| Cyanide is a highly toxic substance,which has great harm to environment and human body.With the increasingly stringent emission standards,the treatment of cyanide containing wastewater needs further improvement.At present,the reports about cyanide treatment are comprehensive without considering different kinds of cyanide species.For the more stable metal complex cyanide,there is a lack of corresponding discussions.Taking nickel cyanide as the breakthrough point,this paper explores the treatment of synthetic wastewater and raw wastewater by ozone method,persulfate activation method and sodium hypochlorite oxidation method,in order to develop effective treatment technology to make pollutants like nickel and cyanide meet the comprehensive discharge standard of Shanghai sewage(DB31199—2009)with total cyanide less than 0.3 mg/L and nickel less than 1.0 mg/L.On the basis of these three technologies,a comparative study of ferricyanide is carried out.The study shows that the presence of cyanide has a great influence on the removal of nickel,making the general precipitation method unable to make the nickel concentration lower than 1.0 mg/L emission standard.When the concentration of cyanide in synthetic wastewater exceeds 0.001 mol/L,the minimum concentration of nickel in water exceeds 1.0 mg/L,exceeding the emission standard.The ozone method,the persulfate activation method and the sodium hypochlorite oxidation method are good for nickel cyanide.Under the optimal conditions,the total cyanide and nickel concentration in synthetic wastewater can meet the discharge standard.When the reaction time is 10 minutes,the ozone concentration is 2.0 mg/L and the initial pH value is 10.0,the synchronization of two kinds of pollutants can be achieved.In the persulfate thermal activation process,the total cyanide and nickel can be achieved under the condition that the reaction time is 60 min,the reaction temperature is 60?,and the persulfate dosage molar is 6.The reaction time of the sodium hypochlorite oxidation process is 1 h and the initial pH value is 9.0,hypochlorite molar is 10 can meet the discharge limit.When the raw wastewater containing nickel cyanide is treated,a large amount of foam woud be produced during the experiment of ozone method,which leads to the failure of the experiment so it is not suitable for the treatment of the actual wastewater.When the sodium persulfate heat activation process is used to treat the raw wastewater,the total cyanide and nickel can be reached at the same time by increasing the dosage of sodium persulfate.The reaction conditions are initial pH is 10.0,the thermal activation temperature is 80,the reaction time is 2 h and the dosage of sodium persulfate is 100 g/L.When the sodium hypochlorite oxidation process is treated with the raw wastewater,the treatment conditions are pH is 9.0,the reaction time is 1 h,and the dosage of sodium hypochlorite is 1.25 mL/L,the total cyanide concentration can be reduced to below the emission standard,but the nickel is still unable to reach the standard.Ozone treatment of iron cyanide artificial water is worse than ozone treatment of nickel cyanide artificial water distribution.The removal rate of total cyanide is only 38%under the optimum reaction conditions,and the effluent concentration is higher than 15.0 mg/L,which does not meet the requirements of the emission standard.The activation oxidation technology of persulfate has a good effect on the breaking of the potassium ferricyanide.Under the optimal conditions,ultraviolet activation and thermal activation can completely remove the total cyanide.Compared with the nickel cyanide,the specific conditions required for the iron cyanide are different,and the sodium hypochlorite method has certain effect on the treatment of iron cyanide,but it can not make it achieve the discharge of the standard.The best reaction time is 60 min,and the best pH value is 9.0.When mole ratio is 36.5,the total cyanide concentration is reduced to 9.3 mg/L,which has not yet reached the discharge standard. |
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