Adsorption Behavior of Cr(VI) on Al-Fe Cointercalated Bentonite

Abstract

An efficient Al-Fe co-intercalated bentonite composite material (Al-Fe/Bent) able to remove hexavalent chromium (Cr(VI)) from aqueous solutions was prepared. The batch experiments studies were conducted to evaluate the adsorption performance of Cr(VI) contained in aqueous solution. The XRD results showed the spacing of layers of bentonite was increased due to the Downloaded by [University of Otago] at 14:26 08 October 2015 aluminum and iron polycation intercalated into the layer of bentonite. The removal rate of Cr(VI) from the aqueous solution could be up 87.4% under the condition of the dosage of Al-Fe/Bent 8 g/L, pH 4, and contact time 60 min. The equilibrium data fitted well to the Freundlich model.The adsorption process could be well described by the pseudo-second-order kinetic model.

Removal of Cr(VI) by a simply prepared biochar‐supported nanoscale zero‐valent iron

“…The BC only adsorbed 7.1% of Cr(VI) within 120 min, indicating that BC was inactive for removal of Cr(VI). The Cr(VI) existed in the forms of anions (HCrO 4 − , Cr 2 O 7 2− and CrO 4 2− ) in solution, 25,26 and the surface of BC was negatively charged 27 . Therefore, a strong electrostatic repulsion force between Cr(VI) and BC resulted in the poor performance of Cr(VI) removal.…”

“…The ionic forms of Cr(VI) and the activity of NZVI/BC under different pH values were responsible for these observations. The Cr(VI) species presented in the form of HCrO 4 − , Cr 2 O 7 2− and CrO 4 2− under varying pH conditions in the aqueous phase 25,26 . At low pH, the predominant species of Cr(VI) were HCrO 4 − and Cr 2 O 7 2− , and their removal was more easily due to the low adsorption free energy 26 .…”

“…This implied that the rate-limiting step of the Cr(VI) removed by NZVI/BC was chemisorption. 25 Furthermore, the Elovich model could also describe the process of Cr(VI) removal when taking R 2 (larger than 0.9) into account, which further indicated that Cr(VI) removal was a heterogeneous or multi-mechanism process. [37][38][39]…”

“…The removal of Cr(VI) by BC and NZVI/BC was first investigated under the conditions of initial Cr(VI) concentration of 10 mg L −1 , solution pH 5, NZVI/BC dosage 300 mg L −1 , reacting at 30 °C for 120 min; the results are listed in ) in solution, 25,26 and the surface of BC was negatively charged. 27 Therefore, a strong electrostatic repulsion force between Cr(VI) and BC resulted in the poor performance of Cr(VI) removal.…”

“…The Cr(VI) species presented in the form of HCrO 4 − , Cr 2 O 7 2− and CrO 4 2− under varying pH conditions in the aqueous phase. 25,26 At low pH, the predominant species of Cr(VI) were HCrO 4 − and Cr 2 O 7 2− , and their removal was more easily due to the low adsorption free energy. 26 Furthermore, the surface of BC was more positively charged at low pH, 26,32 which resulted in improving removal of Cr(VI) due to electrostatic attraction.…”