Selective removal of lead ion from polluted seaport water using a highly porous functionalized monolithic silica sorbent prepared by agarose template

Abstract

A simple and inexpensive method for the synthesis of silica-based highly porous monolithic sorbents using agarose gel templates was developed for selective and efficient removal of Pb2+ from polluted seaport water samples. By controlling the agarose gel concentration, sorbents with different porosities could be obtained. The agarose gel was shaped as discs, silanized with (3-aminopropyl) triethoxysilane, calcined in 700 °C and functionalized by (E)-2-hydroxy-5-(phenyldiazenyl) benzaldehyde. The synthesized monolithic sorbent was then characterized by Fourier transform infrared spectrometry, X-ray diffraction, scanning electron microscopy and nitrogen sorption measurements. The results confirmed the mesoporous structure of the sorbent. Using two agarose gel concentrations of 2.5 and 7%, silica sorbents with porosities of 32.2 and 33.8 m2 g−1 were obtained. Evidences of variations in the structures and particle sizes were observed for the two sorbents. The influence of four parameters on the removal of Pb2+ from aqueous samples were optimized using a multivariate central composite design method. Under the optimized conditions, i.e. using 100 mg of the adsorbent for a 9.1 mL water sample in pH 7.9 and stirring for 56 min, 96.8% removal efficiency was obtained with a relative standard deviation of 7.4% for 5 replicates. The sorbent could be easily regenerated by a 0.2 mol L−1 HCl solution to be also used for enrichment and sensitive determination of the target ion.