Optimization of the Synthetic Procedure for Functionalizing Activated Carbon Produced from Canarium Ovatum with Iron Oxide Nanoparticles Toward Effective Adsorption Using a Central Full Factorial Design

This work concerns the determination of conditions for optimizing the synthesis of a composite material consisting of activated carbon and iron (III) oxide nanoparticles in order to improve adsorptions properties such as adsorption yield and enthalpy of adsorption of malachite green. A three-point central full factorial design was used for this purpose to evaluate impact of optimal synthesis parameters namely the concentration of iron nitrate, the annealing temperature, the synthesis pH and the citric acid/iron nitrate molar ratio. The existence of interaction between the synthesis parameters increases the effects of the latter on the properties of the composite material obtained. The increase in the concentration and the decrease in the annealing temperature favors an increase in the adsorption yield from 60% to 76%. There is also an increase in the adsorption enthalpy up to values greater than or equal to 40 kJ.mol<sup>-1</sup> when there is an increase in the synthesis pH and the iron nitrate concentration simultaneously with the drop in the molar ratio citric acid/iron nitrate and the annealing temperature. Composite material obtained following the optimal conditions: annealing temperature at 400°C, with an ionic iron concentration of 0.150 mol.L<sup>-1</sup> at pH 5 and a molar ratio close to 0.250 exhibited an adsorption yield of ~80%, higher than pristine activated carbon (~70%) and an increase in the variation of enthalpy (from -12.010 kJ.mol<sup>-1</sup> to 52.612 kJ.mol<sup>-1</sup>). The results of this work provide a basis from which to effectively functionalize an adsorbent with iron oxide nanoparticles with the aim of having more improved adsorbent properties.