As the cheap substitution of commercial iron carbon microelectrolyte filler to remove Cr(Ⅵ) in waste water

the red mud/coal based material was prepared from the mixtures of red mud

pulverized lignite and sodium carboxymethyl cellulose via a carbothermal method. The different preparation parameters (carbonization temperature

carbonization time

mass ratio of red mud/coal) and adsorption conditions (solution pH

concentration) were investigated to improve the removal efficiency of Cr(Ⅵ). The results demonstrated that the red mud/coal based material carbonizated at 800℃ for 1 h with the mass ratio (red mud/coal) of 1/3 can reach the highest Cr(Ⅵ) removal capacity (4.03 mg·g-1)

the lowest Fe dissolution ratio (< 0.19 mg·g-1) and the maximum adsorption capacity (12.97 mg·g-1

according to the Langmuir adsorption isotherm models). The adsorption isotherm of Cr(Ⅵ) on the red mud/coal based material was well consistent with Freundlich equation model

and its adsorption kinetics can be described by the pseudo-first-order or pseudo-second-order equation. The multiple characterization methods (XRD

XRF

BET

and SEM) further revealed that the red mud/coal based material had higher reduction degree of Fe element

bigger BET area and volume and better particle dispersion than the commercial iron carbon microelectrolyte filler

which accounted for its excellent removal efficiency of Cr(Ⅵ).