Synthesis and Characterization of Iron Oxides onto Cellulose Supports for Adsorption of Roxarsone
Date
2017-08-23
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
This thesis reports on a systematic experimental study for the preparation of cellulose supported iron oxide (goethite and hematite) composite adsorbent materials, and the use of such materials for the adsorption of arsenic species from arsenic containing water. The research is divided into two sections: 1) Synthesis and characterization of the goethite and goethite-cellulose composites for the sorption of roxarsone (4-hydroxy-3-nitrobenzenearsonic acid) and 2) Synthesis and characterization of the hematite and hematite-cellulose composites for the sorption of roxarsone. Adsorption properties of the cellulose, goethite, hematite, goethite-cellulose, and hematite-cellulose adsorbents were studied with roxarsone as a model organoarsenical adsorbate.
Iron nanoparticles (NPs) and their cellulose composites were prepared with good yield, goethite and hematite were 98% and 97%, respectively. The characterization of various adsorbent materials used several techniques: Thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, nitrogen gas adsorption/desorption (BET), 13C solid state NMR (ssNMR) spectroscopy, Transmission electron microscopy (TEM) and powder X-ray diffraction (pXRD). To understand the mode of interaction between the adsorbent and the adsorbate, Roxarsone (ROX) was used to study the molecular aspects of the adsorption process. The comparison between goethite-cellulose composites and hematite-cellulose composites was made by examining the surface area and available active adsorption sites on the iron oxide and cellulose materials surfaces. The nitrogen adsorption/desorption experiments showed hematite NPs have a relatively high surface area while TEM showed better dispersion of 10 nm hematite NPs onto the surface of cellulose at low iron coating. The maximum monolayer uptake (Qm) of the hematite was 0.155 mmol/g which was two-fold greater than goethite. The Qm value for the 25% Fe coated hematite-cellulose was 0.10 mmol/g and was 1.5-fold greater than the Qm value for the 30% Fe coated goethite-cellulose composite. The kinetic uptake results for the 25% Fe coated hematite-cellulose was 0.186 min-1, and exceeded the uptake rate for the 35% Fe coated goethite-cellulose. The better dispersion of hematite NPs resulted in more available active sites on the cellulose surface which increased the overall uptake of the roxarsone.
Both goethite and hematite NPs provide adsorption sites that can bind with arsenic containing species. It is a cost effective and efficient way to disperse iron NPs onto a cellulose surface because such supported NPs are involved in the adsorption of arsenic species. On the other hand, the composite materials have an advantage over the pure mineral phase since composites can reduce NP leaching whilst enhancing the uptake of arsenic species at a lower levels of iron oxide doping.
Description
Keywords
Cellulose, Goethite, Hematite, Composite, Adsorption, Isotherm, Roxarsone
Citation
Degree
Master of Science (M.Sc.)
Department
Chemistry
Program
Chemistry