| In recent years,with the rapid development of economy and the continuous progress of science and technology,a new type of pollutants PPCPs to meet the needs of human beings came into being.As one of them,antibiotics have been widely used because of their good inhibitory effect on pathogenic microorganisms.Tetracycline,as the most widely used typical antibiotic,has good water solubility,but it is difficult to degrade.A large number of tetracycline residues discharged into the water after abuse will aggravate the pollution of water environment,accumulate in the human body and endanger human health.Adsorption technology is widely used in the treatment of tetracycline wastewater because of its low cost,high efficiency and simple operation.Diatomite is a rich natural clay mineral with porous structure,high specific surface area,abundant silicon hydroxyl functional groups and many active sites on its surface,which endows it with good adsorption properties.In China,diatomite is mainly of medium and low grade with high impurity content.It needs to be modified properly to improve the adsorption performance of diatomite,which provides a new idea for the efficient utilization of medium and low grade diatomite.In this study,diatomite was used as raw material,and some impurities in the pore were removed by roasting and grinding pretreatment.Then diatomite was modified by biochemical fulvic acid,and the optimal preparation conditions were determined by orthogonal experiment:diatomite 8g,biochemical fulvic acid 0.5g,reaction temperature 40℃,reaction time 5h.Through The structure and morphology of purified diatomite and modified diatomite were analyzed by XRD,FT-IR,BET and SEM.The results showed that the porous structure of diatomite was not damaged by biochemical fulvic acid modification,and the specific surface area of modified diatomite was increased to 13.7744m~2/g.The prepared modified adsorbent was used in the adsorption experiment of removing tetracycline The results show that the temperature rise is beneficial to the adsorption reaction,and p H has a significant effect on the adsorption performance of BFA-DE.the adsorption capacity reaches the maximum at p H 5,and the reaction reaches equilibrium at 18 h.The adsorption behavior of tetracycline on modified diatomite conforms to the quasi second order kinetics and Freundlich isothermal model,and the maximum adsorption capacity can reach 66.67 mg/g.Liquid film diffusion is the main rate limiting step.The adsorption of tetracycline on biochemically fulvic acid modified diatomite is a multi-layer adsorption on heterogeneous surface,and the adsorption mechanism is mainly electrostatic adsorption.On the basis of pretreatment,diatomite was modified with sodium humate to prepare a new composite adsorption material,which was used to remove tetracycline.The optimum preparation conditions of adsorbent were determined by orthogonal experiment:diatomite 4g,sodium humate 0.5g,reaction temperature 55℃,reaction time 6h.XRD,FT-IR,BET and SEM were used to characterize the materials before and after modification.The results showed that alkali modification did not destroy the porous structure of diatomite,and the specific surface area of modified diatomite was11.4913m~2/g.The effects of p H,adsorbent dosage,initial concentration and temperature on the adsorption performance of the modified materials were discussed.The adsorption capacity was the largest when p H was 5,and the reaction reached equilibrium in 18 h.The adsorption capacity of diatomite could be increased by increasing temperature.The quasi second order kinetic model is more suitable to describe the adsorption process of tetracycline on modified diatomite,and the liquid membrane diffusion is the main rate limiting step.Freundlich and Redlich-Peterson isotherm models have high fitting degree,and the maximum adsorption capacity can reach 63.64mg/g.The adsorption of tetracycline on sodium humate modified diatomite is a heterogeneous multi-layer adsorption process,mainly chemical adsorption. |
