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MnO2-loaded activated carbon and its adsorption of formaldehyde

Coconut shell activated carbon (AC) loaded with MnO2 was tested as an adsorbent for formaldehyde. Preparation conditions of MnO2-loaded AC (MnO2-AC) were optimized. The resulting AC and MnO2-AC were characterized by scanning electron microscopy, Brunauer-Emmet-Teller analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, and X-ray diffraction. The results showed that the adsorption efficiency of formaldehyde (3.5 mg/L) by MnO2-AC (concentration of manganese nitrate/sodium carbonate was 0.3 mol/L, impregnation oscillation time of 4 h, calcination temperature and time of 350 C and 4 h, respectively) was 93.1%, which increased by 251% compared to that of the AC. The adsorption equilibrium of MnO2-AC was achieved after 4 h. With increasing dosage of MnO2-AC, the rate of increasing of the adsorption efficiency became more gradual. The adsorption process of the formaldehyde solution with a low concentration fit the Langmuir adsorption isothermal model, where the adsorption capacity was 9.22 mg/g. The stability and regenerability of MnO2-AC were good.