Complex Roles of Solution Chemistry on Graphene Oxide Coagulation onto Titanium Dioxide: Batch Experiments, Spectroscopy Analysis and Theoretical Calculation

Abstract

Although graphene oxide (GO) has been used in multidisciplinary areas due to its excellent physicochemical properties, its environmental behavior and fate are still largely unclear. In this study, batch experiments, spectroscopy analysis and theoretical calculations were addressed to promote a more comprehensive understanding toward the coagulation behavior of GO onto TiO2 under various environmental conditions (pH, co-existing ions, temperature, etc.). The results indicated that neutral pH was beneficial to the removal of GO due to the electrostatic interaction. The presence of cations accelerated GO coagulation significantly owing to the influence of electrical double layer compression. On the contrary, the presence of anions improved the stability of GO primarily because of electrostatic repulsion and steric hindrance. Results of XRD, FTIR and XPS analysis indicated that the coagulation of GO on TiO2 was mainly dominated by electrostatic interactions and hydrogen bonds, which were further evidenced by DFT calculations. The high binding energy further indicated the stability of GO + TiO2 system, suggesting that TiO2 can be used as an effective coagulant for the efficient elimination and coagulation of GO from aqueous solutions. These findings might likely lead to a better understanding of the migration and transformation of carbon nanomaterials in the natural environment.

Photocatalytic degradation of ibuprofen in water using TiO2 and ZnO under artificial UV and solar irradiation

“…Borosilicate material is chemically inert and stable under UV irradiation. But presence of iron content in borosilicate glass can cause decrease in degradation rate as compared to Quartz tubes (Yu et al., ). Demineralization potential of degraded samples by UV/TiO 2 , Solar (Quartz)/TiO 2 , and Solar (Borosilicate)/TiO 2 at optimum catalyst loading were evaluated by finding total organic carbon (TOC) values and chemical oxygen demand (COD).…”

Promotional Effect of Cu2S–ZnS Nanograins as a Shell Layer on ZnO Nanorod Arrays for Boosting Visible Light Photocatalytic H2 Evolution

“…The binding energy peak at 530.1 eV represents the lattice vibration of O atoms with metal atoms, that is, O–Cu/Zn bonding in the matrix system. The binding energy peak at 531.2 eV represents the oxygen-deficient states (Ov), such as oxygen vacancies, while the peak position at 532.6 eV represents the chemisorbed adsorbed O 2 functionalities of surface hydroxyl species (O–OH) on the surface . The intensity of the O 1s peaks at M–O (530.1 eV) is significantly reduced after Cu 2 S deformation when compared to the pristine ZnO and ZnO–Cu 2 O NR arrays, suggesting that Cu 2 S nanograins are amassed on top of the NR surface and that deep level surface defects might be influenced by the deformation of Cu 2 S, which induces oxygen vacancy states.…”

Efficient Removal of Cobalt(II) and Strontium(II) Metals from Water using Ethylene Diamine Tetra‐acetic Acid Functionalized Graphene Oxide

“…[17a], , The decrease of adsorption at pH ≈ 9 could be due to the presence of excess hydroxyl ions competing with Co II and Sr II for the hydrogen bond formed with water molecules coordinated with GO in interlayer . Also, coagulation of GO layer could be the reason for decreasing adsorption capacity at higher pH …”