Adsorption And Fixation Of Sulfamethoxazole And Copper In Water And Soil By Biochar

With the development of medicine,animal husbandry and aquaculture,the problem of antibiotic residues in the environment is becoming more and more prominent.At the same time,copper is the main heavy metal pollutant in the environment at present.At present,many studies have shown that biochar can be used as an excellent adsorbent,and it has a wide application prospect in the remediation of antibiotics and heavy metal contamination.In this study,sulfamethoxazole(SMX)and Cu(II),which have higher detection rates in the environment,were selected as target pollutants,and corn stover was used as biomass raw material to obtain biochar by pyrolysis and carbonization at 300 ℃ and 600 ℃ respectively.(labeled as BC300 and BC600,respectively)and its by HCl pickling,pickling biochar was(HBC300 and HBC600).Biochar was characterized by elemental analysis,scanning electron microscopy(SEM)and infrared spectroscopy.The adsorption mechanism of biochar to SMX and Cu(Ⅱ)in water was studied by batch equilibrium method.At the same time,soil column leaching method was used to study the effect of biochar on the migration of SMX and composite pollutants,and to reveal the resistance and control mechanism of pollutant migration in soil.It provides reference value and basis for removal of heavy metals and antibiotics in water environment and migration in soil.The main findings are as follows:(1)With the increase of pyrolysis temperature,the yield of biochar decreased,the ash content increased,the content of C increased,the contents of O,H and N decreased,the specific surface area increased,the polarity decreased,and the aromaticity increased.After pickling,the C content of biochar increased,the specific surface area and t-pLot micropore area increased,the polarity decreased,and the aromaticity did not change significantly.The results of scanning electron microscopy(SEM)show that BC300 is mainly irregular and has no obvious pore structure,while BC600 is strip-like,and it can be observed that obvious pore structure can be observed.After HCl treatment,the pore structure of biochar was exposed,and the surface structure was more clear.Through quantitative analysis of infrared spectrum,it can be seen that the positions of characteristic absorption peaks of BC300 and BC600 are approximately the same,but the peaks and peak widths are different,and both have functional groups such as-OH,-COOH and R-COO-R’.(2)The effects of adsorption time,concentration of SMX,temperature,initial solution pH,ash content and ionic strength on the adsorption of SMX by HBC300 and HBC600 were studied.The results showed that the amount of SMX adsorbed by HBC300 and HBC600 increased rapidly with time and then remained at a certain level.The equilibrium adsorption of SMX increased sharply with the increase of SMX equilibrium concentration and gradually became flat at 60 mg/ L.The fitting effect of Freundlich equation was better.The adsorption effect of two adsorbents on SMX is absorption reaction and the elevated temperature is beneficial to the reaction.The adsorption amount of SMX increased with the increase of pH,which reached the maximum when pH is 5,and then decreased with the increase of pH.The adsorption of SMX to both adsorbents increased significantly after ash removal.The ionic strength had no significant effect on the adsorption of SMX by two kinds of bio-carbon.(3)The effects of adsorption time,Cu(II)concentration,temperature,initial solution pH,ash and ionic strength on the adsorption of Cu(II)by BC300 and BC600 were investigated.The results show that the adsorption capacity of Cu(II)on BC300 and BC600 increases rapidly with time,and the adsorption reaches equilibrium at 16 h,which accords with the quasi-second-order kinetic equation.The equilibrium adsorption capacity of Cu(II)on the two adsorbents increases rapidly with the increase of equilibrium concentration and then tends to balance.The LangmuirFreundlich equation fits better.The adsorption of Cu(II)by the two adsorbents is an endothermic reaction,and raising the temperature is beneficial to the reaction.The adsorption amount of Cu(II)increases as the pH increases.The adsorption capacity of Cu(II)by the two adsorbents was significantly reduced after HCl treatment.(4)Compared with the single system,the adsorption capacity of HBC300 and HBC600 to SMX and Cu(Ⅱ)in the mixed system was increased to a certain extent,and the adsorption equilibrium time was shortened,which was in accordance with the pseudo-second-order kinetic model.That is,the chemical reaction in the mixed condition is the rate control step.In the cases of Cu(Ⅱ),adsorption of SMX HBC300 significantly increased,while HBC600 adsorption had no significant effect of SMX.The existence of SMX,enhanced the adsorption of HBC300 and HBC600 on Cu(Ⅱ).(5)The breakthrough curves of SMX migration in soil columns are asymmetrical,and the trailing phenomenon is obvious.Increasing the amount of biomass carbon,decreasing the pH value of SMX solution and decreasing the ionic strength of the solution,the longer the outflow time of SMX and the lower the peak value,indicating that the resistance of biochar and soil to SMX is enhanced and the migration of SMX can be effectively reduced.