Metal oxide-modified biochar can effectively remediate or adsorb heavy metals in polluted soil and wastewater. However, the interaction between cellulose and hemicellulose on the surface of biochar/biomass and metal oxides is unclear, and the loading stability, adsorption capacity and mechanism of metal oxides remain to be explored. In this work, weakly crystalline birnessite (δ-MnO₂) rice husk biomass composites (MBC) were prepared via hydrothermal impregnation and then used to immobilize heavy metals in cadmium-polluted soil and wastewater. The surface of MBC was covered by sheet-like manganese oxides with a regular layered stacking structure. The adsorption of Cd(II) by MBC could be mainly attributed to monolayer chemisorption, which could achieve a maximum adsorption capacity of 115.04 mg g⁻¹. The addition of 1.0 % MBC reduced the effective Cd concentration in CaCl₂ extractant in the soil from 0.24 mg kg⁻¹ to 0.09 mg kg⁻¹, and the highest decreasing rate reached 62.5 %. Additionally, MBC could also reduce the concentration of H₂O-leachable Cd from 22.44 μg kg⁻¹ to 9.50 μg kg⁻¹. MBC facilitated the transformation of exchangeable Cd (EX-Cd) to iron-manganese bound Cd (OX-Cd) mainly comprising crystalline Mn oxide and Fe oxide. In addition, the mechanisms for MBC immobilization of Cd in polluted-soil and aqueous systems may include complexation-dominated and ion exchange-assisted processes, which contribute to a better understanding of the chemical structures and characteristics of metal oxides used to directly modify biomass. Overall, the findings indicate the possibility of applying MBC for soil and water remediation.

金属氧化物改性生物炭可以有效修复或吸附污染土壤和废水中的重金属。然而，纤维素和半纤维素在生物炭/生物质与金属氧化物表面的相互作用尚不清楚，金属氧化物的负载稳定性、吸附能力和作用机理等仍有待探索。在这项工作中，弱结晶水钠锰矿 (δ-MnO ₂ ) 稻壳生物质复合材料 (MBC) 通过水热浸渍制备，然后用于固定镉污染土壤和废水中的重金属。MBC表面覆盖有规则层状堆叠结构的片状氧化锰。MBC对Cd(II)的吸附主要归因于单层化学吸附，最大吸附容量为115.04 mg g ^-1. 添加1.0% MBC可使土壤中CaCl _{2萃取剂中Cd有效浓度由0.24 mg kg} ^-1降低至0.09 mg kg ^-1，降幅最高可达62.5 %。此外，MBC 还可以将 H ₂ O-可浸出 Cd 的浓度从 22.44 μg kg ^-1降低到 9.50 μg kg ^-1. MBC 促进可交换的 Cd (EX-Cd) 转化为铁锰结合的 Cd (OX-Cd)，主要包括结​​晶 Mn 氧化物和 Fe 氧化物。此外，MBC 在污染土壤和水系统中固定 Cd 的机制可能包括络合主导和离子交换辅助过程，这有助于更好地了解用于直接修饰生物质的金属氧化物的化学结构和特性。总体而言，研究结果表明应用 MBC 进行土壤和水体修复的可能性。