Experimental Study On Enhanced Degradation Of Crystal Violet And Methyl Orange By Carbon-based Catalysts In Fenton-like System

With the gradual growth of my country’s economy,water resources are facing unprecedented challenges as the most precious resource for human survival.Dye wastewater has deep color,complex composition,high content of organic pollutants,strong biological toxicity,and is difficult to biodegrade and purify.It causes serious environmental problems and is related to carcinogenic,mutagenic or teratogenic effects.Whether it can solve the problem of water pollution,it is related to human survival.Therefore,this experiment explored the use of activated carbon to support active metals(Fe,Zn,Cu)to prepare catalysts and degraded dye model compounds(crystal violet(CV)and methyl orange(MO))through Heterogeneous Fenton-like technology.The research results are as follows:(1)0.5%Fe3+loaded AC(0.5Fe@AC)had better catalytic activity for dyes degradation compared with Cu@AC and Zn@AC.The surface of 0.5Fe@AC contained abundant functional groups and developed pore structure.For degradation experiment of dyes,the best parameter processes were obtained by combining single factor analysis and response surface method:CV:catalyst dosage 0.042 g,H2O2 volume 1.85 mL,pH 8.44,degradation capacity 397.81 mg/g;MO:catalyst dosage 0.061 g,the volume of H2O2 1.39 mL,pH 3.66,and degradation capacity 373.62 mg/g.(2)The degradation kinetics of dyes were suitable for the pseudo-second-order model(Langmuir-Hinshelwood).After reacting for 30 minutes under the conditions of CV volume 30 mL,catalyst volume 0.05 g,H2O2 volume 1 mL and pH 7.7,400 mg/L CV was almost completely decolorized(99.7%).However,under the same conditions,the decolorization of MO reached 98.2%.The pyrolysis carbon(PC)of dyeing sludge(DS)also used the heterogeneous Fenton-like method to degrade dyes.It was found that the degradation capacity of CV was equivalent to the catalyst,which provided a new insight for resource utilization of PCs from DS.(3)The research also explored dyes possible degradation products and degradation pathways using techniques such as HPLC-MS.There are three possible competing pathways for CV degradation:(ⅰ)N-demethylation;(ⅱ)cleavage of the ring structure of the CV chromophore;(ⅲ)benzene ring cleavage and oxidation to carboxylic acid.There are four possible competing pathways for MO degradation:(ⅰ)cleavage of the phenyl ring amino group;(ⅱ)cleavage of the azo bond of the chromophore group;(ⅲ)N demethylation and oxidation to nitric acid;(ⅳ)benzene ring cracked and oxidized to carboxylic acid.This study provided insights into the catalytic degradation of triphenylmethane and aromatic azo-based substances.