/h+ pairs. In addition, FLZ-20 showed the superior reusability and stability during three successive recycling. Moreover, the facile magnetically separation of the sonocatalyst from the aqueous solution was another outstanding feature, which prevents the formation of secondary pollutants. It can be concluded that the fabrication of heterojunctions is an efficient procedure to promote the sonocatalytic acting of the catalyst.

An optimized sono-heterogeneous Fenton degradation of olive-oil mill wastewater organic matter by new magnetic glutarlaldehyde-crosslinked developed cellulose

The present study highlights the olive mill wastewater (OMW) treatment characteristics through a sono-heterogeneous Fenton process using new designed [GTA-(PDA-g-DAC) @Fe₃O₄] and characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), magnetic properties measurements, and point of zero charge (pH pzc) analysis. A preliminary removal study showed significant degradation efficiency (75%) occurred combining the magnetic synthesized catalyst [GTA-(PDA-g-DAC)@Fe3O4] ([catalyst] = 2 g/L) with US /H₂O₂ and maintaining 500WL^-1 ultrasonic power (US). The values obtained by US only were (13%), H₂O₂/US (18%), US/Fe₃O₄ (28%), and US /Fe₃O₄/H₂O₂(35%). The catalytic findings have shown that [GTA-(PDA-g-DAC)@Fe₃O₄] exhibited good properties for OMW compound's degradation. The sonocatalytic process coupling and extra oxidant addition resulted in the degradation substantial levels. For instance, the concomitant effect of degradation optimized parameters; H₂O₂ 10 mM, [GTA-(PDA-g-DAC) @Fe₃O₄] nanocomposites 2.5 g/L, at pH 3, and T 35 °C for 70 min resulted in an almost complete mineralization of aqueous OMW solution followed by a significant decolorization. Oxidation results exhibited efficient degradation rates in total phenolic compounds (TPC), total amino compounds (TAC), and chemical oxygen demand (COD) oxidation rate were 89.88, 92.75, and 95.66 respectively following the optimized sono-heterogeneous catalytic Fenton process. The prepared magnetic catalyst exhibited a good stability during repeated cycles. The gathered findings gave the evidence that sono-heterogeneous catalytic Fenton process is a promising treatment technology for OMW effluents.

Catalytic Wet Peroxide Oxidation of Anionic Pollutants over Fluorinated Fe3O4 Microspheres at Circumneutral pH Values

Fluorinated Fe3O4 microspheres with 7.1 ± 1.4 wt% of fluoride (F-Fe3O4-1) were prepared via glycothermal synthesis. Fluorination significantly enhanced the activity of F-Fe3O4-1 in catalytic wet peroxide oxidation of anionic dyes (including orange G (OG) and congo red) at pH ~7. However, the promotional effect of fluorination became less obvious for amphoteric rhodamine B and was not observed for cationic methylene blue. After reacting with H2O2 (40 mM) for 2 h at pH 6.5 and 40 °C, the decolorization rates of OG (0.1 mM) and the pseudo-first-order rate constant were 96.8% and 0.0284 min−1 over F-Fe3O4-1 versus 17.6% and 0.0011 min−1 over unmodified Fe3O4. The effects of reaction parameters (initial H2O2 concentration and pH value and reaction temperature) on OG decolorization with H2O2 over F-Fe3O4-1 were investigated. The reusability of F-Fe3O4-1 was demonstrated by OG decolorization in eight consecutive runs. Fluorination increased the isoelectric point of F-Fe3O4-1 to 8.7 and facilitated the adsorption and degradation of anionic dyes on the surface of F-Fe3O4-1 at pH ~7. Scavenging tests and EPR spectra supported that hydroxyl radicals were the main reactive species for the OG decolorization over F-Fe3O4-1.

Sonophotocatalytic degradation of malachite green in aqueous solution using six competitive metal oxides as a benchmark

