Removal of fluoride from semiconductor wastewater by electrocoagulation- flotation
Journal
Water Research
Journal Volume
39
Journal Issue
5
Pages
895-901
Date Issued
2005
Author(s)
Abstract
This work employs an anodic surfactant, sodium dodecyl sulfate (SDS), to improve the flotation performance of the electrocoagulation-flotation (ECF) process to treated fluoride containing semiconductor wastewater following calcium precipitation. The dissolved fluoride ions and CaF2 particles in the wastewater after calcium precipitation were effectively removed in the ECF process simultaneously. The dosage of SDS required for ECF was much less than those for dispersed air flotation (DiAF) or dissolved air flotation (DAF) processes because the CaF2 particles can be collected by hydro-fluoro-aluminum flocs in ECF. Thus, SDS only served as a frother to make the bubbles tiny and stable in the ECF defluoridation process. The interference of co-existing anions can be overcome by increasing the dosage of calcium ions and SDS. The optimum initial acidity for ECF is close to the initial fluoride concentration after calcium precipitation; the amount of SS removed dropped rapidly if the initial acidity exceeded the optimal value because the surface charge of the hydro-fluoro-aluminum particles increased. The initial acidity of the wastewater after calcium precipitation can be modified by changing the [Ca(OH)2]/[Ca2+]T ratio and the appropriate ratio is approximately given by the acid dissociation constant of hydrofluoric acid and the initial pH of the wastewater before calcium precipitation. © 2005 Elsevier Ltd. All rights reserved.
Subjects
Calcium precipitation; Electrocoagulation-flotation (ECF); Fluoride; Sodium dodecyl sulfate (SDS)
SDGs
Other Subjects
Acidity; Calcium; Dissociation; Flotation; Fluorine compounds; Inorganic acids; Precipitation (chemical); Surface active agents; Defluoridation processes; Dissolved air flotation (DAF); Flotation performance; Sodium dodecyl sulfate (SDS); Chemicals removal (water treatment); aluminum derivative; calcium; calcium fluoride; dodecyl sulfate sodium; fluoride; hydrofluoric acid; hydrofluoroaluminum; surfactant; unclassified drug; Coagulation; electrochemical analysis; Flotation; fluoride; pollutant removal; semiconductor; Wastewater treatment; acidity; air; article; defluoridation; dispersion; dissociation constant; dissolution; electrocoagulation; flotation; pH measurement; precipitation; priority journal; semiconductor; waste water management
Type
journal article