Preparation And Catalytic Properties Of Titanium Dioxide-Based Activated Persulfate Catalyst

As the synthesis and utilization of emerging organic compounds increase,addressing the treatment of organic substances in wastewater has become a pressing issue.Consequently,investigating efficient and eco-friendly methods for degrading organic pollutants in wastewater holds significant practical value.Advanced oxidation processes primarily employ catalysts to activate oxidants,which generate reactive species that break down organic pollutants into smaller molecules,CO₂ and H₂O.Among these processes,persulfate-based advanced oxidation process relies on catalysts to activate persulfate,producing sulfate radicals that initiate chain reactions,attacking organic pollutants and converting them into low-toxicity or non-toxic small molecular compounds.Activating persulfate through external energy inputs like ultrasound or heating is inefficient and consumes a substantial amount of energy.Harnessing solar energy effectively can circumvent the need for external energy inputs and conserve resources.Therefore,discovering a catalyst that synergistically activates persulfate under visible light represents a sustainable and efficient approach to degrading organic pollutants.The limitations of TiO₂,including its wide bandgap,exclusive response to UV light,and high electron-hole recombination rate,significantly hinder its application in synergistically activating persulfate under visible light.To address the limited visible light absorption of TiO₂ and the subsequent low solar energy utilization,this study uses transition-metal-modified titanium dioxide as a heterogeneous catalyst to activate persulfate and enhance the degradation efficiency of organic pollutants.The prepared catalyst materials were analyzed for their phase,morphology,elemental composition,valence states,and photochemical activity using characterization techniques such as XRD,TEM,XPS,DRS,PL,BET,and EPR.Single-factor experiments were conducted to investigate the influence of various parameters on catalytic performance and to explore the catalytic mechanism.The specific results are as follows:1.Preparation and catalytic performance of Fe/{001}TiO₂ catalyst:Using titanium butoxide as the titanium source and hydrofluoric acid under hydrothermal conditions to control the crystal facets,{001}TiO₂ was synthesized,and Fe/{001}TiO₂ catalyst was prepared through secondary hydrothermal synthesis,forming a45 nm square plate-like structure.Fe doping introduced numerous oxygen vacancies in TiO₂,reducing the bandgap from 3.24 e V to 2.97 e V and extending the absorption wavelength from 382 nm to 404 nm in the visible light region.When the doping amount of Fe/TiO₂ is3%,the catalyst can produce synergic effect with potassium persulfate by visible light,and improve the catalytic performance.When the concentration of catalyst and potassium persulfate are both 0.6g/L,and p H=4,10 mg/L Rhodamine B acts for 80 min,the degradation rate can reach 97.81%.Under visible light irradiation,the Fe³⁺/Fe²⁺cycle accelerated and promoted persulfate activation for the degradation of organic pollutants.The main active species for the degradation of Rhodamine B in the Fe/TiO₂ synergistic photocatalytic persulfate system were·OH,SO₄^-·,h⁺,and e^-.2.Preparation and catalytic performance of Co/{001}TiO₂ catalyst:A Co/TiO₂ nanocatalyst was synthesized using the hydrothermal method,with a crystal size of approximately 45 nm and a thickness of roughly 7 nm.Cobalt doping generated numerous oxygen vacancies on the surface,significantly enhancing the absorption wavelength in the visible light region and reducing electron-hole recombination.XPS spectra confirmed the catalyst’s composition of Ti,O,and Co.Catalytic degradation experiments were conducted using Rhodamine B as the target pollutant,investigating key parameters such as catalyst dosage,persulfate dosage,initial p H value,and initial organic pollutant concentration.At room temperature,using 0.6 g/L of catalyst and 0.6 g/L of potassium persulfate,the degradation rate of 10 mg/L Rhodamine B reached 97.23%within80 min,with a reaction rate constant higher than that of pure TiO₂.The main active species were h⁺,SO₄^-·,and·OH·In the quenching experiment,the most significant inhibition was observed with disodium ethylenediaminetetraacetate and potassium dichromate,indicating that photocatalytically generated electron-holes were the primary active substances.Compared with the characterization tests of Fe/TiO₂ and Co/TiO₂,the amount of surface oxygen vacancy of Fe/TiO₂ in Co/TiO₂ catalyst is more.The band gap of Co/TiO₂ is reduced more,and the electron holes are not easy to recombine.Under the same experimental conditions,the kinetic constants are similar,but Co/TiO₂ catalyst has a better ability to degrade organic pollutants in persulfate system.3.Preparation and catalytic performance of the Fe S₂@TiO₂ composite catalyst:The Fe S₂@TiO₂ catalyst was synthesized using a precipitation-calcination method,exhibiting a core-shell structure with an approximate diameter of 200 nm.Based on Brunauer-Emmett-Teller and Barrett-Joyner-Halenda calculations,the surface area was determined to be 43.43 m²/g,and the average pore size was 11.87 nm.Under ambient conditions and with the use of 10 mg of catalyst to activate 10 mg of potassium persulfate,95.15%degradation of 100 m L of 20 mg/L Rhodamine B was achieved,resulting in an apparent rate constant of 0.063.This value is significantly higher than those of Fe S₂（0.009）or TiO₂（0.002）.Tetracycline hydrochloride,methyl orange,and methylene blue served as model compounds in the experiments,demonstrating that the catalyst effectively degrades a variety of organic pollutants.Further investigation through free radical capture experiments and EPR testing revealed that the primary active species within the Fe S₂@TiO₂/PS/light system are SO₄^-·,O₂·^-,h⁺,and·OH.