The current research focuses on the valorization of red clay waste (RCW) to develop alumino-silicate geopolymer binders (GPP) and geopolymer spheres obtained from GPP powder modified with sodium alginate (Alg/GPP). GPP and Alg/GPP were applied in the environmental field for the retention of methyl orange (MO) from an aqueous solution. The raw material and the synthesized geopolymers were characterized by various physico-chemical methods. The results of XRF, XRD, and FTIR confirmed the successful synthesis of GPP and Alg/GPP, while the SEM/EDX findings revealed the homogeneous surface of the adsorbents. A significant specific surface area was detected for GPP (73.56 m/g) and Alg/GPP (91.24 m/g) with a high cation exchange capacity around 122 meq/100g for GPP and 185 meq/100g for Alg/GPP. The removal process was performed using the response surface methodology according to the Box-Behnken design, optimizing the retention efficiency of MO by different factors, including temperature, initial concentration, solution pH, and contact time. The obtained data was treated through the analysis of variance (ANOVA) and fitted by a quadratic polynomial model based on multiple regression analysis. In an acidic medium at 45 °C, the optimal conditions for MO retention were estimated to be 120 mg/L of MO concentration in 55 min using GPP and 180 mg/L of MO concentration in 20 min using Alg/GPP. The pseudo-second-order kinetics were more appropriate for describing the MO removal onto GPP and Alg/GPP adsorbents. The Langmuir model identified a high retention capacity of MO around 94.78 mg/g via GPP and 224.85 mg/g via Alg/GPP. The thermodynamic data confirmed that the elimination of MO dye onto GPP and Alg/GPP adsorbents was endothermic, favorable, and spontaneous. This study provided insights into the valorization of composite materials based on solid waste in dye retention, which can potentially be employed in wastewater treatment.

中文翻译：

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基于红粘土废料合成地质聚合物粉末和珠子用于从水溶液中吸附甲基橙染料：表征、响应面方法的应用和成本分析

目前的研究重点是红粘土废物（RCW）的增值，以开发铝硅酸盐地质聚合物粘合剂（GPP）以及由海藻酸钠改性的GPP粉末获得的地质聚合物球（Alg/GPP）。 GPP和Alg/GPP应用于环境领域，用于保留水溶液中的甲基橙（MO）。通过各种物理化学方法对原材料和合成的地质聚合物进行了表征。 XRF、XRD 和 FTIR 的结果证实了 GPP 和 Alg/GPP 的成功合成，而 SEM/EDX 结果显示了吸附剂的均匀表面。检测到 GPP (73.56 m/g) 和 Alg/GPP (91.24 m/g) 具有显着的比表面积，GPP 的阳离子交换容量约为 122 meq/100g，Alg/GPP 的阳离子交换容量约为 185 meq/100g。根据 Box-Behnken 设计，使用响应面法进行去除过程，通过不同因素（包括温度、初始浓度、溶液 pH 值和接触时间）优化 MO 的保留效率。通过方差分析（ANOVA）对获得的数据进行处理，并通过基于多元回归分析的二次多项式模型进行拟合。在 45 °C 的酸性介质中，使用 GPP 估计 MO 保留的最佳条件为 55 分钟内 MO 浓度为 120 mg/L，使用 Alg/GPP 20 分钟内 MO 浓度为 180 mg/L。准二级动力学更适合描述 GPP 和 Alg/GPP 吸附剂上的 MO 去除。 Langmuir 模型确定，通过 GPP 的 MO 保留能力约为 94.78 mg/g，通过 Alg/GPP 的 MO 保留能力约为 224.85 mg/g。热力学数据证实 MO 染料在 GPP 和 Alg/GPP 吸附剂上的消除是吸热的、有利的且自发的。这项研究为基于固体废物的染料保留复合材料的增值提供了见解，该材料可用于废水处理。