Preparation Of Modified Activated Alumina Fluoride Removal Adsorbent In Drinking Water Treatment Applied Research

Fluoride is a necessary trace element for human since it plays important role in bone development as well as bone and tooth strengthening.Proper quantity of Fluoride intake are helpful for human,however,excess absorption will cause a kind of disease called "Fluorosis".Long term of over dose Fluoride intake will lead to bone distortion,bone aching,anchylosis,muscle and tendon calcium,walking trouble and even paralysis for severe victims.In china there are several ten millions peoples sutler from endemic disease caused by extra intake of fluoride from drinking water.It is important to explore the methods of fluoride removal from drinking water.Manganese-oxide-coated alumina HMOCA and MOCA were prepared through a redox process and precipitation process,respectively.Adsorbents were characterized by scanning electron microscope(SEM),BET analyses,pH_zpcmeasurement,X-ray diffraction(XRD),FTIR spectrum.Batch experiments were carried out to investigate the adsorption potential of the adsorbents.It was found that HMOCA,which was synthesized much more easily,has a more rapid adsorption rate and an approximate adsorption capacity compared to MOCA.The Langrnuir equilibrium model was found to be suitable for describing the fluoride adsorption onto HMOCA.The maximum adsorption capacity was 7.0872 mg/g.A marked decrease in the amount of adsorbed fluoride by HMOCA was observed with increasing pH.Optimum removal of fluoride occurred in a pH range of 4～6.The addition of SO₄^2-and HCO₃^-had different effects on the adsorption of fluoride.The adsorbent can be regenerated by alkali solution when pH≥12.The beakthrough curves of fluoride on MO2 modified adsorbent were measured by dynamic method.Column studies indicated that the breakthrough bed volume was 669 BV while influent F-concentration was 5 g/L and flow rate was 0.3 mL/s.The kinetic results showed that the fluoride adsorption onto HMOCA followed pseudo second-order equation well with a correlation coefficient greater than 0.99. Both external and intraparticle diffusion contributed to the adsorption process.