Multi-walled carbon nanotubes-CoFe2 O4 nanoparticles as a reusable novel peroxymonosulfate activator for degradation of Reactive Black 5

Activation of persulfate for degradation of sodium dodecyl sulfate by a hybrid catalyst hematite/cuprous sulfide with enhanced FeIII/FeII redox cycling

Surfactants are recalcitrant compounds that require advanced treatment for their degradation. Heterogeneous advanced oxidation processes (AOPs) using iron-based catalysts can be a promising method for surfactant degradation. The acceleration of the Fe^III/Fe^II redox cycling is the key to enhance the catalytic degradation. Herein, a hybrid catalyst composed of α-Fe₂O₃ and Cu₂S was synthesized to improve the reduction of Fe^III in a heterogeneous persulfate-AOP system. The results of XRD, Raman and TEM demonstrated the successful preparation of the hybrid catalyst. Because of the optimized Fe^II regeneration, the AOP containing the catalyst FC₇₅ achieved 100.0% removal of sodium dodecyl sulfate (SDS) in a neutral aquatic environment, significantly higher than 22.9 ± 2.4% with pure α-Fe₂O₃ or 39.6 ± 2.5% with pure Cu₂S. The catalyst FC₇₅ demonstrated effective SDS removal in the recycling test (82.7 ± 7.0% after six recycling test) and in actual wastewater (84.4 ± 4.5%). The regeneration of Fe^II was confirmed by the increased proportion of Fe^II from 39.5% in the fresh catalyst to 42.6% in the used catalyst. The main active species was revealed to be sulfate radicals under an acidic condition and shifted to hydroxyl radicals under a basic condition. In the hybrid catalyst, α-Fe₂O₃ provided Fe^II to activate persulfate to radicals, with an oxidation product of Fe^III, which was then reduced to Fe^II by Cu^I provided by Cu₂S, coupling with the oxidation of Cu^I to Cu^II. The S element in Cu₂S could directly or indirectly facilitate the Fe^III/Fe^II redox cycling as an electron donor. Those results have demonstrated that the developed hybrid catalyst is able to promote Fe^II regeneration for effective SDS removal.

The analysis and probabilistic health risk assessment of polycyclic aromatic hydrocarbons in cereal products

The analysis and probabilistic health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in cereal products were done by using magnetic solid-phase extraction (MSPE) method and gas chromatography/mass spectrometric (GC/MS). The results of method showed LOQ and LOD of PAHs compounds were 0.105-0.180 and 0.035-0.060 µg/kg, and the recorded values were 4.3-12.1 and 6.1-20.3% for repeatability and reproducibility with an estimated recovery of 94.4-103.4%. In this study, we analyzed kind of bread (Barbari, Sangak, Baguette, Taftoon, Lavash), macaroni, lasagna, and cooked rice that mean of total PAHs were 98.2, 121.7, 134.9, 166.3, 176.3, 176.2, 130.1, and 248.3 μg/kg, respectively. Further, the correlation between the type and amount of 16 PAHs with cereal products samples evaluated with multivariate principal component analysis and heat map visualization. The highest incremental lifetime cancer risk (ILCR) was found in cooked rice (7.80E-6), while the lowest ILCR was found in Lasagna (2.35E-07). In conclusion, the PAHs content in the tested products were in low health risk ranges (1 × 10^-6 < ILCR < 1 × 10^-4), and all of the cereal products sold in Tehran are considered safe for consumers. Therefore, cereal products should be regularly evaluated and monitored by regulatory agencies to reduce contaminants in these high-consumption products.

Magnetic CuNiFe2O4 nanoparticles loaded on multi-walled carbon nanotubes as a novel catalyst for peroxymonosulfate activation and degradation of reactive black 5

Novel copper-nickel ferrite nanocatalyst loaded on multi-walled carbon nanotube (MWCNTs-CuNiFe₂O₄) was synthesized and applied to activate peroxymonosulfate (PMS) in the degradation of the reactive black 5 (RB5). The structure of the catalyst was well characterized by scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray powder diffraction (XRD). The MWCNTs-CuNiFe₂O₄/PMS system showed a high performance in the degradation of RB5 with a kinetic rate of 1.5-2.5 times higher than homogeneous and heterogeneous systems. Maximum degradation efficiency (99.60%) was obtained at an initial pH of 7, catalyst dosage of 250 mg/L, PMS dosage of 4 mM, the temperature of 25 °C, and reaction time of 15 min. Anion experiments emphasized that the presence of nitrate, carbonate, and phosphate in the solution reduced the degradation efficiency by producing reactive species with low oxidation potential. The RB5 degradation rate evolved with temperature, and the activation energy was obtained to be 44.48 kJ/mol. The mechanism of PMS activation and production of free radicals was proposed based on tert-butyl alcohol (TBA), ethanol (EtOH), and potassium iodide (KI) scavengers. Trapping experiments showed that both sulfate (SO₄^•-) and hydroxyl (^•OH) radicals are involved in the catalytic degradation of RB5. The effective treatment of real wastewater and tap water by the MWCNTs-CuNiFe₂O₄/PMS system requires a long reaction time. Gas chromatography-mass spectrometry (GC-MS) analysis indicated that RB5 can be degraded via methylation, decarboxylation, hydroxylation, and ring/chain cleavage pathways. The stable catalytic activity after three consecutive cycles suggested that MWCNTs-CuFe₂O₄ is a novel reusability catalyst in PMS activation.

Catalytic degradation of mefenamic acid by peroxymonosulfate activated with MWCNTs-CoFe2O4: influencing factors, degradation pathway, and comparison of activation processes

The cobalt ferrite loaded on multi-walled carbon nanotubes (MWCNTs-CoFe₂O₄) was synthesized and used as a novel catalyst for the degradation of mefenamic acid (MFA) in the presence of peroxymonosulfate (PMS). The results showed that MWCNTs-CoFe₂O₄ has higher catalytic performance in the activation of PMS and degradation of MFA compared with MWCNTs, Co²⁺, Fe²⁺, and CoFe₂O₄. The highest kinetic constant rate (0.0198 min^-1) and MFA degradation (97.63%) were obtained at pH = 7, PMS = 4 mM, catalyst = 500 mg/L, MFA = 10 mg/L, and time = 150 min. MFA degradation accelerated with increasing PMS and catalyst dosage but decreased by initial pH. The influence of different anions and water matrix on the catalytic system was investigated, and the results explained a decrease in the MFA rate in the presence of the interfering substances. Scavenging experiments showed that both sulfate radical anion (SO₄^•-) and hydroxyl radical (^•OH) were effective on MFA degradation, but SO₄^•- had a greater effect on the degradation of MFA. In addition, the stability and recyclability of MWCNTs-CoFe₂O₄ were evaluated in the consecutive reaction cycle; the MFA degradation rate reached 89.75% after 4 cycles of reaction. The MFA degradation products were identified by gas chromatography-mass spectrometry (GC-MS) and their degradation pathway was suggested. Finally, a comparison was conducted among the methods used for PMS activation, and the results showed that the cobalt ferrite-based catalyst has high degradation efficiency. However, ultrasound, heat, and ultraviolet (UV) processes can be used to improve the degradation rate of the MWCNTs-CoFe₂O₄/PMS system at different reaction times.

Bifunctional reusable Co0.5Ni0.5Fe2O4 nanoparticle-grafted carbon nanotubes for aqueous dye removal from contaminated water

Highly stable and reusable CNF-grafted CNTs for efficient and effective aqueous dye removal from contaminated waters.