Gas Hydrates Formation for High - Efficiency Waste Water Treatment: Experimental Removal of NH4+ from Water via CO2 Hydrates Formation

Waste water treatment is an essential and mandatory step for most of the industrial processes involving water. It has been widely proved that the overconsumption of this source, together with the exponential growth of anthropogenic damaging processed, lowered the quality of groundwater and, more in general, water resources, at an alarming pace. The removal of salts, ions dissolved in water and other effluents, can be carried out through several methods. Membrane separation, evaporation and crystallization are the most applied for water recovery, while membrane, chemical precipitation, adsorption, ion exchange and freezing/thawing are the most effective techniques for heavy metal ion solutions. When applying these procedures, some critical aspects must be considered, mainly associated to removal efficiency, costs, availability and non-toxicity of the raw materials, environmental concerning and other. In this context, gas hydrates can be considered an alternative solution for water treatment, capable to overcome all the critical issues related to the traditional strategies. In particular, the formation of gas hydrates for ion removal from waste water, was proved to reach extremely high efficiencies; moreover, the removal efficiency was found to be proportional to the size of ions and to decrease with their charge. Based on these experimental considerations, this study deals with preliminary research on the removal of NH4+ from water. This species consists of one of the most affecting pollutants in bio - refineries and its removal is often energy intensive, with consequent high costs. Experiments were carried out in a lab - scale apparatus, where water was initially threated with ammonium chloride at specific concentration. Carbon dioxide was finally chosen for the formation of hydrates.