부산대학교 도서관

Excessive fluoride in groundwater is becoming a worldwide environmental problem increasing the risk of fluorosis. In this study, an eco-friendly new defluorination resin (Al-CPCM) was synthesized by a modified emulsion method. The skeleton of the resin is cross-linked N-methylene phosphonic chitosan and the incorporated Al(III) is the binding site of fluoride. The batch experiments conducted using pure synthetic sodium fluoride solutions showed that Al-CPCM exhibited a fast fluoride removal within 30min, maintained stability from pH 3-10. Effect of presence of other anions was studied by adding one extra anion at a time and it was observed that presence of phosphate and carbonate ions significantly degraded the adsorption capacity of the resin. The maximum adsorption capacity was 15.067mg/g at 30 oC and the adsorption behavior was well-fitted with the pseudo-second-order kinetic model and Hill isotherm model. The results of in-situ flow ATR-FTIR and thermodynamics studies show that the fluoride adsorption dominantly implemented by ion exchange with surface hydroxyl of chelated Al3+ in the resin. In addition, the adsorption capacity only decreased by 5.5% after six successive sorption/desorption cycles, indicating a better regeneration efficiency among other defluorinated resins. Finally, a column experiment was performed using ground water and, in this case, it is observed that the adsorption capacity of the resin was much lower and the decrease in adsorption capacity after elution/regeneration is was larger (both mainly due to the presence of alternate anions/cations in the feed solution). More elaborate column experiments with real-life groundwater samples are required to assess the suitability of the proposed resin for use as a commercial adsorbent.