Increasing the Adsorption Efficiency of Methylene Blue by Acid Treatment of the Plant Carpobrotus edulis

This article deals with the valorization of local natural materials of vegetable origin, which are less expensive and non-toxic through their use in water treatment. We have shown that the acid solution (HCl, 0.5 N) pretreatment of the Carpobrotus edulis plant increases its adsorbent potential towards Methylene Blue and reduces the levels of soluble organic matter that can be released into the water. The bio-adsorbents were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Elemental Analysis (EDX), Zero Point of Charge (PHz), Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD5). The acid treatment allows a reduction in soluble organic matter characterized by a decrease in BOD5 and COD of 91.9% and 88.3% respectively. For the initial concentration of 100 mg/L of MB, the biomaterial obtained after acid treatment (HMCE) has an equilibrium adsorption capacity of 19.61 mg/g compared to 9.91 mg/g for the native plant (NCE). Acid treatment also reduces the amount of adsorbent required to achieve a maximum rate of adsorption. pH, temperature and ionic strength do not have a major influence on the adsorption of Methylene Blue on the biomaterials studied. This adsorption follows the pseudo-second order kinetic model and is represented by the Langmuir and Freundlich isotherms. It is a spontaneous and endothermic process.