A Potassium Methyl Silicate/MnO2 Composite for the Rapid Removal of Dyes from Water

Abstract

Dye wastewater causes significant harm to the environment and human health. Adsorption is one of the most effective technologies for treating dye wastewater owing to its straightforward operation, strong applicability, and low cost. However, traditional adsorbents have drawbacks, including complicated preparation processes, low adsorption capacity, and challenges with separation, recovery, and regeneration, which fail to meet practical application requirements. Therefore, the development of adsorbents with high adsorption capacity, easy separation, and reusability is urgently required for the treatment of dye-contaminated wastewater. Potassium methyl silicate (PMS)@MnO₂ complex particles (PMS@MnO₂) were successfully synthesized by adding a PMS solution to a potassium permanganate (KMnO₄) solution at a molar ratio of PMS to MnO₂ of 1:1. The PMS@MnO₂ complex is rich in functional groups and exhibits good hydrophobicity. The PMS@MnO₂ complex particles demonstrated excellent adsorptive capacity (989.1 mg/g) for methylene blue (MB) with rapid degradation, achieving over 75% of their adsorptive capacity within 5 min. The adsorption process was found to be pH-responsive and exothermic. Under neutral and alkaline conditions, the negative charges in the oxygen-containing groups on PMS@MnO₂ combine with the positive charges in the nitrogen atoms of MB via electrostatic forces. However, under acidic conditions, MB was adsorbed via hydrogen bonding and n-π interaction between MB and PMS@MnO₂. The spent adsorbent was reused for at least five cycles.