Study On Modification Of Banana Pseudostem Biochar And Its Adsorption Properties For Methylene Blue

The dye was used widely in various industries such as dyeing,textile and leather.A large amount of dye wastewater was produced every year,which poses a serious threat to the domestic water environment.As an emerging adsorbent,biochar has attracted great attention from researchers due to its high adsorption capacity and low cost.Methylene blue(MB)is a typical cationic dye and is considered to be a model adsorbate for evaluating the adsorption capacity of different adsorbents.Banana pseudostem,which is a common tropical biomass waste,is used as feedstock.In this thesis,the adsorption performances of phosphomolybdic acid and seawater modified banana pseudo-stem biochars toward methylene blue were eministed in aqueous solution,and the adsorption mechanism was investigated by analysis of experimental data and characterization of biochars.The specific research contents are as follows:(1)Both phosphomolybdic acid modified banana pseudostem biochar(MBBC)and seawater modified banana pseudostem biochar(SBC)were prepared.It was found that the biochar modified with phosphomolybdic acid has an increase in specific surface area,pore volume and pore diameter,etc.,and the content of oxygen-containing functional groups on the surface of biochar has also been improved.There are new functional groups in the biochar,which greatly improves the adsorption performance of biochar.(2)The batch adsorption experiments were conducted to optimize the preparation conditions and adsorption conditions of these two biochars,and the adsorption kinetics and thermodynamics were investigated under the optimized conditions.The optimized pyrolysis are 200 and 300℃ for MBBC and SBC,respectively.The kinetic experimental datas are well described by pseudo-secondary kinetic models.It shows that the adsorptions of both biochars are mainly chemical adsorption.The Langmuir isotherm model can better simulate the thermodynamic experimental data of the two types of biochar,indicating that the adsorptions of both types of biochar are attributed to monolayer adsorption.Among them,the maximum adsorption capacity of MBBC200 reaches up to146.23 mg/g at 45℃,and the maximum adsorption capacity of SBC300 is up to 501.56 mg/g at 35℃,which is much higher than PBC300.(3)Basing on the adsorption results and the characterizations of biochar,the adsorption mechanism of biochar is proposed:The adsorption of MBBC200 can be mainly attributed to hydrogen bonding interaction,electrostatic interaction and ion exchange.The adsorption of SBC300 is mainly determined by hydrogen bond interaction,electrostatic interaction and cation exchange.(4)In the desorption experiment,both types of biochar can be regenerated in acidic solution.The adsorption capacity of MBBC200 after desorption can still be maintained above 80%,which proves that MBBC200 is an adsorption material with good regeneration performance.MBBC200 and SBC300 exhibit good adsorption capability,and can be potential adsorbents for treatment of MB-polluted water in practice.This will provide a novel method for efficient utilization of banana pseudostem.