Structural Characteristics Of Biochar In Wetland Aquatic Plants And Its Adsorption To Methylene Blue In Water Plants And Its Adsorption To Methylene Blue In Water

The riparian zone has the function of purifying water quality,while the riparian zone width in cities and its suburbs is usually not wide enough,so its function of purifying water quality is limited.With the development of printing and dyeing industry,the discharge of printing and dyeing pollutants has been increased,and the requirement for water purification is urgent.Methylene blue(MB)is a typical and common organic pollutant.Reeds,cattails and other wet plants flourish,which affects flood discharge,and the annual accumulation of waste causes environmental problems.In this study,reeds and cattails,which are common plants in rivers,were used to prepare biomass charcoal to treat waste and provide materials for river ecological restoration.Using reed straw and cattail stalk as raw materials,biochar was prepared by slow pyrolysis without oxygen at five different pyrolysis temperatures of 350?,400?,500?,600?and 700?.In the experiment,the elemental composition,microstructure,surface morphology and surface functional groups of cattail straw powder and reed straw powder,cattail biochar and reed biochar materials were characterized.In addition,ten kinds of biochar materials were used to carry out adsorption experiments,and the adsorption performance of methylene blue was compared and analyzed.The results show that:(1)The carbon surface of straw biochar is rich in oxygen-containing functional groups,such as carbonyl group,ester group,hydroxyl group and carboxyl group.With the increase of temperature,the types and amounts of functional groups of cattail straw biochar and reed straw biochar decreased gradually.When the temperature rises to a certain level,the functional groups on the surface of biochar are destroyed to some extent.(2)With the increase of pyrolysis temperature,the carbon yield of biochar decreased,the electric neutralization increased,the specific surface area increased(the carbon yield of CR350 was 40.397%and that of CR700 was 28.793%;the yield of R350 was 48.893%and that of R700 29.912%),the number of surface pores increased(the specific surface area of CR_I is 1.930 m~2/g,and that of CR700 is 4.481 m~2/g;the specific surface area of R_I is 3.002 m~2/g,and that of R700 is 21.990 m~2/g).The number of pores on the surface increased,and the degree of folding became obvious.The surface structure of biochar changed,and the physical and chemical properties also changed correspondingly,which improved the adsorption capacity of biochar.(3)The adsorption kinetics equations of biochar from reed straw and cattail straw are consistent with the second-order kinetic models.The adsorption rate increased sharply within 60min,and the adsorption amount tended to moderate after 60min,and reached the adsorption equilibrium at 120min.Both kinds of straw biochar had better effect on the removal of methylene blue from rivers,but the adsorption rate of methylene blue by reed biochar was faster and stronger.(4)Considering the amount of methylene blue removal per unit of biomass charcoal and the amount of methylene blue removal per unit of biochar corresponding to the unit of raw material,and considering the carbon yield and preparation cost,it is concluded that the optimum preparation temperature of the two kinds of straw biochar is 400?.The adsorption capacity(q_e)of methylene blue by CR400 is 14.56mg/g,which is the excellent material for adsorption of organic pollution.