生物炭负载铁锰氧化物对铅砷镉多金属固废稳定化研究
Study on Stabilization of Lead, Arsenic, Cadmium and Multi-Metal Solid Waste by Biochar Loaded with Iron and Manganese Oxides

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, Mn？O？)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 ？)与Mn？O？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-AsO？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, Mn？O？) 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 ？) and oxidation of Mn？O？ to generate PbO？ (XRD verification); As stabilization depends on the oxidation of As(III) by Mn(IV) (As(V) accounts for 82% in XPS) and Fe-AsO？ co-precipitation (EDS surface scan shows As-Fe co-localization); Cd is fixed by biochar carboxyl ion exchange (C=O peak intensity in FTIR decreases by 63%) and pore physical adsorption (average pore size 6.2 nm). Compared with the traditional cement solidification method, FMBO@BC