There is an indication from one set of experiments using solutions with a mix of Cu and Zn that there were differences in the ability of mussel shell to capture the different metal ions. In this experiment the mussel shell showed a reduced ability to retain Zn while Cu continued to be efficiently retained. In other studies Cu has typically been found to be adsorbed more easily than other metals (Coşkun et al. 2006), although this can vary with the type of sorbent media and pH (Wu and Zhou 2009). Unfortunately, in this current experiment no measurements of pH were reported despite the potential for changes in pH to be caused by chemical reactions between the dissolved metal compounds and the shell material (Färm 2002; Genç-Fuhrman et al. 2007; Wu and Zhou 2009). It is important for future research to either measure pH or control for possible effects from varying pH