Thermodynamic description of CO2 hydrates production in aqueous systems containing NH4Cl; evaluation of NH4+removal from water via spectrophotometric analysis

Similar to ice, the crystalline structure of hydrates does not involve contaminants diffused in the aqueous phase. In this study, carbon dioxide hydrates were formed in demineralised water mixed with ammonium chloride, at concentrations ranging from 1.5 to 14.9 wt%. The experiments aimed to establish if the formation of hydrates could be considered a suitable option for NH4+ removal from water. Hydrates were formed in excess of water and into a small - scale reactor, in batch conditions. The effect of electrolytes on the process thermodynamics was defined and compared with the ideal trend for CO2 hydrates.Finally, hydrate samples were processed via spectrophotometric analyses to detect the lowering of NH4+ concentration in the hydrate phase, thus proving the selectivity of the process and definitively establish its viability for NH4+ removal from water.