过硫酸钠氧化脱色罗丹明B——影响因素和机理

采用过硫酸钠(PDS)直接氧化和催化活化氧化脱色罗丹明B(RhB),分别考察了PDS剂量、pH、催化剂、Cl-浓度对RhB脱色的影响.结果表明,PDS在无外加催化剂下能够有效脱色RhB,pH越低,脱色率越高;当pH 2.4,PDS用量为3.5 g·L^-1,在120 min内RhB的脱色率可达92%;自由基淬灭实验表明,酸性条件下主要为PDS直接氧化脱色RhB,并存在小部分硫酸根自由基(SO₄4·-)作用.在pH 5.6、pH 8.0条件下,外加活性炭纤维(ACF)、四氧化三铁(Fe₃O₄4)、Fe₃O₄4负载型催化剂(ACF/Fe3O₄4)可促进PDS对RhB脱色;在pH 2.4条件下,外加ACF对RhB脱色的促进作用较小,Fe₃O₄4、ACF/Fe₃O₄4对RhB脱色有一定抑制作用.不同pH和催化剂处理下,低浓度Cl-(0.01、0.04 mO₄l·L^-1)对RhB脱色速率都呈现抑制作用,高浓度Cl-(0.08 mO₄l·L^-1)相对于低浓度Cl-处理都呈促进作用.不同浓度Cl-处理在反应前60 min RhB脱色速率差异较大,而反应120 min后脱色率差异较小.提出Cl-通过调控SO₄4·-脱色RhB途径来影响RhB脱色速率的机理,Cl-竞争消耗SO₄4·-降低RhB脱色速率,但经一系列反应生成的Cl2·-能与RhB快速反应而提高RhB脱色速率;Cl-对RhB的脱色反应速率的影响存在抑制-促进双重机制,且与Cl-浓度相关.研究结果为基于PDS直接氧化和催化氧化处理含盐染料废水的研究和应用提供了一定的理论依据.

Rhodamine B decolorization by sodium persulfate oxidation:Influencing factors and mechanism

Rhodamine B(RhB)was decolorized by direct oxidation and catalytic oxidation of sodium persulfate(PDS).Effects of PDS dosage,solution pH,and Cl-concentration on the decolorization of RhB were investigated.The results demonstrated that PDS can directly oxidize and decolorize RhB without adding catalyst.The lower the pH,the higher the decolorization rate was.The decolorization rate of RhB could reach 92%in 120 minutes with initial pH at 2.4 and PDS dosage at 3.5 g·L^-1.Free radical quenching experiments showed that PDS direct oxidation was the main contribution to RhB decolorization under acidic condition,and there was a small part contribution from sulfate radical(SO₄·-).The addition of activated carbon fiber(ACF),ferroferric oxide(Fe₃O₄),and Fe₃O₄supported catalyst(ACF/Fe3O₄)can promote RhB decolorization by PDS under pH conditions at 5.6 and 8.0.However,under the pH condition at 2.4,adding ACF presented negligible impact on RhB decolorization,and Fe₃O₄and ACF/Fe₃O₄even showed a certain inhibitory effect on RhB decolorization.Among the different pH and catalyst treatments,Cl-at lower concentrations(0.01,0.04 mol·L^-1)showed an inhibitory effect on RhB decolorization rates,while Cl-at higher concentrations(0.08 mol·L^-1)promoted RhB decolorization rates.The differences of RhB decolorization rates among treatments with Cl-at various concentrations were more obvious within 60 min than those after 120 min of the reaction.It is proposed that Cl-influences RhB decolorization rate by regulating the RhB decolorization path with SO₄·-.Although Cl-could quickly react with SO₄·-to reduce RhB decolorization by SO₄·-,Cl2·-generated after a series of reactions may react very fast with RhB to accelerate RhB decolorization.Therefore,Cl-has a dual mechanism of inhibition and promotion effects on RhB decolorization rate,which is closely related to Cl-concentration.The results provide a theoretical basis for the research and application of direct oxidation and catalytic oxidation based on PDS to treat salty dye wastewater.