Kubheka Gugu, Adeola Adedapo O, Forbes Patricia B C
Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria Lynnwood Road, Hatfield Pretoria 0002 South Africa
RSC Adv. 2022 Aug 24;12(37):23922-23936. doi: 10.1039/d2ra04641e. eCollection 2022 Aug 22.
In this study, three novel hexadecylamine graphene quantum dots (hexadecyl-GQDs) with varying moieties on the surface were synthesised and characterised to examine the effect of surface functionalisation on their adsorption efficiency. Introducing hydrophobic moieties generation of an amide bond by coupling hydrophilic carboxylic acid-functionalised GQDs with hexadecylamine improved the adsorption capacity of GQDs. The AFM and Raman spectroscopy results revealed the formation of multilayered GQDs with an average diameter of 10.0, 9.8, and 7.0 nm for C-GQDs, C-NGQDs and C-SNGQDs, respectively. According to the sum of squared error (SSE) values obtained from fitting phenanthrene adsorption experimental data to two- and three-parameter models, the Sips hybrid isotherm model best described the adsorption of sorbate to the doped hexadecyl-GQDs (0.55 ≥ SSE ≤ 0.72), with values >0.9. Furthermore, doping of the GQDs favoured a multilayer adsorption mechanism over monolayer adsorption, enhancing adsorption capacities ( & ). Hexadecylamine sulphur and nitrogen co-doped GQDs (C-SNGQDs) gave the highest maximum adsorption capacity ( ) of ∼1377 mg g. Pristine GQDs interact with phenanthrene endothermically, while the adsorption of phenanthrene onto modified GQDs is spontaneously exothermic. The adsorption of phenanthrene is most affected by the presence of sulfate and phosphate anions and is best at ambient temperature and acidic pH. Co-doping with nitrogen and sulphur groups and modification of hydrophilic to hydrophobic form enhanced the physicochemical and adsorption performance of C-SNGQDs, making them potentially suitable as materials for the extraction of hydrophobic organic pollutants from water.
在本研究中，合成并表征了三种表面具有不同基团的新型十六烷基胺石墨烯量子点（十六烷基-GQDs），以研究表面功能化对其吸附效率的影响。通过将亲水性羧酸官能化的GQDs与十六烷基胺偶联引入疏水基团并生成酰胺键，提高了GQDs的吸附容量。原子力显微镜（AFM）和拉曼光谱结果表明，C-GQDs、C-NGQDs和C-SNGQDs分别形成了平均直径为10.0、9.8和7.0 nm的多层GQDs。根据将菲吸附实验数据拟合到双参数和三参数模型所获得的误差平方和（SSE）值，Sips混合等温线模型最能描述吸附质在掺杂十六烷基-GQDs上的吸附（0.55≥SSE≤0.72），相关系数值>0.9。此外，GQDs的掺杂有利于多层吸附机制而非单层吸附，从而提高了吸附容量（qe和qm）。十六烷基胺硫和氮共掺杂的GQDs（C-SNGQDs）具有最高的最大吸附容量（qm），约为1377 mg g-1。原始GQDs与菲的相互作用是吸热的，而菲在改性GQDs上的吸附是自发放热的。菲的吸附受硫酸根和磷酸根阴离子的存在影响最大，在环境温度和酸性pH条件下效果最佳。氮和硫基团的共掺杂以及亲水性到疏水性形式的改性增强了C-SNGQDs的物理化学和吸附性能，使其有可能适合作为从水中提取疏水性有机污染物的材料。
