Study On The Preparation Of Composites Containing Iron And Their Catalytic Properties In Degradation Of Acid Red 73

Sulfate radical-based advanced oxidation process is a new advanced oxidation technology,which utilizes highly reactive sulfate radical(SO₄^-·)generated via persulfate?PS?to oxidize organic contaminants.Nevertheless,little SO₄^-·could be produced by PS under common conditions.The reason why it is so low efficienct is that activating persulfate at room conditions is difficult,which is a popular research field investigated by environmentalists.Currently,a lot of refractory waste water comes from printing and dying.Therefore,we selected Acid Red 73?AR 73?as target pollutant,and prepared two iron-containing catalysts and investigated their properties of catalyzing PS in degradation of AR 73.Firstly,a novel Fe-Ag/GAC composite was prepared through two-step impregnation method,and its property for activating PS in decolorization of AR 73was investigated.Compared to Fe/GAC and Ag/GAC,Fe-Ag/GAC had a highest efficiency about activating PS for the removal AR 73 under neutral pH condition.At35?,with the addition of 7.5 g catalyst,0.5 g?L^-1 PS,the AR 73 decolorization efficiency could be 99%and TOC removal rate was 84.1%by Fe-Ag/GAC/PS system.The results of characterization and mechanism study of Fe-Ag/GAC/PS showed that both Fe and Ag were supported on GAC as the forms of FeO,Fe₃O_4,FeOOH,and Ag,respectively.Ag could accelerate the electron transfer and promote the redox cycle of Fe²⁺/Fe³⁺in this system.Cycling experiment showed the decolorization efficiency remained 90%after reuse by five times.ICP-MS analytical result showed that the percent leaching iron was 1.3%and the trace of leaching Ag.SEM and XPS characterization results of Fe-Ag/GAC also did not find any significant change for fresh and used catalysts,indicating the activity of Fe-Ag/GAC was relatively stable and efficient.Secondly,due to the catalytic degradation efficiency of Fe-Ag/GAC/PS was unsatisfactory at ambient temperature,another novel efficient catalytic system was proposed.Fe-N/O composite was synthesized by the calcination of the blend of melamine and ferrous sulfate in N₂ atmosphere.It was found that Fe-N/O exhibited excellent catalytic activity towards the degradation of AR 73.The addition of Fe-N/O?1.0 g?could get 96%removal rate of AR 73(50 mg?L^-1)and 72.5%removal rate of TOC in 10 min with the presence of PS(1.0 g?L^-1),respectively.Cycling experiment showed the leaching of iron was low,hinting the composite was stable,and no extra sludge was about to be disposed.Moreover,Fe-N/O/PS exhibited excellent removal ability towards AR 73 at different pHs?3-9?.FTIR and XRD characterization results showed Fe₃N and Fe₃O₄ formed together.Radical quenching test proved SO₄^-·radical was the main reactive specie.Characterization and mechanism study indicated that the highly catalytic activity could be attribute to the interface of Fe₃N and Fe₃O₄.Based on the above research,it can be confirmed that when iron is chose as basic element of catalyst,and Ag or N is co-loaded,the efficiency of PS for the degradation and mineralization of AR 73 can be improved greatly.Moreover,the high activity and stability of these catalyst are significant for the treatment of printing and dying wastewater.