Leaching And Ecotoxicity Of Antimony In Flame Retardant Plastic Particles

With the rapid development of the polymer materials industry,plastics are widely used in people’s daily life,however,it often cause fires due to polymer materials flammability.If the burnt plastic is improperly processed,more microplastics will be produced.Microplastics can easily carry pollutants into the environmental medium,posing potential damage to the ecosystem.Antimony trioxide（Sb₂O₃）is usually added to flame retardant plastics to improve its flame retardancy.Sb has been recognized as a global pollutant with long-range migration,and its toxicity and environmental effects have attracted international attention.In order to further understand the environmental behavior and toxicity of microplastics containing heavy metals Sb to scientifically evaluate its ecological environment risks,In this paper,the tube furnace experiment and the universal material testing machine experiment were carried out to simulate the fire scene and daily life scene,and the effects of different temperature,different atmosphere and different external force conditions on the flame retardant microplastics of flame retardant PP plastics were studied.The particle size analysis of the flame retardant microplastics was carried out,and the flame retardant microplastics were characterized by Raman spectroscopy and infrared spectroscopy.The flame retardant microplastics are also exposed to different environmental media.The flame retardant microplastics were placed in different water bodies for heavy metal Sb leaching experiments to investigate the leaching law of Sb in different water bodies,and the effects of leaching solution on the growth stress of Microcystis aeruginosa were also studied.Fluorescence quenching titration of soil soluble organic matter was carried out to study the complexation mechanism between Sb and dissolved organic matter.The flame retardant microplastics were mixed with soil and used for the cultivation of maize to explore the pollution characteristics of heavy metal Sb in maize tissue and the stress effect of Sb on maize.The results show:（1）In the temperature range of 150⁷00°C,when the temperature reaches 250°C,microplastics will be formed.the increase of combustion temperature and the increase of external force will promote the formation of more flame retardant microplastics in the flame retardant PP plastic masterbatch.The combustion atmosphere has little effect on the formation of microplastics;The particle size of microplastics produced by flame retardant PP plastic is in the range of 200³500μm,and the number of particle size segments of 20¹00μm is the largest,and the amount of microplastics decreases with the increase of particle size;The combustion temperature will affect the structure of the flame retardant microplastic.With the increase of temperature,the damage of the flame retardant PP plastic structure is more serious,and the flame retardant Sb₂O₃ is also less and less with the increase of temperature.Sb volatilizes most at 700°C,but remains.The combustion atmosphere has no obvious effect on the structure of the flame retardant microplastics;the combustion temperature and combustion atmosphere will affect the enrichment of Sb in the flame retardant microplastics.With the increase of temperature,the enrichment coefficient of Sb in flame retardant PP plastics is getting lower and lower.Under high temperature conditions,the N₂ atmosphere is more conducive to the enrichment of Sb in the flame retardant microplastic.（2）Sb leaching occurred in all the flame retardant microplastics in river water,seawater and humic acid solution.The concentration of Sb leaching in the river water after burning at 450℃and N₂ conditions exceeded the standard.The pretreatment combustion temperature of the flame retardant microplastics and its own Sb content will affect the amount of Sb leaching in the water.In the temperature range of 0⁴50°C,the flame retardant microplastics in the water body will increase with the increase of the combustion treatment temperature.The increase of humic acid concentration promoted the coordination ability with Sb,which led to the increase of Sb leaching amount in solution;The growth condition and light intensity of Microcystis aeruginosa were determined by OD₆₈₀ and F_v/F_m,respectively.As the concentration of Sb in the leachate increased,the growth and light intensity were inhibited,but the light intensity of Microcystis aeruginosa was promoted at low concentration.（3）Rhizosphere and non-rhizosphere DOM are strong ligands of Sb,which can produce a good complexation reaction with Sb,and the binding ability of DOM and Sb in rhizosphere is stronger than that of non-rhizosphere DOM.rhizosphere DOM can promote the release of Sb in soil by flame retardant microplastics containing antimony.The soluble microbial byproducts contained in the rhizosphere DOM have stronger binding ability to Sb than humic acid.Maize can absorb heavy metal Sb from the soil with Sb-containing flame retardant microplastics.The absorbed Sb is mainly concentrated in the roots of maize,and the accumulation of Sb in the underground tissue is higher than that of aboveground tissues.The transfer coefficient from underground tissue to aboveground tissue is between 0.65 and 0.73.As the amount of flame retardant microplastics added to the soil increases,the amount of Sb contained in the soil increases.Sb can inhibit the growth of maize seedlings and roots,it also can inhibit photochemical efficiency.