Study of the Formation of Stable High Concentrated Monochloramine Solutions

Disinfection is a very important step in the water treatment independent on the water application. Chlorination is the practice adopted in many industries, but chlorine can cause environmental damage and health hazards in the industry. A less aggressive agent to the environment is desirable to be found. The objective of this work is to prepare stable monochloramine solutions without any residual of chorine. The inorganic chloramine is less effective as a disinfection agent than free chorine but is capable to reduce the total population of bacteria to an acceptable level. For the synthesis of rich monochloramine solutions many are the variables that need to be considered, such as the reagent ratio, pH and temperature. Since the monochloramine solution is very unstable several others precautions should be taken for keep its concentration stable during the experiments. To find out the best way to prepare monochloramine solutions several experiments were carried out to verify the hypochlorite consumption using solutions with excess of hypochlorite or ammonium chloride, according to the stoichiometry of the reaction. Additional experiments were conducted to study the effect of monochloramine evaporation on the concentration of the chloramine solution. The results of this work reveal that an excess of ammonium chloride is necessary to avoid residuals of chlorine and the pH should be higher than 8. Also, the influence of evaporation on the decrease of monochloramine concentration has greater importance than that due to chloramine decomposition, room light and/or temperature.