Duarte Emanuele D V, Vieira Wedja T, Góes Rodrigo O, de Azevedo Luiz E C, Vieira Melissa G A, da Silva Meuris G C, de Carvalho Samira M L
School of Chemical Engineering, University of Campinas, Av. Albert Einstein, Nº 500, CEP: 13083-970, Campinas, São Paulo, Brazil.
School of Chemical Engineering, Federal University of Pará, Rua Augusto Corrêa, Nº 01, CEP: 66075-110, Belém, Pará, Brazil.
Environ Sci Pollut Res Int. 2023 May;30(22):62602-62624. doi: 10.1007/s11356-023-26454-y. Epub 2023 Mar 22.
A clay-based adsorbent (CBA) was purified from a sustainable precursor (raw clay, RC), which was obtained from the Amazon region in Brazil. The CBA was characterized using X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Brunauer-Emmet-Teller surface area (S, RC = 23.386 m.g, CBA = 33.020 m.g), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), thermogravimetric analysis (TGA), cation exchange capacity (CEC, CBA = 44.75 cmol/kg), and point of zero charge analyses (pH, CBA = 2.20). Subsequently, CBA was used to adsorb basic yellow 2 (BY2) dye from aqueous solutions. A CBA dosage (1 g/L), initial concentration of dye (C = 15 mg/L), and pH (5.6) were ideal conditions for the BY2 dye removal of ~ 98%. The BY2 kinetics was better represented by the pseudo-first-order (PFO) model while the BY2 equilibrium was well represented by the Sips model, with a maximum adsorption capacity of q = 18.04 mg/g at 28 °C. The negative values of ΔG° and ΔH° showed that the studied process is spontaneous and exothermic, while the values of isosteric heat (∆H, -16 to -20 kJ/mol) suggest a predominance of physical interactions. The molecular chemical reactivity of BY2 was investigated using quantum chemical descriptors calculated based on Density Functional Theory (DFT) optimization of the dye molecule, and the results revealed a large energy gap value (4.3900 eV) and considerable chemical hardness (η = 2.1950 eV). Therefore, the correlation between DFT and experimental results consistently sustains that BY2 dye tends to be adsorbed on the CBA surface by electrostatic interactions, thus, this is the possible adsorption mechanism of this process.
一种基于粘土的吸附剂（CBA）是从一种可持续的前驱体（生粘土，RC）中提纯得到的，该前驱体取自巴西的亚马逊地区。使用X射线衍射（XRD）、傅里叶变换红外光谱（FTIR）、布鲁诺尔-埃米特-泰勒比表面积（S，RC = 23.386 m²/g，CBA = 33.020 m²/g）、扫描电子显微镜（SEM）、能量色散X射线光谱（EDS）、热重分析（TGA）、阳离子交换容量（CEC，CBA = 44.75 cmol/kg）以及零电荷点分析（pH，CBA = 2.20）对CBA进行了表征。随后，使用CBA从水溶液中吸附碱性黄2（BY2）染料。CBA用量（1 g/L）、染料初始浓度（C = 15 mg/L）和pH值（5.6）是去除BY2染料达到约98%的理想条件。BY2的动力学用伪一级（PFO）模型能更好地描述，而BY2的平衡用Sips模型能很好地描述，在28℃时最大吸附容量为q = 18.04 mg/g。ΔG°和ΔH°的负值表明所研究的过程是自发且放热的，而异构热的值（∆H，-16至-20 kJ/mol）表明物理相互作用占主导。使用基于染料分子密度泛函理论（DFT）优化计算得到的量子化学描述符对BY2的分子化学反应性进行了研究，结果显示出较大的能隙值（4.3900 eV）和相当大的化学硬度（η = 2.1950 eV）。因此，DFT与实验结果之间的相关性一致支持BY2染料倾向于通过静电相互作用吸附在CBA表面，所以，这是该过程可能的吸附机制。
