Study On Foam Fractionation/Three-dimensional Electrode Method Treating Heavy Metals Wastewater

Heavy metal, one of the most potential environmental hazards pollutants, can migrate and enrich in the organism through the food chain which is serious threat to the ecological environment and human health. Therefore, seeking an effective method for heavy metal treatment in the waste water is imminent. The heavy metal wastewater of leather industry and electroplating industry has these characteristics of wide range of sources, large amount of wastewater, complex composition, very difficult to deal with. In order to solve the problem,this article has researched in three parts: the surfactant foaming property and the foam stability of casein were studied by investigating the factors of concentration, temperature and p H etc.; The removal effect of Cr(III) ion in the chrome tanning process simulation wastewater were studied by investigating the p H value, air flow, casein, stirring speed and liquid product of foam separation process; By investigating the p H value, channel current, the electrode gap, and ratio of the particle activated carbon electrode and the processing volume,the test result of heavy metal were studied in the electroplating wastewater treatment by the three-dimensional electrode method as the pretreatment. After the pretreatment, the electroplating heavy metal waste water was treated deeply with the foam separation process.Meanwhile, the removal effect of the ammonia nitrogen, the total phosphorus and COD were examined in the process.(1) The study on the surfactant casein properties had concluded that the foamability and the stability of casein were the strongest in aqueous solution when the concentration of casein was 0.14 g/L, the temperature was 25 ℃ and p H=8.0.(2) The foam separation process was used for removing the Cr(III) ions in the chrome tanned industrial waste water, and the optimal process conditions of chromium ion were obtained by the single factor test and the orthogonal test. When the initial concentration of Cr(III) ion was 100 mg/L, the processing time was 1.5 h, p H = 9.5, the air flow was 9.5 L/min,the addition volume of 4 g/L casein was 25 m L, the mixing speed was 800 r/min, the fluid volume was 1500 m L, the removal rate could reach 99.78%. Through the comparisonexperiment of casein instead of the conventional surfactant of sodium dodecyl benzene sulfonate(SDBS), the results showed that the removal rate of Cr(III) ion in waste water could increase by 1.73%.(3) The combined process of three dimensional electrode and foam separation was used for the heavy metals treatment in the electroplating wastewater. In the break complex pretreatment stage of electroplating wastewater by a three-dimensional electrode, the results of the single factor and orthogonal experiments showed that: when the initial concentration of nickel, copper and zinc in the waste water were 82.3093mg/L, 52.7615mg/L and 1.9431 mg/L respectively, the activated carbon volume was 1000 m L, the processing time was 2.0h, the best removal process conditions of p H = 4, the slot current of 0.6A, the main electrode spacing of20 cm, the water-carbon ratio of 10:9 were obtained, and the removal rate were 83.40%,86.20%, and 88.09%, respectively; In the depth treatment stage of electroplating wastewater by the foam separation, when p H=8.0~8.5, the air flow was 0.75L/min to 1.00 L/min, the added volume of casein was 25ml~30ml, the mixing speed was 800r/min to 1000 r/min and the fluid volume was 1500 ml, the concentration of nickel ion and copper ion in the waste water below 0.5 mg/L were obtained after treatment.The quality of effluent water reached the emission limits of electroplating pollutants discharge standard(GB 21900-2008) and the zinc ions in the effluent water reached the emission limits of electroplating pollutants discharge standard(GB 21900-2008). Meanwhile,the ammonia nitrogen, the total phosphorus and COD also decreased respectively to1.231mg/L, 2.234mg/L and 51.512mg/L from 15.491mg/L, 6.925mg/L and 1578.932mg/L in the complexing heavy metal wastewater, where the ammonia and COD reached emission limits of electroplating pollutants discharge standard(GB 21900-2008) in Table 2, but the total phosphorus needed further deal with.This research provides an effective method for the heavy metal wastewater treatment in the leather industry and the electroplating industry. In this paper, the methods of the foam fractionation and three dimensional electrodes provides the test basis and parameters reference for industrial application of in the field of heavy metal wastewater treatment.