水铁矿-稻杆生物炭复合材料的制备及其对土霉素吸附、稳定性研究

Preparation,stability and oxytetracycline adsorption of a ferrihydrite-rice straw biochar composite

以700℃稻杆裂解制得的生物炭为原料,通过碱液浸泡、加Fe^(3+)沉淀,制备了水铁矿-稻杆生物炭复合材料(Fh-BC),研究了Fh-BC对典型抗生素污染物土霉素的吸附性能,及其在Fe^(2+)共存时的稳定性。结果表明,pH=4.5、土霉素平衡质量浓度为27 mg/L时Fh-BC对土霉素的吸附容量高达6171 mg/g,远超已报道的系列活性炭吸附剂。根据表征分析,Fh-BC表面具有明显的Fe—O—Si红外吸收峰,生物炭的晶体衍射峰减弱,且比表面积比水铁矿及稻杆生物炭大幅增加,意味着Fh-BC在碱浸泡和Fe^(3+)沉淀处理中,生物炭的硅组分可能通过形成Fe—O—Si增强2线水铁矿的分散、降低生物炭结晶度增加比表面积,从而产生了土霉素的高吸附容量。与水铁矿不同,Fh-BC能够在Fe^(2+)共存时稳定存在,可在有Fe^(2+)的环境中持续发挥吸附作用以缓解土霉素污染。

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 Fe^(3+)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 Fe^(2+)were examined.The results showed that the adsorption capacity of Fh-BC for oxytetracycline approached 6171 mg/g(pH=4.5,C e=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 Fe^(3+)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 Fe^(2+)coexisted,suggesting that the Fh-BC could act as an adsorbent persistently in environments containing Fe^(2+)to alleviate oxytetracycline pollution.