A new modified walnut shell was prepared by grafting l‐aspartic acid (ASP) to walnut shell (WNS) in the hydrochloric acid solution (1.0 M). The effects of stirring speed, particle size, solid‐liquid ratio, temperature, and modifying agent concentration on grafting yield were studied. The grafting process conditions were optimized, and the grafting yield of WNS reached ∼14 wt%. The kinetics of the grafting reaction was investigated in the temperature range of 348‐368 K. A three‐step hypothesis was proposed to describe the grafting process: The ASP molecules diffuse to the out surface of WNS through the liquid film, then attend to the internal surface and react with WNS. The shrinking core models with different controlling steps were used to fit the kinetic data of the grafting process, and the results showed that the model controlled by a product layer fitted well with the experimental data. The internal diffusion coefficient D_A of ASP in WNS has been calculated, and it was applied to predict the grafting yield at different ASP concentrations by a shrinking core model. The results showed that the shrinking core model controlled by internal diffusion is suitable.

中文翻译：

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通过接枝l-天冬氨酸的新型改性核桃壳：合成与动力学

一种新的改性的核桃壳的制备是通过接枝升将天冬氨酸（ASP）置于盐酸溶液（1.0 M）中的核桃壳（WNS）中。研究了搅拌速度，粒径，固液比，温度和改性剂浓度对接枝率的影响。优化了接枝工艺条件，WNS的接枝收率达到〜14 wt％。在348-368 K的温度范围内研究了接枝反应的动力学。提出了一个三步假设来描述接枝过程：ASP分子通过液膜扩散到WNS的外表面，然后参与内表面并与WNS反应。使用具有不同控制步骤的收缩核模型来拟合接枝过程的动力学数据，结果表明由产品层控制的模型与实验数据吻合得很好。d_阿在WNS ASP的已计算出，并将其应用于由收缩核模型来预测在不同ASP浓度接枝率。结果表明，内部扩散控制的收缩核模型是合适的。