Wastewater defluoridation
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Our company’s wastewater treatment plant is responsible for treating phosphate-containing wastewater, reclaimed water from ion exchange beds used in desalination processes, as well as some hydrochloric acid and sulfuric acid wastewater. Lime water is used for neutralization, followed by filtration using Gore filters; however, the filter membranes used are not of Gore brand. The fluoride content in the filtered water amounts to 25 mg/L, which is above the allowable emission standards. I would like to ask: are there any effective methods for removing fluoride from wastewater? This post was last edited by yunanshu on 2009-2-3 14:59]
Currently, the main methods for removing fluoride from fluoride-containing wastewater include adsorption, electrocoagulation, reverse osmosis, ion exchange, chemical precipitation, and coagulation sedimentation. Among these methods, chemical precipitation is the most widely used. However, ion exchange is costly, while electrocoagulation and reverse osmosis involve complex equipment and high power consumption, which is why they are rarely used. The adsorption method, chemical precipitation method, and coagulation sedimentation method are commonly used. Calcium hydroxide is added to the wastewater to react with hydrofluoric acid as follows: 2HF + Ca(OH)2 = CaF2↓ + 2H2O. This reaction produces a CaF2 precipitate, thereby separating the remaining fluoride ions from the wastewater. The limit for removing fluoride by forming calcium fluoride precipitate is determined by the saturated solubility of CaF2. Theoretically, the maximum solubility of calcium fluoride (CaF2) at 18°C is 16.3 mg/L, which corresponds to 7.9 mg/L of elemental fluorine. In other words, the limit for treating fluoride-containing wastewater using lime coagulation is 7.9 mg/L. In practical engineering applications, lime is used for precipitation treatment, reducing the mass concentration of fluorides to only 10–20 mg/L. This is due to the poor sedimentation properties of lime precipitates, as well as the slow rate at which these precipitates are formed. If the wastewater is in contact with lime for 24 hours, the mass concentration of fluoride can be reduced to the theoretical limit value. Therefore, it is generally necessary to add additional flocculants such as alum, PAM, Al2(SO4)3, etc., and use the flocculation principle for auxiliary treatment in order to increase the precipitation rate. The mass concentration of fluoride in the treated wastewater is less than 10 mg/L, meeting the **discharge standards. This post was last edited by libj520 on 2009-2-3 15:29]
Adding flocculants can only aid in precipitation; it cannot further reduce the concentration of fluoride ions. Allowing wastewater to come into contact with lime milk for 24 hours is not practical in actual production, and reaching the theoretical limit is also unfeasible. Adding subsequent treatment methods is a relatively feasible approach
Using a defluorination filter with activated alumina as the adsorbent can meet the **standards** in slightly acidic water
For general precision removal, resin adsorption can be used; the treatment accuracy can reach below 1 ppm, with an adsorption capacity of 3–6 g/l. We are the largest manufacturer of specialty resins in China, and we have resins specifically designed for fluoride removal. If you are interested, feel free to get in touch.
Our company specializes in providing fluorine-containing wastewater treatment technologies, resulting in high-quality fluorite as the final product. Wastewater is discharged up to standard or reused