Preparation Of Lignin-based Transition Metal Catalysts And The Application In The Catalytic Degradation Of Rhodamine B

In order to solve the problems of traditional homogeneous Fenton oxidation technology,researchers developed heterogeneous Fenton oxidation technology,which not only retains its high efficiency in degrading organic pollutants,but also improves the utilization rate of H₂O₂and reduces the production of Fenton sludge.It can effectively realize the recycling utilization of catalyst.In this paper,a heterogeneous Fenton catalyst with iron and copper-iron bimetals supported by lignin-based activated carbon was prepared by pyrolysis using papermaking process waste-black liquor acid extract and Fenton sludge as raw materials.In this way,high-value utilization of papermaking solid waste can be carried out,and organic pollutants can be efficiently treated.First,the Fe@AC_FLK1.5 catalyst prepared from black liquor acid precipitant and Fenton sludge（mixing ratio of 1.5）and KOH as activator has excellent mesoporous structure and abundant active functional groups,and the total pore volume is 0.120 cm³ g^-1,the mesopore volume is 0.101 cm³ g^-1.Compared with the Fe@AC_FK1.5 catalyst,the addition of black liquor acid extract increased the pore volume of the catalyst.The main metal component supported by Fe@AC_FLK1.5 is ZVI.Compared with Fe@AC_FL1.5 and Fe@AC_FK1.5 catalysts,the addition of black liquor acid precipitates and activator provides sufficient reduction for the pyrolysis process gas,which promoted the conversion of iron components in Fenton sludge to ZVI.Second,the catalytic degradation ability of Fe@AC_FLK1.5 towards Rh B dyes was investigated.Under the conditions of initial p H=3,the dosage of hydrogen peroxide is 2mmol L^-1,and the dosage of catalyst is 0.2 g L^-1,the Rh B dye can be degraded in 20 min.The Fe@AC_FLK1.5 catalyst has good recyclability and stability after 5 cycles of reaction.The experiments confirmed that·OH(·OH_free and·OH_surface)and ¹O₂ were the main reactive oxygen species for the degradation of Rh B dyes in the Fe@AC_FLK1.5/H₂O₂ system.XPS spectroscopy further explained that the reactive functional groups of persistent radicals（such as sp² C=C and C=O）in both ZVI and AC supports accelerated the reduction of Fe（III）,thereby enhancing the degradation performance.Thirdly,an iron-copper bimetallic heterogeneous Fenton catalyst Fe/Cu@AC₉₀₀ was prepared by loading the transition metal element copper.The Fe/Cu@AC₉₀₀ catalyst has a specific surface area of 201.1 m² g^-1,a total pore volume of 0.254 cm³ g^-1,and a mesopore volume of 0.211 cm³ g^-1.FTIR analysis showed that the addition of copper metal significantly increased the relative strength of the O-C=O bond of the catalyst.The main metal components supported by Fe/Cu@AC₉₀₀ are ZVI,Fe₃O₄ and Cu O,and a small amount of Cu₂O and Cu.Finally,the catalytic degradation ability of Fe/Cu@AC₉₀₀ for Rh B dyes was investigated.Under the conditions of initial p H=3.5,hydrogen peroxide dosage of 2 mmol L^-1,and catalyst dosage of 0.2 g L^-1,the degradation of Rh B dyes was completed within 20 min.Compared with the Fe@AC_FLK1.5 catalyst,the Fe/Cu@AC₉₀₀ catalyst loaded with bimetals increased the optimal initial p H of the reaction and greatly reduced the leaching of iron metal in the reaction.Due to the high specific surface area and mesoporous structure of the catalyst,the adsorption reaction plays an important role in the degradation of Rh B,confirming that¹O₂ and·OH_free are the main reactive oxygen species catalyzing the oxidative degradation of Rh B dyes in the system.XPS indicates the redox cycle of Cu（II）/Cu（I）and Fe（III）/Fe（II）,and the synergistic effect of Cu and Fe on the catalyst surface makes Fe/Cu@AC₉₀₀/H₂O₂ system effective for Rh B degradation good catalytic activity.In addition,the active functional groups of persistent free radicals in the activated carbon support are also involved in the redox cycle.