Synthesis and characterisation of cerium(iv)-incorporated hydrous iron(iii) oxide as an adsorbent for fluoride removal from water. Issue 42 (16th May 2017)

• Record Type: Journal Article
• Authors: Mukhopadhyay, Kankan; Ghosh, Abir; Das, Supriyo Kumar; Show, Bibhutibhushan; Sasikumar, Palani; Chand Ghosh, Uday
• Is Part Of: RSC advances. Volume 7:Issue 42(2017)
• Page Start: 26037
• Page End: 26051
• Publication Date: 2017-05-16
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c7ra00265c
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : Surface-altered hydrous iron(iii ) oxide incorporating cerium(iv ) (CIHFO) was prepared and characterised via modern analytical tools for applications in fluoride removal from groundwater. Abstract : Surface-altered hydrous iron(iii ) oxide incorporating cerium(iv ) (CIHFO) was prepared and characterised via modern analytical tools for applications in fluoride removal from groundwater. The material with a Fe : Ce ratio of 1.0 : 0.5 (mol : mol) calcined at 473 K shows 24.8 ± 0.5 mg F − g −1 adsorption capacity at pH 5.0–7.0 from a solution with a concentration of 15.0 mg L −1 ; the material was established to be microcrystalline (∼5 nm) with a 140.711 m 2 g −1 surface area, irregular surface morphology and porous structure. The time-dependent fluoride adsorption capacities of CIHFO at 293, 303 and 313 K are well described by the pseudo-first order, pseudo-second order and Weber–Morris kinetic models, respectively. The adsorption reaction occurs via a film/boundary layer diffusion process. The very low Arrhenius activation energy ( E a = 0.026 kJ mol −1 ) indicates the high feasibility of fluoride adsorption over CIHFO. The equilibrium data fit better with the Freundlich and Redlich–Peterson ( g < 1.0) isotherms than with the Langmuir isotherm, which suggests multilayer adsorption. The values of the Freundlich parameters, n = 3.10, 4.47 and 7.57 and K F = 8.58, 10.88 and 11.25 at 293, 303 and 313 K, respectively, indicate high affinity for fluoride. Thermodynamic analysis of the reaction equilibrium shows that the reaction is highly exothermic (Δ H 0 = −25.924 and −36.279 kJ mol −1 for C i = 25.0 and 35.0 mg L −1 ), whereas the negative Δ G 0 values indicate the spontaneous nature of the reaction. The fluoride adsorption over CIHFO occurs via ion-exchange that progresses to chemisorption. The presence of sulphate shows an adverse influence on fluoride adsorption by CIHFO, and the fluoride level of 2.4 g per L groundwater (9.05 mg F L −1 ) can be reduced below the permissible value.