A B S T R A C TA set of copolymers poly(N-hexadecyl-4-vinylpyridinium bromide) [4VP-C 16 Br-X] (X = 22, 50 and 78%) obtained by quaternization of poly(4-vinylpyridine) (P4VP) with 1-bromohexadecane (C 16 H 33 Br) at various modification percentages was perfectly characterized by conductivity, 1 H NMR, and by thermogravimetric analysis (TGA). New organophilic hybrid materials [BC-4VP-C 16 Br-X] were obtained from bleaching clay (BC) and [4VP-C 16 Br-X] copolymers. Indeed, the intercalation of these copolymers in interlayer spaces of the clay introduces new properties such as hydrophobic balance. The interlayer structure of the bentonite receives more or less easily, the polycations [4VP-C 16 Br-X] in order to increase the interlayer volume in the mineral bentonite, then to give it an organophobic character. The characterization of the new composite materials [BC-4VP-C 16 Br-X] by TGA shows a good stability at high temperature. In order to quantify the hydrophobic nature of the prepared organoclay, these composites were dispersed in aqueous solution in the presence of paranitrophenol (PNP) as indicating agent for the water diffusion into the material. Kinetic measurements of the retained PNP percentages show clearly that water diffusion is directly proportional to the hydrophobic nature of the material. Consequently, more the hydrophobic balance of the composite, less the water diffusion speed.
In this paper, a simple method was proposed to obtain hydroxyapatite (HA) and hydroxyapatite/partially hydrolysed polyacrylamide (HA/AD37) composite materials which where applied to lead retention from aqueous solution by means of the batch method. The characterization of the materials verified that the presence of AD37 created interconnected porosity in the composite HA/AD37 giving it a good swelling properties that conducted to an easy separation of the material from aqueous solutions. Retention experiments carried out by varying the dose of lead and the contact time between adsorbent and adsorbate showed that the maximum adsorption capacity (Qmax) obtained for 2072.2 mg/L as initial concentration of Pb2 + was equal to 984.63 mg/g for HA and 924.50 mg/g for HA/AD37. Furthermore, AD37 used alone cannot retain Pb2 + ions. Indeed, the calculated Qmax of AD37 part of the composite was of 806.57 mg/g. The obtained Qmax values was elevated more than the reported values in many literatures. Based on the correlation coefficient, the kinetic study proved that pseudo-second order model agrees well with the obtained experimental data for Pb2+ retention by both HA and HA/AD37. Also, isotherm study explored that adsorption of lead was best fitted by Langmuir model for HA and Temkin model for HA/AD37. At last, the mechanism of retention was probed by characterizing the adsorbents after contact with lead ions by XRD and SEM. The results showed the transformation of calcium-hydroxyapatite to different structures of lead hydroxyapatite confirming the presence of ion exchange mechanism between Ca2+ and Pb2+.
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