氧化石墨烯纳米颗粒对抗生素类污染物吸附特征及影响因素

Factors controlling adsorption of tetracycline antibiotics onto graphene oxide nanoparticles

本文通过吸附动力学和吸附等温线探究了氧化石墨烯(GO)纳米颗粒对3种典型的四环素类抗生素(即四环素(TC)、土霉素(OTC)和金霉素(CTC))吸附特征.结果表明,伪二级动力学模型可以很好的拟合吸附动力学的结果,吸附速率可能受化学吸附控制.吸附等温线的结果显示GO对3种抗生素均有较高的吸附能力,且吸附能力依次为:CTC>OTC>TC.这主要是由于四环素类抗生素可以通过π-π作用、阳离子-π键、疏水作用以及静电作用等机制与GO产生结合.此外,四环素类抗生素在GO上的吸附行为与背景溶液的水化学条件(如pH、离子强度和二价金属离子)密切相关.总体来讲,由于静电斥力的增强,抗生素在GO上的吸附量随着背景溶液pH值的升高或离子强度(NaCl)的增加而降低,这主要是由于静电引力和吸附点位的减少所致;二价阳离子(Cu^(2+))可以通过表面桥连作用,显著促进抗生素在GO上的吸附.本研究结果清楚地表明抗生素本身的化学性质和背景溶液的水化学条件在GO去除抗生素的过程起着重要作用.

In this study,adsorption kinetics and adsorption isotherms were employed to investigate the adsorption of tetracycline antibiotics(tetracycline(TC),oxytetracycline(OTC),and chlortetracycline(CTC))onto graphene oxide(GO)nanoparticles.The results of adsorption kinetics demonstrated that the data were fitted well by the pseudo-second-order kinetic models,which indicated that the adsorption rate was probably controlled by chemisorption.Meanwhile,the results obtained by the adsorption isotherm experiments showed that GO exhibited high adsorption capacity for all the three tetracycline antibiotics,and the adsorption capacity followed the order of CTC>OTC>TC.The main mechanisms involved in the adsorption behaviors wereπ–πinteraction,cation–πbonding,hydrophobic effect,and electrostatic interaction.Furthermore,the adsorption characteristics were related to solution chemistry conditions such as pH,ionic strength and divalent metal ions. The adsorption capacities of tetracycline on GO decreased with the increasing pH or ionic strength (i.e., NaCl concentration), which was stemmed from the reduction in electrostatic attraction and the increased electrostatic repulsion between tetracycline antibiotics and GO. Additionally, the presence of divalent cations (i.e., Cu^(2+)) could significantly promote the adsorption of tetracycline antibiotics due to the surface-bridging mechanism. Our observations indicate that properties of tetracycline antibiotics and solution chemistries play important roles in the removal of tetracycline antibiotics from aqueous solutions by GO nanoparticles.