Reduction of fluoride ions from phosphate tank overflow water in an automotive paint shop using the electrocoagulation method
Subject Areas : مهندسی شیمی (آلودگیهای محیط زیست)
سید جواد مدبر
1
,
Ali Sayadi malakami
2
,
Amir Emami
3
,
Naeemeh Shirakbari
4
,
زهره رشمئي
5
1 - IKCO, Deputy of Technical Services, Energy Management, Water Quality Control Laboratory
2 - IKCO, Deputy of Technical Services, Energy Management, Water Quality Control Laboratory
3 - IKCO, Deputy of Technical Services, Energy Management, Water Quality Control Laboratory
4 - IKCO, Deputy of Quality, Management of Chemicals Quality Assurance
5 - IKCO, Deputy of Quality, Management of Chemicals Quality Assurance
Keywords: Fluoride ions, Phosphate tank, Electrocoagulation, Industrial wastewater,
Abstract :
Various methods such as ion exchange, membrane processes, chemical coagulation, and electrocoagulation are employed to reduce fluoride ions from water. In this study, electrocoagulation was applied to reduce fluoride concentration in the overflow water from the phosphate chemical tank in the pre-treatment section of an automotive paint shop. The influent, which is the continuously flowing rinsing overflow from the phosphate tank, contained fluoride concentrations ranging from 22 to 35 mg/L, pH between 5.2 and 6.3, turbidity of 31–35 NTU, electrical conductivity of 1815–2008 μS/cm, and TDS levels between 909 and 952 mg/L. A rectifier supplying 50 volts and 110 amperes was used to energize 2, 3, 4, and 5 aluminum and iron electrodes in a 1 m³ electrocoagulation reactor. The system was operated over four days, with samples taken at 15, 30, 45, and 60-minute intervals each day. The effects of electrode number and retention time on fluoride removal efficiency were evaluated. Results from pilot-scale and laboratory experiments showed that the electrocoagulation process achieved fluoride removal efficiencies between 75% and 85%. The highest fluoride reduction—from 24.2 to 3.7 mg/L—was observed in the system with 4 electrodes and a retention time of 60 minutes. Notably, as the initial fluoride concentration decreased over time, turbidity and current intensity also declined. However, the pH of the treated water became strongly alkaline, reaching as high as 10.27 in one of the tests.
