Removal of Sodium Ascorbate from Water by Adsorption onto composite Beads (calcium-Alginate/Activated carbon)

Abstract

A biomaterial was prepared by encapsulating an activated carbon powder with sodium alginate, thus forming composite beads. These composite gel beads have been studied in terms of their adsorption capacity on the food additive Sodium Ascorbate in aqueous solution. For this, several parameters were evaluated using UV-visible spectroscopy. The maximum retention of SA is for an average time of 3 hours with a very small quantity of adsorbent m= 0.25g, and the sorption mechanism is described by pseudo-first-order. The adsorption isotherm is compatible with Langmuir's theoretical adsorption model. The thermodynamic parameters showed that the adsorption process is spontaneous, disordered and endothermic (ΔG < 0, ΔS > 0, ΔH>0). The process thus obtained is of a physical nature (physisorption). Finally, the pH of the acidic medium favors the increase in the adsorption capacity, this effect is due to the formation of hydrogen bonds. On the other hand, the increase in pH inversely influences the adsorption capacity by the repellent effect of the functional groups with the same negative charge present on the adsorbent and the adsorbate.