Study Of Rotating Type Internal Electrolysis Reactor For The Pretreatment Of Phosphatizing Wastewater

Phosphatizing is widely used in the metal pretreatment processes for the surface finishing of ferrous and nonferrous metallic components. Due to its economy, speed of operation and ability to yield excellent wear resistance, corrosion resistance, adhesion and lubrication properties, it plays a significant role in the automobile, process and appliance industries. The phosphatizing process includes several rinsing processes and ions such as PO43-, Fe2+, Ni2+, Mn2+ and Zn2+ are found in the generated wastewater. Emission reduction and eutrophication control require wastewater treatment to removal phosphorus and heavy metal ions. Phosphatizing wastewater of the Automobile Co., Ltd of suzhou is studied, select the process for phosphatizing wastewater characteristics. In the current research, using internal electrolysis as the primary treatment process and combining the electrocoagulation as subsequent treatment method that carried out phosphatizing wastewater treatment research test. Studied the basic operation conditions of phosphate removal by internal electrolysis and the effective of phosphatizing wastewater treatment by internal electrolysis under the optimum conditions was investigated, proposed the subsequent treatment of wastewater; Studied the physical and chemical characteristics of precipitate and pollutants removal mechanism of phosphatizing wastewater, and further investigated the desorption process of phosphorus in precipitate. Conclusions of the study are as follows:(1) Firstly, design and manufacture a rotating type internal electrolysis reactor which can automatic aeration and easy to implement onsite treatment, and the effect of Fe/Cu mass ratio and rotational speed on the phosphorus removal efficiency was studied by single factor experiment in the reactor with synthetic wastewater. Without adjusting the pH value of wastewater after 3 h internal electrolysis treatment, obtained the basic operating conditions :Fe/Cu mass ratio was 3/1 and the rotational speed was 8 r/min.(2) The phosphatizing wastewater was studied by rotating type internal electrolysis reactor under the basic operating conditions, and electrocoagulation subsequent treatment methods was proposed. The initial pH value is 6.42, the concentration of total phosphorus, COD, nickel and manganese of wastewater were 71.831 mg/L, 40 mg/L, 13.933 mg/L and 9.245 mg/L, ironshavings mixed with copper as packing material. After 360 min continuous run, the pH value was changed to 9.24, residual total phosphorus, COD, nickel and manganese were 0.303 mg/L,18.86 mg/L, 0.144 mg/L and 0.305mg/L, the removal efficiency reached 99.58 %, 54.1 %,98.97 % and 96.7 %, respectively. The result of kinetics study indicated the removal of phosphate from wastewater followed pseudo first-order kinetic model well. The ORP, DO and electrical conductivity of wastewater have also changed a lot. Phosphatizing Wastewater after internal electrolysis treatment, reacted aqueous solution having a high phosphorus removal accompanies a color of yellow; the wastewater is treated by electrocoagulation, the solution become clear and the contaminants are further removed.(3) In terms of mechanism, the characteristics of precipitate was also studied by TG-DSC,XRD, FT-IR, Raman, HRTEM and FESEM/EDX. The analysis results showed that the precipitate mainly consisted of FeOOH with amorphous crystalline layered structure, after calcined at different temperatures for 12 hours gradually transformed into the monophasicα-Fe2O3. The results of FT-IR, XRD and Raman indicated that the mainly mechanisms of phosphate removal from wastewater includes adsorption and coprecipitation processes.(4) According to the test results shows that the precipitate phosphorus content is 42.451 mg P/g, adjusting the pH with NaOH to specific values for the phosphorus desorption test, results showed that pH higher phosphorus desorption efficiency more, when the pH value was 14, the desorption efficiency of phosphorus in the precipitate reached 86.5%.All results showed that the internal electrolysis is an efficient technology in treating phosphatizing wastewater.