A novel method for the synthesis of a nanostructured silica sorbent using agarose as template and its use for the removal of Pb2+ from aqueous solution

In recent years, the use of nanostructured silica such as MCM-41[1] and SBA-15[2] due to their unique characteristics such as high porosity, which leads to a higher surface area to be used absorbents, have been widely used in separation techniques and removing pollutants. This work, reports the synthesis and application of a novel silica based nanoporous sorbent by using bioactive agarose[3] polymer as a template. The main advantage of this method is that the porosity and shape and the physical strength of the adsorbent can be controlled by changing the concentration of the agarose template. First, a composite is made by using TEOS and agarose in basic solution, and then by removing the agarose polymer by calcining, a silica-based nanoporous absorbent is prepared. The synthetic adsorbent was studied and characterized by SEM, FT-IR and XRD techniques. The prepared absorbent was functionalized with 3-aminopropyltrimethyl methoxyethylane (APTES) and subsequently, it was modified with the (E)-2-hydroxy-5-(p-tolyldiazenyl)benzaldehyde as a ligand. The modified absorbent was applied for the adsorption and preconcentration of lead (II) in aqueous samples before its determination by AAS. For optimization, the adsorption conditions, response surface method using the Mini-tab software was applied. Limit of detection (LOD) and limit of quantification (LOQ) were 0.339 and 1.13 mg/L, respectively. Linear dynamic range (LDR) was 0.05–100 mg/l and determination coefficient (R2) was 0.998. The relative standard deviation (RSD) was 3.2% (n = 5).