Study On Aqueous Fluoride Removal By Chemically Modified Boehmite(γ-AlOOH)

As an essential trace element fluoride plays an important role in human health.The right amount of fluoride has a positive effect on human bone development, butwhen the concentration of fluoride in drinking water exceeds the national standard, itwill cause diseases like dental fluorosis, skeletal deformities, movement difficulties,and even paralysis. The main source of fluoride for human is drinking water. Manycountries are facing the problem of excessive fluoride in drinking water. As to China,the high-fluoride groundwater is mainly located in the northwest, northeast, north,and the Huang-Huai Plain. The problem of fluorine pollution need to be solved asquickly as possible, so seeking cost-effective fluoride materials have far-reachingsignificance.In this paper, the raw boehmite is conducted chemical modified by the ferricsulfate, manganese dioxide, sodium hydroxide and sulfuric acid respectively. Theexperimental results show that the adsorption capacity of the unmodified boehmite is1.83mg/g, while the adsorption capacities of the boehmite modified by the ferricsulfate, manganese dioxide, sodium hydroxide and sulfuric acid is4.68mg/g,6.14mg/g,1.12mg/g,9.25mg/g, respectively. It is obvious that except sodiumhydroxide modification, the other three modified methods improve the adsorptioncapacity substantially. Particularly the boehmite modified by sulfuric acid, theadsorption for fluoride in water is approximately five times compared with theunmodified boehmite. Further study is carried out to seek the optimum sulfuric acidmodification conditions for boehmite modified by sulfuric acid solution, including theconcentration of the sulfuric acid solution, the time of modification, the amount ofsulfuric acid. The results show that the optimum concentration of sulfuric acidsolution is0.02mol/L, the soaking time for modified is3h, the optimal modifiedcondition: the unmodified boehmite2g immersed in100mL,0.02mol/L sulfuric acidsolution for3h, washing and vacuum filtration, drying at105℃for2h, and sealed.This modified method has a mild condition, simple and easy to operate, has a goodpractical application value. In order to investigate the adsorption properties of boehmite modified by sulfuricacid, exploring the interfering ions, the adsorption time, amount of adsorbentinfluence on the adsorption capacity. The results showed that HCO3-has the largestimpact on the adsorption capacity, followed by SO42-, Cl-is the smallest; theadsorption reached equilibrium in40min; the adsorption process conforms to theLangmuir monolayer adsorption and the pseudo-second-order rate equation.Using four methods for regeneration, regeneration by sodium hydroxide, sulfuricacid, sodium hydroxide united with sulfuric acid, sulfuric acid united with sodiumhydroxide. The results show that the adsorption capacity of the saturated modifiedboehmite desorbed by the four regeneration methods is very low, the adsorptioncapacity recovered after activated by the sulfuric acid solution. Regenerated modifiedboehmite recycles triple, no significant decrease in the adsorption capacity. Thesulfuric acid modified boehmite are characterized including the specific surface area,XRD, thermal analysis, SEM, FTIR.