A comparison study examines six different metal oxides (CuO, ZnO, Fe3O4, Co3O4, NiO, and α-MnO2) for the degradation of malachite green dye using four distinct processes. These processes are as follows: sonocatalysis (US/metal oxide), sonocatalysis under ultra-violet irradiation (US/metal oxide/UV), sonocatalysis in the presence of hydrogen peroxide (US/metal oxide/H2O2), and a combination of all these processes (US/metal oxide/UV/H2O2). The effective operating parameters, such as the dosage of metal oxide nanoparticles (MONPs), the type of the process, and the metal oxides’ efficiency order, were studied. At the same reaction conditions, the sonophotocatalytic is the best process for all six MOsNPs, CuO was the better metal oxide than other MOsNPs, and at the sonocatalysis process, ZnO was the best metal oxide in other processes. It was found that the metal oxide order for sonocatalytic process is CuO > α-MnO2 ≥ ZnO > NiO ≥ Fe3O4 ≥ Co3O4 within 15–45 min. The order of (US/metal oxide/UV) process is ZnO ≥ NiO ≥ α-MnO2 > Fe3O4 ≥ CuO ≥ Co3O4 within 5–40 min. The order of (US/ MOsNPs/ H2O2) process is ZnO ≥ CuO ≥ α-MnO2 ≥ NiO > Co3O4 > Fe3O4 within 5–20 min. The maximum removal efficiency order of the sonophotocatalytic process is ZnO ≥ CuO > α-MnO2 > NiO > Fe3O4 ≥ Co3O4 within 2–8 min. The four processes degradation efficiency was in the order US/MOsNPs ˂ US/MOsNPs/UV ˂ US/MOsNPs/H2O2 ˂ (UV/Ultrasonic/MOsNPs/H2O2). Complete degradation of MG was obtained at 0.05 g/L MONPs and 1 mM of H2O2 using 296 W/L ultrasonic power and 15 W ultra-violet lamp (UV-C) within a reaction time of 8 min according to the MOsNPs type at the same sonophotocatalytic/H2O2 reaction conditions. The US/metal oxide/UV/H2O2 process is inexpensive, highly reusable, and efficient for degrading dyes in colored wastewater.

Graphical abstract

Pyrolysis of hydrothermally dewatering sewage sludge: Highly efficient peroxydisulfate activation of derived biochar to degrade diclofenac

The resource utilization of sewage sludge can solve its disposal issue essentially. Meanwhile the removal of diclofenac (DCF) in wastewater is an emerging environmental problem. In this study, a novel strategy of sludge utilizing via hydrothermal - peroxydisulfate (PDS) dewatering coupled pyrolysis process was proposed. The obtained sludge-derived biochar (HSC) could be as candidate to activate PDS to degrade DCF. Results indicated that exceed 90% of DCF was eliminated within 30 min in HSC-PDS/DCF ternary system under the optimized condition (0.6 mmol/L PDS and 0.5 mg/L HSC, without temperature and pH pre-adjusting). The inner mechanism of HSC-PDS/DCF system was revealed as follows: (1) Major: CO in quinones and ketone structure in HSC accelerated the degradation of DCF via non-radical pathway (electron transfer and ¹O₂). (2) Minor: Graphitic N structure accelerated the electron transfer and O₂^•- originated from defective sites involved into the redox. Several by-products were identified and two tentative degradation pathways of DCF (eg. dechlorination and C-N cleavage) were proposed.

Recent progress in Fenton/Fenton-like reactions for the removal of antibiotics in aqueous environments

The frequent use of antibiotics allows them to enter aqueous environments via wastewater, and many types of antibiotics accumulate in the environment due to difficult degradation, causing a threat to environmental health. It is crucial to adopt effective technical means to remove antibiotics in aqueous environments. The Fenton reaction, as an effective organic pollution treatment technology, is particularly suitable for the treatment of antibiotics, and at present, it is one of the most promising advanced oxidation technologies. Specifically, rapid Fenton oxidation, which features high removal efficiency, thorough reactions, negligible secondary pollution, etc., has led to many studies on using the Fenton reaction to degrade antibiotics. This paper summarizes recent progress on the removal of antibiotics in aqueous environments by Fenton and Fenton-like reactions. First, the applications of various Fenton and Fenton-like oxidation technologies to the removal of antibiotics are summarized; then, the advantages and disadvantages of these technologies are further summarized. Compared with Fenton oxidation, Fenton-like oxidations exhibit milder reaction conditions, wider application ranges, great reduction in economic costs, and great improved cycle times, in addition to simple and easy recycling of the catalyst. Finally, based on the above analysis, we discuss the potential for the removal of antibiotics under different application scenarios. This review will enable the selection of a suitable Fenton system to treat antibiotics according to practical conditions and will also aid the development of more advanced Fenton technologies for removing antibiotics and other organic pollutants.

