Synthesis and Characterization of Iron Oxides onto Cellulose Supports for Adsorption of Roxarsone A Thesis Submitted to the College of Graduate and Postdoctoral Studies In Partial Fulfillment of the Requirements For the Degree of Master of Science In the Department of Chemistry University of Saskatchewan Saskatoon By Dexu Kong © Copyright Dexu Kong, March 2017 All rights reserved. PERMISSION TO USE In presenting this thesis in partial fulfillment of the requirements for a Postgraduate degree from the University of Saskatchewan, I agree that the Libraries of this University may make it freely available for inspection. I further agree that permission for copying of this thesis in any manner, in whole or in part, for scholarly purposes may be granted by the professor or professors who supervised my thesis work or, in their absence, by the head of the Department or the Dean of the College in which my thesis work was done. It is understood that any copying, publication, or use of this thesis or parts thereof for financial gain shall not be allowed without my written permission. It is also understood that due recognition shall be given to me and to the University of Saskatchewan in any scholarly use which may be made of any material in my thesis. Requests for permission to copy or to make other use of material in this thesis in whole or part should be addressed to: Head of the Department of Chemistry University of Saskatchewan Saskatoon, SK (S7N 5C9) Canada i 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. ii 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. iii ACKNOWLEDGEMENTS I thank Professor Dr. Lee D. Wilson for his generous advice, inspiring guidance, and encouragement throughout my research. I also would like to thank him for reading the thesis manuscript and providing me with significant and constructive suggestions. I want to thank the funding provided by Saskatchewan Research Council (SRC) and University of Saskatchewan Department of Chemistry. I also would like to thank Thomas Bonli from the Department of Geological Sciences for helping me with the pXRD analysis, Jianfeng Zhu from (Saskatchewan Structure Science Centre) SSSC for helping me with the ssNMR measurements, and the environmental analytical lab at SRC for assisting me with water chemistry analyses. To the committee members, who acted as advisors and spared time from their busy schedules to guide my research, I offer my thanks: Dr. David Palmer (Chair 2016), Dr. Marek Majewski (Committee Advisor), Dr. Matthew Paige, Dr. Robert Scott, and Dr. Dale Ward. I would like to thank my group members Dr. Abdalla Karoyo, Leila Dehabadi, Chen Xue, Asghar Dolatkhah, Inimfon Udoetok, Savi Bhalkaran and Mohammad Hassan Mahaninia. I wish them the best of luck in their research projects, and I also thank Wendy Wang for assisting in my research projects, too. I also thank my family for supporting me through my graduate study work. iv TABLE OF CONTENTS PERMISSION TO USE ................................................................................................................. I ABSTRACT: ................................................................................................................................ II ACKNOWLEDGEMENTS ....................................................................................................... IV LIST OF TABLES ....................................................................................................................... X LIST OF FIGURES .................................................................................................................. XII LIST OF SCHEMES ................................................................................................................. XV LIST OF ABBREVIATIONS ................................................................................................. XVI CHAPTER 1 : INTRODUCTION ............................................................................................... 1 1.1 ROXARSONE (ROX) ......................................................................................................... 1 1.1.1 Sources of arsenic pollution ........................................................................................... 1 1.1.2 Physical and chemical properties of the roxarsone and inorganic arsenic species ........ 2 1.1.3 Toxicity of arsenic species in the environment .............................................................. 4 1.1.4 Remediation of roxarsone .............................................................................................. 5 1.2 IRON CHEMISTRY ................................................................................................................... 7 1.2.1 Introduction .................................................................................................................... 7 1.2.2 Iron oxide ....................................................................................................................... 7 1.2.2.1 Iron oxide crystal structure ................................................................................... 10 1.2.2.2 Iron and its oxides’ electronic properties .............................................................. 12 1.2.2.2.1 Electronic properties – free iron .................................................................... 12 1.2.2.2.2 Iron oxide electronic properties – crystal field theory ................................... 13 1.2.2.2.3 Electronic properties – molecular orbital theory ........................................... 15 1.3 CELLULOSE .......................................................................................................................... 16 1.3.1 Iron oxide-cellulose composite materials as adsorbents for water treatment .............. 17 1.4 PHYSICAL ADSORPTION ....................................................................................................... 18 1.4.1 Introduction .................................................................................................................. 18 1.4.2 Solution vs. Gas based adsorption ............................................................................... 19 1.4.3 Types of isotherms ....................................................................................................... 20 1.4.3.1 Hysteresis in solid-gas adsorption/desorption curves ........................................... 23 v 1.4.4 Models of sorption isotherms....................................................................................... 24 1.4.4.1 Langmuir isotherm model ..................................................................................... 24 1.4.4.2 Freundlich isotherm model ..................................................................................