2.2. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX)
WWT samples were prepared for SEM by resuspension of liquid by manual shaking of containers followed by high-speed vortexing for 1min, pipetting 1.5 μL of the dilution to a highly ordered pyrolytic graphite substrate mounted to stainless steel SEM stub by carbon tape, and drying (≥3 h). SEM imaging was conducted using a LEO 1550 SEM with a Schottky field emitter source at 5 kV accelerating voltage, using a 30 μm aperture, at a working distance of 3–6 mm, with an InLens detector (acting as a 20 kV beambooster). Images obtained with LEO's proprietary software were analyzed by ImageJ (NIH) software's “threshold” and “analyze particles” tools to determine surface area, in conjunctionwithMicrosoft Excel and GraphPad Prism software for statistical analysis.