Fig. 4. Kinetics experiment to determine the Cu–HA dissociation rate. 2 μM SA was added to pH 8.2 UV–SW in the presence of 1mg L−1 HA and 5 nM Cu with an adsorption time of 60 s. The CuSA peak height over time (red squaremarks) plotted over amodelled fit (blue dashes). The rate coefficient was calculated from ln[CuHA] as a function of time (inset) which gave a value of 0.00016 s−1. This is equivalent to a half-life of 72.4 min.