A comparative investigation for strengthening the adsorptive phenomenon by activated natural minerals and plant waste-carbon for defluoridation in water milieu

Abstract

Fluoride in drinking water plays a dual role, beneficial or detrimental depending on its concentration and total amount consumed. The fluoride contamination in drinking water is perhaps the most common drinking water related problem which becomes a global problem and widely spreads worldwide. Adsorption-based defluoridation systems are well known as the best feasible option. The endeavor of the present work is to investigate the defluoridation by three effective adsorbents, developed from minerals and used tea leaves carbon. On the whole the proposed treatment method relies on adsorptive phenomenon for defluoridation in water reclamation process. Effects of pH, adsorbent dose, contact time, temperature and initial fluoride ion concentration were evaluated. To understand the pivotal role of developed materials, evaluation of best optimized conditions for kinetics, thermodynamics and isotherm modeling has been explored for decontamination processes and assess their characteristics along the processes. The data were fitted by different kinetics model viz. pseudo first-order, second-order, Elovich and Ritchie. Langmuir isotherm was applied to evaluate the adsorption capacity. Linear correlation regression coefficient R 2 was used to judge the favorable kinetic and isotherm models for adsorption. Adsorbents were characterized by scanning electron microscope, energy dispersive X-ray analysis and fourier transform infra red spectroscopy. Ecotoxicological assessment of developed material was carried out on adult freshwater teleosts Poecilia reticulata (Guppy fish) for its safe disposal of SACS. Expected outcome of this research work provides a barrier against the release of fluorides into waters thus improve water quality for human consumption. Pseudo second-order kinetic model was found to be most suitable for all the three adsorbents. Langmuir was a better fitting model in AdAA but Freundlich isotherm had a better fitting model for AdTC and SACS than the Langmuir. Silver impregnated-alumina-carbon-sand (SACS) was found most suitable among the studied adsorbents having adsorption capacity of 71.43 mg/g. Thermodynamics study reveals the endothermic nature of the adsorption. Significant details the obtained from the IR analysis, which also support the defluoridation by the possible groups/ions found on the surface of the adsorbents. The developed adsorbents were found effective for defluoridation from lower to higher concentration range of fluoride ion. The adsorbents can be disposed safely after their use.