Degradation of Reactive Brilliant Red X-3B by Photo-Fenton-like Process: Effects of Water Chemistry Factors and Degradation Mechanism

Azo dye wastewater belongs to the highly concentrated organic wastewater, which is difficult to be treated by traditional biological processes. The oxidation efficiency of a single physicochemical method is not considerable. Recent research indicated that the advanced oxidation processes (AOPs) based on the highly reactive hydroxyl radical (∙OH) became one of the preferred methods in dealing with such dye wastewater. In this paper, the typical azo dye, reactive brilliant red X-3B, was employed as the target pollutant, and the transition metal Mn and hydrogen peroxide as the catalysts. A photo-Fenton-like process, UV/Mn2+-H2O2 system, was established, which enables a combination of various technologies to improve azo dye degradation efficiency while reducing disposal costs. The results indicated that the UV/Mn2+-H2O2 system had the synergism of Mn2+/H2O2 and UV/H2O2, which was 2.6 times greater than the sum of the two individual effects. And the degradation of X-3B reached the optimum under the conditions of 0.59 mmol/L of the Mn2+, 10 mmol/L of the H2O2, pH = 6 and a high level of DO. The ∙OH, generated from chem-catalytic and photocatalytic decomposition of H2O2, played the predominant role in the decolorization of X-3B and mineralization of its intermediates. The ∙OH tended to attack and break the chromophore group, resulting in the rapid decolorization of X-3B. The azo bond in X-3B was easy to be decomposed in the form of N2, while the triazinyl group was recalcitrant for ring opening. The degradation process of the UV/Mn2+-H2O2 system preferred to be conducted at an acidic condition and appropriate concentrations of Mn2+ and H2O2. The alkaline condition would decrease the utilization of H2O2, and excessive H2O2 would also quench the ∙OH.

Degradation of Acid Red 1 Catalyzed by Peroxidase Activity of Iron Oxide Nanoparticles and Detected by SERS

Magnetic iron oxide nanoparticles (MIONPs) were synthesized using tannic acid and characterized by Raman, FTIR, UV, and DRX spectroscopy. In a heterogeneous Fenton-like reaction, the catalytic peroxidase-like activity of MIONPs in the degradation of Acid Red 1 (AR 1) dye was investigated. TEM/STEM was used to determine the quasi-spherical morphology and particle size (3.2 nm) of the synthesized MIONPs. The XRD powder patterns were indexed according to the reverse spinel structure of magnetite, and SEM-EDS analysis confirmed their chemical composition. At pH = 3.5, the decomposition of H₂O₂ in hydroxyl radicals by MIONPs results in high AR 1 degradation (99%). This behavior was attributed to the size and surface properties of the MIONPs. Finally, the Surface Enhanced Raman Spectroscopy (SERS) technique detected intermediary compounds in the degradation process.

Fe/N-doped carbon magnetic nanocubes toward highly efficient selective decolorization of organic dyes under ultrasonic irradiation

Fe/N-doped carbon magnetic nanocubes (Fe/N-C MNCs) were feasibly fabricated through in situ thermal transformations of Prussian blue nanocubes (PB NCs) in an inert atmosphere, and the resultant composite employed as the heterogeneous noble-metal-free catalyst possessed satisfactory catalytic performance in hydrogen peroxide activation. By examining the properties of Fe/N-C MNCs, we demonstrate for the first time that the catalyst could act in synergy with ultrasonic irradiation and accelerate the selectivity of the degradation reaction of dyes. The degradation efficiency of the organic positively charged dye (methylene blue) is significantly increased after ultrasonic irradiation addition, probably owing to charge matching between a positively charged dye and the Fe/N-C MNCs. Interestingly, organic pollution degradation mainly follows a non-radical pathway. Furthermore, singlet oxygen (¹O₂) is predominantly produced by Fe/N-C MNCs on H₂O₂ activation, and it is the contributor to catalytic degradation instead of hydroxyl and/or superoxide anion radicals. Moreover, the Fe/N-C MNCs exhibit excellent stability and reusability. These findings offer interesting insights into the potential application of functional noble-metal-free materials in catalysis and wastewater remediation under ultrasonic radiation.

Copper-promoted heterogeneous Fenton-like oxidation of Rhodamine B over Fe3O4 magnetic nanocatalysts at mild conditions

Rhodamine B (RhB) is used in various industries and its effluent must be effectively treated because of its harmful and carcinogenic nature. In this work, ionothermally synthesized Cu-doped Fe₃O₄ magnetic nanoparticles (Cu-Fe₃O₄ MNPs) were found to be a highly efficient heterogeneous Fenton-like catalyst for complete decolorization of the RhB solution with H₂O₂ at pH ~ 7 and 25 °C. The effects of the catalyst loading, initial concentrations of RhB and H₂O₂, co-existing natural organic matter and inorganic salts, reaction temperature, and radical scavengers on the catalytic performance of Cu-Fe₃O₄ were investigated. Monte-Carlo simulations revealed that copper dopants facilitated the activation of H₂O₂ via adopting a terminal end-on adsorption mode and increased collision frequency by bringing the RhB molecules closer to H₂O₂ and the magnetite surface. These theoretical calculations provide new insight into the promotional effect of copper dopants in magnetite at molecular level.

