Chitosan/montmorillonite nanocomposites for the treatment of dyehouse effluents

Dyehouse effluents often cause severe water pollution. There is an urgent need to develop effective and economically variable techniques for the treatment of the dyeing process wastewaters. Chitosan, an environmentally friendly and biodegradable natural polymer, exhibits promising potential for the effective treatment of dyehouse effluents. Due to its specific properties, montmorillonite is also gaining interest in removing organic pollutants from aqueous compositions. The combination of these two adsorbents has resulted in the creation of materials that lead to the enhanced decoloration of dyehouse effluents. In this thesis, a detailed experimental study of the treatment of dyehouse effluents, that contained hydrolysed Remazol Black B (major interest), hydrolysed Remazol Brilliant Blue R and hydrolysed Reactive Brilliant Red M-3BE, using a cationic quaternary chitosan derivative N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (HTCC)/ montmorillonite (MMT) composite, organically modified montmorillonite (OMMT), and the HTCC/OMMT composite is reported. In particular, this thesis focuses on commercially-feasible materials and commercial dyes, providing an efficient, universal adsorbent for industrial anionic dyes and a strong link to actual applications. Factors of relevance to the dye adsorption process, such as pH, temperature, initial dye concentration and the solubility issues of the adsorbent have been systemically optimised for the HTCC/MMT composite. Various techniques have been employed in elucidating the properties of the flocs that were formed after the adsorption process. The desorption mechanism was also established. Montmorillonite was modified to improve the dye uptake capacity. The adsorption uptake and mechanism of hydrolysed dye adsorption was investigated and linked to the structural changes of the organo-clays. Key parameters that influence the anionic hydrolysed dye adsorption have been identified. Finally, the polyelectrolyte HTCC has been combined with the organo-clay to further improve the dye uptake capacity and efficiency for different hydrolysed dyes. The composites showed great potential for the adsorption of dye mixtures.