Treatment of waste coolants by coagulation and membrane filtration

In this study, the treatment of waste coolant (mobile cut 232) from cutting tools was studied by three processes. The first pre-treatment process, coagulation was tested using four conventional industrial coagulants, aluminium sulphate hydrate, aluminium chloride, iron sulphate pentahydrate and iron chlorite. The second process was filtering the supernatant produced from the first stage using two nanofiltration membranes of 500 and 2000 Da. The third process used ultrafiltration method using a 100,000 Da membrane. The critical coagulation concentration of the different coagulants was determined and the quality of the supernatant was compared to the permeate produced by ultrafiltration. The parameters compared were TOC, absorbance at 400 nm and pH. The performances of both nanofiltration membranes were evaluated. In addition, the surface morphology and pore size distribution of the NF and UF membranes were investigated with an Atomic Force Microscope.