Preparation And Modification Of Biochar And Its Adsorption Capability

Biochar has been widely used in environmental management due to its special structure and physical and chemical properties.In recent years,biochar has shown great potential in the treatment of water pollution and has become a research hotspot.In this paper,biochar was prepared from Hainan’s characteristic agricultural and forestry wastes such as banana pseudostem,rubber bark and coconut shell for the removal of pollutants in water.The biochar was studied in depth by a variety of material characterization methods combined with batch adsorption experiments.Fourier transform infrared(FTIR)spectroscopy,BET surface analysis,scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)were used to characterize biochar,and the physical and chemical properties of biochar were investigated.Exploring the adsorption properties of biochar,studying the relationship between physicochemical properties and adsorption properties of biochar,and elucidating the adsorption mechanism.Through the preparation and study of the primitive biochar of banana pseudostem under different pyrolysis temperatures,the changes of physical and chemical properties of biochar with pyrolysis temperature were obtained.The content of oxygen-containing functional groups on the surface of the primitive biochar of banana pseudo-stalk gradually decreased with the increase of pyrolysis temperature,and when the pyrolysis temperature reached 500℃.,the biochar had a strong aromatization reaction,which adsorbed biochar.The performance impact is tremendous.The specific surface area of biochar increases with the increase of pyrolysis temperature and gradually stabilizes.The adsorption kinetics and adsorption isotherm of Cr(Ⅵ)adsorbed on the primitive biochar of banana pseudostem were studied,and indicate the adsorption process was an endothermic chemisorption process.XPS analysis found that the surface of the pseudo stem biochar after adsorption was mainly trivalent chromium ion,indicating that the biochar first reduced Cr(Ⅵ)to Cr(Ⅲ)and then fixed Cr to its surface by complexation or ion exchange.The rubber bark modified biochar was prepared by the synergistic modification of FeCl3/H2O2.By studying the adsorption properties of modified biochar and raw biochar,it was found that FeCl3/H2O2 synergistic modification method can effectively improve the adsorption performance of biochar on methylene blue(MB)and Cr(Ⅵ)in water.Characterization of biochar by elemental analysis,FTIR analysis and XPS analysis confirmed:1)The pretreatment process of FeCl3 significantly increases the iron content in the prepared biochar,which helps to promote the subsequent modification of H2O2;2)The oxidation reaction occurs during the post-treatment of H2O2,which significantly increases the surface oxygen-containing functional groups of biochar,Which has a great influence on the chemical properties of biochar.The adsorption performance studies show that the adsorption of MB by modified biochar is mainly chemical adsorption,while the adsorption of Cr(VI)may be accompanied by chemical adsorption and physical adsorption.In order to investigate the universality of the FeCl3/H2O2 synergistic modification method.the method was applied to the modification of coconut shell biochar,and prepare a biochar with certain ferromagnetism.Through the adsorption experiment on MB,it was found that the modification method can increase the adsorption capacity of coconut shell biochar to MB from 1.72 mg/g to 185.96 mg/g.This also indicates that the FeCl3/H2O2 synergistic modification method has certain universality,and can prepare magnetic biochar with high adsorption performance,which is convenient for subsequent separation of biochar.