生物炭/凹凸棒石复合材料对铅镉的吸附

为探讨生物炭/凹凸棒石复合材料对废水中重金属的吸附效果与作用机理，以水稻、小麦秸秆与凹凸棒石为原料，在缺氧条件下热解制备生物炭/凹凸棒石复合材料。通过批量吸附实验研究时间、浓度及pH等因素对复合材料吸附溶液中Cd²⁺和Pb²⁺的影响，利用SEM、BET、XRD、FTIR等方法对吸附前后的复合材料进行表征分析，从定性和定量的角度分析其作用机理，明确主导吸附机制。结果表明：准二级动力学和Langmuir等温模型更符合复合材料对Cd²⁺和Pb²⁺的吸附过程。与原始生物炭和凹凸棒石相比，水稻秸秆与凹凸棒石比例为5∶1时制备的复合材料RABC5-1和小麦秸秆与凹凸棒石比例为3∶1时制备的复合材料WABC3-1具有更好的吸附效果，对Cd²⁺的最大吸附量分别为132.97 mg·g^-1与132.39 mg·g^-1，对Pb²⁺的最大吸附量分别为222.60mg·g^-1与220.55 mg·g^-1。机理分析表明，复合材料对Cd²⁺和Pb²⁺的吸附机理主要包括沉淀作用、官能团络合作用、离子交换作用和阳离子-π作用。定量分析进一步证明，沉淀作用在RABC5-1、WABC3-1吸附Cd²⁺的过程中所占比例分别为84.6%、77.3%，在吸附Pb²⁺的过程中所占比例分别为82.0%、78.3%，是复合材料吸附重金属的主要机理，其次为阳离子交换作用，官能团络合作用和阳离子-π作用对吸附的整体贡献率较小。研究表明，复合材料RABC5-1与WABC3-1具有良好的吸附Cd²⁺和Pb²⁺的性能，是一种极具潜力的吸附材料，且沉淀作用是复合材料吸附重金属的主导机制。

Adsorption characteristics of Cd2+ and Pb2+ on biochar/attapulgite composites

A novel low-cost biochar/attapulgite composite material was prepared by pyrolysis under anoxic conditions with different proportions of rice straw, wheat straw, and attapulgite. Batch adsorption experiments were conducted to investigate the effects of adsorption time, initial concentration, and pH on the adsorption efficiency of Cd²⁺ and Pb²⁺. SEM, BET, XRD, and FTIR were used to characterize the composite materials before and after adsorption, and the adsorption mechanisms were studied from qualitative and quantitative perspectives. The results showed that the Pseudo-second-order kinetic model and the Langmuir isotherm model could describe the Cd ²⁺ and Pb²⁺ adsorption processes of the composites better. Compared with the original biochar and attapulgite, the composites RABC5-1(the ratio of rice straw to attapulgite was 5:1) and WABC3-1(the ratio of wheat straw to attapulgite was 3:1) showed better adsorption performance. The maximum adsorption capacities for Cd²⁺ were 132.97 mg·g^-1 and 132.39 mg·g^-1; for Pb²⁺, they were 222.60 mg·g^-1 and 220.55 mg · g^-1, respectively. The quantitative analysis revealed that precipitation was calculated to be 84.6% and 77.3% in the Cd²⁺ adsorption, 82.0% and 78.3% in the Pb²⁺ adsorption by RABC5-1 and WABC3-1, respectively, which was the main mechanism for heavy metal adsorption by composite materials, followed by cation exchange, functional group complexation, and cation-π interaction, which contributed less to the overall adsorption. The study demonstrates that the composites RABC5-1 and WABC3-1 have great adsorption properties for Cd²⁺ and Pb²⁺ and are potential adsorption materials. The mechanism analysis also reveal that precipitation is the dominant mechanism for the adsorption of heavy metals by the composites.