污泥焚烧灰免烧轻质骨料性能及重金属固化效果研究

Research on properties and heavy metal curing effect of non-sintered lightweight aggregates prepared by sewage sludge ash

焚烧技术能有效减少城市污泥(以下简称污泥)的有机污染物、细菌含量和污泥体积等,污泥焚烧后产生的污泥焚烧灰(SSA)大多采用填埋的方式处理,给生态环境和土地资源利用带来严峻挑战。以碱性激发剂制备SSA免烧轻质骨料(以下简称骨料),并探究了矿渣掺量对骨料物理力学性能的影响规律。结果表明:骨料的粒径主要集中在4.75~9.50 mm;骨料的密度等级和筒压强度分别介于700~900与1.86~4.20 MPa,符合《结构性轻骨料混凝土指南》(ACI-213R-03)和《轻集料及其试验方法第1部分:轻集料》(GB/T 17431.1—2010)要求;扫描电子显微镜(SEM)、能量弥散X射线分析仪(EDS)、X射线衍射仪(XRD)、全自动压汞仪(MIP)和电感耦合等离子体发射光谱仪(ICP-OES)测试结果表明,矿渣发生地质聚合反应生成的地质聚合物凝胶能包裹SSA颗粒,并相互黏结形成球状颗粒骨料,增加矿渣掺量能有效减少骨料中的有害孔隙,达到增强骨料结构致密性的效果;SSA中的离子态Mn浸出值超出了非危险固体废弃物排放限值(3 mg/L),而骨料中的重金属离子浸出值均满足要求。上述研究成果能为SSA的资源化高效利用提供新途径。

Incineration technology can reduce organic pollutants,bacteria and volume of municipal sewage sludge(sludge for short).However,the sewage sludge ash generated after incineration is mainly treated by landfills,which brings severe challenges to environmental protection and land resource utilization.The non-sintered lightweight aggregate of sewage sludge ash(aggregate for short)were prepared by using alkaline activator,and the influence of slag content on the physical and mechanical properties of aggregates were investigated.The results showed that aggregate particle size was mainly concentrated in 4.75-9.50 mm.The density grade and cylinder compressive strength of aggregates were between 700-900 and 1.86-4.20 MPa,respectively,which met the requirements of“Guide for structural lightweight-aggregate concrete”(ACI-213R-03)and“Lightweight aggregates and its test methods-Part 1:lightweight aggregates”(GB/T 17431.1-2010).SEM,EDS,XRD,MIP and ICP-OES test results showed that the geopolymer gel generated by the geological polymerization of slag could wrap sewage sludge ash particles and bond to each other to form spherical aggregate particles.Increasing the slag content could effectively reduce the harmful spores in the aggregate and enhance the density of the aggregate structure.The leaching value of ion-state Mn in sewage sludge ash exceeded the limit of non-hazardous solid waste discharge specification(3 mg/L).In contrast,the leaching value of heavy metal ions in aggregates met the requirements of the specification.The above research results provided a new way to efficiently utilize sewage sludge ash.