Dyes used by the textile, tannery, and food industries tend to pollute water bodies and must be removed to get clean water. Hydroxyapatite (HAP) was synthesized from eggshells using the wet precipitation process. The as-synthesized HAP was characterized using Fourier Transform Infrared (FTIR) and X-ray powder diffraction (XRD). The synthesized HAP was mixed with three different clays: halloysite (HNT), kaolinite (KAO), and bentonite (BENT). The removal efficiency values of methylene blue (MB) from the data showed that HAP-BENT adsorbents had higher values, followed by HAP-HNT and then HAP-KAO adsorbents. The combined masses of 24 mg, 34.5 mg, and 33 mg (representing 20%, 15%, and 10% of HAP-BENT mass) had average adsorption capacity values of 20.7 mg/g, 17.2 mg/g, and 17.9 mg/g, respectively. For each mass percentage, the adsorption capacity values were found to decrease with adsorbent dosage. The HAP-BENT composites had removal efficiency values of 98.4, 91.9%, and 91.9%, respectively. Adsorption data for the HAP-BENT adsorbents were found to be well described by the Langmuir isotherm model and pseudo-second-order kinetic model. The effect of temperature on adsorption capacity was evaluated and thermodynamical modeling was undertaken. The thermodynamical modeling predicts that based on the value of the change in enthalpy and Gibbs free energy the process was exothermic and spontaneous. This work confirms the potential of HAP-clay composites in removing MB from water.

中文翻译：

---

羟基磷灰石-（HAP-）粘土复合材料的合成和表征以及对水处理亚甲蓝的吸附研究

纺织、制革和食品工业使用的染料往往会污染水体，必须去除才能获得干净的水。羟基磷灰石 (HAP) 是使用湿法沉淀法从蛋壳合成的。使用傅里叶变换红外 (FTIR) 和 X 射线粉末衍射 (XRD) 对合成的 HAP 进行表征。合成的 HAP 与三种不同的粘土混合：埃洛石 (HNT)、高岭石 (KAO) 和膨润土 (BENT)。数据中亚甲蓝 (MB) 的去除效率值表明 HAP-BENT 吸附剂具有更高的值，其次是 HAP-HNT，然后是 HAP-KAO 吸附剂。24 mg、34.5 mg 和 33 mg（代表 HAP-BENT 质量的 20%、15% 和 10%）的组合质量的平均吸附容量值为 20.7 mg/g、17.2 mg/g 和 17.9 mg/ g 分别。对于每个质量百分比，发现吸附容量值随吸附剂用量而降低。HAP-BENT 复合材料的去除效率值分别为 98.4、91.9% 和 91.9%。发现 HAP-BENT 吸附剂的吸附数据由 Langmuir 等温线模型和伪二级动力学模型很好地描述。评估了温度对吸附能力的影响，并进行了热力学建模。热力学模型预测，基于焓和吉布斯自由能的变化值，该过程是放热和自发的。这项工作证实了 HAP-粘土复合材料在从水中去除 MB 方面的潜力。发现 HAP-BENT 吸附剂的吸附数据由 Langmuir 等温线模型和伪二级动力学模型很好地描述。评估了温度对吸附能力的影响，并进行了热力学建模。热力学模型预测，基于焓和吉布斯自由能的变化值，该过程是放热和自发的。这项工作证实了 HAP-粘土复合材料在从水中去除 MB 方面的潜力。发现 HAP-BENT 吸附剂的吸附数据由 Langmuir 等温线模型和伪二级动力学模型很好地描述。评估了温度对吸附能力的影响，并进行了热力学建模。热力学模型预测，基于焓和吉布斯自由能的变化值，该过程是放热和自发的。这项工作证实了 HAP-粘土复合材料在从水中去除 MB 方面的潜力。