PMMA-titania floating macrospheres for the photocatalytic remediation of agro-pharmaceutical wastewater Adam C. Hartley, Joseph B. Moss, Kyle J. Keesling Jr., Nathanael J. Moore, Justin D. Glover and Joel E. Boyd ABSTRACT Antibiotics such as tetracycline are used on a large scale in agriculture, and can become concentrated in wastewater lagoons that are used in conjunction with confined animal feeding operations. Solar-illuminated titanium dioxide can be used to photocatalytically degrade aqueous tetracycline, but its application in a lagoon environment requires that the photocatalyst be supported on a macroscopic support material to prevent loss of the nanoscale photocatalyst into the environment. In this work, titanium dioxide was deposited within a porous poly(methyl methacrylate) film on the surface of floating 7.0 cm diameter acrylic spheres. Six of these floating spheres removed over 96% of the tetracycline in 3.5 L of 60 mg/L tetracycline in natural pond water during 24 hours of solar illumination. The durability of these spheres under long-term solar exposure was also investigated along with the amount of photocatalyst lost from the sphere surface during use. These macroscale floating composite spheres provide a new method for removing tetracycline from wastewater lagoons with minimal risk of being displaced in the environment due to the large size of the spheres. Adam C. Hartley Joseph B. Moss Kyle J. Keesling Jr Nathanael J. Moore Justin D. Glover Joel E. Boyd (corresponding author) Erskine College Department of Chemistry and Erskine Center for Environmental Stewardship, P.O. Box 338, Due West, SC 29639 E-mail: boyd@erskine.edu Key words | composite, floating, photocatalysis, polymer, tetracycline, titania INTRODUCTION Pharmaceutical waste is an increasingly significant environ- mental concern. Agricultural antibiotics such as tetracyclines are utilized in large quantities due to both therapeutic and con- tinuous non-therapeutic application that aids in rapid and consistent growth of the livestock, and helps prevent epidemic disease in confined animal feeding operations (CAFO) (Lind- sey et al. ; Borghi & Palma ). Unfortunately, a large percentage of the applied antibiotic is excreted from the animal un-metabolized. Runoff from areas containing the effected animal waste then becomes a source of pharma- ceutical contamination (Maroga Mboula et al. ; Borghi & Palma ). In a typical CAFO, runoff is collected in waste- water lagoons (Pei et al. ). Excess nutrients are eliminated from the lagoon water through biological action and through coagulation and precipitation as sludge on the lagoon bottom. Wastewater lagoons are not designed for the degra- dation of pharmaceutical waste, and much of the pharmaceutical compounds exit the lagoon in aqueous form to contaminate ground or surface water or within sludge that is broadcast on crop fields for fertilizer. Since antibiotics are bio-active in very low concentrations, agro-pharmaceutical waste has the capacity for significant environmental impact. The presence of tetracyclines in the environment has numer- ous negative impacts, most notably the promotion pathogens with antibiotic resistance genes (Lindsey et al. ; Jiao et al. ; Zhang et al. ). Wastewater lagoons are an essential environmental protection component of most large livestock feeding operations, and any technique used for elim- inating agro-pharmaceuticals from lagoon wastewater should be designed to work in concert with the primary function of the lagoon, nutrient control. Affecting water quality on a lagoon-scale is certainly nothing new. HDPE spheres with a diameter around 10 cm are commonly used as a UV-blocking, evaporation-slowing, and bird-deterring barrier on the surface of water reservoirs. Often referred to as ‘shade balls’, these large water-ballasted spheres cover the water surface and 1 © IWA Publishing 2017 Water Science & Technology | in press | 2017 doi: 10.2166/wst.2017.003 Uncorrected Proof