Bone char from an invasive aquatic species "devilfish" as a sustainable adsorbent for the removal of fluoride in water for human consumption

Abstract

In this study, bone chars were obtained from an alien acuatic species “devilfish” bones by pyrolysis of 500–800°C. Bone chars were evaluated as a sustainable adsorbent of fluoride, it was found pyrolysed bone char at 500°C adsorbed the most amount of fluoride. The effect of pH indicated that the adsorption capacity increased as the pH decreased. Thermodynamic parameters of fluoride adsorption on devilfish bone chars were estimated as ΔH°= 7.213 kJ mol− 1, ΔG°= 23.61 kJ mol− 1 and ΔS° = 103.4 J mol− 1 K− 1 indicating that adsorption is endothermic, spontaneous and with great affinity of fluoride on bone char from devilfish. The fluoride desorption study showed that fluoride is desorbed from the material of 0.24 to 20.06 %, so the adsorption is considered to be partly reversible. The regeneration of the bone char at 400, 500 and 600°C was studied and it was noted that its adsorption capacity decreases slightly so it could be considered appropriate for the use in water treatment technologies. Adsorption of fluorides from drinking well water of a rural community with dental fluorosis problems and high levels of fluoride in water, revealed that by increasing the amount of the bone char of 0.05 to 0.8 g, the disposal of fluoride increases from 69.1 to 98.7 %. Lastly, it was established that the bone char synthesized from devilfish is a low-cost, viable a sustainable material to remove fluorides from water and represents an environmental management strategy of this alien species.