Effect of co-existing kaolinite and goethite on the aggregation of graphene oxide in the aquatic environment

Abstract

Broad applications of graphene oxide (GO) will result in the release of GO into aquatic environments, where clay minerals and metal (hydr)oxides are commonly present. Thereby the interactions between GO and a binary system containing clay minerals and metal (hydr)oxides can occur. We investigated the aggregation of GO with kaolinite and kaolinite-goethite associations (KGAs) in aquatic systems under different pHs, ionic strengths, and GO concentrations. GO suspension was unstable at low pHs, and the aggregation of GO occurred in the presence of KGA-4% and KGA-10% until pH 5 and 6, respectively. Kaolinite decreased the critical coagulation concentration (CCC) of GO at pH 5.5 from around 50 to 20 mM NaCl due to the reduced energy barrier. Heteroaggregation of GO with KGAs was extremely sensitive to ionic strength at pH 5.5, and the CCC of GO in the presence of KGA-10% increased from less than 1 mM NaCl to 5 mM NaCl with the increase of pH from 5.5 to 9. The heteroaggregation extent of GO with KGAs was enhanced firstly, then reduced with the increase of GO concentrations at pH 5.0, which is likely because KGA plates were more efficiently wrapped by large-size GO sheets with increasing GO concentrations. These findings are useful for understanding and predicting the fate of GO in the relatively complicated aquatic and soil environments where binary minerals co-exist.

Nitrogen‐doped self‐shrinking porous 3D graphene capacitor deionization electrode

“…Graphene has a high theoretical specific surface area and excellent electrical conductivity and is an ideal CDI electrode material. However, due to the aggregation effect of graphene, the actual specific surface area is much lower than the theoretical value . The preparation of graphene into a 3D network structure or composite can overcome the abovementioned aggregation effect and improve the desalination performance.…”

“…However, due to the aggregation effect of graphene, the actual specific surface area is much lower than the theoretical value. [25][26][27] The preparation of graphene into a 3D network structure or composite can overcome the abovementioned aggregation effect [28][29][30][31] and improve the desalination performance. However, the conventional 3D graphene has a relatively large pore structure, which makes the electrode material unable to interact well with anions and cations during the desalination process, thereby affecting the CDI performance of the 3D graphene.…”

Colloidal properties and stability of aqueous suspensions of few-layer graphene: Importance of graphene concentration

“…Agglomeration and stability of fullerene (nC 60 ) (Anderson and Barron, 2005; Bouchard et al, 2009; Chen and Elimelech, 2006, 2008, 2009), carbon nanotube (CNT) (Sano et al, 2001; Smith et al, 2008; Smith et al, 2009), and graphene oxide (GO) (Chowdhury et al, 2013; Chowdhury et al, 2015; Huang et al, 2016; Konkena and Vasudevan, 2012; Wu et al, 2013) have been extensively studied in the literature. These studies showed that the agglomeration of CNMs follows the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, and the CNM-specific properties have strong effects on the colloidal stability of CNMs.…”

Graphene-family nanomaterials in wastewater treatment plants

“…In all the cases, LDH-Cl was better than LDH-CO 3 , perhaps because the first one was more positively charged than the later. Huang et al [30] performed similar experiments with kaolinite and goethite associated with kaolinite (10% or 4% goethite) in a mixture of deionised water bearing 20 mg/L of GO, 2000 mg/L of mineral and with pH adjustment. It was found that, after 24 h, GO sheets could be aggregated in presence of kaolinite, kaolinite with 4% goethite and kaolinite with 10% goethite if pH was lower than 4, 5 and 6, respectively.…”