Qualitative and quantitative characterization of Cd²⁺ adsorption mechanisms was performed with rice-straw and sewage-sludge biochars produced at different temperature (300–700 °C), respectively. The pH effect, adsorption kinetics and isotherms were investigated, and chemical analyses of Cd²⁺-loaded biochars were conducted by SEM-EDS, XRD, FTIR and Boehm titration. This demonstrated that rice-straw biochars (RSBs) have greater adsorption capacities for Cd²⁺ than sewage-sludge biochars (SSBs), which was mainly due to precipitation and cation exchange mechanisms, with their contribution proportion to total adsorption from 76.1% to 80.8%. While in SSBs, both mechanisms were overshadowed by coordination with π electrons mechanism accounting for 59.2%–62.9% of total adsorption, even the role of cation exchange was negligible in the adsorption mechanisms accounting for 2.3%–6.7%. The relationship of each mechanism with biochar’s properties were discussed, which further deepen our understanding of adsorption on biochars. These results suggest RSBs have great potential for removing Cd²⁺ from aqueous solutions.

Cd ²⁺吸附机理的定性和定量表征分别是在不同温度（300-700°C）下生产的稻草和污水污泥生物炭。研究了pH值的影响，吸附动力学和等温线，并通过SEM-EDS，XRD，FTIR和Boehm滴定法对负载了Cd ^2+的生物炭进行了化学分析。这表明稻草生物炭（RSB）对Cd ^2+的吸附能力更大。与污水污泥生物炭相比，这主要是由于沉淀和阳离子交换机制所致，它们对总吸附的贡献率从76.1％增至80.8％。在SSB中，这两种机理都被与π电子机理的协调作用所掩盖，后者占总吸附量的59.2％–62.9％，即使阳离子交换的作用在占2.3％–6.7％的吸附机理中也可以忽略不计。讨论了每种机制与生物炭特性的关系，这进一步加深了我们对生物炭吸附的理解。这些结果表明，RSB具有从水溶液中去除Cd ^2+的巨大潜力。