Study On Removal Of High Concentration Ammonia Nitrogen From Tail Water Treated With Alkaline Etching Solution

In this paper,the research object was prepared by NH₄Cl solution which has an ammonia nitrogen concentration of 3,000 mg/L,the chemical precipitation,zeolite adsorption,break point chlorination process was optimized in the experimental conditions,the influence of different factors on the ammonia nitrogen removal rate（W）and the optimal experimental conditions was concluded,and the economical efficiency and the feasibility were analyzed.It is expected to provide a pretreatment idea for denitrification of tail water after alkaline etching solution treatment and other wastewater with similar ammonia nitrogen concentration.The optimal experimental conditions of chemical precipitation process:using Mg SO₄·7H₂O+Na H₂PO₄·2H₂O,adding agents according to n（n）:n（Mg）:n（P）=1:1.4:1.2,stirring on the magnetic stirrer,controlling the speed of 200 r/min,with 5 mol/L Na OH solution adjusting constant p H to 10.5,stirring for 1 hour and standing 40 minutes after it,the value of W was as high as 98.64%,the concentration of RAN reached 40.8 mg/L.Dealing with the simulated wastewater by zeolite adsorption method under the optimal experimental conditions:first,modifying the zeolite by NaCl solution,weighing 40g artificial spherical zeolite in 250 m L conical flask,adding 100 m L NaCl solution which concentration is 2 mol/L,the zeolite get the water bath that was oscillated at speed of 200r/min for 24h under 25℃,the modified zeolite is washed with deionized water for many times,then dried in the electrothermal at 105℃for 2 hour,the zeolite modified by NaCl solution is made.When the p H of the wastewater to be adsorbed was adjusted to 7,the NaCl modified zeolite was added and the wastewater oscillated at 30℃for 2 hour under the condition of 200 r/min.Under these conditions,the value of W was only 57.14%,and the concentration of RAN was 1285.8 mg/L.The optimal experimental conditions for the treatment by the breaking point chlorination method are as follows:adjusting the p H of the wastewater to 7,adding sodium hypochlorite solution with 10%effective chlorine according to n（Cl₂）/n（NH₃-N）=1.6:1,and then put it in a magnetic stirrer for stirring reaction for 70 min.The value of W was 96.69%,and the concentration of RAN was 99.3mg/L.After obtaining the optimal experimental conditions of each method,denitrification and cost calculation were carried out on the tail water which from alkaline etching solution’s treatment.The value of W under chemical precipitation method was 95.3%,the material cost was 75.07 yuan/ton,and the profit was 117.70 yuan/ton.The value of W under zeolite adsorption method was 45.5%,and the material cost is 70.57 yuan/ton.The value of W under folding point chlorination method was 95.7%,and the material cost is 98.1 yuan/ton.In addition,the chemical precipitation method and zeolite adsorption method have certain removal effect on the total phosphorus and copper ions in the water while removing ammonia nitrogen.The value of W from wastewater by chemical precipitation method was 95.5%,and the concentration of RAN was 116 mg/L.The removal rate of copper ion also reached 97.7%,the remaining concentration of copper ion was 1.3mg/L,the content of total phosphorus was reduced by 75%,the remaining concentration of total phosphorus was 0.01 mg/L.The value of W in wastewater under zeolite adsorption method was poor,with the removal rate of 43.9%,the concentration of RAN is 1446.26 mg/L,the removal rate of copper ion is 21.5%,the remaining total copper concentration is 44.58 mg/L,the removal rate of total phosphorus is 50%,the remaining total phosphorus concentration is 0.02 mg/L.But the removal effect of the folding point chlorination method is more obvious,reaching 95.7%.