Journal of Water Process Engineering 38 (2020) 101667 Available online 26 September 2020 2214-7144/© 2020 Elsevier Ltd. All rights reserved. Novel photo-activated method for removal of mercury from industrial wastewater Anna I. Casasús a , Ana M. Hagan-Rogers b , Regina Rodriguez b, * , 1 , David W. Mazyck b a 855 Ramsden Run, Alpharetta, GA, 30022, United States b University of Florida, Environmental Engineering Sciences, 312 AP Black Hall, Gainesville, FL, 32611, United States A R T I C L E INFO Keywords: Ultraviolet Mercury Photocatalysis Oxidation Reduction ABSTRACT Mercury-laden wastewaters need new treatment options to meet current and pending regulations. Some facilities employ a sulfde precipitation process to lower the concentrations of Hg in their discharge through chelation and fltration. However, this process still results in mercury concentrations higher than the imposed limits for discharge by upcoming U.S. EPA regulations. This paper focuses on a simple approach, Ultraviolet Activated Chelation (UVAC), which has resulted in mercury concentrations as low as 10 ppt when applied to wastewaters from three industrial facilities. An investigation into the effect(s) of certain variables on the treatment process, such as pH and residence time, was carried out through batch experiments using plant wastewater. A discussion on UVAC effectiveness is based on results from the completion of a pilot-scale UVAC system that was designed, fabricated, and operated based on bench-scale experimental data. Concentrations as low as 12 ppt were obtained for the majority of the four-month pilot study. 1. Introduction Mercury (Hg) is a widespread and persistent pollutant that accu- mulates in the environment. In the U.S. approximately 5%–10% of women of childbearing age are estimated to exceed federal exposure guidelines due to dietary intake of Hg-contaminated fsh [1]. This exposure can lead to adverse neurological effects, particularly in the developing fetus and during early childhood, affecting cognitive thinking, memory, attention, language, and fne motor and visual spatial skills. In order to protect the environment, wildlife, and human health, technologies that can effectively and economically remove Hg from gases and liquids are needed. Although promising technologies for gas-phase Hg removal are becoming more apparent (e.g., [2–6]), far fewer viable technologies exist for achieving trace levels of Hg from industrial process waters. Hg is released into the environment from a variety of anthropogenic sources. The best available technology for Hg removal from water in industrial facilities is the sulfde precipitation process [7]. The process consists of the addition of sulfde to Hg-laden water for production of mercuric sulfde (HgS), an insoluble particle. HgS is either removed via settling tanks and/or via fltration prior to discharge to nearby rivers. This treatment will not remove some species of Hg, including, for example, Hg that is bound to organic compounds and elemental Hg. Because of potentially more stringent effuent requirements than what this treatment alone can achieve (e.g., as low as 12 ppt at point of discharge based on United States Environmental Protection Agency’s Effuent Limitation Guidelines), this work set out to determine the effectiveness of heterogeneous photocatalysis using Silica-Titania Composites (STC) [8–13] versus TiO 2 for the removal of Hg from water. The STC technology has been developed/commercialized for Hg recovery from air [3]. In batch experiments using wastewater from a U. S. industrial facility, an interesting phenomenon was observed. Control experiments not including STC nor titania resulted in Hg removal that was at least as good as that obtained through heterogeneous photo- catalysis using STC or TiO 2 (results discussed later). This phenomenon (i.e., exposure to UV followed by fltration) was termed Ultraviolet Activated Chelation (UVAC). When commercially ready, this approach would offer a simple and economical solution that would result in low operation and maintenance costs, would require minimal servicing, could be easily added to a treatment train, is not sophisticated in operation, and would have the robustness to remove Hg from a variety of different waters of interest. This article will discuss bench-scale * Corresponding author. E-mail addresses: annaisa@yahoo.com (A.I. Casasús), am.hagan@gmail.com (A.M. Hagan-Rogers), reggie17r@uf.edu (R. Rodriguez), dmazyck@uf.edu (D.W. Mazyck). 1 Present address: University of Florida, Environmental Engineering Sciences, 312 AP Black Hall, Gainesville, FL, 32611, United States. Contents lists available at ScienceDirect Journal of Water Process Engineering journal homepage: www.elsevier.com/locate/jwpe https://doi.org/10.1016/j.jwpe.2020.101667 Received 27 May 2018; Received in revised form 1 September 2020; Accepted 5 September 2020