Preparation And Performance Study Of Volcanic Rock Modified Catalysts

According to the technical requirements for the treatment of printing and dyeing wastewater,natural volcanic rocks were used as raw materials.and after pre-treatment for them,Fe⁰/volcanic rock,Fe₃O₄/volcanic rock,new Fe⁰@Fe₃O₄/volcanic rock were prepared by complexation treatment and high-temperature heat treatment,respectively.The adsorption and catalytic oxidation of methylene blue wastewater by modified volcanic rocks were studied,the effects of catalyst dosage,reaction temperature,p H on their catalytic performance were discussed.The main conclusions drawn from this study are as follows:1)In situ preparation of Fe⁰/volcanic rock and Fe₃O₄/volcanic rock catalysts,and adsorption and catalytic oxidation of methylene blue wastewater were carried out.The results of wastewater decolorization showed that the Fe₃O₄/volcanic rock catalyst prepared by complexation treatment and high-temperature heat treatment were superior to Fe⁰/volcanic rock catalyst.2)A new type of catalyst,Fe⁰@Fe₃O₄/volcanic rock catalyst,was synthesized by using N-hydroxyethylenediamine triacetic acid（HEDTA）as a complexing agent and by adding ferrous sulfate Fe⁰@Fe₃O₄/volcanic rock catalyst.The physical and chemical properties were characterized by XRD,TEM,FT-IR and BET,the results showed that a stable Fe⁰@Fe₃O₄ core-shell structure could be formed on the catalyst surface when the molar ratio of Fe⁰ to Fe₃O₄ was 1:1,and the specific surface area of Fe⁰@Fe₃O₄/volcanic rock increased to eight times compared with that of volcanic rock.The optimal adsorption and decolorization effects on methylene blue wastewater were achieved when the dosage of modified volcanic rock catalyst being 0.5 g,the temperature being 25℃and the p H value of the solution being 7.The decolorization rate reached 99.21%at 30 minutes,and the adsorption process followed a quasi second-order kinetic model.The saturated adsorption mass ratio was 36.59 mg·g^-1,and the initial adsorption rate was 8.17 mg·（g·min）^-1.3)A new Fe⁰@Fe₃O₄/volcanic rock catalyst was prepared after high-temperature heat treatment with the addition of ferrous sulfate.The experiments were conducted for the catalytic hydrogen peroxide oxidation of methylene blue wastewater.In a reaction system at 25℃,with a volume of 2 m L H₂O₂,a volcanic rock dosage of 0.5 g,and a p H value of5,the decolorization rate of methylene blue reached 98.47%at 180 minutes.The results indicated that high-temperature heat treatment could significantly increase the·OH content in the catalytic oxidation system significantly and improve the mineralization degree of organic pollutants dramatically.The catalyst was easily recovered by magnetic separation,and its decolorization efficiency was maintained above 92%after seven consecutive uses.