The Pennsylvania State University The Graduate School The Department of Civil and Environmental Engineering EVALUATION OF TAILORED GRANULAR ACTIVATED CARBON TO REMOVE PERCHLORATE IN THE PRESENCE OF OXYANIONS A Dissertation in Environmental Engineering by Judodine Patterson © 2009 Judodine Patterson Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy December, 2009 The Dissertation of Judodine Patterson was reviewed and approved* by the following: Frederick S Cannon Professor of Environmental Engineering Dissertation Advisor Chair of Committee Brian A Dempsey Professor of Environmental Engineering Rachel Brennan Assistant Professor of Environmental Engineering Kwadwo Osseo-Asare Professor of Material Science and Engineering Peggy A Johnson Professor of Civil Engineering Head of the Department of Civil and Environmental Engineering *Signatures are on file in the Graduate School iii ABSTRACT In this research, laboratory studies demonstrated that some anions greatly competed with perchlorate for adsorption sites, thus reducing the capacity of surfactant tailored granular activated carbon (GAC) to remove perchlorate. It was observed that thiosulfate, an oxyanion and intermediate-valence sulfur species, competed with perchlorate for adsorption sites onto granular activated carbons that were tailored with quaternary ammonium surfactant. A reduced capacity of 50% of the surfactant tailored GAC was observed when Rapid Small Scale Column Tests (RSSCT) were employed. Rapid Small Scale Column Tests that employed Redlands, CA groundwater, with perchlorate of 30 µg/L, showed that 33,000 bed volumes of groundwater was processed through Arquad 2C-75 tailored GAC, before perchlorate was observed in the effluent at 6 µg/L. When the same water had 1000 µg/L of thiosulfate, 17,000 BV of Redlands, groundwater was processed through the surfactant tailored carbon before perchlorate was observed at 6 µg/L. It was determined that an implementation of a pretreatment step that utilized 2,500 µg/L of chlorine, diminished the effects of thiosulfate, by oxidizing the thiosulfate anion to sulfate and thus, returned the surfactant tailored GAC capacity to 90% of its capability. With this pre-treatment method, the surfactant tailored GAC technology can be a viable method in the removal of perchlorate from groundwater, in the presence of intermediate –valence sulfur species. iv Nitrate, another oxyanion that is common in ground waters, was also observed to strongly compete with perchlorate for adsorption sites on activated carbon loaded with quaternary ammonium surfactant. It was observed that at 3 times the concentration of the initial nitrate of 30 mg/L in Fontana, CA groundwater, the surfactant tailored GAC capacity to adsorbed perchlorate was reduced to 46 %. Additional experiments demonstrated that surfactant tailored GAC works best at removing perchlorate from aqueous systems at low nitrate concentrations. This research also evaluated the scaling technology that employed the RSSCT scaling equations for proportional diffusivity. The proportional diffusivity model was designed to predict the performance of pilot and field scale experiments by utilizing smaller fixed bed columns over a shorter test period. The proportional diffusivity model used an intra-particle coefficient of 1. A comparison of pilot scale tests and RSSCT indicated that the RSSCT design that employed the proportional diffusivity model, and used surfactant tailored GAC, over predicted the removal of perchlorate, by a ratio of 0.58. This result differs from activated carbon that was not tailored with surfactants, in that proportional diffusivity accurately predicts the performance of pilot scale tests. These results suggest that intra-particle diffusivity does not linearly correlates to particle radius when activated carbon was tailored with surfactants, as was demonstrated with non tailored activated carbon. An intra-particle diffusivity coefficient that is 0.5 less than the coefficient used for proportional diffusivity scale was evaluated. Results showed that v RSSCT that used a diffusivity coefficient of 0.5 under predicted the model for the pilot scale system and gave a ratio of 0.38. vi TABLE OF CONTENTS LIST OF FIGURES .....................................................................................................ix LIST OF TABLES.......................................................................................................xii ACKNOWLEDGEMENTS.........................................................................................xiv 1 CHAPTER 1 - INTRODUCTION...................................................................................1 2 CHAPTER 2 - LITERATURE REVIEW........................................................................6 2.1 Perchlorate ..................................................................................................................6 2.1.1 Fate and Transport of Perchlorate ...................................................................8 2.1.2 Contamination................................................................................................10 2.1.3 Risk Assessment of Perchlorate ......................................................................12 2.1.4 Analytical Analysis of Perchlorate..................................................................13 2.1.5 Remediation of Perchlorate.............................................................................14 2.1.5.1 Ion Exchange Treatment.......................................................................14 2.1.5.2 Tailored Granular Activated Carbon ....................................................17 2.2 Granular Activated Carbon ......................................................................................21 2.2.1Regeneration of GAC.......................................................................................24 2.3 Surfactants .................................................................................................................26 2.3.1Types of Surfactants.........................................................................................26 2.3.1.1 Anionic Surfactants ..............................................................................26 2.3.1.2 Cationic Surfactants..............................................................................28 2.3.1.3 Zwitterionic Surfactants .......................................................................28 2.3.2 Surfactant Adsorption to Solid Surfaces .........................................................29 2.4 Intermediate Valence Sulfur Species.........................................................................34 2.4.1Thiosulfates and Polythionates.........................................................................37 2.4.2Dithionite..........................................................................................................42 2.4.3Dithionate.........................................................................................................43 2.4.4Polysulfides ......................................................................................................44 2.4.5Analytical Processes for Intermediate Sulfur Species......................................45 2.5 Oxidation of Reduced Sulfur Compounds to Intermediate and Oxidized Sulfur species ......................................................................................................................47 2.5.1Aeration............................................................................................................48 2.5.2Chlorination......................................................................................................50 2.5.2.1 Chlorine and Activated Carbon ............................................................51 2.6 Why does Thiosulfate compete but not Sulfate? ........................................................53 2.7 Anions Competition for Adsorptions Sites in Ion Exchange Processes .....................54 2.8 References...................................................................................................................60 vii 3 CHAPTER 3 - Oxidation of Reduced sulfur species (Thiosulfate) by Free Chlorine to increase the bed life of Tailored GAC to remove Perchlorate. ....................................74 3.1 Abstract.......................................................................................................................74 3.2 Introduction.................................................................................................................75 3.2.1Sulfur Redox Species .......................................................................................75 3.2.2Motivation for Hypothesis Regarding Intermediate-Sulfur Oxyanions ...........79 3.2.3Objective and Hypothesis.................................................................................80 3.2.4Chlorine Oxidation of Intermediate-valence sulfur oxyanions ........................81 3.3 Experimental...............................................................................................................82 3.3.1Materials...........................................................................................................82 3.3.2Methods............................................................................................................84 3.3.2.1 Sodium Thiosulfate Solution Preparation.............................................84 3.3.2.2 Rapid Small Scale Column Tests .........................................................84