PCB Ammonia Nitrogen Wastewater Treatment

The wash water in the process of ammonia etching,acidic etching and ammonium persulfate micro etching section in printed circuit board(PCB)factory was the main source of ammonia nitrogen wastewater.As ammonia nitrogen pollution control was one of obligatory targets of saving energy and reducing pollutant in Twelfth Five-Year Plan of China,the ammonia nitrogen wastewater treatment for printed circuit board enterprises was imperative.Based on the various domestic and international ammonia nitrogen wastewater treatment technologies,the method of "ion exchange resin A+air sensitive gas membrane" was selected to treat ammonia nitrogen wastewater from printed circuit board enterprises.Two types of modified resin A,H-R and Na-R,were respectively employed to remove Cu2+and NH4+in the waste water.The experimental results showed that the water quality met the emission standards after the treatment.The regeneration liquid of the resin was treated by the air sensitive gas membrane,the H-R and Na-R type resin regeneration liquid were recused in multiple times as recycling resource.In this work the penetration curves,the saturated exchange capacity,operating exchange capability of A resin to NH4+and Cu+2were measured.The following operating conditions,pH,Na+,the types of resin regeneration liquid and conditions of elution were studied.The operation parameters of air sensitive gas membrane and the treatment effect of resin regeneration liquid were also investigated.The main experiment results were as follows:both H-R and Na-R resin had a good adsorption ability for NH4+,and the exchange capacity were 2.27 mmoi·g-1 and 2.17 mmol·g-1 respectively.The resin exchange capacity of Cu2+for H-R,Na-R,NH4-R were 1.03 mmol·g-1,1.02 mmol·g-1 and 1.00 mmol·g-1 respectively.The optimum adsorption conditions of Na-R resin to NH4+were as the followings,the pH of 5-8 and the concentration of Na+less than 400 mg·L-1.The regeneration effect was well and the elution rates were more than 90%when regenerated the H-R and Na-R resins with 10%HCl and 15%NaCl.The resins had the stable adsorption ability after multiple regenerations.When strong hydrochloric acid was added to H-R resin regeneration liquid and sodium hydroxide was added to Na-R resin regeneration liquid,the operation parameters of 16 m2 area air sensitive gas membrane were as follows:the alkali and acid liquor flow were 4 L·min-1 and 5 L·min-1 respectively,the pressure of alkali liquor and acid liquor were 0.05 MPa and 0.03 MPa respectively.The pH value of alkali liquor was more than 10 and the pH value of acid liquor was less than 2.The treatment effect of the ammonia nitrogen using air sensitive gas membrane was well and the removal efficiency of ammonia nitrogen in single circle was above 50%.The ammonia nitrogen wastewater of printed circuit board enterprise met the emission standard after treatment by "ion exchange resin A+air sensitive gas membrane" technology.H-R resin regeneration liquid was reused when the concentration of Cu2+was larger than 40 g·L-1 and the ammonia nitrogen concentration was larger than 15 g·L-1.Na-R resin regeneration liquid and the NaCl and NaOH liquid were also recycled in the process.The technology passed the pilot plant test and was successfully applied to the process of a PCB factory in Shen Zhen which had good potiential in Shen Zhen PCB industry.