Abstract Hydrochloric acid-treated Macadamia nutshell (AMM) powder was grafted with acrylic acid monomers at different doses of 0.5, 1.0 and 2.0 M to incorporate the carboxylic groups on its surface. The grafted materials were labeled 0.5 GAM, 1 GAM and 2 GAM signifying the grafting ratios. The incorporation of acrylic acid was demonstrated by an increase in oxygen content from 0.18% to 1.20% in the elemental analysis. The splitting and shifting of the alcohol intermolecular bonded –OH functional groups at 3330 cm−1 to 3396 and 3321 cm−1 observed after grafting was further proof of the addition of acrylic acid. Scanning electron microscopy (SEM) images revealed that the materials exhibited stacked sheets with spherical halo openings typical of biomaterials. The maximum conditions for chromium(VI) removal were obtained at pH 2, 180 min contact time, 7.5 g/L adsorbent dosage concentration and a temperature of 40 °C. The adsorption mechanism was best described by the monolayer sorption postulated by Langmuir with reported adsorption capacity of 39.21 mg/g. The best fit for the kinetic data was obtained with the pseudo-second-order rate model suggesting a chemisorption nature of interaction. Accordingly, the thermodynamic factors were feasible, spontaneous and endothermic. The acrylic acid-functionalized Macadamia adsorbent showed greater potential compared to other biosorbents in the removal of hexavalent chromium from aqueous solution in the presence of competing anions.

中文翻译：

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聚丙烯酸接枝澳洲坚果壳粉通过吸附还原机制去除六价铬：吸附等温线、动力学和热力学

摘要 盐酸处理的澳洲坚果壳 (AMM) 粉末接枝了 0.5、1.0 和 2.0 M 不同剂量的丙烯酸单体，以在其表面引入羧基。接枝材料被标记为 0.5 GAM、1 GAM 和 2 GAM，表示接枝率。元素分析中氧含量从 0.18% 增加到 1.20% 证明了丙烯酸的掺入。接枝后观察到的醇分子间键合 -OH 官能团在 3330 cm-1 到 3396 和 3321 cm-1 处的分裂和转移进一步证明了丙烯酸的加入。扫描电子显微镜 (SEM) 图像显示，这些材料呈现出具有生物材料典型的球形光环开口的堆叠片。去除铬 (VI) 的最大条件是在 pH 2、180 分钟接触时间、7.5 g/L 吸附剂剂量浓度和 40 °C 的温度。Langmuir 假设的单层吸附最好地描述了吸附机制，据报道吸附容量为 39.21 mg/g。动力学数据的最佳拟合是通过伪二级速率模型获得的，表明相互作用的化学吸附性质。因此，热力学因素是可行的、自发的和吸热的。与其他生物吸附剂相比，丙烯酸官能化的澳洲坚果吸附剂在竞争阴离子存在的情况下从水溶液中去除六价铬方面表现出更大的潜力。动力学数据的最佳拟合是通过伪二级速率模型获得的，表明相互作用的化学吸附性质。因此，热力学因素是可行的、自发的和吸热的。与其他生物吸附剂相比，丙烯酸官能化的澳洲坚果吸附剂在竞争阴离子存在下从水溶液中去除六价铬方面表现出更大的潜力。动力学数据的最佳拟合是通过伪二级速率模型获得的，表明相互作用的化学吸附性质。因此，热力学因素是可行的、自发的和吸热的。与其他生物吸附剂相比，丙烯酸官能化的澳洲坚果吸附剂在竞争阴离子存在下从水溶液中去除六价铬方面表现出更大的潜力。