油基钻井岩屑固化体中多环芳烃释放特征

油基钻井岩屑资源化利用的有效方式是制备成块状固化体,但固化体在应用过程中存在多环芳烃浸出的风险。采用固体中无机组分有效量测试(NEN7371)方法和块状材料中无机组分的扩散实验(NEN7375)方法,研究固化体内萘、蒽、荧蒽、苯并(b)荧蒽和苯并(a)芘5种多环芳烃的释放特性,评估其浸出释放风险。结果表明:5种多环芳烃的有效释放率均在2%以下,其中苯并(a)芘有效释放率最高,浸出液中浓度超过GB/T 14848—2017《地下水质量标准》中Ⅲ类限值;在静态浸泡释放特征试验中,5种多环芳烃的释放集中在浸出前期,前16 d累积释放量占64 d累积释放总量的比值均超过78%;5种多环芳烃释放机理包括扩散控制、溶解释放、延滞释放、耗竭和表面冲刷,固化体中不同多环芳烃释放特征存在一定的差异,但总体上以扩散控制为主,后期均表现为耗竭机制。

Release characteristics of PAHs in oil-based drilling cuttings solidified body

An effective way to further dispose and utilize resources is to make oil-based drilling cuttings into blocky solidified body. However, when solidified body is used, PAHs may leach out. The release characteristics of 5 kinds of polycyclic aromatic hydrocarbons (PAHs) in solidified body, including naphthalene, anthracene, fluoranthene, benzo (b) fluoranthene and benzo (a) pyrene (BaP), were studied by using the test method of effective amount of inorganic components in solid (NEN7371) and the diffusion test method of inorganic components in bulk materials (NEN7375) and to assess their leaching release risks. The results showed that the effective release rates of the 5 kinds of PAHs were all below 2%. The effective release amount of BaP exceeded the limiting value of Category Ⅲ in Groundwater Quality Standard (GB/T 14848-2017). In static immersion release characteristic experiments, 5 kinds of PAHs released at the early stage, and their accumulated release amount at the previous 16 days accounted for more than 78% of the cumulative total release amount of 64 days. The release mechanism of the 5 kinds of PAHs included diffusion control, dissolution release, delayed release, depletion and surface wash-off. Different PAHs in solidified body had different release characteristics, but in general, they were mainly released in the way of diffusion control. In the later stage, they mainly released in the form of depletion mechanism.