WASTE METAL CUTTING FLUID/COOLANT TREATMENT BY ELECTROCOAGULATION

Abstract

The purpose of this study is treating the waste metal cutting fluid, popularly known as Coolant with the help of electrocoagulation treatment process. Mineral oil, surfactant, anti-rust, anti foam, and biocide make up around 20-70% of coolant emulsion. Cutting fluid is created by combining this emulsified oil with water in a ratio of 1:20 to 1:30. Due to machining operations the coolant contaminated by dust particles, small metal pieces, and bacteria. Before disposal, waste coolant must be treated because the emulsion does not break down naturally in water bodies and forms a film on the surface that prevents natural oxygen mixing, that blocks the light path, and contains toxic materials like heavy metals, biocides, oil, and more. These could endanger aquatic life. Therefore, EC method is being tested for removal purpose of mineral oil emulsion and other pollutants from the waste metal cutting fluid, by precipitating and floating method. Aluminium (Al) electrode was used as sacrifice electrodes and as passive electrodes. Four used sample of metal cutting fluid had obtained from SIDCUL and BHEL, Haridwar. In waste/used coolant, the initial oil concentration was about 2.66 - 40g/L (0.26 - 4%) and the COD ranged from 70000mg/L to 120000mg/L. Using electrocoagulation, in the experiment's COD was reduced in some cases up to 778mg/L. In a batch mode experiment, coolant sample was obtained in a vessel, 1.5g/L NaCl was added to increase coolant conductivity, and observations were taken at various time intervals. Energy requirement found between 0.187 to 0.62 kWh/kg COD removal and electrode consumption was found 0.007 – 0.35kg/m3. Average cost including energy and electrode cost per kl treatment of coolant about 250 and is go upto 800 Rs/kl. The results shows that the electrolysis time, current density, and surface charge (Zeta potential) are the three most essential variables in eliminating COD from cutting oil by EC, by using an aluminium electrode. According to the results, COD removal levels are insufficient to meet discharge regulations in inland water (permissible limit max COD 50mg/L, in India). So, EC would be ideal as a primary treatment that another treatment, like a biological, filtration could follow.