Abstract
Manganese (Mn(II)) is a common contaminant in groundwater, resulting in substantial manganese oxides (MnOx) in groundwater treatment sludge (GTS). In this study, GTS was recycled to fabricate the alkali-modified GTS (AGTS). The kinetics and thermodynamics of Mn(II) removal and the efficiency of continuous Mn(II) removal by AGTS-coated filter media were studied. The pseudo-second-order kinetics and the Langmuir isotherm models effectively described the removal behavior. The maximum removal capacity obtained from the Langmuir isotherm model was 26.39 mg/g. The column experiment results showed that the removal of Mn(II) (10 mg/L) by the AGTS-coated filter media first goes through the initial adsorption and penetration process, followed by the development of the catalytic oxidation ability, finally realizing the continuous removal of 99.98 % Mn(II). The column experiment achieved up to 120.51 mg/g Mn(II) removal capacity by the Thomas model, and the catalytic oxidation rate constant is 0.0140 min−1. The characterization of the sludge particles revealed that AGTS had a rougher surface and massive oxygen-containing functional groups. Through the electrical state, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) analyses, it was elucidated that the AGTS initially binds Mn(II) ions by adsorption and then oxidizes them into a new MnOx layer to remove Mn(II) by long-term catalytic oxidation. The treated water was reliable, and nearly no hazardous compounds were released. This study provides a promising approach for recycling waste GTS and fabricating Mn(II) removal filter media.
Published Version
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