*3.1. SMZ Degradation*

The effects of different concentrations of GO on SMZ degradation were first studied. GO did not adsorb SMZ much in the dark, and little degradation of SMZ occurred under UV illumination without GO (Figure S1). However, the degradation of SMZ was accelerated in the presence of GO. The degradation rates of SMZ were 33.32 ± 2.54%, 34.90 ± 2.69%, and 37.44 ± 2.12% in the presence of 10 mg/L, 30 mg/L, and 50 mg/L GO, respectively (Figure 1a). According to the first-order kinetic fitting of the reaction in the first two hours (Figure S2), the observed reaction rate constants (*k*obs) were 0.0732 <sup>h</sup>−1, 0.0964 <sup>h</sup>−1, and 0.1129 h−<sup>1</sup> (Figure 1b).

**Figure 1.** Effects of GO on SMZ degradation under UV light (**a**) and *k*obs(**b**).
