Dynamic Experimental Research On Air Stripping Of Sulfur-Ammoniac Wastewater In Rare-Earch Industry

In this paper, the experimental research of dynamic air stripping deamination based on static study is performed. The research incorporates the rare earth sulfur ammonia wastewater discharged from a rare earth factory as its water samples. Considering the business-to-run costs and the actual capacity of the company, the experimental program of wastewater management is well planned and the economic, reasonable parameters are determined.The rare earth sulfur ammonia wastewater has the characteristics of high hardness and high density of ammonia-nitrogen. In the measurement of the experimental water samples, the density of ammonia-nitrogen reached 10383.8mg/L, while the hardness is 154.05mmol/L. In order to avoid the equipments from fouling, the hardness of the wastewater must be reduced.The high density rare earth sulfur ammonia wastewater is pretreated with lime and soda ash softening before air stripping. 5g lime was added into 200ml water samples first, the hardness of the wastewater reduced from 154.05mmol/L to 26.06mmol/L, and then 40ml 1mol/L Sodium carbonate solution was added, the hardness reduced from 26.06mmol/L to 0.87mmol/L. It can be seen that the hardness of wastewater has been effectively reduced. Through the respective single-factor experimental researches on the four factors that impact the air stripping efficiency– pH value, air stripping temperature, the gas-liquid ratio and air stripping time, results can be concluded on the most economic and appropriate ranges of these factors: the pH value should be between 12 and 13, the water temperature should be 30~40℃, the air stripping time should be 3~4 hours, and the gas-liquid ratio should be between 3500 and 4500. Under these circumstances, the removal rate can reach over 90%. And also the priorities of these factors can be concluded from the experiments as regards to the air stripping efficiency: The pH value is the most important factor; the air stripping temperature is secondary, then the gas-liquid ratio.Under the condition of pH value of 12.03, air stripping temperature 30℃, air stripping time 3h, gas-liquid ratio 4500, two levels of air stripping were performed on the rare earth sulfur ammonia wastewater. After that, the density of the ammonia-nitrogen was reduced to45.5mg/L, the removal rate exceeded 99.06%. Moreover, the ammonia stripped from the wastewater can be utilized to produce ammoniums sulphate or ammonia solution, therefore avoiding second time pollutions.