关键词:
生物炭
铁锰氧化物
固体废物
协同稳定化
摘要:
本研究针对铅(Pb)、砷(As)、镉(Cd)多金属复合污染固废的稳定化难题,以稻壳生物炭(BC)为载体,通过共沉淀法负载铁锰双金属氧化物(FMBO),制备新型复合材料(FMBO@BC)。通过优化热解温度(500℃)、Fe/Mn摩尔比(3:1)及负载pH值(10),获得比表面积285 m2/g、铁锰负载量15.2 wt%的FMBO@BC,其介孔结构(占比78%)与金属氧化物晶型(FeOOH, Mn₃O₄)协同增强了重金属固定能力。浸出实验表明,当投加量为5%时,Pb、As、Cd的浸出浓度分别由原始固废的6.48 mg/L、27.22 mg/L、8.14 mg/L降至1.2 mg/L、0.8 mg/L、0.3 mg/L,较《危险废物鉴别标准》(GB 5085.3-2007)限值降低76%~97%,且90天后仍低于限值(Pb 1.6 mg/L, As 1.2 mg/L, Cd 0.6 mg/L)。机理研究表明:Pb通过FeOOH表面羟基络合(EXAFS显示Pb-O键长2.32 Å)与Mn₃O₄氧化生成PbO2 (XRD验证)双重机制固定;As的稳定化依赖Mn(IV)对As(III)的氧化(XPS中As(V)占比82%)及Fe-AsO₄共沉淀(EDS面扫显示As-Fe共定位);Cd则通过生物炭羧基离子交换(FTIR中C=O峰强度降低63%)及孔隙物理吸附(平均孔径6.2 nm)实现固定。相较于传统水泥固化法,FMBO@BC成本降低24% (3800元/吨vs. 5000元/吨),为重金属矿区历史遗留固废的绿色修复提供了高效、经济的技术方案。In this study, the stabilization problem of solid waste contaminated by lead (Pb), arsenic (As), and cadmium (Cd) was solved. Rice husk biochar (BC) was used as a carrier to load iron and manganese bimetallic oxides (FMBO) by coprecipitation to prepare a new composite material (FMBO@BC). By optimizing the pyrolysis temperature (500˚C), Fe/Mn molar ratio (3:1) and loading pH value (10), FMBO@BC with a specific surface area of 285 m2/g and an iron and manganese loading of 15.2 wt% was obtained. Its mesoporous structure (accounting for 78%) and metal oxide crystal form (FeOOH, Mn₃O₄) synergistically enhanced the heavy metal fixation capacity. Leaching experiments show that when the dosage is 5%, the leaching concentrations of Pb, As and Cd are reduced from 6.48 mg/L, 27.22 mg/L and 8.14 mg/L of the original solid waste to 1.2 mg/L, 0.8 mg/L and 0.3 mg/L, respectively, which are 76%~97% lower than the limit values of the “Hazardous Waste Identification Standard” (GB 5085.3-2007), and are still below the limit values (Pb 1.6 mg/L, As 1.2 mg/L, Cd 0.6 mg/L) after 90 days. Mechanism studies have shown that Pb is fixed by a dual mechanism of complexation with FeOOH surface hydroxyl groups (EXAFS shows Pb-O bond length of 2.32 Å) and oxidation of Mn₃O₄ to generate PbO₂ (XRD verification);As stabilization depend