I am encountering an issue in my laboratory. My supervisor and I are currently faced with the task of neutralizing a volume of 60 liters of Aqua Regia, which contains suspended metals, at a concentration of 2% or lower. Our current approach involves using Granular Sodium Hydroxide (NaOH) as a neutralizing agent. However, we have observed that we often end up using excessive amounts of NaOH, resulting in an overly basic solution. Therefore, I seek guidance on the appropriate quantity of NaOH required to neutralize the Aqua Regia effectively.
Furthermore, I would like to inquire about the viability of preparing an aqueous solution of NaOH prior to its addition to the 60-liter drum. Will this method enhance the neutralization process?
Any advice is greatly appreciated.
EDIT: At my job we digest silver alloys and we use 10 mL of 30% HNO3 and 5 mL Concentrated HCl. When we filter to collect AgCl we use DI H2O and the amount that we use is not the same through out all of the filtering. So the concentration of the Aqua Regia is most like below 2%. I just used 2% as a guess really.