Key Laboratory for Solid Waste Management and Environment Safety, School of Environment, Tsinghua University, Beijing, PR China.
Key Laboratory for Solid Waste Management and Environment Safety, School of Environment, Tsinghua University, Beijing, PR China.
Waste Manag. 2018 Oct;80:101-111. doi: 10.1016/j.wasman.2018.08.053. Epub 2018 Sep 7.
Solidification/stabilization (S/S) is the most common treatment for municipal solid waste incineration fly ash (MSWI-FA), and is widely applied in developed countries but has a history barely longer than 10 years in China. However, our understanding of the physicochemical characteristics of the solidified FA body after long-term natural aging is comparatively poor. Focusing on cement-solidified FA that was naturally aged for 6 years (hereafter referred to as FA-6), the physicochemical characteristics including elemental composition, mineral composition, microstructure, thermogravimetry, distribution of heavy metals in mineral phases, and leaching characteristics of inorganic salts (Na, K, Ca), anions (Cl and SO) and heavy metals (Cd, Cr, Cu, Pb, Zn) were investigated in this study. By combining pH-dependent leaching results with the geochemical model LeachXS, the chemical forms of heavy metals in the FA solid phase was determined. The main conclusion was as follows: (1) soluble salts of FA-6 decreased by more than 92% compared with fresh FA. (2) In FA-6, the proportions of Pb, Cd and Zn in the non-mineral phase were 100%, 100% and 58%, respectively, which may cause potential environmental risk of heavy metal release. The leaching concentration of Pb was 4007.37 μg/L according to compliance batch test of HJ300, which was far higher than the landfill requirement of 250 μg/L. (3) The controlling phase for Pb in FA-6 was Pb(PO)Cl (pH 2-12) and Pb(OH)Cl (pH > 12). (4) Carbonates, hydrous Fe oxides (HFO) and dissolved organic carbon (DOC) in FA-6 also affected the phase-controlled leaching of heavy metals. The carbonate fraction partly controlled the leaching of Cd, Cu and Zn. For example, smithsonite (ZnCO) controlled the release of Zn (pH 2-13). Adsorption to solid humic acid (SHA) controlled the Cr leaching at pH < 7 and the Cu leaching except pH > 12.
固化/稳定化（S/S）是处理城市固体废物焚烧飞灰（MSWI-FA）最常用的方法，在发达国家得到广泛应用，但在中国的历史还不到 10 年。然而，我们对经过长期自然老化的固化飞灰体的物理化学特性的了解相对较差。本研究聚焦于自然老化 6 年的水泥固化飞灰（以下简称 FA-6），研究了其元素组成、矿物组成、微观结构、热重分析、重金属在矿物相中的分布以及无机盐（Na、K、Ca）、阴离子（Cl 和 SO）和重金属（Cd、Cr、Cu、Pb、Zn）的浸出特性。通过将 pH 依赖性浸出结果与地球化学模型 LeachXS 相结合，确定了 FA 固相中重金属的化学形态。主要结论如下：（1）与新鲜飞灰相比，FA-6 中的可溶性盐减少了 92%以上。（2）在 FA-6 中，Pb、Cd 和 Zn 的非矿物相比例分别为 100%、100%和 58%，这可能导致重金属释放的潜在环境风险。根据 HJ300 的合规批量测试，Pb 的浸出浓度为 4007.37μg/L，远高于 250μg/L 的填埋要求。（3）FA-6 中 Pb 的控制相为 Pb(PO)Cl（pH 2-12）和 Pb(OH)Cl（pH>12）。（4）FA-6 中的碳酸盐、水合铁氧化物（HFO）和溶解有机碳（DOC）也影响重金属的相控浸出。碳酸盐部分控制了 Cd、Cu 和 Zn 的浸出。例如，菱锌矿（ZnCO）控制了 Zn 的释放（pH 2-13）。吸附到固体腐殖酸（SHA）上控制了 pH<7 时 Cr 的浸出以及 pH>12 时除 Cu 以外的 Cu 的浸出。
