Characterization of natural and chemically modified kaolinite from Mako (Senegal) to remove lead from aqueous solutions

Abstract

The chemical and sorption properties of clay minerals from the Mako area, Senegal, were investigated using FTIR spectroscopy, X-ray diffraction, scanning electron microscopy equipped with an X-ray energy dispersion spectrometer, thermal analysis and chemical analysis. The clay sample is essentially dominated by kaolinite and quartz as also shown by treatment with ethylene glycol and dimethylsulfoxide (DMSO). The clay fraction of this natural clay was organically modified by grafting with 3-aminopropyltriethoxysilane (APTES) in order to improve significantly its retention ability of heavy metals. The silane groups of the APTES reagent were partly grafted on the surface of platy kaolinite particles and the remaining ethoxy groups could be hydrolysed by aqueous treatment. The natural clay, its clay fraction and the organo-functionalized clay (with APTES) were investigated as adsorbents for the removal of Pb(II) from aqueous solutions. Evidence for an organic grafting has been demonstrated by comparing the spectroscopic characteristics of the natural clay and those of its chemically modified derivatives. The effects of different parameters (i.e. initial Pb(II) concentration and contact time) on the adsorption efficiency were studied. For an initial concentration of 10 mg L−1Pb(II), the adsorption was maximized after 30 min contact time both for the raw material and its clay fraction and after 90 min for the APTES grafted clay. Although the maximum of sorption for the APTES grafted clay is reached with slower kinetics, this maximum amount of Pb(II) uptake at room temperature (Xmax) is significantly higher since it is 0.99 mg g−1for the raw clay, 1.46 mg g−1for its clay fraction and 3.02 mg g−1for the organically modified clay, i.e. three times greater than the raw clay.

Functionalization of Porous Clay Heterostructures with Silane Coupling Agents

“…The modification of PCH with silane coupling agents (APTES and GPTMS) was highlighted by the apearance of new peaks at 2927 cm -1 (APTES) and 2951 cm -1 (GPTMS) attributed to the streaching vibrations of C-H from CH 2 groups of the coupling agents. Similar results were reported for various inorganic clays (halloysite, montmorillonite, kaolinite, MCM) modified with silane coupling agents [9,[14][15][16].…”

“…The treatment of inorganic materials with organic silane coupling agents is an attractive strategy used to enhance some properties like drug encapsulation efficiency, stability of immobilized enzymes, adsorption capacity, catalytic activity, physical and chemical properties. These modified materials can be used in many fields such as: wastewater purification, catalysis, encapsulation of various therapeutic agents and enzyme immobilization [7][8][9][10][11][12]. For example, modified MSN with APTES exhibited a high drug encapsulation efficiency, controlled drug delivery profile and an enhanced uptake ability for cancer cells [16].…”

“…The TG curves of modified PCHs (Epoxy-PCH, Amine-PCH) samples show a different profile that included three degradation steps: (1) dehydration, due to the physically adsorbed water (20-200 0 C), (2) degradation of organic coupling agents (200-500 0 C) and (3) dehydroxylation process of hydroxyl groups located between the tetrahedral sheets of MMT (500-800 0 C) [9,17]. A higher weight loss value (8.8 % for Amine-PCH and 13% for Epoxy-PCH) of modified PCHs samples confirmed the presence of organic fraction that was introduced into PCHs during the functionalization step.…”

Exploration of Intercalated Kaolinite Clay for the Uptake of Basic Dye by Adsorption − Equilibrium, Kinetics and Thermodynamic Studies

“…Uniformly dispersed smaller particles that seem coarser were noticeable which are likely to be the presence of silt and sandy component of the clay. Similar observation has also been reported [13,15,16]. The SEM/EDX of NRK indicated that the average atomic composition in percentages are; O (66.8%), Si (17.6%), Al (14.1%) and C (1.3%).…”

“…The Fourier transformed infrared spectra graph of NRK and DIK adsorbent are shown Fig 3. FTIR bands ascription was done by relating the result obtained in the literatures [13,14,15]. The inner-hydroxyl stretching band of the interlayer gallery of kaolinite is not by and large affected by the interlayer modification [7,8].…”