Experimental Research On Treatment Of Rare-earth Ammonium Chloride Wastewater

The paper is based on the research of the rare-earth chlorine ammonium wastewater treatment and recycling in Baotou, Inner Mongolia. The rare-earth chlorine ammonium wastewater, inchuding the mother liquor and cleaning solution, is discharged in the production of unitary rare earth carbonate. In practice, many enterprises now directly evaporate and crystallize the mother liquor of high concentration for ammonium chloride products. However, the cleaning solution, because of its large liquid volume, low concentration and high energy consumption, when evaporated and crystallized, it will be too costly for the related enterprises. In this paper, the author researches for the wastewater in the rare-earth factory of Baotou, the ammonia nitrogen in cleaning solution has been treated by using the methods of air stripping and Na-pretreated zeolite.In this paper, the experiments of air stripping and Na-pretreated zeolite adsorption are included. The air stripping experiments include two parts of single-factor experiments and intersecting experiments. Through the single-factor experiment, the best parameter values of the four respective facors that impact the air stripping efficiency– temperature, pH value, the gas-liquid ratio and air stripping time have been determined. Through the intersecting experiments, a conclusion that the primary and secondary parameters order of the influencing factors about blowing has been drawed. The first is pH value, the second is air stripping temperature, the third is air stripping time and the last is gas-liquid ratio.Under the experimental condition of pH value is 11.0, the air stripping teaperature is 40 degrees centigrade, the air stripping time is 3hours and a half, the gas-liquid ratio is 5000, after being treated by air stripping, the ammoniac concentration in chlorine ammonium wastewater reduce from 10025.70 mg/L to 230.59mg/L, and the removal rate can reach to 97.70%. The alkaline air stripped from the wastewater can be imbibed by sulfuric acid and ammoniums sulphate can be obtained; the experiments of Na-pretreated zeolite adsorption conclude three parts: the preparation of Na-pretreated zeolite, Na-pretreated zeolite adsorption and the regeneration of Na-pretreated zeolite. Through the single-factor experiments, the best parameter values of the three respective facors that impact the adsorption efficiency-pH value, the amount of Na-pretreated zeolite and the adsorption time have been determined. Through the intersecting experiments, a conclusion that the primary and secondary parameters order of the influencing factors about adsorption has been drawed. The first is the amount of Na-pretreated zeolite, the second is adsorption time and the third is pH value. Under the experimental condition of pH value is 7.0, the amount of Na-pretreated zeolite is 20.0g, the adsorption time is 180min, after being treated by Na-pretreated zeolite adsorption, the ammoniac concentration in chlorine ammonium wastewater reduce from 230.59 mg/L to 24.15mg/L, the removal rate can reach to 89.53%, and the ammonia nitrogen content in the water is lower than the national discharge standard. The regenerating experiment showed that, the best calcine temperature for the regeneration of Na-pretreated zeolite is 450 degrees centigrade; the calcine time is 1hour and a half.With the increase in the number of regeneration, the removal rate of ammonia nitrogen drops gradually.Dependable reference has been provided for the treatment of rare-earth wastewater by the experimental research on treatment of rare-earth ammonium chloride wastewater.