One-pot preparation of MnOx impregnated cotton fibers for methylene blue dye removal

Using natural cotton fibers (CF) as a matrix, a series of novel MnOx impregnated cotton fibers (designated as Mn-X@BCF) were prepared in this study through a one-pot sono-assisted KMnO4 reduction process with no additional reducers. The as-prepared Mn-X@BCF was covered by a uniform and dense layer of MnOx nanospheres (10–30 nm), the amount of which was significantly improved by CF pretreatment and linearly correlated with KMnO4 concentration. Specifically, when KMnO4 concentrations increased from 5 mmol L−1 to 100 mmol L−1, the impregnation ratios of MnOx on BCF increased from 0.34% to 14.98% accordingly. Mn-X@BCF showed substantial removal for the typical dye MB. Under the studied conditions, MB removal equilibrium was reached within 10 minutes and solution pH showed no significant influence over a wide pH range (2–11). MB adsorption by Mn-25@BCF obeyed the pseudo-second-order kinetic model and Langmuir model well. The calculated maximum adsorption capacity (Qm) of Mn-25@BCF was 46.3 mg g−1, close to the cumulative adsorption capacity (Qc 45 mg g−1) of MB determined during the eight cycles of adsorption. It was proposed that adsorption followed by partial oxidation was the main mechanism of MB removal by Mn-X@BCF. The as-prepared Mn-25@BCF has great potential as an efficient and low-cost material for dye wastewater treatment because of its inexpensive and renewable source of raw materials, fast MB removal kinetics, wide working pH range and easy solid–liquid separation.