A novel CoFe layered double hydroxides adsorbent: High adsorption amount for methyl orange dye and fast removal of Cr(VI)

•Novel sorbents, CoFe-LDH for the removal of MO and Cr(VI) were prepared.•Adsorption kinetics and isothermals of MO and Cr(VI) were studied.•The adsorption mechanisms were discussed in detail.•High adsorption amount of MO and fast removal of Cr(VI) were obtained in CoFe-LDHs.

CoFe-nitrate-layered double hydroxides (LDHs) with Co2+/Fe3+ molar ratios of 2, 3 and 4 were synthesized by a simple co-precipitation method. The as-prepared CoFe-LDHs exhibited a high adsorption activity to the methyl orange (MO) dye and Cr(VI). The adsorption characteristics including adsorption kinetics and isothermals were investigated. Structure analysis of the as-synthesized LDHs before and after adsorption revealed that adsorption proceeds in two processes: external surface adsorption and interlayer anion exchange. The results of MO adsorption experiments showed that LDHs with Co2+/Fe3+ molar ratios of 4 worked best with the largest MO adsorption amount up to 1290 mg/g at an initial concentration of 300 mg/L due to the porous structures. We have also noted that Cr(VI) in a range of 2–25 mg/L can be quickly removed with the maximum adsorption capacity of 27.62 mg/g in the initial 5 min, much faster than other LDH materials. Therefore, CoFe-LDHs are potential cost-effective adsorbents for both MO dye and Cr(VI).

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