Novel magnetically retrievable In2O3/MoS2/Fe3O4 nanocomposite materials for enhanced photocatalytic performance

The current work involves synthesis of hybrid nanomaterial of In2O3/MoS2/Fe3O4 and their applications as photocatalysts for disintegration of esomeprazole under visible light illumination. The data emerged from various analyses testified to the successful construction of the desired nano-scaled hybrid photocatalyst. Tauc plot gave the band gap of In2O3/MoS2/Fe3O4 to be ~ 2.15 eV. Synergistic effects of the integrant components enabled efficacious photocatalytic performances of the nanocomposite. The nanohybrid photocatalyst In2O3/MoS2/Fe3O4 showed photodecomposition up to ~ 92.92% within 50 min. The current work realizes its objective of constructing metal oxide based hybrid nano-photocatalyst supported on MoS2 sheets for activity in the visible spectrum, which displayed remarkable capacity of disintegrating emerging persistent organic contaminants and are magnetically recoverable.

A review on MXene-based nanomaterials as adsorbents in aqueous solution

Environmental pollution has intensified and accelerated due to a steady increase in the number of industries, and finding methods to remove hazardous contaminants, which can be typically divided into inorganic and organic compounds, have become inevitable. One of the widely used water treatment technologies is adsorption and various kinds of adsorbents for the removal of inorganic and organic contaminants from water have been discovered. Recently, MXene, as an emerging nanomaterial, has gained rapid attention owing to its unique characteristics and various applicability. Particularly, in the area of adsorptive application, MXene and MXene-based adsorbents have shown great potential in a large number of studies. In this regard, a comprehensive understanding of the adsorptive behavior of MXene-based nanomaterials is necessary in order to explain how they remove inorganic and organic contaminants in water. Adsorption by MXene-based adsorbents tends to be highly influenced by not only the physicochemical properties of these adsorbents but also water quality, such as pH value, temperature, background ion, and natural organic matter. Therefore, in this review paper, the effect of various water quality on the adsorption of inorganic and organic contaminants by various types of MXene and MXene-based adsorbents is explored. Furthermore, this review also covers general trends in the synthesis of MXene and regeneration of MXene-based adsorbents in order to assess their stability.

Synthesis of cost-effective magnetic nano-biocomposites mimicking peroxidase activity for remediation of dyes

The present study describes preparation of cellulose incorporated magnetic nano-biocomposites (CNPs) by using cellulose as base material. The prepared CNPs were characterised by SEM, EDAX, TEM, XRD, and FT-IR and found to exhibit an intrinsic peroxidase-like activity with a K_m and V_max of 550 μM and 3.8 μM/ml/min, respectively. The CNPs exhibited higher pH and thermal stability compared to commercial peroxidase. These nanocomposites were able to completely remove (i) a persistent azo dye, methyl orange at a concentration of 50 ppm, within 60 min under acidic conditions (pH 3.0) and also (ii) decolourize commercial textile dye mixture under acidic conditions within 30 min. CNP-mediated degradation of dyes into simple products was further confirmed by UV-Vis and AT-IR spectroscopy The added advantage of CNPs separation after decolourization by simple magnet due to their magnetic properties and consequent reusability makes them fairy attractive system for dye remediation from environmental samples or textile industries effluents.

MIL-101(Cr)–cobalt ferrite magnetic nanocomposite: synthesis, characterization and applications for the sonocatalytic degradation of organic dye pollutants

In this study, for the first time, a novel magnetically recyclable MIL-101(Cr)/CoFe₂O₄ nanocomposite was prepared via a facile solvothermal method. The morphology, structural, magnetic and optical properties of the nanocomposite were characterized via field emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), UV-visible spectroscopy (UV-visible) and BET surface area analysis. Furthermore, the sonocatalytic activity of the MIL-101(Cr)-based magnetic nanocomposite was explored for the degradation of organic dye pollutants such as Rhodamine B (RhB) and methyl orange (MO) under ultrasound irradiation in the presence of H₂O₂. Under optimized conditions, the degradation efficiency reached 96% for RhB and 88% for MO. The sonocatalytic activity of MIL-101(Cr)/CoFe₂O₄ was almost 12 and 4 times higher than that of the raw MIL-101(Cr) and pure CoFe₂O₄, respectively. The improved sonocatalytic performance of the as-prepared binary nanocomposite can be attributed to the relatively high specific surface area of MIL-101(Cr) and magnetic property of CoFe₂O₄, as well as the fast generation and separation of charge carriers (electrons and holes) in MIL-101(Cr) and CoFe₂O₄. In addition, the trapping tests demonstrated that ·OH radicals are the main active species in the dye degradation process. Moreover, the most influencing factors on the sonocatalytic activity such as the H₂O₂ amount, initial dye concentration and catalyst dosage were investigated. Finally, the nanocomposite was magnetically separated and reused without any observable change in its structure and performance even after four consecutive runs.

