Optimization of metal working fluids treatment using Ferric chloride by application of response surface methodology (RSM)

In metal machining processes, the regulation of heat generation and lubrication at the contact point are achieved by application of a fluid referred to as metalworking fluid (MWF). MWFs inevitably become operationally exhausted with age and intensive use, which leads to compromised properties, there by necessitating their safe disposal. Disposal of this waste through Coagulation-flocculation process is an increasingly attractive option. However, successful chemical coagulation depends on optimization of process. In this study, response surface methodology was used to optimization of process. The removal efficiencies for chemical oxygen demand (COD), turbidity and amount of oil released obtained using ferric chloride were compared with those was predicted using quadratic models. Central composite design (CCD) and response surface method (RSM) were applied to optimize the operating variables including coagulant dosage and pH. Quadratic models were developed for the three responses (COD, turbidity, oil released from metal working fluid). The results of this study indicated that the optimum conditions were ferric chloride dosage of 3.16 g/L at pH 3.52. The COD and turbidity removal efficiency and oil released from metal working fluid were 54.4%, 84.8% and 15.9 ml respectively. The experimental data and model predictions were agreed. Coagulation - Flocculation process using ferric chloride compared with conventional coagulants such as Alum was very effective on pollution indices such as COD and turbidity in treatment of metal working fluid. Response surface methodology and central composite design is a successful method for optimization of coagulation-flocculation using ferric chloride.