Influence of flake size and electrolyte conditions on graphene oxide adsorption of ionic dyes

Two graphene oxide (GO) materials were characterised and their performance as adsorbents for common ionic dyes was investigated. The GOs demonstrated to possess significantly different flake sizes; here termed Smaller Flake GO (SFGO) Larger (LFGO). Kinetics isotherm studies using both cationic Methylene Blue (MB) anionic Methyl Orange (MO) showed adsorption behaviour followed second order kinetics Langmuir monolayer isotherms in all cases. For MB, capacities 526.3 mg/g 384.6 (LFGO) with interaction attributed primarily electrostatic attraction, where the smaller, higher surface area led greater adsorption. In comparison MO, lower at 113.6 149.3 Here, while electrostatically repulsive, occurred via π-π interactions hydrogen bonding, LFGO having more favourable chemistry. Both observed aggregate when dispersed dyes, introduction of sodium (Na+) or magnesium (Mg2+) sulphates adversely affected SFGO, MB reduced by 5.1% 32.4% (Mg2+). Similarly, LFGO, capacity 7% 17.3% Adsorption Mg2+ onto vacant binding sites charge neutralisation principal antagonistic mechanisms. These findings demonstrate potential usage commercial dye removal separation will be significance industrial effluent applications.