| Printing and dyeing wastewater is one of the difficulties in the treatment of industrial wastewater.With the development of the printing and dyeing industry,printing and dyeing wastewater not only contains dye molecules,but the use of surfactants and other auxiliaries in the printing and dyeing process has led to the production of phosphorus-containing printing and dyeing wastewater.Excessive phosphorus would lead to eutrophication of the water body,and most of the dyes have three effects(carcinogenic,teratogenic,and mutagenic).Therefore,it is necessary to treat phosphorus-containing printing and dyeing wastewater before it is discharged into the water body.Biochar has the characteristics of high specific surface area,porous structure and abundant surface functional groups,and it has good adsorption capacity for various pollutants in wastewater.In this paper,pomelo peel,badan shell and Magnolia Grandiflora Linn leaves were used as biomass raw materials,methylene blue(MB)and phosphorus were used as the research objects,and a series of methods such as FTIR,BET,and SEM were used for characterization.Analyze its adsorption mechanism through adsorption isotherms,adsorption kinetics and other models.The influence of factors such as initial concentration,pH value,and pyrolysis temperature on the removal of methylene blue in the biochar solution was tested.On this basis,the modified biochar was impregnated with magnesium chloride and the removal of phosphorus in water was studied,and a high-efficiency adsorbent would be obtained for the treatment of phosphorus-containing printing and dyeing wastewater.The main findings are as follows:(1)Fourier transform infrared analysis showed that the functional groups carboxyl and hydroxyl were the main reactive groups involved in the adsorption of MB.As the initial concentration of the solution increased,the removal rate of MB decreased.Alkaline conditions were more conducive to the adsorption of methylene blue by the badam shell biochar(BBC),Magnolia grandiflora Linn leaves biochar(MBC),and the pomelo peel biochar(PBC).The adsorption of methylene blue on PBC and MBC was an endothermic process,and the adsorption on BBC was an exothermic process.The adsorption process of MB on BBC,PBC and MBC was more in line with the quasi-second-order kinetic model and Langmuir isotherm adsorption model.MBC had a better adsorption effect on MB.(2)As the pyrolysis temperature increased,the types of surface functional groups decreased,and the aromaticity and polarity increased.With the increase of pyrolysis temperature,the adsorption capacity of Magnolia leaf biochar for MB first decreased and then increased.Magnolia grandiflora Linn leaves biochar with a pyrolysis temperature of 450℃ had a better adsorption effect on MB,and its maximum adsorption capacity was 114.15 mg/g.(3)The adsorption of phosphorus by magnesium-modified Magnolia grandiflora Linn leaves biochar(Mg-MBC)conformed to the Freundlich isotherm adsorption model and the quasi-second-order kinetic model.The characterization results showed that the modification made the specific surface area of Magnolia Biochar significantly increased,and MgO was formed on the surface of Mg-MBC,which promoted the adsorption of phosphorus.The theoretical maximum adsorption capacity of the modified biochar for phosphorus could reach 58.75 mg/g.The modified biochar could adsorb and remove phosphorus well,and its theoretical maximum adsorption capacity could reach 58.75 mg/g.The biochar also had a good adsorption effect when simultaneously removing methylene blue and phosphorus,and had practical application prospects. |
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