Advanced Oxidation Technology For Degradation Of Methyl Orange

Advanced oxidation technology has the characteristics of high efficiency,simplicity and less pollution in the second time.So it has wide application prospects in the degradation of organic pollutants.Methyl orange?MO?was used as model pollutant and we employed high oxidation technology based on photocatalysis and radical sulfate radical(SO₄^*-)to degrade it.The degradation effect of Ag₂SO₃ based composite on MO under visible light and/or dark condition was investigated.The main active species of MO degradation were detected,and the related reaction mechanism was also discussed.The following research work was carried out in this article:?1?Graphene oxide enwrapped Ag₂SO₃/AgBr?GO/Ag₂SO₃/AgBr?Z-scheme nanoparticles with enhanced visible-light photocatalysis was fabricated based on the mutual electrostatic interaction and precipitation transformation between GO and Ag ions.The structure,morphology and composition of the composite were confirmed by a series of characterization.The incorporation of GO nanosheets not only significantly improved the visi-ble-light photocatalytic activity of the composites,but also improved the reusability of Ag₂SO₃/AgBr composite nanoparticles.GO/Ag₂SO₃/AgBr still maintained high photocatalytic activity after 4 cycles.Due to the good conductivity of GO,the electron transfer of GO/Ag₂SO₃/AgBr between AgBr ? Ag? Ag₂SO₃ ? GO or AgBr? Ag ? GO,resulting in the effective separation of electrons and holes in the light process.Subsequently,electrons reacted with GO forming rGO or to were captured by dissolved oxygen generating superoxide free radicals(O₂^*-),which further removed MO molecules.Photogenerated hole?h+?and O₂^*- are main active species in the process of MO degradation according to free radical capture experiment.?2?Ag₂SO₃ was prepared by precipitation method,and a series of Ag₂SO₃/AgCl or Ag₂SO₃/Ag₂S nanocomposites with different mass ratios were prepared by precipitation conversion reaction and ion exchange reaction.These two kinds of Ag₂SO₃ based nanocomposites can effectively degrade MO under visible light,and can also degrade MO to some extent under dark conditions.Free radical capture experiments showed that h+ and O₂^*- were the main active species under illumination.Under dark conditions,the addition of appropriate Na₂SO₃ could promote the degradation of MO.SO₄^*- was the main active species for MO degradation.?3?Based on the above research work?2?,we have investigated the effect of Na₂SO₃ activated by a single silver salt catalyst?Ag₂SO₃,Ag₂CO₃,Ag₃PO₄? and several transition metal ions(Ag+,Cu²⁺,Co²⁺,Ni²⁺) in the degradation MO in the goal of activating the Na₂SO₃ to produce SO₄^*- to degrade MO.The dosage of activator,temperature and illumination were investigated.We found that the effect of activated Na₂SO₃ on the degradation of MO is the order of Co²⁺>Cu²⁺>Ag⁺ ?Ag₂SO₃>Ag₂CO₃>Ag₃PO₄.Considering the possible two pollution of the use of transition metal ions,we further-used hydrazine to reduce Ag₂SO₃ to prepare a low solubility Ag/Ag₂SO₃ composite.Compared with Ag₂SO₃,it could degrade MO faster in the dark.The dark radical capture experiment proved that SO₄^*- was the main species in degrading MO.The degradation of MO could be accelerated by increasing temperature and light intensity.