Effect of heat treatment on the efficient adsorption of Cd2+ ions by nanosized SiO2, TiO2 and their composite. (30th January 2017)

• Record Type: Journal Article
• Authors: Waseem, M; Muntha, S T; Nawaz, M; Rehman, W; Rehman, M A; Shah, K H
• Is Part Of: Materials research express. Volume 4:Number 1(2017)
• Publication Date: 2017-01-30
• Subjects: adsorption -- cadmium -- heat treatment -- nanocomposite -- SiO2 -- TiO2; Materials science -- Research -- Periodicals; Materials science -- Periodicals; 620.11
• DOI: 10.1088/2053-1591/aa55b0
• Languages: English
• ISSNs: 2053-1591

Abstract

Abstract: In this study nanosized SiO2, TiO2 and their composite were synthesized via the oil in water (o/w) microemulsion method and their thermal treatment was performed at 378, 573, 973 and 1273 K. The physicochemical properties of the samples were studied by surface area measurements, scanning electron microscopy, Fourier transform infra-red spectroscopy and x-ray diffraction analysis. The Brunauer, Emmett and Teller surface area of all the adsorbents increases from 378 to 573 K, while it decreases upon further heat treatment. The average crystallite size decreases by heating the samples from 378 to 573 K while it increases when the adsorbents were thermally heat treated at 973 and 1273 K. The intensity of a few IR bands was reduced along with the disappearance of most of the bands at higher temperatures. The appearance of the beta-cristobalite phase in SiO2 and the rutile phase in TiO2 was confirmed from the diffraction data. The heat treated samples were subjected to preliminary adsorption of Cd 2+ ions from aqueous solution at 293 K. Based on the preliminary adsorption experiments, SiO2, TiO2 and their composite heat treated at 573 K were selected for further adsorption studies. The Langmuir model was found to be fitted to the sorption data of TiO2 and the nanocomposite while the adsorption of Cd 2+ ions by the SiO2 nanoparticles was explained well based on the Freundlich model. In the present study, the maximum Cd 2+ adsorption capacity of SiO2, TiO2 and their composite was found to be 79.72, 98.55 and 107.17 mg g −1, respectively. The q m and K f values obtained in the present study were found to be far better than those reported in the literature. The negative values of Δ G confirm the feasibility of an adsorption process at higher temperatures. The positive values of Δ H and Δ S represent the endothermic and physical nature of the adsorption process with the increased randomness of Cd 2+ ions at the solid/solution interface.