The Research On Ultrasonic-iron Based Activation Of Persulfate/chlorite And Treatment Of Triphenylmethane Derivatives

In order to extend activation of persulfate（PDS）for treating pollutants in water and broaden its application range,and on account of the research idea of“physical field/activator/oxidant”heterogeneous catalysis,the heterogeneous catalytic systems were established in this study based on ultrasound-driven activation,the composite oxidant(O_SC)（namely,PDS combining with chlorite（CI））,and iron-based/derived activators.The above-mentioned systems could effectively remove the emerging organic pollutants,triphenylmethane derivatives in the environment.Thereinto,the crystal violet(tpm _CV)was used as the indicator to evaluate and reveal the removal process of each progressive system.The effectiveness of ultrasonic-iron activating persulfate/chlorite system was studied.Concretely,PDS and CI with a molar ratio of 5:1 were as the O_SC,and foamed zero-valent-iron（Fe_f⁰）was as the iron-based catalyst（Fe_b）,and ultrasonic（US）was as the physical field.Therefore,the US-Fe_b/O_SC system was established,and the sub-systems for comparisons included US/O_SC and US-Fe_b/CI systems.The US/O_SCsystem was homogeneous,and the removal of tpm _CV showed the apparent degradation kinetics with the non-integer order（n（?）1.2）.After introducing the activation of Fe_f⁰(20 mg·L^-1),the removal of tpm_CV by US-Fe_b/O_SC heterogeneous system tended to be the reaction process in a quasi-first-order kinetics,and 90%of tpm _CV could be removed under low initial temperature（289 K）at 30 min.Compared to US/O_SCsystem,the US-Fe_b/O_SC system had a better catalytic effect with a synergistic effect（S=1.83）.And the US-Fe_b/CI system showed the dependence on the introduction of H⁺,and the removal of tpm _CVshowed a piecewise kinetics process.In addition,the introduction of H⁺could effectively improve the reaction efficiency of several systems in this study.The mechanisms of ultrasonic-iron activating persulfate/chlorite system were studied.The identifications of active species in US-Fe_b/O_SC system and its sub-systems were conducted.The 5,5-dimethyl-1-pyrrolin-N-oxide（DMPO）was used as the trapping agent of some specific kinds of free radicals.The continuous/real-time system of analysis of active species was constructed to identify the presence of hydroxyl radical（·OH）and sulfate radical（SO₄·^-）,and to confirm the presence of the chain transfer transformation process（mainly due to US-induction）.The characteristic dispersion peak（360 nm）of the ultraviolet-visible（UV-Vis）spectrum indicated the presence of chlorine dioxide（Cl O₂）.Electron paramagnetic resonance（EPR）was used to identify the free radicals（·OH and SO₄·^-）comparatively.A strong oxygen atom（[O]）transfer reaction was detected by gas chromatography-mass spectrometer with the chemical probe methylphenylsulfoxide（PMSO）,suggesting the existence of the high-valent-iron-oxo species（HVI=O）.By the comparisons:the mechanism of the US/O_SC system was US-driven catalysis,and co-activation under excitation catalysis of mutual reaction on double oxidants.The US-Fe_b/CI system presented the catalysis of CI process with Fe_f⁰ under US and protonation to generate HVI=O and Cl O₂,and was selective for pollutant removal.In terms of the US-Fe_b/O_SCsystem,the contributions of kinetics inhibition of active species（δ_i）further confirmed that the system was the process of free radicals and non-free radicals（·OH,SO₄·^-,Cl O₂ and HVI=O）.The removal of tpm _CV in this system was mainly manifested as demethylation,central C atom fragmentation,and substitution.The introduction of Fe_f⁰ and US could enrich the types of intermediates and broaden the types of active species under the degradation of tpm _CV.In addition,it could be found that the introduction of US could clean the oxide layer on the surface of Fe_f⁰（the role of polishing）,and promote the continuous corrosion of Fe_f⁰ for releasing Fe source.The reactions of ultrasonic-iron/carbon based materials activating persulfate/chlorite system were studied.Based on US/O_SC system,the heterogeneous activation system was further constructed by introducing iron/carbon-based materials.Magnetic iron/carbon-based materials were prepared by hydrothermal&heat treatment based on different carbon sources including activated carbons,biochars,pyrolytic carbons,and hydrothermal carbons（HCs）.The iron/carbon-based materials(20 mg·L^-1)had better activation properties after carbonthermal reduction.Among them,the reduced iron-based HCs（r Fe_b/HCs）were prepared by response surface optimization and used to activate a variety of oxidants including PDS,CI,and hydrogen peroxide（HP）.The process of US-（r Fe_b/HCs）/O_SC system for removing tpm _CV was the reaction process with a quasi-first-order kinetics.According to the f value of the system action（calculated via the dynamics）,the activation effect of r Fe_b/HCs（f=3.07）was better than that of the above-mentioned Fe_f⁰（f=1.64）.Through the thermodynamic comparison of the progressive coupling system,it was found that the introduction of the activation material r Fe_b/HCs apparently reduced the activation energy of the reaction(E_a,KJ·mol^-1,E_a-（US/PDS）54.393>E_a-(US/O_SC)39.779>E_a-(US-Fe_f⁰/O_SC)33.227>E_a-(US-（r Fe_b/HCs）/O_SC)26.910),which was beneficial to promoting reaction.The effects of different structural pollutants on the treatment effect of the US-（r Fe_b/HCs）/O_SC system suggested the presence of the selective oxidation.The mechanisms of the reaction process including induction and adsorption were affected by adjusting the p H（namely,dosage of H⁺）and dosage of r Fe_b/HCs.The p-benzoquinone and chlorinated p-benzoquinone detected in the removal process could be regarded as important transition intermediates before ring opening.For another perspective,the activating materials,r Fe_b/HCs,could be regarded as a kind of micro-nano iron-carbon microelectrolysis（ICME）materials.By the forced drive of US,the r Fe_b/HCs could present the disorderly collision and dispersion motion in the liquid phase,which could be analogous to the micro-nano motors.A reaction model was extracted in the US-（r Fe_b/HCs）/O_SC system.It was the reaction process of US-driven and micro-nano particle motor for activation of composite oxidant,which was combined with the micro-nano ICME effect and adsorption catalysis.Finally,the continuous flow reaction systems actuated/catalyzed by US were established,and commercial ICME particles were used as the fixed bed to activate a variety of oxidants including PDS,CI,HP,PDS/HP,and PDS/CI for the removal of tpm _CV.The results showed that the above systems with continuous flow maintained the COD removal rate of approximately 70%.A variety of composite systems were established for pollutant removal.The US catalysis and the deep activation of persulfate were expanded.Further,the composite preparation processes of activators were explored.In addition,the degradation processes of different systems,including system coupling,mathematical model,and degradation mechanism,were explored.It provided the extended ideas for removing environmental pollutants.