Defluoridation of water by chemical impregnated Artocarpus hirsutus sawdust

What is it about?

Sawdust of Artocarpus hirsutus impregnated with ferric hydroxide and activated alumina (SFAA) has been studied for defluoridation of water. This paper presents a detailed surface characterization of the adsorbent by studying pore size distribution and surface morphology. By combining the constituents in the right proportion, an adsorbent with a well-developed pore size distribution could be synthesized. The effects of various parameters on fluoride adsorption by SFAA are investigated. The adsorption capacity of SFAA is considerably higher than that of many adsorbents including activated alumina. More importantly, the adsorption capacity remains unchanged for the pH range of 1 to 9, which also makes it attractive for wastewater treatment. Besides a higher efficiency supported by the results of column studies, this adsorbent is economic as the sawdust constitutes 40% by weight of the total adsorbent. Kinetic studies indicate that fluoride adsorption on SFAA follows pseudo second-order model. Breakthrough adsorption capacity of SFAA is 1.21 mg/g, as compared with 0.41 mg/g for activated alumina.

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Why is it important?

The performance of a novel adsorbent, SFAA, which was already reported to be effective for arsenic removal, is demonstrated for defluoridation of water to meet the drinking water standards laid down by WHO. Compared with the fluoride adsorption capacity of 8.6 mg/g for activated alumina, capacity for SFAA is 40.28 mg/g for batch adsorption from initial fluoride concentration of 1,000 mg/L. Superiority of SFAA over activated alumina is explained by detailed surface characterization. SFAA has an optimum pore size distribution, the sawdust contributing to the maximum in the macropore range. Adsorption capacity is unchanged over a wide range of pH, 1 to 9, making it useful for defluoridation of groundwater as well as industrial effluents. Fluoride adsorption by SFAA follows Freundlich adsorption isotherm and follows pseudo second-order kinetic model. Hydroxides, carbonates, bicarbonates, sodiumand potassium decrease the adsorption. Breakthrough adsorption capacity of SFAA is 1.21 mg/g, which is four times higher than that of activated alumina employed in the study.

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