In this present work, the performance of a semifluidized bed adsorption column has been evaluated for the removal of Pb²⁺ and Cd²⁺ in a semi-continuous mode. The composite adsorbents have been synthesized from waste biomass–based biochar and alginate-based biopolymer. Synthesized adsorbent characterized and finally tested its effectiveness in the removal of both Pb²⁺ and Cd²⁺ metal ions by batch and semifluidized bed column adsorption studies. The adsorptive removal efficiencies were found to be dependent on solution pH, initial metal ion concentration, adsorbent dose or initial bed height, static bed height, system temperature and inlet flow rate of semifluidized bed operation. Pseudo-second-order kinetic model was fitted to the batch adsorption experimental data by non-linear and linear regression method and it was found that the non-linear method gives a better way of obtaining the various kinetic parameters and its applicability. A solute phase mass transfer–based dynamic model has been developed to explain the adsorptive behaviour of metal ions onto adsorbents during the semi-continuous mode of operation of a semifluidized bed system. Various mass transfer parameters and degree of dispersion coefficients for the individual packed and fluidized section were obtained from the developed model.

Graphical abstract

中文翻译：

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半流化床吸附柱研究复合吸附剂同时去除水相Pb 2+和Cd 2+的方法：基于实验和传质动力学模型的方法

在本工作中，已经评估了半流化床吸附柱在半连续模式下去除Pb ²⁺和Cd ^2+的性能。复合吸附剂是由基于废物生物质的生物炭和基于藻酸盐的生物聚合物合成的。合成吸附剂表征并最终测试了其在去除Pb ²⁺和Cd ^2+方面的有效性金属离子的分批和半流化床柱吸附研究。发现吸附去除效率取决于溶液pH，初始金属离子浓度，吸附剂剂量或初始床高度，静态床高度，系统温度和半流化床操作的入口流速。利用非线性和线性回归方法将伪二级动力学模型拟合到间歇吸附实验数据中，发现非线性方法为获得各种动力学参数及其适用性提供了更好的方法。已经开发了基于溶质相传质的动力学模型，以解释在半流化床系统的半连续运行模式下，金属离子对吸附剂的吸附行为。

图形概要