Project: Utilisation of green chemicals in non/energy extractive industries: Preparation of modified nanofibrillar celluloses (NFC) for flotation, flocculation and dewatering, and water purification in mining industry

Acronym CELMIN
Duration 01/03/2014 - 31/08/2016
Project Topic Although the majority of dissolved solid substances in waters originates from ore, a small amount of pollutants comes from oil-based chemicals used in flotation as well as other metal concentration processes and dewatering, possibly creating toxicity problems when released in effluents. Thus, the purification of waters coming from both extraction and mineral processing during mining activities is needed. Mine closure and rehabilitation issues have to be taken into account because acid drainages are also generated at abandoned mine sites. The CELMIN project aims to develop concepts for environmental-friendly effective green chemicals by the chemical modification of nanofibrillar celluloses (NFCs) to be functional in mining applications responsible for dissolved and suspended solids load. Four different uses are studied: 1. Use of hydrophobized NFCs as a collector in ore and mineral flotation. 2. Use of anionized, cationized and hydrophobized NFCs as a dewatering agent in concentrate and tailings. 3. Use of anionized and cationized NFCs as a flocculant in suspended solids removal from mining, process and seepage waters. 4. Use of anionized NFCs as adsorbent in removal of heavy metals and ammonium from waters. The results of the CELMIN project are expected to increase sustainability of primary non-energy resource supply by decreasing water pollution of mining industry, lower carbon footprint by using renewable raw materials instead of a fossil feedstock in chemical production and lessen the concern about environmental issues by using biodegradable chemicals in dressing of ores and water purification.
Project Results
(after finalisation)
The progressive industrialization of almost any country worldwide increases the demand of mineral and metal resources. The high demand leads to the processing of ores possessing a high complexity of its components. Annually around 400 million metric tons of ores are crushed and ground to particles to liberate the individual minerals. Froth flotation is the main beneficiation method for the efficient separation of desired minerals from gangue materials. Oil- derived flotation reagents used, however, are potentially harmful for human beings, animals and the environment, and therefore biocompatible candidates would be needed. Nanocellulose or cellulose nanocrystals are potential agents to replace commercial flotation reagents or flocculation agents in dewatering of finely ground particles to achieve a sustainable and efficient processing of ores. The aim of the project was to design various chemical modifications affecting the functional properties of nanocelluloses and study those nanocelluloses with respect to their function in selective flotation (collector/depressant) and flocculation of finely dispersed mineral particles. Additionally, the role of adsorption interaction of cellulose chemicals on given minerals in the performance of froth flotation was aimed to study in order to get fundamental understanding for the basis of the development of tailored nanocellulose chemicals. Project showed that cellulose can be chemically modified and properties adjusted such a way they can be used as green chemicals in froth flotation and dewatering/flocculation of mining industry. During the project it was showed that functionalized nanocellulose collectors, depressants or flocculants have a performance similar than oil-based chemicals with lower environmental impact. Functionalization based on increased hydrophilicity with increasing anionic charge and increased amphiphilicity by attaching the amino groups with extending alkyl chain lengths were designed. The importance of the free surface charges of the nanocellulose on the adsorption behavior on minerals, as well as on the particle- bubble attachments during flotation experiments was recorded. The investigations with binary quartz- hematite and quartz-alumina systems showed that nanocelluloses can selectively interact with one mineral rendering its wetting properties to more hydrophobic and thus separate the mineral efficiently from the gangue mineral. The results also suggest that nanocellulose carboxylation and sulfonation may be a route for selective flocculation e.g. in quartz/hematite separation. Cellulose based chemicals to have a great potential in mineral processing. The periodate oxidation of cellulose to dialdehyde cellulose and the subsequent functionalization of it were proved to be technically feasible. For commercialization, the optimization of each process step would be needed in order to clarify full economical potential. Also a novel route to produce nanocellulose chemicals by using deep eutectic solvents could be an economical and environmental sound alternative and would be a worth of research.
Network ERA-MIN
Call Sustainable And Responsible Supply Of Primary Resources

Project partner

Number Name Role Country
1 University of Oulu Coordinator Finland
2 IST LISBON Partner Portugal
3 NUCBM Partner Romania
4 Sibelco Lda Observer Portugal
5 Sojitz Beralt Tin & Wolfram S.A Observer Portugal