Mesoporous MnO₂ polymorphs as sorbent materials for removal of cationic dyes from water

Scientists have become interested in treating dye-contaminated water due to the health issues and ecological imbalances caused by presence of these injurious compounds water. Herein, two MnO2 polymorphs i.e. ε- γ-MnO2 were prepared comproportionation reaction between KMnO4 MnCl2. In comparison γ-MnO2, ε-MnO2 has greater surface area, pore width, volume. According thermal study, contains more surplus mass form negatively charged hydroxyl groups than γ- phase. The adsorption capability both was examined for removal cationic (methylene blue, malachite green crystal violet) anionic dyes (eosin yellow). efficient using occurred neutral medium, where it had a highly negative as determined zeta potential measurements. It only took few minutes complete removal. electrostatic interactions dye molecules with OH- account this result. While, (40 min) acidic medium γ-MnO2. On other hand, on phases hampered repulsion forces. As result, despite extending contact time 180 min adsorbent dose 50 mg, no seen. contrary, very fast occurs Eosin Y acquired positive charge. influence ionic strength MB elimination investigated. results showed that content NaCl increased, effectiveness decreased from 100% 35%. kinetics studied, discovered mechanism follows pseudo-second order model.