Preparation, characterization and adsorption performance of cetyltrimethylammonium modified birnessite

- A simple hydrothermal synthesis of CTMA-birnessites is developed.
- Comprehensive microstructural characterization of synthetic CTMA-birnessites is provided.
- Detailed characterization on the oxidization states of manganese presented in the birnessite samples is performed.
- CTMA-birnessites show good performance for benzoic acid adsorption.
- The proposed adsorption model well explains the adsorption behavior for CTMA-birnessites adsorbing benzoic acid.

Cetyltrimethylammonium modified birnessite (CTMA-birnessite) is prepared by a simple hydrothermal method. The synthetic birnessite materials are characterized by a number of characterization techniques, including powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results indicate that the prepared CTMA-birnessite has a basal spacing up to 3.28 nm and that both the CTMA-birnessite and the birnessite have layer structures and plate-like forms with a thickness of less than 0.1 μm. The relative contents of Mn2+, Mn3+ and Mn4+ on the sample surfaces are about 22.1%, 56.4% and 21.5% for birnessite, and 9.5%, 62.4% and 28.1% for CTMA-birnessite. The CTMA-birnessites show excellent adsorption/desorption properties for benzoic acid. At least 20% of the benzoic acid is adsorbed to the CTMA-birnessite in the adsorption experiment.