Preparation and Adsorption of Nano-sized Manganese Oxide from Low-Grade Pyrolusite with Walnut Shell Reducing Agent
摘要
With the depletion of high-grade manganese ore resources, the efficient utilization of low-grade manganese oxide ore emerges as a significant topic for discussion. Many prior studies have concentrated on the reductive process and the associated kinetics of low-grade manganese oxide ore; however, the ultimate objective of reduction is to produce useful materials. In this paper, we present the preparation of nano-sized manganese oxides from low-grade manganese oxide ore using walnut shell as a reducing agent. The adsorption capacities for basic magenta and methylene blue (MB) were investigated. The experimental results indicate that when the concentration of sulfuric acid is 3 mol L−1, the amount of walnut shell is 40 g L−1, the ratio of liquid to solid is 10:1, the leaching time is 150 minutes, and the leaching temperature is 369 K, the leaching efficiency reaches 93.18 pct. The leaching process is controlled by a chemical reaction, with an activation energy of 45.50 kJ mol−1. Nano-sized manganese oxides can be synthesized from the potassium permanganate oxidation leaching solution after iron removal using potassium sulfate, with α-MnO2 being the main component. The adsorption process of nano-sized manganese oxide for basic fuchsine follows second-order kinetics and conforms to the Freundlich isotherm adsorption model, demonstrating a maximum adsorption capacity of 144.91 mg g−1. Conversely, the adsorption process for MB adheres to pseudo-first-order kinetics and also conforms to the Freundlich isotherm adsorption model, with a maximum adsorption capacity of 92.24 mg g−1.