可降解共混塑料在海水中的光降解研究

Study on photodegradation of degradable plastic blends in seawater

可降解共混塑料因价格低廉而得到广泛应用,然而共混塑料在海水中的光降解和微塑料的形成有待深入研究.因此,本文以聚乙烯/碳酸钙(PE/CaCO3)和聚乙烯/热塑性淀粉(PE/TPS)共混塑料为研究对象,聚乙烯(PE)作为对照,通过机械研磨制备微塑料,研究微塑料在天然海水中阳光照射下的光降解.结果表明,相同风化条件下,共混塑料比PE更容易产生小粒径的颗粒.光降解后老化共混塑料表面的碎片、颗粒明显多于PE.光降解后PE的ATR-FTIR和C1s XPS光谱没有明显变化;PE/CaCO3因光氧化形成含氧官能团C—O;PE/TPS的TPS特征峰减弱,表明TPS光降解.结合3种微塑料接触角、表面电势的变化可知,老化共混塑料对亲水性污染物的吸附能力可能比PE更强.综上所述,可降解共混塑料在海洋环境中的光降解程度高于PE,海洋环境风险可能更大,应谨慎推广.

Degradable plastic blends have been widely used due to their low cost.However,it is the necessary to investigate the formation of microplastics by the photodegradation of degradable plastic blends in seawater.Three investigated microplastic materials included polyethylene/calcium carbonate blends(PE/CaCO3)and polyethylene/thermoplastic starch blends(PE/TPS),and polyethylene(PE)were prepared by mechanical grinding in this study.The photodegradation of microplastics in natural seawater under solar irradiation was investigated.The results show that degradable plastic blends are more likely to generate small-sized particles than PE under the same weathering conditions.More debris and particles are present on the surface of the aged degradable plastic blends than in the aged PE after irradiation.There are no significant changes in the ATR-FTIR and C1s XPS spectra of PE after irradiation.An oxygen-containing functional group(C—O)is appeared in PE/CaCO3 due to the photooxidation.For PE/TPS,the intensity of the TPS absorption peaks decreased significantly after irradiation,indicating the depletion of the starch fraction.Combined with changes in contact angle and surface potential for the three types of microplastics,aging degradable plastic blends may have a greater adsorption capacity than PE for hydrophilic contaminants.In summary,degradable plastic blends have a higher degree of photodegradation than PE in the marine environment,and may pose a higher risk to the marine environment,thus caution should be taken in promoting plastic blends.