Generally, freshly produced activated alumina contains some fluoride to varying degrees. Therefore, to enhance the quality, it is necessary to de-fluorinate promptly. However, de-fluorination requires certain conditions, and only after meeting these conditions can we proceed with the de-fluorination process. So, let's discuss what these conditions for de-fluorination are?
1. Activated alumina adsorbs fluorine, with its adsorption capacity increasing as the water's pH value decreases. At a raw water pH of approximately 6.0, it meets the conditions for fluorine removal. Starting from the requirement that the pH of the water after fluorine removal should comply with drinking water standards and that the samples have a high adsorption capacity, the experiment used in-house deep well tap water mixed with dilute sulfuric acid to adjust the pH to 6.5 ± 0.1. Then, a standard sodium fluoride solution was added to adjust the fluorine concentration to 4.0 mg/L. The fluorine concentration in the water was measured using the standard fluoride electrode method.
2. The de-fluorination capabilities of active alumina with different coarse diameters were tested, with the de-fluorination conditions utilizing samples with particle sizes ranging from 0.5 to 1.5mm for the experiment. Other characteristic parameters of the adsorbent are as follows: pore volume of 0.44 mL/g, specific surface area of 201 m2/g, bulk density of 0.77 kg/L, strength of 19.2N, particle size distribution with Φ<0.5mg accounting for 3%, and Φ>1.5mm accounting for 2%.
In summary, these are the conditions for the de-fluorination process using activated aluminum oxide. When de-fluorination is necessary, we must ensure that these conditions are met. De-fluorination is a crucial task, but it should also be conducted under certain conditions.