A magnetically separable MIL-101(Cr)/CoFe₂O₄ binary nanocomposite was prepared via a hydrothermal route and applied as a sonocatalyst for the efficient degradation of organic dyes.

Synthesis and characterization of a novel manganese ferrite–metal organic framework MIL-101(Cr) nanocomposite as an efficient and magnetically recyclable sonocatalyst

A magnetic MnFe₂O₄/MIL-101(Cr) nanocomposite was synthesized and applied as a novel sonocatalyst for enhanced degradation of organic dye pollutants.

A novel CoFe2O4@Cr-MIL-101/Y zeolite ternary nanocomposite as a magnetically separable sonocatalyst for efficient sonodegradation of organic dye contaminants from water

In this research, a novel magnetic sonocatalyst nanocomposite, CoFe₂O₄@Cr-MIL-101/Y zeolite, has been successfully fabricated employing a simple hydrothermal method. The as-prepared catalyst was thoroughly identified using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), EDS elemental dot-mapping, transmission electron microscopy (TEM), atomic force microscopy (AFM), vibrating sample magnetometer (VSM), and nitrogen Brunauer–Emmett–Teller (N₂-BET) analyses. The procured CoFe₂O₄@Cr-MIL-101/Y nanocomposite was then assessed for the decomposition of three types of organic dyes namely methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) from water solution using ultrasound irradiation and subsequently monitored via UV-Vis absorption technique. The sonodecomposition reactions of organic dyes were accomplished in the presence of the H₂O₂ solution as a green oxidizing agent. Furthermore, the influence of various experimental independent factors such as irradiation time, process type, initial dye concentration, catalyst dosage, H₂O₂ concentration, scavenger type, and catalyst regeneration on the decomposition of MB, RhB and MO were surveyed. Additionally, a first order kinetic model was applied to investigate the sonodecomposition reactions of dye contaminants. The rate constant (k) and half-life (t_1/2) data were gained as 0.0675 min⁻¹ and 10.2666 min, respectively, for the decomposition of MB in the US/H₂O₂/CoFe₂O₄@Cr-MIL-101/Y system. Besides, evaluating the attained results, the distinctive performance of ˙OH as the radical scavenger originating from H₂O₂ throughout the sonodecomposition process is vividly approved.

A novel magnetically separable CoFe₂O₄@Cr-MIL-101/Y zeolite ternary nanocomposite was prepared and applied as a sonocatalyst for efficient degradation of organic contaminants.

Efficient treatment of saline recalcitrant petrochemical wastewater using heterogeneous UV-assisted sono-Fenton process

An effective hybrid system was applied as a first report for successful treatment of recalcitrant petrochemical wastewater (PCW). In this regards, magnetic powdered activated carbon (MPAC), as a heterogeneous catalyst, was coupled with ultrasound (US) and UV irradiations for activation of H₂O₂ (marked as MPAC/US/UV/H₂O₂). Chemical oxygen demand (COD) removal ratio was evaluated with various influencing operating factors including solution pH, MPAC and H₂O₂ concentrations, US power and quenchers. A possible mechanism for catalytic degradation and generation of reactive species was proposed. To evaluate the biodegradability of both raw and treated PCWs, the activated sludge inhibition experiments were performed based on Zahn-Wellens test. MPAC indicated high catalytic activity, reusability and stability in the studied system. Over 87% of COD was removed under optimum conditions within 80 min treatment and the residual COD concentration reached 82.9 mg/L, which was permissible to discharge surface water sources based on the environmental standards. Leaching of transition metals from catalyst textural was negligible. Compared to homogeneous system (Fe²⁺/US/UV/H₂O₂), heterogeneous system (MPAC/US/UV/H₂O₂) represented a better performance in COD removal. Identification of intermediates by GC-MS showed that a wide range of recalcitrant compounds was removed and/or degraded into small molecular compounds effectively after treatment. A biodegradability ratio of 64% and the residual COD of 28 mg/L for treated PCW, indicating that the biodegradability was improved and refractory organic matters removed effectively. As conclusion, MPAC/US/UV/H₂O₂ hybrid system can be introduced as a successful advanced treatment process for efficient remediation of refractory PCWs.

