Abstract:

In view of the requirements of the subsequent innocuity treatment of metal oxide adsorbents for mercury removal, a brand-new idea of leaching Hg-absorption products from metal oxide using sodium thiosulfate (Na₂S₂O₃) solution was proposed in this paper. Mercury-containing adsorbents (Hg-CeTi) was obtained by CeO₂/TiO₂ sorbents (CeTi) after mercury adsorption. Mercury temperature-programmed desorption (Hg-TPD) was used to determine the occurrence form of adsorbed-Hg on the surface of Hg-CeTi. Then, the extraction capacity of Na₂S₂O₃ solution on the Hg-absorption products from the Hg-CeTi was studied, and the migration mechanism of mercury with different occurrence forms in Na₂S₂O₃ solution was emphatically analyzed. The results of Hg-TPD showed that HgCl₂, HgO and HgS were the main Hg-adsorption products in the syngas. HgO was easy to desorb from Hg-CeTi and migrate to the liquid phase due to the coordination ability of thiosulfate (S₂O{}_{\mathrm{3}}^{\mathrm{2}-}) with Hg²⁺. HgCl₂ reacted with OH^- in the liquid phase to form HgO, which was subsequently leached by Na₂S₂O₃ solution. For two different crystalline forms of HgS, the increase in the concentration of Na₂S₂O₃ solution could promote the migration of HgS (black) to the liquid phase, but it had a slight effect on the HgS (red) due to the stability of HgS (red). After leaching in 1.0mol/L Na₂S₂O₃ solution for 1h, the mercury leaching rate could reach 97.3%, and the remaining mercury existed in stable HgS form.

Key words: leaching, mercury, adsorbents, stability, syngas, waste treatment

摘要：

基于金属氧化物脱汞吸附剂后续无害化处理要求，本文提出采用硫代硫酸钠（Na₂S₂O₃）溶液浸出金属氧化物脱汞产物的新思路。CeO₂/TiO₂吸附剂（CeTi）吸附汞后得到含汞吸附剂（Hg-CeTi），利用汞程序升温脱附实验（Hg-TPD）确定其表面吸附态汞的赋存形态。随后探究Na₂S₂O₃溶液对于Hg-CeTi表面脱汞产物的浸出能力，着重分析不同赋存形态的汞在Na₂S₂O₃溶液中的迁移规律。Hg-TPD结果表明，模拟煤气中脱汞产物以HgCl₂、HgO和HgS为主。由于硫代硫酸根（S₂O{}_{\mathrm{3}}^{\mathrm{2}-}）与Hg²⁺的配合能力，HgO易从Hg-CeTi表面脱附并向液相迁移；HgCl₂会在液相中与OH^-反应生成HgO，再被Na₂S₂O₃溶液浸出；对于两种不同晶型的HgS，提高Na₂S₂O₃溶液浓度可促进HgS(black)向液相迁移，但对于更稳定的HgS(red)收效甚微。在1.0mol/L的Na₂S₂O₃溶液中浸出1h后，汞浸出率可达97.3%，且剩余的汞以稳定的HgS形态存在。

关键词: 浸出, 汞, 吸附剂, 稳定性, 合成气, 废物处置