Study On The Adsorption Of Antimony By Microplastics And The Forms Of Antimony In Soil And Its Absorption By Plant

Antimony is a global pollutant and one of the most concerned toxic metal elements in the world.Due to the impact of human activities,a large number of antimony containing pollutants are discharged into the environment,resulting in a gradual increase in the content of antimony in the environment,endangering the ecosystem and human health.Plastic products are widely used in human daily life,causing a large amount of micro plastic to enter the environment and form new pollution.Microplastics often combine with other organic and inorganic pollutants in the environment,which may affect the transport of these pollutants in the environment.However,at present,there are few systematic studies on the adsorption mechanism of heavy metal antimony by microplastics,and most of the studies on the ecotoxicity of microplastics are aimed at aquatic organisms.This paper first conducts adsorption experiments on five types of microplastics（polypropylene PP,polyethylene PE,polystyrene PS,polyethylene terephthalate PET,and polyvinyl chloride PVC）for Sb（III）and Sb（V）in simulated wastewater,exploring the adsorption mechanism,adsorption efficiency,influencing factors,and changes in antimony valence before and after adsorption of microplastics for antimony in water.Secondly,the soil in the antimony polluted area was taken as the test sample,and the above five kinds of microplastics were injected into the soil sample.After curing for a period of time,the changes of soil physical and chemical properties and soil Sb form were analyzed to explore the effects of microplastics on the bioavailability of heavy metals in soil.Finally,through pot experiment,the soil in antimony polluted area was taken as the test sample,the above five kinds of microplastics were injected into the soil sample,and the water spinach seedlings cultivated in the laboratory were selected for cultivation,to explore the effect of microplastics on the Sb content of water spinach.The experimental results are as follows:（1）The adsorption of antimony on microplastics reached equilibrium within 24 hours.The Langmuir isotherm model well describes the adsorption of Sb（III）and Sb（V）,which indicates that Sb forms a single molecular layer adsorption on five types of microplastics,i.e.,the adsorbates Sb（III）and Sb（V）are uniformly distributed on the surface of the microplastics.（2）The thermodynamic parameter△H of the adsorption of Sb（III）by the five types of microplastics is greater than 0,indicating that the adsorption reaction of Sb（III）by the five types of microplastics is endothermic.The adsorption thermodynamic parameter△H of PET and PVC for Sb（V）is greater than 0,indicating that the adsorption reaction of PET and PVC for Sb（V）is an endothermic reaction.（3）F^-significantly promoted the adsorption of Sb（III）by microplastics,while HCO₃^-slightly inhibited the adsorption of Sb（III）.The adsorption of Sb（III）by microplastics is less affected by the cationic strength,and has relatively obvious stability.F^-significantly promotes the adsorption of Sb（V）by microplastics,which is less affected by the strength of other anions,and exhibits relatively significant adsorption stability.The adsorption of Sb（V）by microplastics is less affected by the cationic strength,and has relatively obvious stability.（4）The introduction of five types of microplastics into a solution containing Sb（III）will convert some Sb（III）into Sb（V）.Five Microplastics entering the solution containing Sb（V）will not change the valence state of Sb（V）in water.（5）In the blank control group and after adding microplastics,the content of heavy metal Sb in soil was ranked as residual>reducible>oxidisable>water-soluble>mild acido-soluble.Compared with the control group,the soil Sb availability coefficient tended to be balanced after microplastics were added.Soil Sb potential availability coefficient decreased slightly with the increase of microplastics dosage.The coefficient of Sb unavailability in soil increased slightly with the increase of microplastics dosage.