| With the continuous development of society and economy,more and more estrogenpollutants in the environment are discharged into the water environment,posing a potential threat to human health and ecological safety.Therefore,it is necessary to provide technical methods for effective removal of estrogen in water bodies under the premise of being technically and economically feasiblefor preventing water pollution and protecting human health.The adsorption removal method has the characteristics of low cost,simple process and hightreatment efficiency,and has a high application prospect for removing environmental estrogen pollutants in water.The biochar prepared from the agricultural and forestry wastes is a multifunctional carbonaceous material with great application potential.Because of its characteristics of green,harmless,low cost and large porosity,application of biochar for removal of water pollutants has become a hot spot in the research field of environment.In this paper,the adsorption and removal properties of biochar materials for representative environmental estrogen estradiol were studied,and the adsorption mechanism and main adsorption mechanism of estradiol were investigated.The adsorption performance of biochar is usually controlled by its own surface and structural properties.Therefore,this paper focuses on the effect of activation by potassium carbonate,graphene oxide and ultraviolet irradiation on the physical and chemical characteristics of biochar and the adsorption of estradiol pollutants.The research results can provide theoretical basis and practical guidance for the removal of estradiol from water using biochar materials.The specific research work and results of this paper can be summarized asfollows:In the first part,the adsorption performance and mechanism of estradiol from water using biochar were studied,and the differences in adsorption of estradiolbetween biochar prepared at different temperatures(400°C,500°C,600°C)were compared.The results showed that different pyrolysis temperatures had a great influence on the physical and chemical properties of biochar.The biochar produced by pyrolysis at600°C hada large specific surface area,a large number of micropores and a relatively rich functional group.The improvement of the physical and chemical propertiesofbiocharwasbeneficialtoincreaseitsadsorptioneffectonestradiol.Theresultsof adsorption experiments showed that the adsorption capacity of estradiol by biochar pyrolyzed at 600°C can increase from 20.3 mg/g to 23.9 mg/g compared with biochar pyrolyzed at 400°C.The increase in pyrolysis temperature c ansignificantly increase the performance of estradiol adsorption.At the same time,the pseudo-second-order kinetic model can better fit the adsorption kinetic data.The Freundlich model was better fitted to the adsorption isotherm data,indicating that t he adsorption occured on a non-uniform surface that was adsorbed by multiple layers.The initial estradiol concentration,initial pH,temperature,ionic strength and background electrolyte of the solution had a great influence on the adsorption of estradiol on biochar.?-?interaction and electrostatic interaction were the main mechanisms of estradiol adsorption bybiochar.In the second part,four kinds of activated biochar materials were obtained by adjusting the proportions of biomass and potassium carbonate(2:1,1:1,1:2 and 1:4).At different proportions,the surface properties of activated biochar materials are quite different.Biochar activated by potassium carbonate shows high aromaticity.With the increase of potassium carbonate,the more porosity is also incseased.At the same time,the addition of potassium carbonate inhibited the formation of tar during high-temperature pyrolysis,thus increasing the yield of biochar.With the increase of the proportion of potassium carbonate added,the adsorption capacity of the modified biochar materials on estradiol pollutants was also significantly increased.In the 4-fold ratio of potassium carbonate activated biochar materials,the adsorption effect on estradiol was the best,with the maximum adsorption capacity reaching 60.2 mg/g.The experimental results show that the adsorption reaction process of activated biochar can reach equilibrium in a relatively short time.The reaction process is a spontaneous exothermic process,and the adsorption capacity is also high under the condition of high pH value.The smaller ionic strength has a greater impact on the adsorption process.In the third part,a new graphene oxide supported activated magnetic biochar(GO-AMBC)was prepared by grafting graphene oxide(GO)and magnetite nanoparticles onto the surface of activated biochar,and used to remove 17?-estradiol(E2)from aqueous solution.GO-AMBC was characterized using SEM,TEM,FTIR,VSM,XRD,XPS,BET surface area and zeta potential measurements.Characterization results indicated that GO-AMBC had a larger surface area and more oxygen-containing functional groups than unmodified biochar.When theinitialconcentrationof E2 was 6mg/L,the adsorption capacity of GO-AMBC(46.22 mg/g)was more than twice higher than that of the original biochar(23.09 mg/g)at 298 K and pH=7.0.The adsorption results showed that the adsorption experimental data of E2 fitted well with thepseudo-second-order kinetics and the Freundlich isotherm model.Thermodynamic analysis indicated that the adsorption process was spontaneous and exothermic.The E2 removal by GO-AMBC was significantly affected by environmental conditions such as solution pH,ionic strength and organic acids.The organic acid had a significant inhibitory effect on the E2 removal process,and the inhibition effect of oxalate was stronger than the benzoate.The adsorption mechanism of E2 on GO-AMBC was mainly hydrogen bond,static electricity and?-?interaction.The experimental results of this study and comparative analysis with other adsorbents showed that GO-AMBC was an economical,efficient and recyclable adsorbent with great potential for removing E2 from pollutedwater.The fourth part adopts the physical modification method(ultraviolet irradiation),atlow concentration and high concentration.It was found that the adsorption effect of UV-irradiated biochar materials on estradiol was higher than that of original biochar materials,which fitted well with the pseudo-first-order model.The alkaline and strong ion concentration environment was not conducive to the adsorption of estradiol by UV-irradiatedbiochar.using the chaff and straw as raw materials to produce ultraviolet-irradiated biochar.Compared with the original biochar,the oxygen content of the ultraviolet-irradiated biochar increased,the oxygen-to-carbon ratio increased,and the hydrocarbon-to-hydrogen ratio did not change significantly.The specific surface areas of the ultraviolet-irradiated straw and the chaff biochar increased from 39.654m~2/gto208.50 m~2/gand 2.574 to 210.50 m~2/g,respectively.It indicated that the ultraviolet irradiation can oxidize the surface of the biochar,the oxygen-containing functional groups increased,and the specific surface area increased obviously,but the aromatic structure did not change.The adsorption kinetics of biochar materials were compared... |
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