Catalysis of hydrogen peroxide with Cu layered double hydrotalcite for the degradation of ethylbenzene

A high catalytic system using Cu layered double hydrotalcite (Cu(II)-Mg(II)-Fe(III)LDHs) and hydrogen peroxide (H₂O₂) was developed for the degradation of ethylbenzene. It was identified that the degradation efficiency of ethylbenzene (0.08 mmol L^-1) and TOC removal were 96.1% and 39.7% respectively in the presence of 0.1 g L^-1 Cu(II)-Mg(II)-Fe(III)LDHs with (Cu²⁺ + Mg²⁺)/Fe³⁺ molar ratio of 5.0 and 0.16 mmol L^-1 H₂O₂ in 6.0 h. Based on ESR and XPS data, hydroxyl radicals (•OH) were the predominant free radical specials generated from the catalytic decomposition of H₂O₂ for the degradation of ethylbenzene. The redox of Cu(II)/Cu(III) on the layered Cu(II)-Mg(II)-Fe(III)LDHs surface active sites accounted for the formation of •OH radicals and the cycle of Cu(II) in the Cu(II)-Mg(II)-Fe(III)LDHs/H₂O₂ system were proposed.

Immobilization of Horseradish Peroxidase on Multi-Armed Magnetic Graphene Oxide Composite: Improvement of Loading Amount and Catalytic Activity

In this study, a novel type of multi-armed polymer (poyltehylene glycol, PEG) magnetic graphene oxide (GO) composite (GO@Fe₃O₄@6arm-PEG-NH₂) has been synthesized as a support for immobilization of horseradish peroxidase (HRP) for the first time. The loading amount of HRP was relatively high (186.34 mg/g) due to the surface of carrier material containing a large amount of amino groups from 6arm-PEG-NH₂, but degradation rate of phenols was also much higher (95.4%), which is attributed to the synergistic effect between the free HRP (45.4%) and the support material of GO@Fe₃O₄@6arm-PEG-NH₂ (13.6%). Compared with the free enzyme, thermal, storage and operational stability of the immobilized HRP improved. The immobilized HRP still retained over 68.1% activity after being reused 8 times. These results suggest that the multi-armed magnetic composite has good application prospect for enzyme immobilization.

Heterogeneous Fenton-like activity of novel metallosalophen magnetic nanocomposites: significant anchoring group effect

Novel magnetically recoverable Fe(iii)- and Mn(iii)salophen complexes were designed for the effective degradation of hazardous organic dyes using a heterogeneous advanced oxidation process.

Ultrasonic degradation of aqueous phenolsulfonphthalein (PSP) in the presence of nano-Fe/H2O2

In this study, nano iron (nano-Fe) was successfully synthesized by sodium borohydride reduction of ferric chloride solution to enhance the ultrasonic degradation of phenolsulfonphthalein (PSP). The nano-Fe was characterized by scanning electron microscopy - energy dispersive spectroscopy (SEM-EDX), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), attenuated total reflection - Fourier transform infrared spectroscopy (ATR-FTIR), and Brunauer, Emmett and Teller (BET) surface area determination. Experimental results demonstrated that a combined ultrasonic/nano-Fe/H₂O₂ system was more effective for PSP removal in combination than they were individually and there was a significant difference between the combined and single processes. The ultrasonic/nano-Fe/H₂O₂ degradation follows the Langmuir-Hinshelwood (L-H) kinetic model. The addition of nano-Fe and H₂O₂ to the ultrasonic reactor greatly accelerated the degradation of PSP (25 mg/L) from 12.5% up to 96.5%. These findings indicated that ultrasonic degradation in the presence of nano-Fe and H₂O₂ is a promising and efficient technique for the elimination of emerging micropollutants from aqueous solution.

Alkaline peroxidase activity of cupric oxide nanoparticles and its modulation by ammonia

We herein report the intrinsic alkaline peroxidase-like activity exhibited by CuO nanoparticles when 3-(4-hydroxyphenyl)propionic acid was employed as a substrate. Based on this observation, a fluorometric assay method with a low detection limit of 0.81 μM was established for H₂O₂ determination under alkaline conditions. Notably, ammonia was found to inhibit the alkaline peroxidase-like activity of the CuO nanoparticles. Thus, a sensing platform for the determination of urea and urease was successfully constructed, with the limits of detection for urea and urease being 27 μM and 2.6 U L^-1, respectively. This platform was then applied for the detection of urea in human urine and urease in soil, which yielded satisfactory results. These results suggest that it is possible to extend the catalytic potential of peroxidase and its mimetics from acidic and neutral conditions to include activity in alkaline media as well. Furthermore, this strategy is a novel method for the analysis of urea and urease. The assay developed in this work is facile, inexpensive, convenient, and highly selective and sensitive. Therefore, it is expected that this system can serve as a template for the development of similar enzyme nano-mimics.

