Selective adsorption of epigallocatechin gallate onto highly reusable gallium doped mesoporous TiO2 nanoparticles adsorbent

Abstract

This work describes a potential selective adsorption of epigallocatechin gallate by Ga-doped TiO2 nanoparticles (NPs) and showed excellent adsorption (∼99%) and desorption capacity even after the 7th run. The work reports about a surfactant mediated template based synthesis of both pristine and Ga-doped TiO2 mesoporous NPs to study the adsorption behavior EGCG. EGCG is the most abundant and bio-active compound capable of showing free radical scavenging activity, anticancer, antibacterial, and several other physiological functions. Therefore, extraction of EGCG is highly desirable for incorporation in food items that can effectively increase their nutritional and medicinal values. The pore diameter of the synthesized materials was found to be in the range 8.76–10.38 nm and the specific surface area was found to be around 25.80–58.72 m2/g. The particle size decreased from 25 nm to 15 nm in presence of Ga. A mixture of anatase and brookite phase was observed for all the synthesized TiO2 NPs. The band gap value initially (3.40 eV) decreased in presence of minute amounts of Ga (3.44 eV) but then increased (3.59 eV) with the increase of Ga percentage. The point of zero charge (PZC) value of the materials lies in the range of 6.6–7.2. The adsorption study was carried out at different pH (1, 3, 5, 7 and 9) with variation of shaking time (1 h, 3 h, 5 h and 7 h). The material containing maximum Ga in the Ga-doped set (Set 3 TiO2 NPs) showed highest adsorption percentage (99.45%) in pH 1 medium after 5 h shaking. The adsorption isotherm and the kinetics follow the Langmuir model and pseudo-second order respectively. Desorption was studied under high energy gamma rays, shaking, sonication and UV irradiation. The highest desorption (∼96%) was obtained with sonication for 30 min.