Application of Nanomaterials in Water Treatment: Arsenic and Natural Organic Matter Removal

Background: Globally, around 150 million people are still supplied with arsenic contaminated drinking water. The groundwaters effected often contain problematic concentrations of natural organic matter (NOM), which plays an important role in releasing As into the aquifer. Thus, this review explores the recent literature relating to the application of various nanomaterials to solve these drinking water supply problems and highlights the work that still needs to be done. Methods: After an extensive initial search patent papers were selected based on their quality and relevance to the topic of this review: the use of magnetic nanomaterials based on pure magnetic materials, magnetic composites of carbon/graphene/biochars, polymeric matrices, metal-organic frameworks and mixed-oxide magnetic nanocomposites, as As adsorbents and as photocatalysts for NOM removal. Results: 160 papers relating to the application of nanomaterials for As removal were reviewed and 38 papers covering photocatalysts for NOM removal. These papers were organised by type of nanomaterial, and their important findings summarised. Although many authors have demonstrated effective solutions in the laboratory, the following areas still need to be addressed: the challenges posed by larger pilot and full scale continuously operated processes; the treatment of complex natural water matrices; which technologies will be required to economically separate nanoparticles from the treated water; whether the nanoparticles will be more economically and environmentally sustainable than other techniques available. Conclusion: Despite these significant gaps in the literature, the body of work carried out thus far, as summarised in this review paper, strongly suggests that full scale treatment solutions applying (magnetic) nanomaterials may prove highly effective in the future for both arsenic and NOM removal.