Abstract
Amino-functionalized SBA-15 mesoporous silica was prepared, characterized, and used as an adsorbent for heavy metal ions. The organic - inorganic hybrid material was obtained by a grafting procedure using SBA-15 silica with 3-aminopropyl-triethoxysilane and bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272), respectively. The structure and physicochemical properties of the materials were characterized by means of elemental analysis, X-ray diffraction (XRD), nitrogen adsorption - desorption, thermogravimetric analysis, FTIR spectroscopy and immersion calorimetry. The organic functional groups were successfully grafted onto the SBA-15 surface and the ordering of the support was not affected by the chemical modification. The behavior of the grafted solids was investigated for the adsorption of heavy metal ions from aqueous solutions. The hybrid materials showed high adsorption capacity and high selectivity for zinc ions. Other ions, such as cooper and cobalt were absorbed by the modified SBA-15 material.
Highlights
A wide variety of toxic inorganic and organic chemicals are discharged into the environment as industrial wastes, causing serious water, air, and soil pollution
The organic functional groups were synthesized by grafting on the SBA-15 surface by a step synthesis procedure (Figure 1)
The surface hydroxyl groups were reacted with the ethoxy groups of aminopropyl triethoxysilane and bis (2, 4, 4-trimethylpentyl) phosphinic acid
Summary
A wide variety of toxic inorganic and organic chemicals are discharged into the environment as industrial wastes, causing serious water, air, and soil pollution. The major disadvantages of these adsorbents are their low loading capacities and their relatively weak interactions with metallic cations, as evidenced by low metal ion binding constants[8,9] To overcome this drawback, many investigators have developed functionalized adsorbents such as organoclays and surface-modified mesoporous materials. In the case of natural clays, quaternary ammonium compounds and/or thiols have been used to modify clays such as smectite and montmorillonite[1,10,11,12,13] Mesoporous silicas, such as MCM-4114-19, HMS20,21, SBA-1522, and SBA-117 have been functionalized by various groups to afford materials able to interact strongly with metallic cations, mercury[14,15,16,20,21,22] or metallic anions such as chromate and arsenate[17,18,19]. We studied the applicability of this material for the removal of heavy metal ions from aqueous solutions and, through the heats of immersion of each of the ions under study, we established the relationship between the modification of SBA and immersion enthalpy
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