Table 3.

Commonly Used Metrics to Quantify Selectivity

Eqn #	Relationship	Definition of Terms	Ref(s)
1	$\%R=\frac{(C_0-C_e)}{C_0}x100\%$	%R is percent removal, C0 is the initial concentration of the adsorbate (ppm) Ce is the equilibrium concentration of the adsorbate (ppm)	15,112
2	$q=\frac{v}{m}\left(C_0-C_e\right)$	$q$ is the equilibrium adsorption capacity for a target contaminant (mg/g), $v$ is the volume of adsorbate solution (mL), and $m$ is the mass of adsorbent (mg)	110
3	$\text{\%I}=q_t-q_{t+c}$	%I is percent interference, qt is the adsorption capacity for the target contaminant and qt+c is the adsorption capacity for the target contaminant with a competitive oxo-anion present.	113
4	$\mathit{\text{Adsorption capacity ratio}}\%=\frac{q_t}{q_{t+c}}x100\%$		114
5	${\propto }_{t/c}=\frac{q_t{C}_{e,c}}{q_c{C}_{e,t}}$	${\propto }_{t/c}$ is the binary separation factor for the adsorption of target oxoanion, t, in the presence of competitive oxo-anion, c, $C_{e,c}$ is the equilibrium concentration of the competitive oxoanion in the mixed ion system, and $C_{e,t}$ is the equilibrium concentration of the target oxoanion in the mixed ion system.	11,24,29,79,110,114–119
6	$K_d=\frac{C_0-C_e}{C_e}x\frac{v}{m}$	Kd is the distribution coefficient, C0 the initial concentration of the target oxo-anion, and Ce the equilibrium concentration	120–123
7	${\beta }_t=\frac{K_{d,t}}{K_{d,c}}$	${\beta }_t$ is the selectivity coefficient for the target anion, $K_{d,t}is$ the distribution coefficient for the target ion with a competitor present, and $K_{d,c}$ is the distribution coefficient for the competitor with the target ion present	124–127