Synthesis and sonocatalytic performance of a ternary magnetic MIL-101(Cr)/RGO/ZnFe2O4 nanocomposite for degradation of dye pollutants

In this study, new ternary magnetic MIL-101(Cr)/RGO/ZnFe₂O₄ catalyst (with 30% wt of ZnFe₂O₄) was synthesized via a hydrothermal route for sonodegradation of organic dyes. The structural, optical and magnetic properties of the nanocomposite were detected by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy (UV-visible), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, vibrating sample magnetometer (VSM), atomic force microscopy (AFM), Raman spectroscopy and BET surface area analysis. To evaluate the sonocatalytic activity of the as-prepared MIL-101(Cr)/RGO/ZnFe₂O₄ nanocomposite, the H₂O₂-assisted degradation of organic dyes such as congo red (CR), methylene blue (MB), Rhodamine B (RhB) and methyl orange (MO) in aqueous solution was studied under ultrasound irradiation. The obtained results indicated that the ternary MIL-101(Cr)/RGO/ZnFe₂O₄ nanocomposite had better performance for sonodegradation of these dyes than MIL-101(Cr)/RGO, pure MIL-101(Cr) or ZnFe₂O₄. The enhanced sonocatalytic performance of the as-prepared ternary nanocomposite could be attributed to the fast generation and separation of charge carriers (electrons and holes) in ZnFe₂O₄and MIL-101(Cr) and their transfer to the surface of graphene sheets. Moreover, the relatively high specific surface area of the MIL-101(Cr)/rGO and magnetic property of ZnFe₂O₄ improve the degradation efficiency of the dyes. The recovery of the ternary magnetic sonocatalyst from treated water could be easily achieved using an external magnetic field. The main influence factors on the sonocatalytic activity such as catalyst dosage and dye initial concentration were also investigated. The trapping experiments indicated that OH radicals are the prominent active species in dye degradation. In addition, the reusability test, was also carried out to ensure the stability of the employed sonocatalyst.

Enhanced removal of basic violet 10 by heterogeneous sono-Fenton process using magnetite nanoparticles

The removal of basic violet 10 (BV10), which is known as a cationic dye, from aqueous solution was studied by employing a heterogeneous sono-Fenton process over the nano-sized magnetite (Fe₃O₄) which had been prepared by the milling of magnetite mineral using a high-energy planetary ball milling process. The magnetite samples were characterized using the X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), and inductively couple plasma mass spectrometer (ICP-MS). It was found that the catalytic activity of the ball-milled magnetite sample was enhanced along with the improvement in its physicochemical properties; also, the ball-milled magnetite of 6 h displayed the highest catalytic activity in BV10 removal by the heterogeneous sono-Fenton process as compared with that for 4 h (66.12% after 120 min) and 2 h (48% after 120 min).The effect of operational parameters, namely, pH solution, catalyst dosage, the initial H₂O₂ concentration, ultrasonic power and the initial BV10 concentration, on the removal efficiency (RE%) of BV10 was investigated. The optimum conditions for the BV10 RE% were: the pH value of 3, the catalyst dosage of 1.5 g L^-1, the initial H₂O₂ concentration of 36 mM, the ultrasonic power of 450 W L^-1, and the initial BV10 concentration of 30 mg L^-1. The RE% of BV10 was 75.94% at these conditions after the reaction time of 120 min. The trapping experiments revealed that OH radicals were the dominant oxidative species, but O₂^-/HO₂ radicals also had a partial role in the removal of BV10.The reusability of the magnetite nanoparticles revealed about 28% decrease in the removal efficiency within five consecutive runs. The results obtained through GC-MS analysis also confirmed the efficient removal of BV10 molecules in the aqueous solution during the process.

Ultrasound-enhanced nanosized zero-valent copper activation of hydrogen peroxide for the degradation of norfloxacin

Commercial nanosized zero-valent copper (nZVC) was used as hydrogen peroxide (H₂O₂) activator in conjunction with ultrasonic irradiation (US) for the oxidative degradation of norfloxacin (NOR) in this study. Compared with silent degradation system, a significantly enhanced NOR removal was obtained in sono-advanced Fenton process, which involved a synergistic effect between sonolysis and Fenton-like reaction. Almost complete removal of NOR was achieved at 30min when the operating conditions were 0.25g/L nZVC and 10mM H₂O₂ with ultrasound power of 240W at 20kHz. The released Cu⁺ during the nZVC dissolution was the predominant copper species to activate H₂O₂ and yield hydroxyl radicals (OH) in US/nZVC/H₂O₂ system. According to the radical quenching experiments and electron paramagnetic resonance technique, hydroxyl radicals in solution (OH_free) were verified as the primary reactive species, and superoxide anion radicals (O₂^-) were regarded as the mediator for the copper cycling by reduction of Cu²⁺ to Cu⁺. NOR removal efficiencies were improved in various degrees when increased nZVC dosage, ultrasound power, hydrogen-ion amount and H₂O₂ concentration. Moreover, the inhibitory effect of different inorganic salts on NOR degradation followed the sequence of Na₂SO₄>NaNO₃≈no salt>NaCl>NaHCO₃. Finally, eleven intermediates were identified and five oxidation pathways were proposed, the cleavage of piperazine ring and transformation of quinolone group seemed to be the major pathway.

