Abstract:

Mg/Al layered compounds were prepared by using Na₂CO₃/NaOH, NaOH and NH₄OH as precipitants. Their Cr(Ⅵ) adsorption properties were studied using simulated wastewater containing Cr(Ⅵ). The structures of Mg/Al layered compounds were discussed in combination with X-ray diffraction XRD and Brunauer Emmett Teller(BET) methods surface area experiments. The results show that Mg/Al layered compounds have higher crystallinity, perfect layered structure, larger specific surface area and suitable pore distribution by using Na₂CO₃/NaOH as the precipitator. The optimal absorption efficiency of Cr(Ⅵ) can be reached when pH values are 7.0~9.0, and solid-liquid ratio at room temperature for 9 h is 1 g to 500 mL. The saturated adsorption capacity of Mg/Al layered compounds is 199.4 mg/g under the optimal conditions. The Cr(Ⅵ) in wastewater is removed by forming layered superamolecular compounds between anions containing Cr(Ⅵ) and Mg/Al layered compounds. The remaining Cr(Ⅵ) concentration of laboratory wastewater initially containing 226.1 mg/L is less than 0.5 mg/L after six absorption cycles with Mg/Al layered compounds. The treated wastewater is in line with national sewage comprehensive emission standard(GB8978-1996). Mg/Al layered compounds are excellent absorbents for disposing laboratory wastewater containing Cr(Ⅵ).

Key words: Mg/Al-layered superamolecular compounds, memory effect, laboratory wastewater, Cr(Ⅵ), removal