摘要
污水和污泥是土壤等生态环境中微塑料的重要来源,受到人们的广泛关注.由于污水和污泥中含有大量的有机质,化学预处理通常被用于提高其中微塑料的提取及分析效率,然而至今关于化学预处理对微塑料的吸附潜力及表面理化特性的影响研究较少.本研究探讨了5种预处理条件,即1 mol·L~(-1) HCl、1 mol·L~(-1) HNO_3、30%H_2O_2、1 mol·L~(-1) NaOH和5 mol·L~(-1) NaOH,对6种微塑料类型(PA、PE、PP、PS、PET和PMMA)Pb吸附潜力的影响,同时通过微塑料表面理化特性的分析,探讨了预处理影响微塑料Pb吸附的机理.结果表明6种微塑料对Pb吸附等温式符合Langmuir模型,Pb吸附能力大小顺序分别为:PA>PMMA>PET>PE>PP>PS,最大吸附量分别为2922.9、699.3、584.8、549.5、510.2和277.8μg·g~(-1).与此同时,不同预处理条件对微塑料Pb吸附特性的影响不同,总体而言,碱预处理会导致微塑料Pb吸附量增加,且随着碱处理浓度的增加而增加,而酸预处理会引起Pb吸附量减小,其中硝酸预处理作用更加显著.进一步分析预处理前后微塑料质量、尺寸、表面官能团及表面形态等的变化情况,发现碱预处理对微塑料的腐蚀作用最大,其次为硝酸预处理组,最后为盐酸和过氧化氢预处理组.此外,与玻璃型(如PS)微塑料相比,预处理对橡胶型微塑料(如PE)的影响更大.
Sewage sludge and wastewater treatment plant is considered as an important source of microplastics(MPs) of natural ecosystem, which is paid extensive attention. Wastewater and sewage sludge contain high content of organic matter, and thus chemical pretreatment is often used to improve extraction and purification efficiency of sludge-based MPs. However, the effect on adsorption potentials and physicochemical characteristics of MPs to pollutants is lacking of knowledge so far. In this study, five chemical pretreatments, i.e., 1 mol·L~(-1) HCl, 1 mol·L~(-1) HNO_3, 30% H_2O_2, 1 mol·L~(-1) NaOH and 5 mol·L~(-1) NaOH, were applied to treat six MPs, i.e., polyamide(PA), polyethylene(PE), polypropylene(PP), polystyrene(PS), Polyethylene terephthalate(PET), polymethyl methacrylate(PMMA). Results showed that the adsorption isotherms of six MPs to Pb conform to Langmuir model, and their adsorption potentials followed the order: PA > PMMA > PET > PP>PE > PS, and the maximums were 2922.9, 699.3, 510.2, 549.5, 277.8, 584.8 and 277.8 μg·g~(-1). Meanwhile, different chemical pretreatment had different effect on adsorption potential of MPs to Pb. Generally, alkaline pretreatment could cause an increase in the adsorption potentials, while acid pretreatment led to a decrease. Analysis of MP physicochemical characteristics before and after pretreatments implied that the pretreatment by alkaline has stronger effect than nitric acid, followed by hydrochloric-acid and hydrogen-peroxide. Additionally, Pretreatment has a greater impact on rubber-type MPs(eg PE) than glass-type MPs(eg PS).
引文
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