核壳结构对石油污染土壤污染物分解转化的促进

Enhancement of pollutant degradation and transformation in petroleum-contaminated soil by core-shell structures

关键词:  石油污染土壤  核壳结构  陶粒  热脱附  热降解

Key words:  petroleum-contaminated soil  core-shell structure  ceramsite  thermal desorption  thermal degradation

摘要:

将石油污染土壤通过一次成核后,在其表面继续包覆清洁材料,并经高温烧结制备成可作为建材骨料的核壳结构陶粒,旨在降低有机污染土壤处理过程中二次污染产生的环境风险,实现污染土壤无害化处置。本研究探讨了加热时间、包覆材料种类及用量对石油-CO₂转化率的影响,并通过XPS和SEM分析核壳结构陶粒的元素组成与表面形貌。研究表明:与未包覆的核心球相比,以不同粒径的粉煤灰和粘土材料包覆含油率为10%的石油污染土壤颗粒制成的核壳结构坯体,污染物去除效果显著提升,石油-CO₂转化率从28.05%提高至62.99%；随着热处理时间和包覆材料用量的增加,转化率进一步提高,且低质量分数的污染土壤在热解过程中更易实现较高转化率；当包覆材料用量为5 wt.%石油污染土壤的1.5倍时,其石油-CO₂转化率可达90.59%,而未进行包覆的核心球转化率仅有34.52%。所制陶粒的堆积密度为1 134 kg/m³,筒压强度可达9.1 MPa,1 h吸水率为4.36%,符合轻骨料的国家标准。包覆层延缓了有机气体的挥发,使其大量热解转化,此外,包覆材料粒径对石油-CO₂转化率无明显影响,但材料中的Ca和Fe元素有利于石油烃的去除。

Abstract:

The petroleum-contaminated soil is initially formed into a core and then coated with a layer of clean material, followed by high-temperature sintering to fabricate core-shell structured ceramsite, which can be utilized as a construction aggregate. This method aims to mitigate the environmental risks associated with secondary pollution during the treatment of organic contaminated soil and facilitate its harmless disposal. The study investigates the effects of heating duration, coating material types, and dosage on the petroleum-to-CO₂ conversion rate, with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) used to analyze the elemental composition and surface morphology of the core-shell ceramsite. The experimental results demonstrate that compared to uncoated core spheres, the core-shell structure created by coating petroleum-contaminated soil particles (with an petroleum content of 10%) coated with fly ash and clay of varying particle sizes significantly improve the pollutant decomposition efficiency, increasing the petroleum-to-CO₂ conversion rate from 28.05% to 62.99%. Prolonged heating and increased coating material dosage further enhances the conversion rate, with low-concentration contaminated soil achieving higher conversion rates during pyrolysis. When the coating material dosage reached 1.5 times that of the petroleum-contaminated soil (5% by weight), the petroleum-to-CO₂ conversion rate increased to 90.59%, while the conversion rate for uncoated core spheres was only 34.52%. The fabricated ceramsite exhibited a bulk density of 1 134 kg/m³,a compressive strength of 9.1 MPa, and a one-hour water absorption rate of 4.36%, meeting national standards for lightweight aggregates. The coating layer delayed the volatilization of organic gases, resulting in a large amount of pyrolysis transformation. In addition, while the particle size of the coating material had no significant effect on the petroleum-to-CO₂ conversion rate, the presence of Ca and Fe elements in the materials was beneficial for the removal of petroleum hydrocarbons.