Highly efficient multifunctional recyclable nanocomposite adsorbent as scavenger for water cleaning

Abstract

This project aims to develop new low-cost inorganic nanowire membrane composites for the treatment of polluted water, typically containing oil spills, heavy metal ions, and organic compounds. The whole process consists of pretreatment polluted water using coated nanowire membranes for selectivity absorbing hydrophobic organic compounds followed by ion-exchange processes based on acid MnO₂ octahedral molecular sieve nanowire membrane with strong ion-exchange capabilities. The multifunctional highly-selective absorbent membrane materials can be an ideal candidate for the separation and removal of pollutants in water, and the applications of the nanowire multifunctional membranes can lead to a significant reduction of energy consumption through low-pressure-permeability. The chosen membrane materials, cryptomelane-type MnO₂ nanowires, which are with unique properties including high selectivity for solvents that need to be separated, high surface area and permeability, good mechanical and thermal stability, good chemical stability, good ion-exchange properties and low cost of the membrane materials. The cryptomelane-type MnO₂ nanowires were successfully synthesized by hydrothermal method under certain controlled condition including temperature, pressure and time. A rinsing process with deionized water was performed to remove any impurities of products. Then the materials were acidified by concentrated nitric acid in order to replace the potassium ions within the tunnels of the nanowires by the hydrogen ions which were from the concentrated nitric acid. Lastly, the materials were made to be the membranes with superhydrophilicity, which were specifically for heavy metal ions. Meanwhile the acidified materials were subsequently coated with PDMS and became superhydrophobicity, which were then specifically for organic compounds. In addition, different characterizations of the materials were performed including crystal structure, arrangement of atoms, constituents, surface and cross-sectional morphology, etc. Finally, several properties of the materials were measured including flowing rate, water contact angle, reversibility, adsorption capacity, etc.