Highly effective removal of formaldehyde from aqueous solution using mesoporous [epsilon]-MnO₂ crystals at room temperature

Without additional templating agent or surfactant, porous and sparse MnCO₃ was synthesized hydro­thermally from Mn²⁺ with a CO₂-storage material (CO₂SM). Through thermal decomposition of the as-synthesized MnCO₃, [epsilon]-MnO₂ crystals with good catalytic performance and stability in HCHO degradation were prepared. The optimum preparation conditions were determined by tuning the preparation conditions and carrying out response surface studies, and the resulting [epsilon]-MnO₂ crystals could degrade 66.1% of a 10 ml 10 mg l⁻¹ HCHO solution. After the HCHO degradation conditions were optimized, the thermodynamic data could be fitted with the Langmuir isotherm and quasi-secondary kinetic models at T = 25–50°C. The degradation mechanism of HCHO is discussed. This work provides a new strategy for the degradation of HCHO at room temperature.