原料种类和热解温度对生物炭吸附Cd2+的影响

以稻秆（RS）、稻壳（RH）、木屑（SD）为原料，在小型流化床实验台上制备生物炭，分析了原料种类和热解温度（400℃、500℃、600℃）对生物炭理化性质及吸附Cd²⁺性能的影响规律，并定性和定量分析了吸附过程中的作用机制。实验结果表明：准二级动力学方程和Langmuir方程能够较好地描述生物炭样品对Cd²⁺的吸附过程。生物炭RS500的平衡吸附量达到30.19mg/g，远远高于生物炭SD500，其中无机矿物的离子交换和沉淀反应吸附贡献值为24.95mg/g，是主导吸附机制；而生物炭SD500吸附Cd²⁺过程中，无机矿物和π键的贡献百分比分别为49.70%和38.21%。随着热解温度的升高，生物炭吸附Cd²⁺过程中含氧官能团的络合反应不断削弱而Cd²⁺-π键作用不断增强；稻秆炭和稻壳炭中无机矿物的吸附贡献值则呈先上升后下降的趋势，并在500℃热解温度下达到最大值。生物炭样品吸附Cd²⁺的作用机制中，离子交换和沉淀反应占比最大，Cd²⁺-π键作用次之，络合反应最小。

Effects of feedstock type and pyrolysis temperature on Cd2+ adsorption by biochar

The biochars were prepared in a lab-scale fluidized bed reactor, using rice straw(RS), rice husk(RH) and sawdust(SD) as raw materials. The influences of feedstock type and pyrolysis temperature(400℃, 500℃, 600℃) on the physicochemical properties and Cd²⁺ adsorption of biochar were researched, and the qualitative and quantitative analysis of adsorption mechanism was conducted. The adsorption process could be preferably described by the Pseudo-second-order kinetic equation and the Langmuir equation. The adsorption capacity at equilibrium of RS500 was up to 30.19mg/g, which was much higher than that of SD500. The ion exchange and precipitation with inorganic minerals contributed 24.95mg/g， serving as the dominant adsorption mechanism. However, the contribution percentages of inorganic minerals and π electrons were 49.70% and 38.21% respectively in the Cd²⁺ adsorption by SD500. With the increase of pyrolysis temperature, the complexation with oxygen-containing functional groups was weakened while the Cd²⁺-π interaction was strengthened. At the same time, the ion exchange and precipitation with inorganic minerals in the Cd²⁺ adsorption by rice straw biochar and rice husk biochar were strengthened firstly and then weakened as the pyrolysis temperature increasing, and the contribution of them reached the maximum at 500℃. Furthermore, the contribution of each adsorption mechanism in the process of Cd²⁺ adsorption by biochar followed this order: ion exchange and precipitation were the largest, followed by Cd²⁺-π interaction, and complexation was the least.