废弃流化催化裂化催化剂中重金属的赋存形态、浸出特性及其健康风险评价

Speciation and Leaching Characteristics of Heavy Metals in Spent Fluid Catalytic Cracking Catalyst and Its Health Risk Assessment

随着炼油行业产生的废弃流化催化裂化催化剂(SFCCC)不断增加,含有大量重金属(主要是V、Fe、Ni和Sb)的SFCCC所造成的生态环境和人体健康风险已不容忽视。为分析SFCCC中重金属的污染特性,采用硫酸硝酸法和改进的BCR连续提取法分别对SFCCC中重金属的浸出毒性和赋存形态进行研究,考察SFCCC粒径、浸出时间、pH和液固比等浸出条件对SFCCC中V、Fe、Ni和Sb浸出行为的影响,评价不同浸沥液环境下SFCCC对人体的健康风险。结果表明:①SFCCC中V的浸出浓度为4.955 mg/L,高于美国通用处理标准(UTS)的限定值(0.2 mg/L),具有浸出毒性。②V、Fe、Ni和Sb四种重金属主要以残渣态的形式存在,V的弱酸提取态和可还原态含量均高于其他3种重金属,环境迁移能力最强。③V的浸出浓度与SFCCC的粒径成正比,Fe、Ni和Sb的浸出浓度均与SFCCC的粒径成反比;4种重金属浸出浓度均与时间成正比,其中V显示出更长的浸出周期;酸性环境促进重金属的浸出,而V和Sb在强碱性环境下也容易浸出;4种重金属的浸出浓度均随液固比的增加呈现先上升后下降的趋势,并最终达到平衡。④健康风险评价结果表明,SFCCC在地表水、酸雨和垃圾渗滤液浸沥环境下的非致癌风险值(HQ)均大于1,对人体存在较高的非致癌风险。其中Sb在3种浸沥液环境下的HQ分别为2.264、1.637和1.744,是主要的非致癌风险元素。因此需要对SFCCC进行固化处置,限制重金属的溶出,减少其对环境和人体的危害。

With the increasing generation of spent fluid catalytic cracking catalysts(SFCCC)in petroleum refining industry,the ecological environment and human health risks caused by SFCCC containing a large amount of heavy metals(mainly V,Fe,Ni and Sb)cannot be ignored.In order to assess the pollution characteristics of heavy metals in SFCCC,the leaching toxicity and speciation of heavy metals in SFCCC were studied using sulfuric acid and nitric acid method and improved BCR sequential extraction method.The effects of leaching conditions such as particle size of SFCCC,pH,leaching time and liquid-solid ratio on the leaching behavior of V,Fe,Ni and Sb in SFCCC were studied.The health risks of SFCCC in different leachate environments were also evaluated.The results showed that:(1)The leaching concentration of V in SFCCC was 4.955 mg/L,which exceeded the limit value(0.2 mg/L)of the Universal Treatment Stand(UTS),indicating undesirable leaching toxicity.(2)On SFCCC,the four heavy metals V,Fe,Ni and Sb mainly exist in residual states with reliable stability for immersion migration.The weak acid extraction state and reducible state of V were higher than the other three heavy metals,enabling it the highest environmental migration ability.(3)The leaching concentration of V was positively proportional to the particle size of SFCCC,while the leaching concentrations of Fe,Ni and Sb were inversely proportional.The leaching concentrations of all four heavy metals increase with the prolongation of leaching time.The leaching of V was a quite long against the other three heavy metals,with a continuous increasing trend.The leaching of the four heavy metals was totally enhanced in acidic environment.Furthermore,V and Sb were also easy to leach in a strong alkaline environment.With the increase of liquid-solid ratio,the leaching concentrations of the four heavy metals first increased and then decreased,ultimately reaching equilibrium.(4)The health risk assessment results indicated that SFCCC has non-carcinogenic risk values(HQ)of in the surface water,acid rain and landfill leachate environments were all greater than 1,indicating a high non-carcinogenic risk to humans.The HQ of Sb in the three leachate environments were 2.264,1.637 and 1.744,respectively,which was identified as the main non-carcinogenic risk element.Therefore,it is necessary to solidify the heavy metals in SFCCC to limit their leaching and reduce the harm to the environment and human health.