Removal of carbon nanomaterials by co-precipitation with chitosan: a facile method for water pre-treatment

Anthropogenic contamination of the environment by engineered nanomaterials (ENM) is an emerging environmental problem; therefore, it is important to develop efficient technologies for contaminated water treatment. Chitosan was used as a flocculant for the co-precipitation and removal of water-dispersed carbon nanomaterials (hydroxylated carbon nanotubes (CNT-OH) and fullerenes (C-60-OH)) by changing the solution pH, which affects chitosan solubility. The precipitation of chitosan was accompanied by efficient entrapment of water-dispersed ENM into an insoluble precipitate which resulted in >90% ENM removal during single treatment. Factors controlling the efficiency of ENM removal by the chitosan-assisted co-precipitation method, such as the molecular weight of chitosan, the presence of low-molecular-weight electrolytes, the separation method, etc., are discussed.