水土环境中微塑料对磷的吸附行为

The adsorption behavior of phosphorus in microplastics in water and soil

为了探究微塑料在水体和土壤环境中对磷的吸附特性及不同因素对磷等生源物质在微塑料及土壤中赋存的影响,采用聚丙烯(PP)、聚苯乙烯(PS)这两种常见的微塑料进行吸附试验。结果表明:疏松多孔的PP拥有比PS更强的吸附性能和更大的吸附容量;两种微塑料的Zeta电位随pH的增加而降低,并且PS和PP的零电荷点(pHPZC)分别在pH为5.92和6.45时达到;PP、PS对磷的吸附以单层饱和吸附为主,吸附方式主要为物理吸附,并且吸附过程为放热和熵减的自发反应;微塑料对磷的单位吸附量随pH的增大呈现出先降低后升高的“U型”趋势,且温度的升高不利于PP、PS这两种微塑料对磷的吸附;随土壤中微塑料质量添加比的增加,土壤-微塑料体系对磷的吸附量增大幅度有限。研究表明,不同类型的微塑料其吸附能力存在差异,且环境因素能够对其吸附磷造成明显影响,微塑料的持续性积累对土壤-微塑料体系吸附磷的促进作用十分有限,并且这个促进作用也不会因微塑料的种类不同而产生较大差异。

In order to explore the adsorption characteristics of phosphorus(P)in microplastics in water and soil,and the influence of different factors on the adsorption of P in microplastics and soil,two types of common microplastics[polypropylene(PP)and polystyrene(PS)]were used to conduct adsorption experiments.The results showed that the loose and porous PP possessed a stronger adsorption performance and larger adsorption capacity than PS.The Zeta potential of both microplastics decreased with increasing pH,and the point of zero charge of PS and PP was reached at a pH of 5.92 and 6.45,respectively.The adsorption of P on PP and PS was mainly single-layer saturated adsorption,the adsorption method was mainly by physical adsorption,and the adsorption process was a spontaneous reaction of exothermic and entropy reduction.The unit adsorption of P by microplastics showed a"U-shaped"trend that decreased first and then increased with the increase in pH,while increasing temperature was not conducive to the adsorption of P on PP and PS.With the increase of the mass addition ratio of microplastics in soil,the increase of phosphorus adsorption in soil-microplastics system was limited.In conclusion,the experiments showed that different types of microplastics had different adsorption capacities,and environmental factors considerably affected their adsorption of phosphorus.The continuous accumulation of microplastics had a limited promotion effect on P adsorption in soil,and the promotion effect did not vary greatly with the different types of microplastics.The results lay a foundation for further research on the adsorption behavior of microplastics in soil.