二氧化锰对氟喹诺酮类抗生素在多孔介质中吸附和迁移的影响

Effects of manganese oxide on adsorption and transport of fluoroquinolone antibiotic in porous media

土壤中的金属氧化物如二氧化锰等能够影响污染物(如氟喹诺酮类抗生素)的吸附、迁移和降解等环境行为。本实验以环丙沙星(CIP,一种广泛使用的氟喹诺酮抗生素)为目标污染物,用二氧化锰覆盖石英砂(MOCS)模拟土壤中金属氧化物,采用等温吸附实验和土柱迁移实验探究金属氧化物对CIP在多孔介质中吸附和迁移的影响规律及机制。其中,等温吸附实验的主要目的是使用Freundlich模型定量分析二氧化锰对CIP的吸附作用,土柱迁移实验的主要目的是探究不同含量的二氧化锰(0、55和109μg Mn·g-1sand)在多孔介质中对CIP迁移的影响。结果表明,较大比表面积的MOCS对CIP吸附的KF值是石英砂的1.63倍,导致随着锰含量从0增加至109μg Mn·g-1sand,最大出流比C/C0从0.96降低至0.72,说明随着二氧化锰含量的增加,其对CIP迁移产生的抑制作用逐渐增强。该结果与一维对流扩散模型拟合结果一致,109μg Mn·g-1sand土柱的katt1、katt2和Smax1值是55μg Mn·g-1sand土柱相应值的2.04~2.33倍,是0μg Mn·g-1sand土柱相应值的4.21~12.69倍。使用低表面张力溶液(20%乙醇背景溶液)淋洗土柱后,CIP总的质量回收率达到95%以上,表明本实验中二氧化锰对CIP的吸附是可逆的。由CIP迁移实验结果可知,二氧化锰对有机阳离子有较强的吸附作用,使机阳离子在土柱中的迁移受到抑制。

Metal oxides(such as manganese oxides)have received great concerns,due to its reactive surfaces which could affect the fate of fluoroquinolone antibiotics(FQs)in soil.In this study,batch and column experiments were conducted to investigate the effects of manganese oxides coated sand(MOCS,mimicking soil metal oxides)on transport of target compound ciprofloxacin(CIP,a widely prescribed fluoroquinolone).Batch experiments were carried out using Freundlich model to quantify the adsorption of CIP on manganese oxides.Column experiments were conducted at three levels of manganese oxides in sand(0,55 and 109μg Mn·g-1 sand)to explore the effects of manganese oxides on CIP transport.Results showed that the KFvalues were1.63-fold higher on MOCS than on sand,indicating that CIP had higher affinity in adsorption MOCS,due to the microporous structure of manganese oxides.It resulted in manganese oxides reducing the transport of CIP,as the content of manganese oxides increased from 0 to 109μg Mn·g-1 sand and C/C0 decreased from 0.96 to 0.72.These were consistent with the two-site kinetic estimated parameters of katt1 values,katt2 values and Smax1 values,which with 109μg Mn·g-1 sand column were 2.04-2.33 and 4.21-12.69 times higher than the corresponding values with 55μg Mn·g-1 sand column and 0μg Mn·g-1 sand column,respectively.After eluting with a low surface tension solution(20%v/v ethanol in background solution),the total recovery rates reached up to 95%,illustrating that the adsorption of CIP on manganese oxides was reversible.Based on the transport behavior of CIP,our results showed that manganese oxides had higher affinity in adsorption cationic microorganic pollutants,which reduced the transport of cationic microorganic pollutants.