Basha Zakriya Waseem, Kumar Annamalai Senthil, Muniraj Sarangapani
P. G. & Research Department of Chemistry, RKM Vivekananda College (Autonomous), Mylapore, Chennai, 600004, Tamil Nadu, India.
Nano and Bioelectrochemistry Research Laboratory, Carbon Dioxide and Green Technology Research Centre and Department of Chemistry, School of Advance Science, Institute of Technology University, Vellore, 632 014, Tamil Nadu, India.
Environ Sci Pollut Res Int. 2024 Mar 11. doi: 10.1007/s11356-024-32816-x.
The objective of this study was to completely eliminate environmentally harmful cationic organic dye from aqueous solutions using the one-step ultrasonication method, renowned for its energy efficiency, user-friendliness, and minimal requirement for chemical resources, making it particularly suitable for large-scale applications. To achieve effective environmental remediation, we employed carbon dots derived from teak leaf biomass (TBCDs) layered with graphene oxide. We conducted a thorough characterization of the TBCDs using UV-vis spectroscopy (with absorption peaks at λ = 208 and 276 nm), FTIR spectroscopy (confirming the presence of various functional groups including -OH, -CH, C = O, COO, C-O-C, and = C-H), Raman spectroscopy (with bands at 1369 cm (D-Band) and 1550 cm (G-Band), and an intensity ratio (I/I) = 0.88, indicating structural defects correlated with the sp hybridization sites on the TBCDs), XRD analysis (indicating an amorphous nature of particles), HRTEM imaging (showing homogeneous dispersal of TBCDs with typical sizes ranging from 2 to 10 nm), FESEM analysis (showing a flat surface and minuscule particles), and Zeta potential analysis (revealing a surface charge peak at -51.0 mV). Our adsorption experiments yielded significant results, with a substantial 50.1 % removal rate and an impressive adsorption capacity of 735.2 mg g. Theoretical adsorption parameters were rigorously analyzed to understand the adsorption behavior, surface interactions, and mechanisms. Among these models, the Langmuir isotherm in conjunction with pseudo-second-order kinetics provided an exceptional fit (with R values closer to 1) for our system. The Gibbs free energy (ΔG) was found to be negative at all temperatures, indicating the spontaneity of the reaction. Regarding mechanism, electrostatic attraction ((+ve) MB dye + (- ve) TBCDs), π-π stacking adsorption facilitated by the graphitic structure, formation of multiple hydrogen bonds due to polar functional groups, and a pore-filling mechanism wherein the cationic MB dye fills the pores of TBCDs with graphene oxide layers, forming an adduct were identified. Furthermore, we demonstrated the regenerative capacity of our system by effectively extracting and recovering the MB dye (with a regeneration rate of 77.1%), utilizing ethyl alcohol as the solvent. These findings not only provide valuable insights into the adsorption capabilities of TBCDs but also highlight the potential of our approach in the recovery of expensive cationic organic dye compounds from polluted environments.
本研究的目的是使用一步超声法从水溶液中完全去除对环境有害的阳离子有机染料，该方法以其能源效率高、用户友好且对化学资源需求极少而闻名，特别适用于大规模应用。为实现有效的环境修复，我们采用了由柚木叶生物质衍生的碳点（TBCDs）与氧化石墨烯层叠而成的材料。我们使用紫外可见光谱（在λ = 208和276 nm处有吸收峰）、傅里叶变换红外光谱（确认存在包括 -OH、-CH、C = O、COO、C-O-C和 = C-H在内的各种官能团）、拉曼光谱（在1369 cm（D带）和1550 cm（G带）处有谱带，强度比（I/I）= 0.88，表明与TBCDs上的sp杂化位点相关的结构缺陷）、X射线衍射分析（表明颗粒为无定形性质）、高分辨率透射电子显微镜成像（显示TBCDs均匀分散，典型尺寸范围为2至10 nm）、场发射扫描电子显微镜分析（显示表面平整且颗粒微小）和zeta电位分析（揭示表面电荷峰值为 -51.0 mV）对TBCDs进行了全面表征。我们的吸附实验取得了显著成果，去除率高达50.1%，吸附容量令人印象深刻，达到735.2 mg/g。对理论吸附参数进行了严格分析，以了解吸附行为、表面相互作用和机制。在这些模型中，朗缪尔等温线与伪二级动力学相结合，对我们的系统提供了出色的拟合（R值更接近1）。发现吉布斯自由能（ΔG）在所有温度下均为负值，表明反应具有自发性。关于机制，确定了静电吸引（（+ve）亚甲基蓝染料 + （-ve）TBCDs）、由石墨结构促进的π-π堆积吸附、由于极性官能团形成的多个氢键以及阳离子亚甲基蓝染料填充带有氧化石墨烯层的TBCDs孔隙形成加合物的孔隙填充机制。此外，我们通过使用乙醇作为溶剂有效地提取和回收亚甲基蓝染料（再生率为77.1%），证明了我们系统的再生能力。这些发现不仅为TBCDs的吸附能力提供了有价值的见解，还突出了我们的方法在从污染环境中回收昂贵的阳离子有机染料化合物方面的潜力。
