Abstract

The effectiveness of NaOH-functionalized Aspergillus niger-filled sodium alginate microbeads on methylene blue (MB) removal was investigated in this study. First of all, Aspergillus niger biomass was obtained, then functionalized using sodium hydroxide (NaOH). Lastly, the composites were prepared by dispersing NaOH-treated-Aspergillus niger in sodium alginate gel. The cross-linked composite microbeads in a 3% CaCl₂ solution were characterized by Fourier-transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, atomic force microscope (AFM), and scanning electron microscope (SEM). FTIR-ATR results indicated that the hydroxyl, amine, and carboxyl groups on the surface of the composite beads acted as binding sites. It was determined that the biosorption of MB occurred via the electrostatic interactions, Van der Waals interactions, π-π interactions, and H-bonding between functional groups and dye molecules. SEM and AFM analyses proved the presence of adsorbed dye molecules on the surface. Besides, optimum conditions were determined by examining the effects of different physicochemical parameters on biosorption. The maximum biosorption capacity of microbeads was obtained as 322.6 mg/g in pH = 7 at 25 °C. Moreover, various isotherms were used, including Freundlich, Langmuir, Dubinin-Radushkevich, and Harkins-Jura. The Langmuir model was found to be the best feasible when the correlation coefficients were taken into account. Biosorption followed the pseudo-second-order kinetic and occurred exothermically and spontaneously. This study indicates that NaOH-treated Aspergillus niger-filled sodium alginate microbeads are promising material as a biosorbent.

摘要

本研究研究了NaOH 功能化黑曲霉填充的海藻酸钠微珠去除亚甲基蓝 (MB) 的有效性。首先，获得黑曲霉生物质，然后使用氢氧化钠（NaOH）进行功能化。最后，通过将 NaOH 处理的黑曲霉分散在海藻酸钠凝胶中制备复合材料。_{3% CaCl 2}中的交联复合微珠通过傅里叶变换红外衰减全反射（FTIR-ATR）光谱、原子力显微镜（AFM）和扫描电子显微镜（SEM）对溶液进行了表征。FTIR-ATR结果表明复合珠表面的羟基、胺基和羧基作为结合位点。确定MB的生物吸附是通过官能团与染料分子之间的静电相互作用、范德华相互作用、π-π相互作用以及氢键发生的。SEM 和 AFM 分析证明表面存在吸附的染料分子。此外，通过考察不同理化参数对生物吸附的影响来确定最佳条件。在 25 °C、pH = 7 条件下，微珠的最大生物吸附能力为 322.6 mg/g。此外，使用了各种等温线，包括 Freundlich、Langmuir、Dubinin-Radushkevich 和 Harkins-Jura。当考虑相关系数时，朗缪尔模型被发现是最可行的。生物吸附遵循准二级动力学并且放热且自发地发生。这项研究表明，NaOH 处理的黑曲霉填充的海藻酸钠微珠是作为生物吸附剂的有前途的材料。