生物可分解塑膠微粒吸脫附重金屬之研究

Adsorption and Desorption Characteristics of Heavy Metals on Biodegradable Microplastics

王熙姸(Hsi-Yen Wang)

指導教授 ： 駱尚廉

國立臺灣大學/工學院/環境工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202101103

摘要

由於塑膠成本低、質量輕且具有生物惰性，被廣泛應用於一次性之包裝材料，但在塑膠為生活帶來便利的同時亦產生了塑膠微粒環境污染問題，而環境中的塑膠微粒會吸附重金屬，並進入食物鏈進而對人體健康造成負面影響。近年來，生物可分解塑膠被認為是塑膠污染之解決方案，其產量逐年增加，但許多生物可分解塑膠只能在特定環境下被分解，因此，生物可分解塑膠微粒污染亦會對環境造成負面影響。
本研究以「聚乙烯(Polyethylene, PE)」和「聚乳酸(Polylactide, PLA)」分別代表非生物分解和生物可分解塑膠微粒，進行鉛、銅、鋅和鎳之吸附研究。結果顯示，聚乳酸塑膠微粒「具有含氧官能基」、「較高的比表面積」和「較低的結晶度」，使聚乳酸塑膠微粒對重金屬的吸附量皆高於聚乙烯塑膠微粒，且重金屬吸附量大小為鉛 > 銅 > 鋅 > 鎳。除了鎳以外，塑膠微粒對於重金屬之吸附量隨著pH值增加而增加。「聚乙烯塑膠微粒吸附鉛和銅」及「聚乳酸塑膠微粒吸附鉛」在15 oC的條件下有較低的吸附量，鋅和鎳之吸附量在15至35 oC時受溫度的影響較不顯著。聚乳酸塑膠微粒吸附銅、鋅和鎳較符合Langmuir等溫吸附模式，吸附鉛時則是較符合Freundlich等溫吸附模式；而聚乙烯塑膠微粒吸附鉛和鎳時較符合Langmuir等溫吸附模式，吸附銅和鋅時，則是較符合Freundlich等溫吸附模式。
以先前吸附實驗的結果中，吸附量最大的「鉛」做為脫附實驗所探討之重金屬，將吸附鉛之塑膠微粒放入人工配置水樣中進行脫附。實驗結果顯示：聚乙烯和聚乳酸塑膠微粒在淡水及海水環境中僅有約10 %之脫附率，但在水生生物及恆溫動物的消化道中達到約100 %之脫附率。

關鍵字

塑膠微粒 ； 重金屬 ； 吸附 ； 脫附 ； 生物可分解塑膠

並列摘要

Plastics are widely used as disposable packaging materials due to their low cost, lightweight, and biological inertness. However, while plastics bring convenience to life, they also cause environmental pollution problems. Microplastics can adsorb heavy metals in the environment and enter the food chain. In recent years, biodegradable plastics have been considered as a solution to plastic pollution, and their production has been increased. However, many biodegradable plastics can only be decomposed under certain conditions. Therefore, biodegradable microplastics still pose a threat to the environment.
In this study, polyethylene (PE) and polylactide (PLA) represent non-biodegradable and biodegradable microplastics, respectively, for the adsorption of lead, copper, zinc, and nickel. The results show that PLA microplastics have oxygen-containing functional groups and higher specific surface areas so that the amount of heavy metal adsorption onto PLA microplastics is higher than that of polyethylene microplastics. The adsorption capacities onto the microplastics are lead > copper > zinc > nickel. Except for nickel, the adsorption capacity of microplastics for heavy metals increases with the solution pH. The level of adsorption of lead and copper onto PE and that of lead onto PLA were lower at the lower temperature, 15 oC, while those of zinc and nickel were less affected by the temperature from 15 oC to 35 oC. The adsorption of copper, zinc, and nickel by the PLA microplastics fits the Langmuir isotherm well; while the adsorption of lead fits the Freundlich isotherm well. For the PE microplastics the adsorption of lead and nickel fits the Langmuir isotherm; while adsorption of copper and zinc is more in line with the Freundlich isotherm.
Comparison to the other metals, lead onto the microplastic shows a higher risk and conducted the desorption investigation. The results show that PE and PLA microplastics have a desorption rate of only about 10% in freshwater and seawater, but almost 100% in the digestive tracts of aquatic organisms and warm-blooded animals.

並列關鍵字

microplastic ； heavy metal ； adsorption ； desorption ； biodegradable plastic

參考文獻

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