Study On Treatment Of Aluminum Cutting Fluid Wastewater By Demulsification-Catalytic Oxidation At Neutral PH

Metal cutting fluid wastewater has the properties of high emulsification,complex constituent,high concentration in COD,stable chemical characters and non-biodegradability.It usually needs pretreatment before biological process.Using Fenton process to deal with refractory organic wastewater and hazardous contaminants is more thoroughly,which can obviously increase the biodegradability of the wastewater.But the limits is that the reaction exists in acid condition,for example,pH is 2~4,and the catalysts are difficult to recovery with large amount of iron sludge.This article employed the modified sepiolite as the carrier,loaded with transition metal as the neutral catalyst,combined the oxidant H2O2 with demulsification to pretreat Aluminum cutting fluid wastewater.It determines the optimum process and parameters of demulsification process,and investigates the scope of the pH of the catalyst.Then the performance of the catalyst under neutral conditions is studied.Compared with traditional Fenton process,it analyzes the economic and technical feasibility of this neutral catalyst,which has a important guiding significance to the practical application of the neutral catalyst oxidation technology.Deemulsifying agent PAC+XZ771 has a good demulsification effect on aluminum cutting fluid wastewater.Pilot experiments showed that when PAC and the dosage of the demulsifier are 13 g/L and 2.2 g/L,respectively,the effluent COD is about 7700 mg/L,and turbidity is 270 NTU.The average removal rate of COD and turbidity were 73.9% and 84.7%,respectivel.The emulsificaton level of wastewater is decreased obviously.Catalyst has a wide scope in pH.It has higher catalytic activity between 3.0 ~ 8.0.The catalytic property is higher When pH is at 6,with 82.4% COD removal rate.Under the condition of neutral pH at 7,the COD removal rate reached 77.1%,after pH at 5 and 6.It suggested that the catalyst has strong catalytic ability under nearly neutral condition.By using neutral catalytic oxidation technology to treat cutting fluid wastewater after demulsification,the results show that it has great effect in it.It can achieve the optimal influence with the initial pH of 7,initial concentration of hydrogen peroxide is 50 ml/L which are averaged added by three times,the dose of the catalyst is 10 g/L and the reaction time is 120 min.Under this condition,the COD removal rate was 87.2%,turbidity removal rate was 95.6%,B/C increased from 0.22 to 0.36,which the biodegradability is obviously increased.With the quality of the wastewater is stable in the pilot system,neutral catalytic oxidation technology is more economic than traditional Fenton process in cutting fluid wastewater treatment.Neutral catalytic oxidation technology simplify the adjustment process compared with traditional Fenton oxidation technology,with saving the cost of acid and alkali reagent and reducing sludge by 85.7% and 80%,respectively.