“…Even though this review covers a broad spectrum of pharmaceutical compounds, but from the data of adsorption performances compiled in Tables 1 and 2, it is evident that the optimum sample pH falls into three categories. The majority of the pharmaceuticals listed in Tables 1 and 2 had an optimum sample pH at weakly acidic conditions (pH 3–6) (Ahsan, Islam, Imam, et al, 2018, Ahsan, Jabbari, Islam, et al, 2018, Benyekkou et al, 2020, Boushara et al, 2022, S. Wong, Lim, et al, 2018), others at neutral pH (pH 7) (Khenniche et al, 2022; Nguyen et al, 2021, 2022) and another group at weakly basic range (pH 8–10) (El‐Azazy et al, 2021; He et al, 2021; Silva et al, 2020). Tetracycline (TC) for example, is an interesting pharmaceutical, which possesses three disassociation constants at pKa 1 = 3.3, pKa 2 = 7.8 and pKa 3 = 9.6 (Chico et al, 2012).…”