Synthesis of l-glutamic acid containing silica gel for the adsorption and immobilization of Zn2+ in water

Abstract A porous silica gel with both COOH and NH 2 groups was synthesized in one pot by the addition of l -glutamic acid ( l -GA) into a synthesis medium consisting of tetraethyl orthosilicate, water, ethanol, and 1-butylamine. The inclusion of l -GA in the as-synthesized product ( l -GA-SiO 2 ) was evidenced by FT-IR and TG measurements. The l -GA was chemically bonded with silica as indicated by the shift of FT-IR bands at 1510 and 1400 cm −1 in the spectrum of l -GA to higher wavenumbers of 1540 and 1460 cm −1 in the one of l -GA-SiO 2 . The TG analysis showed that the l -GA-SiO 2 had an increase of weight loss by 5.6% due to the decomposition of the included l -GA which was centered at around 313 °C, suggested by a new peak in the DTG curve. Compared with the one synthesized without l -GA, the l -GA-SiO 2 was more aggregated with smaller surface area. However, the latter showed a higher removal efficiency by 17.1% toward zinc ions in water than the former and the adsorbed ions were hardly released again into water from the used adsorbent. Graphical abstract