Preparation,stability and oxytetracycline adsorption of a ferrihydrite-rice straw biochar composite
In this study,a ferrihydrite-rice straw biochar composite(Fh-BC)was prepared by producing biochar via pyrolysis of rice straw at 700 ℃,soaking the biochar in alkaline solution to promote silicon dissolution,and adding Fe3+to load ferrihydrite onto the biochar.Subsequently,the adsorption performance of Fh-BC for typical antibiotic pollutant oxytetracycline and the stability of Fh-BC in the presence of Fe2+were examined.The results showed that the adsorption capacity of Fh-BC for oxytetracycline approached 6 171 mg/g(pH=4.5,Ce=27 mg/L),far exceeding that of other reported biochar adsorbents.Significant infrared absorption peak from Fe—O—Si vibration,weakened biochar crystal diffraction peak,and high specific surface area exceeding those of ferrihydrite and biochar were observed on Fh-BC,suggesting two probable roles of biochar in generating the high adsorption capacity of oxytetracycline in the process of alkaline soaking and Fe3+loading.Firstly,the silicon component of biochar might promote the dispersion and surface area of 2-line ferrihydrite colloids through the formation of Fe—O—Si;secondly,the carbon component might increase the surface area by reducing crystal arrangement of biochar.Unlike the ferrihydrite,Fh-BC could stably exist when Fe2+coexisted,suggesting that the Fh-BC could act as an adsorbent persistently in environments containing Fe2+to alleviate oxytetracycline pollution.
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