介质阻挡放电等离子体老化微塑料及对Zn(Ⅱ)吸附的影响

Dielectric barrier discharge plasma aging of microplastics and its effect on Zn(Ⅱ) adsorption

为了在实验中缩短微塑料的老化时间,更真实地模拟自然老化条件,采用介质阻挡放电(DBD)等离子体老化聚乙烯微塑料(PE-MP)和聚丙烯微塑料(PP-MP),同时研究了老化前后PE-MP和PP-MP对Zn(Ⅱ)的吸附过程和机理.随着放电时间延长和输入电压升高,微塑料表面出现微小裂纹或孔洞,形成含氧官能团.老化后PE-MP和PP-MP对Zn(Ⅱ)的吸附容量分别提高了22.7%和14.8%.老化前后微塑料对Zn(Ⅱ)的吸附均符合准二级动力学模型.颗粒内扩散模型表明,Zn(Ⅱ)在微塑料上的吸附过程可分为快速吸附,慢速吸附和吸附平衡3个阶段.同时,老化前后微塑料对Zn(Ⅱ)的吸附均符合Langmuir吸附等温线模型.热力学结果表明,微塑料对Zn(Ⅱ)的吸附是自发的吸热过程.Ca^(2+)、腐殖酸和低pH值不利于微塑料对Zn(Ⅱ)的吸附.

In order to shorten the aging time of microplastics and mimic the natural aging conditions in the experiment,dielectric barrier discharge(DBD)plasma was used in the aging experiments of polyethylene microplastics(PE-MP)and polypropylene microplastics(PP-MP).And the adsorption process and mechanism of Zn(Ⅱ)on PE-MP and PP-MP before and after aging was investigated.With the extension of discharge time and the elevation of input voltage,tiny cracks or holes appeared on the surface of microplastics and oxygen-containing functional groups were formed.The Zn(Ⅱ)adsorption capacity of aged PE-MP and PP-MP was increased by 22.7%and 14.8%,respectively.The adsorption of Zn(Ⅱ)on microplastics before and after aging conformed to the pseudo-second-order kinetic model.The intra-particle diffusion model showed that the adsorption process of Zn(Ⅱ)on microplastics could be involved three processes:rapid adsorption,slow adsorption and adsorption equilibrium.In addition,the adsorption of Zn(Ⅱ)on microplastics before and after aging conformed by Langmuir model.The thermodynamic results indicated that the adsorption of Zn(Ⅱ)on microplastics was a spontaneous endothermic process.Ca^(2+),humic acid and low pH were not conducive to the adsorption of Zn(Ⅱ)by microplastics.