Magnetic carbon-based nanocomposites for environmental applications: the case of arsenic and mercury removal from water

Water is necessary to all human activities and to life in general. Because of this, it was made central to all components of the EU Green Deal and to several United Nation Sustainable Development Goals, starting with SDG6 on «clean water and sanitation». Industrialization, population grow, and their needs have contributed to the degradation and scarcity of safe water. Inorganic elements are one example among many of water contaminants. Arsenic and mercury are two elements that cause great concern. Chronic As exposure could cause cancer, neuropathies, bronchopulmonary and cardiovascular diseases, and chromosome aberrations. The World Health Organization guideline of As in drinking water is set to 10 μg/L, but in different parts of the world, As concentrations significantly higher than 50 μg/L have been detected (Smedley and Kinniburgh, 2002). Mercury is neurotoxic, volatile, persistent, and bioaccumulates in the organisms. For these reasons efforts have been made to develop effective pollution control technologies towards the efficient and enhanced As and Hg removal from contaminated sites. In this communication it will be reported the synthesis, characterization, and application of hybrid nanostructures to remove As and Hg from water, and their concentration in a solid phase, promoting the recycling of these elements. The nanocomposites combine the interesting properties of graphite nanoplatelets, with the magnetic properties of cobalt and manganese spinel ferrites, and exhibit good sorption properties towards As and Hg. For some systems (nanocomposite/element) the sorption process was sensitive to solution pH, evidencing that electrostatic interactions could be the main binding mechanism involved. Removal efficiencies up to 80% were achieved using only a few milligrams per liter of nanocomposite. In binary solutions, occurred a preferential removal of Hg, however the initial As concentrations was higher. The kinetic behavior was well described by pseudo-second order or Elovich equations, suggestion chemisorption process.