C0 = concentrations of benzene and toluene in mg L−1 at the start

Ce = concentrations of benzene and toluene in mg L−1 at equilibrium

V = benzene and toluene volume at mL

m = Fe3O4@ZIF-8 masses in mg

KL = (L mg−1) is the Langmuir adsorption constant

KF = Freundlich constant (L g−1)

n = heterogeneity factor (If the value of n < 1, the adsorption is a chemical process; if n > 1, then it is a physical process).

qe = adsorption capacity at equilibrium

qm = maximum adsorption capacity

RL = dimensionless separation factor

The values of RL show whether the biosorption process is irreversible (RL = 0), linear (RL = 1), favorable (0 < RL < 1) or undesirable (RL > 1)

ΔG° = Gibbs free energy (kJ mol−1)

ΔS° = entropy (kJ mol−1 K−1)

ΔH° = enthalpy (kJ mol−1)

K1 = equilibrium rate constant for pseudo-first order kinetics (PFO) (1.min−1)

K2 = equilibrium rate constant for pseudo-second order kinetics (PSO) (g mg−1 minmg)

Kb =Intra-Particle Diffusion (IPD) rate constant (mg g−1 min−1/2)

C= thickness of the boundary layer

$\mathsf{\beta }=$ D-R isotherm constant (mol2 kJ−2)

$\mathsf{\epsilon }=$ Polanyi potential

E = The adsorption energy (kJ.mol−1)

KT = constant of equilibrium binding (L.mg−1)

B = Temkin constant associated with the heat of adsorption (J/mol)

D-R = Dubinin-Radushkevich

XRD = X-ray Powder Diffraction

FTIR= Fourier Transform Infrared Spectrometer

SEM = Scanning electron microscope

TEM = Transmission Electron Microscope

VSM = Vibrating Sample Magnetometer

BET = Brunauer–Emmett–Teller

MOF = Metal-organic framework