Manganese dioxide improves the efficiency of earthenware in fluoride removal from drinking water

The paper presents a detailed study of the effect of manganese dioxide on the defluoridation potential of disposed earthenware (DEW) of the particle size less than 300 μm. Manganese dioxide was added to DEW with weight content from 0.01 to 0.025%. The defluoridation was investigated in static experiments, at pH 5–11 and with contact time of 35 min. The fluoride removal increased with the increasing content of manganese dioxide. In static sorption, the defluoridation with DEW dispersed with 0.025% of manganese dioxide increased from 1198 to 1888 mg-kg− 1 when the pH increased from 5 to 7. In the simulating equilibrium data, simple kinetic models namely, pseudo I and II order, particle and pore diffusion, Elovich and isothermal models of Langmuir and Freundlich were used. The fluoride removal was investigated in the presence of co-existing ions. It was found that the reduction in fluoride sorption was greater in the presence of SO42− ion than in the presence of HCO3−, Cl− and NO3−. DEW with dispersed manganese dioxide, showed an ability to lower the fluoride concentration to acceptable levels and improved the defluoridation efficiency of unmodified DEW. The spent sorbent was easily regenerated by NaOH solution.

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► Disposed Earthenware (DEW) was efficient in fluoride removal.
► Doping of DEW with manganese dioxide improved its defluoridation activity.
► Various kinetic models have been applied to the fluoride sorption by DEW.
► Co-existing ions were interfering of fluoride anion.
► Spent DEW was recycled thanks to a washing with NaOH solutions.