The Chelating Precipitation Treatment And Post-chemiluminescence Mesurement Of Cadmium Ammonia Complex In Wastewater

Cadmium is one of priority controlled pollutants in water blacklist. The existence form of Cadmium in water not only stated in ionic condition, but also formed complex with many kinds of ligands. Those complex compounds could dissolubled in water; the cadmium ammonia complex is the typical one. The cadmium ammonia complex wastewater was intractable. The treated effect was ineffective through ordinary chemical precipitation. So, a high efficiency and no secondary pollutants treatment should be eatablished to treate the cadmium ammonia complex wastewater.In this paper, the Cd(Ⅱ) determination and cadmium ammonia complex wastewater treated were studied through experiments, the following findings can be drawn:(1) A post-chemiluminescence method for determination of cadmium with potassium ferricyanide-calcein system was established, the experimental conditions of the CL reactions were optimized. The linear response ranger of this method was from 1.0×10-5 to 1×10-3mol/L with a linear correlation of 0.9980. The detection limit was 3.6×10-6mol/L and the relative standard deviztion was 2.84%(n=11). The method was applied to the determination of Cd(Ⅱ) in catalyst wastewater with satisfactory results.(2) The possible PCL mechanism of Cd(Ⅱ) in calcein-potassium ferricyanide reaction system was discussed:Calcein reacted with potassium ferricyanide in the alkaline solution, generated the excitated calcein and potassium ferrocyanide. When the excitated calcein came to original state, a chemiluminescence reaction was observed. When Cd(Ⅱ) added in to the complete reacted mixture solution, Cd (Ⅱ) may catalysis potassium ferrocyanide reacted with calcein generated the excitated calcein again. A chemiluminescence reaction was observed when the excitated calcein came to original state. At the same time, Cd(Ⅱ) could reacted with calcein generated the reaction which could produced fluorescence.(3) Comparing the effects of treating wastewater containing cadmium by common chemical precipitation process and TMT chelation precipitation process. The results showed that, comparison of removing cadmium among NaOH, Na2S, Na2CO3 and chelating agent TMT, TMT treating the wastewater containing cadmium was the best.2×10-3mol/L cadmium ions wastewater treated by TMT, cadmium remaining in the filtrate was only 0.103mg/L. After TMT chelation precipitation process, adding flocculant could make the wastewater meet the discharge standards.(4) Through the TMT chelation precipitation treated cadmium ammonia complex wastewater experiments, the results show:when the wastewater pH value was 7, the TMT/Cd ratio was 0.855:1 and the flocculants dosage were PAC 100mg/L or PAFC 60mg/L, the treatment effect was good.2×10-3mol/L cadmium ammonia complex wastewater after treated, cadmium were reducted to 0.09mg/L and 0.06mg/L respectively, lower than the industrial wastewater discharge standard of 0.1mg/L. TMT chelated cadmium ammonia complex and formed precipition finished in 30 minuts. The precipitation has more stabilization and it will not cause secondary pollution on the environment.