Properties And Influencing Factors Of Pyrite-activated Persulfate Degradation Dye Reactive Black 5

With the rapid development of the printing and dyeing industry,the demand for dyes is also increasing,among which azo dyes occupy an important position in the entire industry.Dyestuff wastewater is difficult to decolorize and degrade,which has become a major problem in water treatment.Advanced oxidation based on activated persulfate to produce SO₄^·-has attracted much attention because of its high oxidation potential,which can oxidatively degrade most organic compounds,but the use of this technology requires maintaining a good acidic condition and providing a stable activator.Pyrite oxidation can not only release Fe²⁺continuously to activate persulfate,but also maintain good acidic conditions,and can be used as a good natural substance for activating persulfate.Based on this,in this paper,pyrite（Pyrite）activated persulfate（PS）was selected to degrade reactive black 5（RB5）in dye wastewater,and its degradation performance and influencing factors were studied.Through carrying out this research work,the main understandings and conclusions obtained in the full text are as follows:（1）The PS/Pyrite system can efficiently degrade RB5,4 mmol·L^-1 PS and 0.4 g·L^-1 Pyrite degraded 50 mg·L^-1 RB5 at 30°C,and the degradation rate was 94.2%within 60 min,while PS and pyrite alone cannot degrade RB5.Combined with the characterization data of scanning electron microscope（SEM）and the change of iron during the degradation system,it is speculated that pyrite activates PS through Fe²⁺released from the oxidation of ultrafine particles on the surface to generate free radicals to degrade RB5.The quenching experiments and electron paramagnetic resonance（EPR）tests of ethanol and tertbutanol showed that the free radicals in the system were·OH and SO₄^·-,in which SO₄^·-played a leading role in the degradation of RB5.It is speculated that the degradation process of RB5 may be the-N=N-structure and the cleavage of the naphthalene ring by scanning the UV-visible light spectrum of the RB5degraded samples at a specific time point.（2）The effects of pyrite and PS dosage,p H,pyrite particle size,reaction temperature and initial concentration of RB5 on the degradation of RB5 in PS/Pyrite system were studied.The increase of pyrite and PS concentrations can enhance the degradation rate and degradation rate of RB5.The oxidation of pyrite can produce acid,so that the PS/Pyrite system can maintain a good acid condition for a long time,which to a certain extent broadens the application scope of PS/Pyrite,an advanced oxidation technology.Appropriately reducing the particle size of pyrite can significantly improve the degradation rate and degradation rate of RB5 by PS/Pyrite system.In the range of 20～40℃,the degradation rate of RB5 will increase slightly with the increase of temperature.（3）The effects of inorganic anions,inorganic cations,humic acids and chelates on the degradation of RB5 in PS/Pyrite system were investigated.Inorganic anions Cl^-,HCO₃^-and NO₃^-would react with free radicals to generate inorganic radicals with redox potential lower than SO₄^·-,while inorganic cations Mn²⁺and NH₄⁺would consume free radicals,thereby inhibiting the degradation of RB5.Cu²⁺is inhibited at low concentration,and at high concentration,it will form a virtuous cycle with Fe²⁺to promote the degradation of RB5.The interference of humic acid on the PS/Pyrite system was small,and the chelate complex significantly inhibited the degradation of RB5 by PS/Pyrite due to the formation of a stable complex with Fe²⁺.