Validity of Egyptian Na‐montmorillonite for adsorption of Pb²⁺, Cd²⁺ and Ni²⁺ under acidic conditions: characterization, isotherm, kinetics, thermodynamics and application study

Abstract

This study investigated the applicability of natural Egyptian Na-montmorillonite (Na-MMT) to remove Pb 2+ , Cd 2+ and Ni 2+ under acidic conditions that mimic industrial wastewater acidity. Cation exchange capacity of Na-MMT was found 91 meq/100 g and the specific surface area 42 m 2 g À1 . The adsorbent was characterized using X-ray fluorescence, scanning electron micrograph that showed significant morphological changes after adsorption and Fourier transform infrared spectroscopy, which confirmed that the adsorption occurred mainly in the lattice region. Removal efficiency was evaluated as a function of pH, contact time, initial concentration, and adsorbent mass. Acidic pH value was chosen for the following experiments. Langmuir and Freundlich isotherm models were applied. Freundlich model showed better fitting suggesting heterogeneous adsorption scenario. Freundlich capacity values decreased in the order of Pb 2+ (3.71 mg g À1 ) > Cd 2+ (2.45 mg g À1 ) > Ni 2+ (1.76 mg g À1 ). Kinetic data were accurately fitted to pseudo-second-order, indicating the adsorption occurrence in the interior surface of Na-MMT and the contribution of internal diffusion mechanism was significant. Intraparticle diffusion model gave multi-linear curves so more than onestep controlled the adsorption process. Under temperature range 290-328 K, thermodynamic parameters revealed that adsorption of Pb 2+ and Cd 2+ was spontaneous but Ni 2+ non-spontaneous. Adsorption was exothermic for Pb 2+ and Ni 2+ but endothermic for Cd 2+ . Arrhenius activation energy values were 5.78, 8.51 and 11.45 kJ mol À1 for Pb 2+ , Cd 2+ and Ni 2+ respectively stating the physical adsorption. Na-MMT reusability was confirmed by regeneration experiments. Application study showed excellent efficiency of Na-MMT within range (23.4-81.2%) removal for Pb 2+ , Cd 2+ and Ni 2+ from textile dyeing and tannery wastewater. *Effect of pH was studied in the pH range 2-7 while keeping other parameters constant at 't = 60 min; C o = 10 mg L À1 ; adsorbent mass = 0.25 g; agitation speed = 100 rpm and T = 298 K'.A. A. TAHA ET AL. Figure 6. Effect of adsorbent mass 'adsorbent mass (0.12-0.500) g, t = 60 min, pH = 3.8, C o = 10 mg/L, agitation speed = 100 rpm and T = 298 K'.Figure 7. Linearized isotherm models (a) Langmuir model and (b) Freundlich model. 'C o = (5-30) mg/L, t = 60 min, pH = 3.8, adsorbent mass = 0.25 g, agitation speed = 100 rpm and T = 298 K'.Figure 8. The linear plots of the pseudo-second-order model for (a) Pb +2 , (b) Cd +2 and (c) Ni +2 . 'C o = (5-20) mg/L, t = (1-60) min, pH = 3.8, adsorbent mass = 0.25 g, agitation speed = 100 rpm and T = 298 K'.Figure 9. Intraparticle diffusion plots for (a) Pb +2 , (b) Cd +2 , and (c) Ni +2 . 'C o = (5-20) mg/L, t = (1-60) min, pH = 3.8, adsorbent mass = 0.25 g, agitation speed = 100 rpm and T = 298 K'.

Biosorption characteristics ofPennisetum glaucumfor the removal of Pb(II), Ni(II) and Cd(II) ions from aqueous medium

“…While for lead 35 min and for cadmium 30 min were observed. The reason was attributed to the fact that after the equilibrium time maximum biding sites of the biosorbent became occupied and repulsive forces were developed between the solute particle in solid and bulk phases (26,27).…”

Facile Synthesis of Silica Coated Magnetic Nanoparticles via Green Microwave-Solventless Technique for Purification of Water from Toxic Heavy Metals

“…which decreases the saturation of the active sites. In addition, the agglomeration of the nano-adsorbent particles (because of London interaction) at high dosage might also have a negative effect on the adsorption capacity [10,26].…”

Kinetics and Thermodynamics of Methylene Blue Adsorption on Polyfurfuryl Alcohol-Derived Templated Carbon and Activated Carbon from H3PO4-Impregnated Moringa oleifera Seed Hull

“…The optimized [5] particle size sample (0.5 g) of MOSH was weighed and impregnated with varying concentrations (2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5 and 6.0 mL) of aqueous phosphoric acid (H 3 PO 4 ) by drop-wisely adding H 3 PO 4 (with stirring) to produce swelling until incipient wetness of fresh portions of seed hull sample. The impregnated samples were carbonized at different temperatures (373, 523, 623 and 723 K) for various residence times (15,20,25,30,35,40, 45 and 50 min.). The carbonized samples were cooled and sequentially washed several times with de-ionized water until neutral to litmus paper.…”