Influence of VO₂ Nanoparticle Morphology on the Colorimetric Assay of H₂O₂ and Glucose

Nanozyme-based colorimetric sensors have received considerable attention due to their unique properties. The size, shape, and surface chemistry of these nanozymes could dramatically influence their sensing behaviors. Herein, a comparative study of VO₂ nanoparticles with different morphologies (nanofibers, nanosheets, and nanorods) was conducted and applied to the sensitive colorimetric detection of H₂O₂ and glucose. The peroxidase-like activities and mechanisms of VO₂ nanoparticles were analyzed. Among the VO₂ nanoparticles, VO₂ nanofibers exhibited the best peroxidase-like activity. Finally, a comparative quantitative detections of H₂O₂ and glucose were done on fiber, sheet, and rod nanoparticles. Under the optimal reaction conditions, the lower limit of detection (LOD) of the VO₂ nanofibers, nanosheets, and nanorods for H₂O₂ are found to be 0.018, 0.266, and 0.41 mM, respectively. The VO₂ nanofibers, nanosheets, and nanorods show the linear response for H₂O₂ from 0.025-10, 0.488-62.5, and 0.488-15.625 mM, respectively. The lower limit of detection (LOD) of the VO₂ nanofibers, nanosheets, and nanorods for glucose are found to be 0.009, 0.348, and 0.437 mM, respectively. The VO₂ nanofibers, nanosheets, and nanorods show the linear response for glucose from 0.01-10, 0.625-15, and 0.625-10 mM, respectively. The proposed work will contribute to the nanozyme-based colorimetric assay.

Iron oxide magnetic nanoparticles combined with actein suppress non-small-cell lung cancer growth in a p53-dependent manner

Actein (AT) is a triterpene glycoside isolated from the rhizomes of Cimicifuga foetida that has been investigated for its antitumor effects. AT treatment leads to apoptosis in various cell types, including breast cancer cells, by regulating different signaling pathways. Iron oxide (Fe₃O₄) magnetic nanoparticles (MNPs) are nanomaterials with biocompatible activity and low toxicity. In the present study, the possible benefits of AT in combination with MNPs on non-small-cell lung cancer (NSCLC) were explored in in vitro and in vivo studies. AT-MNP treatment contributed to apoptosis in NSCLC cells, as evidenced by activation of the caspase 3-signaling pathway, which was accompanied by downregulation of the antiapoptotic proteins Bcl2 and BclXL, and upregulation of the proapoptotic signals Bax and Bad. The death receptors of TRAIL were also elevated following AT-MNP treatment in a p53-dependent manner. Furthermore, a mouse xenograft model in vivo revealed that AT-MNP treatment exhibited no toxicity and suppressed NSCLC growth compared to either AT or MNP monotherapies. In conclusion, this study suggests a novel therapy to induce apoptosis in suppressing NSCLC growth in a p53-dependent manner by combining AT with Fe₃O₄ MNPs.

Synergistic Catalysis by "Polymeric Microzymes and Inorganic Nanozymes": The 1+1>2 Effect for Intramolecular Cyclization of Peptides

In this work, we developed an efficient "molecularly imprinted polymer microzymes and inorganic magnetic nanozymes" synergistic catalysis strategy for the formation of disulfide bonds in peptides. The polymeric microzymes showed excellent selectivity toward the template peptide as well as the main reactant (linear peptide), and the Fe₃O₄ magnetic nanoparticle (MNP) nanozymes inhibited the intermolecular reaction during the formation of disulfide bonds in peptides. As a result, the integration of the two different artificial enzymes in one process facilitates the intramolecular cyclization in high product yields (59.3%) with excellent selectivity. Mechanism study indicates the synergistic effect was occurred by using a "reversed solid phase synthesis" strategy with an enhanced shift of reaction balance to product generation. We believe the synergistic catalysis by "polymeric microzymes and inorganic nanozymes" presented in the present work may open new opportunities in creation of multifunctional enzyme mimics for sensing, imaging, and drug delivery.