The Adsorption Efficiency And Mechanism Of Phosphate And Tetracyline In Water By Modified Straw Biochar

In recent years,with the development of agricultural production level,the treatment and disposal of crop waste has become the focus of attention in the environmental field.The waste biomass is prepared to biochar with good physicochemical properties,which can be used as a new type of adsorbent to adsorb and remove pollutants.Livestock and poultry wastewater contain a large number of inorganic pollutants and antibiotics.Taking phosphate and tetracycline as examples,they will cause serious harm to the natural water environment.Using biochar as an adsorbent to adsorb and remove phosphate and tetracycline in water,which not only realizes the resource utilization of biomass but also provides an environmentally friendly,economical and effective strategy for the treatment and disposal of livestock and poultry wastewater.In this paper,corn stalks are used as raw materials to prepare biochar at the high temperature,calcium chloride is employed to modify the corn stalks and further the calcium-loaded modified biochar was obtained via pyrolysis.The influence factors on the physicochemical properties of biochar were explored during the modification process,and the optimal modification condition was achieved.The modified biochar was used as an adsorbent to adsorb phosphate and tetracycline,the influence factors for the adsorption efficiency was analyzed,the optimal adsorption conditions were determined,and the adsorption mechanism was proposed.The physicochemical properties of the modified biochar were characterized,and the effect of modification on the changes of the crystal structure,surface morphology,surface element component and graphitization degree of the as-prepared biochar was studied.The adsorption conditions including the effects of temperature,solution concentration,p H and other factors on the adsorption of pollutants were discussed in the adsorption process.After the modification,the calcium content in the biochar increased nearly 2 times,the specific surface area increased nearly 8 times,and the content of oxygen-containing functional groups such as carboxyl and carbonyl increased.When the adsorption process finished,the removal efficiency of phosphate reached to 91.10%,the adsorption capacity is 27.33 mg/g.And the removal efficiency of tetracycline is 71.35%,the adsorption capacity is 14.27 mg/g.The adsorption model fitting results showed that the adsorption process of phosphate and tetracycline by the modified biochar conforms to the quasi-second-order kinetics and Langmuir adsorption isotherm.Through the characterization analysis of the biochar before and after adsorption,it was concluded that the adsorption of phosphate mainly depends on the OH~-in the solution,and the precipitation of calcium and phosphorus from the calcium oxide on the surface of the biochar and phosphate in the solution.The main mechanism for the adsorption of tetracycline is theπ-πinteraction between the modified biochar and tetracycline,and the interaction of electrostatic interaction,hydrogen bond interaction and oxygen-containing functional group interaction.Moreover,with the presence of phosphate and tetracycline at the same time,the modified biochar shows a good adsorption effect on tetracycline and phosphate.It demonstrated that the prepared biochar by calcium chloride modification was a favourable adsorbent to be used in the wastewater treatment.Modified biochar was prepared via the calcium chloride impregnation using the waste corn stalks as the raw materials,the modified biochar showed an effective result on the removal of phosphate and tetracycline in livestock and poultry wastewater.This study provides a basis for the resource utilization of agricultural waste and the effective treatment and disposal of livestock and poultry wastewater in the future.