Abstract
Fluoride ions present in drinking water are beneficial to human health when at proper concentration levels (0.5–1.5 mg L−1), but an excess intake of fluoride (>1.5 mg L−1) may pose several health problems. In this context, reducing high fluoride concentrations in water is a major worldwide challenge. The World Health Organization has recommended setting a permissible limit of 1.5 mg L−1. The application of electrocoagulation (EC) processes has received widespread and increasing attention as a promising treatment technology and a competitive treatment for fluoride control. EC technology has been favourably applied due to its economic effectiveness, environmental versatility, amenability of automation, and low sludge production. This review provides more detailed information on fluoride removal from water by the EC process, including operating parameters, removal mechanisms, energy consumption, and operating costs. Additionally, it also focuses attention on future trends related to improve defluoridation efficiency.
Highlights
Fluoride anion is naturally found in the environment
The formation of AlnFm(OH)3n−m has already been confirmed by the results of scanning electron microscopy (SEM), X-ray energy dispersive analysis (EDX), X-ray diffraction (XRD), fourier transform infrared spectrophotometer (FTIR), and time-of-flight secondary ion mass spectroscope system (ToF-SIMS) analyses conducted on the flocs produced during the EC process
The overall performance significantly improved in the combined processes compared to both electrocoagulation and adsorption alone
Summary
Fluoride anion is naturally found in the environment. Fluoride is released into groundwater from fluoride-containing minerals owing to interactions between water and rocks [1]. More than 70 countries report high concentration levels of fluoride in their drinking water sources. Different processes have been evaluated to reduce high fluoride concentrations in water and, to prevent hazardous health effects. Some examples of examined technologies include adsorption [11,12,13], chemical precipitation using lime or magnesium salts [14,15], co-precipitation and adsorption through coagulation-flocculation with alum [16,17], ion exchange [18,19], electrodialysis [20,21,22], and electrocoagulation [23,24]. The EC process is considered as an advanced technology, associating three conventional water treatment pieces of knowledge, including electrochemistry, coagulation, and flotation [28,29]. Flocculation, a gentle mixing stage, helps to increase the size of the suspended particles into larger flocs (visible)
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