t	time (min)
qe	the amount of Cr(VI) adsorbed at equilibrium (mg·g−1)
qt	the amount of Cr(VI) adsorbed at time t (mg·g−1)
ce	the equilibrium concentration of Cr(VI) (mg·dm−3)
c0	the initial concentration of Cr(VI) (mg·dm−3)
m	the adsorbent mass (g)
V	the solution volume (dm3)
q1	the adsorption capacity of Cr(VI) at equilibrium for pseudo-first-order model (mg·g−1)
k1	the rate constant of pseudo-first-order model (min−1)
q2	the adsorption capacity of Cr(VI) at equilibrium for pseudo-second-order model (mg·g−1)
k2	the rate constant of pseudo-second-order model (g·mg−1·min−1)
kIPD	the intraparticle diffusion rate constant (mg·g−1·min−1/2)
B	the parameter related to the thickness of the boundary layer (mg·g−1)
kLFD	the external mass transfer coefficient (min−1)
kF	the Freundlich constant indicative of the relative adsorption capacity of the adsorbent ((dm3)1/n·mg(1−1/n)·g−1)
n	the Freundlich equation exponent (-)
qL	the maximum adsorption capacity in Langmuir model (mg·g−1)
kL	the Langmuir constant related to the energy of adsorption (dm3·mg−1)
R	the universal gas constant (kJ·mol−1·K−1)
T	temperature (K)
BT	the Temkin constant related to heat of sorption (kJ·mol−1)
kT	the Temkin equilibrium isotherm constant (dm3·g−1)
RL	the separation parameter (-)
q	the amount of Cr(VI) adsorbed (mg·g−1)
c	the concentration of Cr(VI) (mg·dm−3)