Graphene oxide is a very high capacity adsorbent due to its functional groups and π-π interactions with other compounds. Adsorption capacity of graphene oxide, however, can be further enhanced by having synergistic effects through the use of mixed-matrix composite. In this study, silica-decorated graphene oxide (SGO) was used as a high-efficiency adsorbent to remove Congo red (CR) and Cadmium (II) from aqueous solutions. The effects of solution initial concentration (20 to 120 mg/l), solution pH (pH 2 to 7), adsorption duration (0 to 140 min) and temperature (298 to 323 K) were measured in order to optimize the adsorption conditions using the SGO adsorbent. Morphological analysis indicated that the silica nanoparticles could be dispersed uniformly on the graphene oxide surfaces. The maximum capacities of adsorbent for effective removal of Cd (II) and CR were 43.45 and 333.33 mg/g based on Freundlich and Langmuir isotherms, respectively. Langmuir and Freundlich isotherms displayed the highest values of Qmax for CR and Cd (II) adsorption in this study, which indicated monolayer adsorption of CR and multilayer adsorption of Cd (II) onto the SGO, respectively. Thermodynamic study showed that the enthalpy (ΔH) and Gibbs free energy(ΔG) values of the adsorption process for both pollutants were negative, suggesting that the process was spontaneous and exothermic in nature. This study showed active sites of SGO (π-π, hydroxyl, carboxyl, ketone, silane-based functional groups) contributed to an enormous enhancement in simultaneous removal of CR and Cd (II) from an aqueous solution, Therefore, SGO can be considered as a promising adsorbent for future water pollution control and removal of hazardous materials from aqueous solutions.
The functionalized graphene oxide by silica and chitosan helped to prepared an adsorbent with high adsorption potential for removing cadmium(II). In this study, the adsorbent was synthesized and the batch system of adsorption method was examined to find the potential of the new adsorbent with the various factors of the concentration, pH, time and temperature. The characterization of adsorbent was analyzed by FT-IR, TEM, Zeta potential and XRD analysis. Regards to the analysis it can be understood that the adsorbent was synthesized successfully. The investigational results were validated and analyzed by applying the 5 models of isotherm and 4 models of kinetic. The Langmuir, Freundlich, Temkin, Harkins-Jura and Dubinin-radushkevich models were used which the Langmuir, Freundlich and Temkin fitted well for removing cadmium(II). The Qmax value was achieved 126.58 mg/g by using the Langmuir model for removing Cd(II) respectively. The pseudo-first-order, pseudo-second-order, Elovich and Intra-particle models were used to validate the kinetic models of the process. The pseudo-second-order and Elovich models were the best fitted kinetic model in this investigation. Thermodynamic parameters of the energy of gibes, the enthalpy, and the entropy were calculated. Generally, the adsorption process was distinguished as an exothermic and spontaneous.