Retention Factors for Trace Metal Elements in Solid Phase and Applicable Adsorption Models: Case of <i>Moringa oleifera</i>

Moringa oleifera is an edible plant cultivated throughout the tropical belt. It belongs to the family Moringaceae and is one of its 14 known species. This paper presents a synthesis of the main factors responsible for the retention of trace metal elements (TMEs) by Moringa oleifera seed powder, a natural adsorbent. The five main factors studied are metal concentration, solution pH, adsorbent particle size, adsorbent dose and adsorbent/adsorbate contact time. Through these factors, we present the optimal conditions for removal of these TMEs, as well as adsorption isotherm models appropriate for the conditions of retention of these metal cations by the adsorbent. The times of 20 min (GD) and 50 min (GND) are the equilibrium times obtained in our study. An optimal adsorbent mass (GD and GND powders) of 4.5 g was found. 20% to 97% abatement is observed for average pH values between 6 and 8. The coefficients of determination (R2) obtained (0.972, 0.963, 0.991 and 0.799) during the isotherm experiments carried out at 20°C, 30°C, 40°C and 50°C are close to 1. Also, the separation factor (RL), an essential characteristic of the Langmuir isotherm whose values are between 0 and 1, attest to the applicability of the Langmuir isotherm model to fit the experimental data of copper adsorption by Moringa powders. In this paper, we are particularly interested in the following TMEs (Mn, Ni, Cr, Cu, Cd, Co, Pb, Fe, Zn, Ag).

Modeling of Copper Adsorption by <i>Moringa oleifera</i>Seed Powders

In this work, an inexpensive and environmentally friendly natural adsorbent obtained from shelled (GD) and unshelled (GND) Moringa oleifera seeds was used for copper adsorption from aqueous solutions. A series of experiments were performed to assess the parameters influencing the adsorption phenomenon such as pH, adsorbent mass, adsorption equilibrium time and temperature. The kinetic results of adsorption described a pseudo-second order model. The adsorption isotherms are satisfactorily described by the Langmuir mathematical model. The thermodynamic data revealed a spontaneous and endothermic adsorption phenomenon. The level of copper in surface water before and after addition of moringa powders was carried out to verify the effectiveness of the adsorbent. A maximum adsorption rate of 51.28% and 61.96% was obtained with GD and GND powders respectively. Moringa oleifera seed powders are an effective alternative for the removal of copper from surface water.