Effect of the Oxidation Degree of Graphene Oxides on their Adsorption, Flocculation, and Antibacterial Behavior

Abstract

The effect of the oxidation degree of two graphene oxides (GOs) on the adsorption of cationic methylene blue (MB) and anionic methyl orange (MO) dyes and on the coagulation of cationic goethite and anionic kaolin minerals was studied with respect to water treatment in the textile and mining industries. To this purpose, two GOs with high (GO-H) and low (GO-L) oxidation degrees were synthesized by the Hummer method and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and zeta potential. The antibacterial behavior against Gram-negative Escherichia coli bacterium was further tested under continuous agitation. GO-H and GO-L presented a high capacity for removing MB with maximum monolayer adsorption capacities (q m ) of 476.2 and 312.5 mg/g, respectively. Despite its negative charge, GO-L adsorbed MO with a q m of 263.2 mg/g that was higher than the values from GO-H (105.3 mg/g). Regarding the coagulation process, GO-H interacted with goethite decreasing the turbidity of the respective clay suspension, while GO-L presented a much lower effect. In kaolin suspensions the flocculation was less pronounced confirming the relevance of the minerals on the GO behavior. Both types of GO were able to kill Escherichia coli species at 0.5 mg/mL of particles with GO-L presenting the highest effectivity. All these results allow the generation of a general mechanism explaining the interactions of GO with the different contaminants based on its functional groups. Our results show that GO nanoparticles can be designed as a universal agent for water treatment removing ionic dissolved organic dyes and cationic particles as well as bacteria such as Escherichia coli.

Strain-boosted hyperoxic graphene oxide efficiently loading and improving performances of microcystinase

“…Our preliminary experimental results indicated that higher total oxygen content (CTO) in CGOs was associated with higher loading capacities of CGOs for CMlrA ( Table S2 ). Thus, their different immobilization performances could be related to their degree of oxidation ( Tan et al., 2017 ; Zolezzi et al., 2018 ). To systematically explore the degree of oxidation on the immobilization performance of GO for MlrAs, nine types of HGOs (HGO 1 -HGO 9 ) were prepared using HGO 0 as raw material and by altering the amount of added KMnO4 oxidant and the method of synthesis (M1 or M2) ( Hummers and Offeman, 1958 ; Marcano et al., 2010 ) ( Figures 1 A and S2 ; Table S3 ).…”

“…In solutions with pH values ranging from 5.3 to 9.3, HGO 5 zeta potentials were lower than those of HGO 0 , indicating that a high degree of oxidation in HGO 5 led to greater stability than HGO 0 over a wider pH range ( Table S6 ). The stabilities of HGOs in aqueous solutions can be attributed to the concentration of oxygenated functional groups and the dissociation of acid functional groups such as carboxylic acid (-COO - + H + ) and hydroxyl (OH − ) groups ( Reynosa-Martínez et al., 2020 ; Zolezzi et al., 2018 ).…”

“…Graphene oxide (GO) nanomaterials have been widely used as promising treatments in many fields because they typically achieve considerably improved performances by tuning morphology, composition, and physicochemical properties ( Chaudhary et al., 2021 ; Sun et al., 2021 ). However, the structural characteristics of GOs, including their functionalized molecules, microenvironments, and degree of oxidation, have important influences on their performance characteristics including their loading capability, stability, and potential toxicity ( Chaudhary et al., 2021 ; Zhang et al., 2020a ; Zolezzi et al., 2018 ). Our preliminary studies showed that several commercial GOs (CGOs) exhibited different carrying capacities for CMlrA ( Table S2 ).…”

Zeta Potential of Pyrite Particles in Concentrated Solutions of Monovalent Seawater Electrolytes and Amyl Xanthate

“…That oscillating ion cloud produced an alternating voltage at the two electrodes, the streaming potential, which is proportional to the zeta potential of the particles. This zeta potential technique implemented in the Stabino has been used recently and successfully in various applications of interest in mineral processing [24][25][26][27]. The solution pH was adjusted with analytical grade KOH, NaOH, LiOH, and CsOH, at a concentration of 0.5 M (Merck) and HCl 0.020 M (Merck), the latter in order to not introduce a base other than Cl − ; this disparity in concentration is to achieve an alkaline pH without using too much base and to have a slow and controlled evolution of the zeta potential to the acid pH.…”

High-sorption terpyridine–graphene oxide hybrid for the efficient removal of heavy metal ions from wastewater

“…Furthermore, it has been shown that the changes in the adsorption capacity and selectivity are strictly correlated with the chemical functionalization GO surface 37,38,[40][41][42][43] and degree of oxidation of graphene oxide. 44,45 Unfortunately, there are still some limitations that, if solved, can make utilization of GO-based materials in the wastewater-derived adsorption processes a widely applied methodology. In particular, these materials are typically highly dispersible in water, therefore their regeneration and repeated utilization are not economically feasible.…”