Applied Surface Science 307 (2014) 665–676 Contents lists available at ScienceDirect Applied Surface Science jou rn al h om ep age: www.elsevier.com/locate/apsusc Agglomerated nanoparticles of hydrous Ce(IV) + Zr(IV) mixed oxide: Preparation, characterization and physicochemical aspects on fluoride adsorption Abir Ghosh, Sharadindra Chakrabarti, Krishna Biswas 1 , Uday Chand Ghosh ∗ Department of Chemistry and Department of Environmental System Management, Presidency University, 86/1 College Street, Kolkata 700073, India a r t i c l e i n f o Article history: Received 13 January 2014 Received in revised form 12 April 2014 Accepted 14 April 2014 Available online 24 April 2014 Keywords: Adsorption Fluoride Cerium(IV)–zirconium(IV) mixed oxide Removal Thermodynamics Desorption a b s t r a c t Hydrous Ce(IV)–Zr(IV) oxide (Ce/Zr ∼ 1:1, mol/mol) (HCZMO) prepared by simple chemical precipita- tion was nanoparticles (60–70 nm) agglomerate with irregular surface morphology. The BET surface area, pore volume and pH zpc were estimated to be 185.04 m 2 g -1 , 0.1219 cm 3 g -1 and 5.8 (±0.2), respec- tively. Investigation of fluoride adsorption over HCZMO from its aqueous phase at an optimized pH ∼ 6.0 showed that the adsorption kinetics and equilibrium data described, respectively, the pseudo-second order equation (R 2 = 0.98–0.99) and the Langmuir isotherm (R 2 > 0.99) very well. Values of the com- puted Arrhenius activation energy, E a (1.16 kJ mol -1 ), Langmuir monolayer capacity,  (19.5 mg g -1 ), D–R adsorption energy, E D–R (15.05 kJ mol -1 ) and isosteric heat of reaction, H r (0.518 kJ mol -1 ) suggested that the fluoride has high affinity for homogeneous HCZMO surface for adsorption. Evidences appeared from the equal distribution co-efficient values and too well Langmuir isotherm fit. The fluoride adsorp- tion reactions at 298–313 K with HCZMO were spontaneous (G 0 = negative) despite endothermic nature (H 0 , kJ mol -1 = +3.53, +4.04), owing to the increase of entropy (S 0 , J mol -1 K -1 = +12.4, 13.8). More than 95% fluoride was released from F - HCZMO (24.8 mg F - g -1 ) by 1.0 M NaOH, confirming the ion-exchange adsorption mechanism inclining to chemisorption. 1 g HCZMO per liter of a groundwater (F - : 4.40 mg L -1 ) can reduce fluoride level below 1.5 mg L -1 in batch treatment. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Rapid industrial growth with population meets the societal need globally, but causes the scarcity of hygienic water owing to con- tamination of the water sources with inorganic and organic toxic species for discharging untreated or partially treated waste efflu- ent. The scarcity of hygienic water is most critical in third world countries where ground waters are naturally contaminated with fluoride (>1.5 mg L -1 ) and/or arsenic (>0.01 mg L -1 ). Thus, the use of surface and/or ground water is risky without prior treatment to public health of the third world countries like India. Amongst the technologies reported for wastewater treatment and recycling, the adsorption is considered to be the best and most universal option because it could be used for the removal of a wide variety of organic and inorganic pollutants. It is also a simple process with a low cost of construction, maintenance ∗ Corresponding author. Tel.: +91 33 2241 3893; fax: +91 3322413893. E-mail address: ucghosh@yahoo.co.in (U.C. Ghosh). 1 Maharaja Manindra Chandra College, Kolkata, India. and operation [1]. The purification possibility of water contam- inated with different organic compounds had been explored by adsorption over various low cost materials [2–9]. Occurrence of fluoride/arsenic in ground water has been established well since long back. Thus fluoride/arsenic adsorptions over different materi- als were also reported from wastewater and ground water [10,11]. Some materials are reported to be efficient at least in lab bench scale, but the materials when applied for the field water treatment showed poor performances encouraging continuation of investiga- tion for the efficient materials. Thus the synthesis of new materials for searching has been continued for searching materials, which may be capable for the efficient treatment of fluoride or arsenic rich ground waters. In India, fluoride concentration in groundwater even at 30 mg L -1 had been reported [12–14], which is much above its permissible value (1.5 mg L -1 ). Materials over which fluoride adsorption from aqueous solutions studied are some geomateri- als [12], coal based sorbents [13], manganese coated alumina [14], waste carbon slurry [15], fly ash [16], silica gel [17], bone char [18], spent catalyst [19], zeolites [20], activated alumina [21], granular calcite [22], mixed rare earth oxides [23] and alumina supported carbon [24]. However, fluoride adsorption over most materials was http://dx.doi.org/10.1016/j.apsusc.2014.04.095 0169-4332/© 2014 Elsevier B.V. All rights reserved.