负载铁生物炭对雄黄矿尾渣砷的钝化效果

湖南石门雄黄矿矿区内大量As含量极高的尾渣，严重威胁着当地环境安全与居民生命健康.为推动实现对雄黄矿高As尾渣的稳定化处理，系统分析了FeBC（负载铁生物炭）对雄黄矿尾渣中As的钝化效果，并对FeBC钝化As的发生机制进行探讨.结果表明:水平振荡试验和合成沉降浸出试验（synthetic precipitation leaching procedure，SPLP）中尾渣As的浸出浓度分别为103.7和173.5 mg/L；FeBC的加入矿渣与FeBC的比例（w/w）为4:1]使尾渣中As的浸出浓度降低72.2%~79.2%.在以模拟酸雨为淋溶液的柱试验中，FeBC处理使淋出液中ρ（As）下降79.1%~99.3%，As淋失总量减少92.8%，但酸雨淋溶量的持续增加使出水中ρ（As）随pH的降低而缓慢上升.FTIR（傅里叶红外光谱）分析发现，FeBC表面负载的Fe原子通过羟基与砷酸根之间的配位基交换作用吸附As是FeBC高效钝化尾渣中As的关键机制；同时，生物炭载体表面含氧官能团还可能通过氢键与As氧合阴离子或分子发生了吸附反应.研究显示，FeBC在钝化雄黄矿尾渣中高含量As方面具有突出优势，可用于快速降低矿渣中As的浸出毒性；但在长期酸雨淋溶条件下，可能需要设置酸度缓冲层以充分保障FeBC钝化As作用的稳定性和持久性. 

Effects of Fe-Impregnated Biochar on Arsenic Immobilization in Realgar Mine Tailings

In Shimen realgar mine, a huge amount of tailings with extremely high arsenic (As) concentration is seriously threatening the local environmental safety and public health. To drive the implementation of the stabilization of these high As-containing tailings, the effects of FeBC (Fe-impregnated biochar) on As immobilization in the realgar tailings was systematically analyzed with the underlying mechanisms being unraveled. As shown by the experimental results, soluble As levels in the horizontal vibration and Synthetic Precipitation Leaching Procedure (SPLP) were 103.7 and 173.5 mg/L, respectively. Upon the application of FeBC (tailings:FeBC=4:1, w/w), the extractable As from the realgar tailings was reduced by 72.2%-79.2%. In the column tests with simulated acid rain, 79.1%-99.3% reductions in the leachate As and a total of 92.8% decrease in the cumulative amount of As leached were determined in the FeBC treatment as compared to the control tailings. Nevertheless, with prolonged acid leaching, a gradual increase in the leached As concentration was observed along with a simultaneous decline of the leachate pH. Based on Fourier Transform Infrared analysis, As complexation onto the hydroxylated surface of Fe through ligand exchange between hydroxyl and As oxyanions was proposed to be the key mechanism governing As immobilization by FeBC. Meanwhile, the formation of hydrogen bond between oxygen-containing groups on biochar surface and As oxyanions may also be responsible for As sorption onto FeBC.According to the results of this study, FeBC exhibited an extraordinary ability to immobilize As in the realgar tailings, and hence can be used to reduce the leaching toxicity of As quickly and efficiently.Nevertheless, under long-term acid precipitation, an acid-buffering layer seems to be essential to ensure the stability and persistence of As immobilization by FeBC.