Tetragonal prism shaped Ni-Al bimetallic adsorbent for study of adsorptive removal of fluoride and role of ion-exchange

Water with high fluoride content is detrimental to health and drinking water quality needs to be closely monitored. Among the various techniques used for fluoride removal, adsorption processes have been found to yield satisfactory results. Herein, NiAl adsorbent has been synthesized by a simple co-precipitation method and utilized efficiently for fluoride adsorptive removal studies. The surface properties, functionality, and crystallinity were analyzed by techniques such as FESEM, EDX, TEM, BET, XPS, XRD, and FTIR. XPS and FTIR studies were used to explain the fluoride adsorption mechanism by the hydroxyl group ion-exchange and ion-pair formations. The kinetics of the adsorptive removal process follow the pseudo-second-order and Freundlich isotherm fitted best in the adsorption process. Equilibrium was reached within 16 min, up to the permissible limit >1.5 mg/L. The adsorption process was exothermic, feasible and by physisorption. The excellent adsorption capacity of the adsorbent together with other advantages, such as reusability, easy separation, the absence of interfering ions makes it a suitable adsorbent for the removal of fluoride from water. [Display omitted] •The adsorption capacity and surface area of Ni-Al@TPS adsorbent were found 111.11 mg/g and 256 m2/g, respectively•The role of ion-exchange mechanism has been expressed by y = 8.51*exp(x/50.72) + 0.36.•The Ni-Al bimetallic mixed oxide formed the crystals of tetragonal prism shape during controlled conditions.