Graphene oxide functionalized with cobalt ferrites applied to the removal of bisphenol A: ionic study, reuse capacity and desorption kinetics.

A new adsorbent material based on graphene oxide (GO) functionalized with magnetic cobalt ferrite nanoparticles (γCoFe2O4) was synthesized via ultrasonication to remove the endocrine-disrupting-chemical bisphenol A (BPA) from aqueous solutions. The synthesized material (GO-γCoFe2O4) was characterized by TEM, SEM, DRX and FTIR analysis. Magnetization measures proved that the adsorbent had superparamagnetic characteristics that facilitated its separation from the aqueous solution. The maximum adsorption capacity obtained was 30 mg g-1 with adsorbent concentration of 1 g L-1, temperature of 55°C and natural pH of the solution. The experimental data were better adjusted to the kinetic models of pseudo-second-order and Langmuir isotherm. The thermodynamic parameters showed that the BPA adsorption on GO-γCoFe2O4 was spontaneous, exothermic and thermodynamically favourable. Desorption kinetics was performed using 50% ethanol as solvent, resulting in an equilibrium time of 4 h with better adjustment to the pseudo-second order kinetic model. The adsorbent showed a high regeneration capacity maintaining adsorptive capacity above 75% after 6 cycles of reuse.

Adsorption of sodium diclofenac in aqueous medium using graphene oxide nanosheets.

In this work, the adsorption of sodium diclofenac (DCF) on graphene oxide nanosheets (GON) was evaluated. GON was synthesized by the modified Hummers method and characterized regarding its composition, morphology, and surface load. It was applied in batch adsorption tests. The process was evaluated from the kinetic, isothermal and thermodynamic properties, and parameters such as adsorbent mass and solution pH were optimized. The best working condition was observed at the natural pH of the solution (6.2) and 0.25 g L-1 adsorbent dosage. The pseudo-first-order and pseudo-second-order models were applied to verify the behaviour of the adsorption kinetics, and the adsorption isotherms were also developed at temperatures ranging from 25°C to 45°C. The isotherm models of Langmuir, Freundlich, and Temkim were applied to the equilibrium data. The thermodynamic parameters of enthalpy, entropy, and Gibbs free energy were evaluated to describe the behaviour of the adsorptive process. The maximum adsorption capacity of DCF at 25°C was 128.74 mg g-1 with a removal rate of 74% in 300 min. The process was favourable and spontaneous with adsorptive capacity decreasing with increasing temperature. In addition, an adsorption mechanism was proposed to show the possible bonds that occur between adsorbate and adsorbent and the interactions formed through the influence of pH.

Application of graphene nanosheet oxide for atrazine adsorption in aqueous solution: synthesis, material characterization, and comprehension of the adsorption mechanism.

The present study aimed to investigate the application of graphene oxide (GO) as adsorbent material for the removal of atrazine (ATZ). The material produced was characterized to investigate the characteristics and applied as an adsorbent. The material obtained after the synthesis process presented oxygenated functional groups, which contributed to the development of a good adsorbent material. Studies were carried out to verify the influence of adsorbent material mass and initial pH of ATZ solution in adsorption capacity. Kinetic study determined that pseudo-second-order model best describes adsorbate-adsorbent interaction, with equilibrium time of 72 h. The effect of temperature on the material adsorption capacity was also studied. The Langmuir isotherm is the best fit to describe adsorption process GO-ATZ and maximum adsorption capacity obtained was 23.844 ± 0.694 mg g-1, at 318 K. Variations in process energies were determined, being a spontaneous adsorption, endothermic and characteristic of physical and chemical adsorption. Finally, influence of salts in solution on adsorption capacity was studied; the conclusion was that the presence of electrolytes affects the adsorption capacity of the material.