胶结充填用冶金渣协同垃圾焚烧飞灰固镉机理

Mechanisms of solidification of cadmium in municipal solid waste incineration fly ash usinga slag cemented backfill agent

胶结充填采矿协同利用垃圾焚烧飞灰是解决飞灰日益激增的新思路,可大量资源化利用飞灰并固化其中的重金属离子.本文以矿渣-钢渣基胶凝材料（简称冶金渣胶凝材料）分别结合4种城市垃圾焚烧（MSWI）飞灰制备胶凝材料,并以全尾砂作为骨料制成胶结充填料,测定充填料试样的流动度、抗压强度以及Cd-（2＋）浸出质量浓度：冶金渣-垃圾焚烧飞灰基充填料试样的流动度为240-265 mm,满足矿山充填的泵送要求;28 d抗压强度均大于8.88 MPa,满足一般矿山充填1-6.5 MPa的强度要求;Cd-（2＋）浸出液质量浓度低于饮用水标准5μg·L-1的限值.通过X射线衍射（XRD）、红外光谱（IR）和热重-差示扫描量热法（TG-DSC）分析表明胶凝材料的主要水化产物组成为钙矾石、Friedel盐和C-S-H凝胶;通过X射线光电子能谱（XPS）发现Cd-（2＋）对Al3＋的结合能有较大影响,钙矾石、Friedel盐可能对镉离子有固化作用.

In cement production,the synergistic use of municipal solid waste incineration（ MSWI） fly ash provides a novel approach to solve the problem of the increasing productions of fly ash and heavy metal ions. In this study,slag-steel slag based cementitious material（ referred to as metallurgical slag cementitious materials） was combined with four types of MSWI fly ash for preparing cementitious materials,all of which use sand as a binder. According to the determination of fluidity,compressive strength and Cd^（2＋） leaching concentration of filler samples,the following are found：（ 1） the flow rate of filler material prepared from metallurgical slag and fly ash is 240-265 mm,which fulfills the pumping requirement of mine filling;（ 2） the 28-day compressive strength values are 8. 88 MPa,which meets the general mine filling strength requirements（ 1-6. 5 MPa）; and（ 3） the Cd^（2＋） leachate concentration is lower than the drinking water standard of 5 μg·L-1 limit. The results of X-ray diffraction,infrared spectroscopy,and thermogravimetry-differential scanning calorimetry show that the leading hydration products of gelling materials are ettringite,Friedel,and C-S-H. Furthermore,X-ray photoelectron spectroscopy results reveal that Cd^（2＋） has a great effect on the binding energy of Al3 ＋. Ettringite and Friedel salts are found to have a curing effect on cadmium ions.