Electrochemical treatment of chemical mechanical polishing wastewater: removal of fluoride — sludge characteristics — operating cost

The aim of this paper is to propose an efficient and low-cost treatment of chemical mechanical polishing wastewater process based on electrocoagulation with iron bipolar electrodes. The performance of a pilot scale electrochemical reactor equipped with iron bipolar electrodes and an anode active area surface of about 170 cm2 was studied. In addition, sludge settling after electrocoagulation were characterized. The pilot study yield promising results, suggesting that further in-depth development study is worth to be considered in a future work.

Fig. 6. MEB images of sludge in the wastewater. The current efficiency (j) of EC process was calculated (Eq. (3)). This calculation was based on the comparison of electrode mass difference before and after the electrocoagulation process (ΔMexp) with theoretical amount of iron Table 4 Characteristics parameters calculated for EC process E (kWh L−1) Mexp (g) Mtheo (g) j (%) OC (US $/m3) 0.04 0.976 0.928 0.988 Electrochemical treatment of chemical mechanical polishing wastewater containing fluoride in small bipolar batch reactor was investigated. This work has uncovered some aspects of electrocoagulation that provide promise for improved wastewater treatment. Cations and anions can affect the removal process. Anions give a negative effect on fluoride removal. This may be due to the competitive adsorption between fluoride ion and other anions. Moreover, this process, which consumes 0.976 g of iron for 1 L of treated wastewater. Treatment of real wastewater indicate that some cations and anions interfere with fluoride removal. Cost calculations show that, in the case of iron electrode, operating cost is approximately 0.059 US$ per liter of wastewater treated.