Preparation Of Bamboo Charcoal-based Composites And Their Adsorption/Catalytic Degradation Properties Of Methylene Blue

With the rapid development of a series of chemical industries such as textile and papermaking,the discharge of organic dye wastewater is rising rapidly.However,the self-purification capacity of the natural environment is not enough to purify the excess discharge of dye wastewater,so the world environmental problems caused by dye wastewater are increasingly serious.However,the complex composition and stable organic structure of dye wastewater make it impossible to achieve excellent removal effect by traditional means.Therefore,it is urgent to find a green,stable and efficient dye wastewater removal method.In this paper,bamboo charcoal（BC）was prepared by high temperature roasting with bamboo as raw material,and further modified by chemical modification and compound with metal oxide.These materials were used to study the adsorption and catalytic properties of methylene blue.The specific research contents are as follows:（1）Bamboo charcoal（BC）was prepared by high temperature pyrolysis method,and then modified bamboo charcoal（BC-I）by Na OH simple impregnation strategy.Fe O_x-bamboo charcoal composite（BC-IM）was further prepared by chemical co-precipitation method.The physical and chemical properties of BC,BC-I and BC-IM materials were studied.The results showed that simple Na OH impregnation could optimize the crystal structure,pore size distribution and surface functional groups of the materials,and significantly increase the specific surface area of the materials.Further magnetization not only makes the specific surface more optimized,but also makes it superparamagnetic,realizing the rapid separation of the material from the solution under the action of the external magnetic field.The adsorption process of methylene blue was studied by adsorption isotherm model,thermodynamic model and adsorption kinetics model.The results showed that the maximum adsorption capacity of BC,BC-I and BC-IM for methylene blue was135.13 mg/g,220.26 mg/g and 497.51 mg/g,respectively.The results indicate that simple subsequent impregnation and further magnetization can effectively improve the structural properties and adsorption capacity of bamboo charcoal.The adsorption process is spontaneous,and the adsorption behavior of the three bamboo charcoal materials conforms to the quasi-second-order kinetic model,and the adsorption is mainly monolayer adsorption.（2）Bamboo charcoal supported metal oxide composites（Fe/BC-I2,Fe-Cu/BC-I2 and Fe-Cu-Zn/BC-I2）were prepared by one-step chemical coprecipitation method using the high temperature roasted product of bamboo charcoal（BC-I2）impregnated with sodium hydroxide as the substrate.The new synthetic process can avoid the long impregnation and calcination steps in the conventional preparation process.The physicochemical properties of three kinds of composite bamboo charcoal were studied by a series of structural characterization methods.The results show that the specific surface area can be increased from 201.39 m²/g to 244.54 m²/g by the co-modification of Fe and Cu compared with that of single Fe O_xmodified bamboo charcoal.The further co-modification of Fe,Cu and Zn has richer surface functional groups and more diverse metal synergistic effects,although the specific surface area is not improved.The three kinds of composite bamboo charcoal have certain magnetic strength and can be quickly separated from the solution under the action of external magnetic field.The catalytic performance and reaction mechanism on the modified bamboo charcoal-based composites for methylene blue degradation in the presence of H₂O₂or PMS were studied,The results showed that Fe-Cu-Zn/BC-I2 has the strongest catalytic performance for PMS degradation of methylene blue,and the degradation rate of methylene blue reaches 99.9%in 120 min.Fe-Cu/BC-I2 and Fe-Cu-Zn/BC-I2 have similar catalytic performance for H₂O₂ degradation of methylene blue,and the degradation rate of methylene blue reaches 99.9%at about 6 h.The results of structure-activity analysis showed that the activity was not only related to the specific surface,but also to the type and number of functional groups on the surface and the synergistic effect between metals.The results of active species quenching experiment showed that singlet oxygen ¹O₂ contributed the most to the degradation of methylene blue by PMS,while·OH was the main active radical in the degradation of methylene blue by H₂O₂.The intermediates in the reaction were monitored by LC-MS,and the possible reaction mechanism was proposed.