RESEARCH ARTICLE Calcium ion incorporated hydrous iron(III) oxide: synthesis, characterization, and property exploitation towards water remediation from arsenite and fluoride Abir Ghosh 1,2 & Suparna Paul 4,5 & Sayan Bhattacharya 3 & Palani Sasikumar 2 & Krishna Biswas 1 & Uday Chand Ghosh 2 Received: 17 September 2018 /Accepted: 27 November 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Calcium ion-incorporated hydrous iron(III) oxide (CIHIO) samples have been prepared aiming investigation of efficiency enhancement on arsenic and fluoride adsorption of hydrous iron(III) oxide (HIO). Characterization of the optimized product with various analytical tools confirms that CIHIO is microcrystalline and mesoporous (pore width, 26.97 Å; pore diameter, 27.742 Å with pore volume 0.18 cm 3 g -1 ) material. Increase of the BET surface area (> 60%) of CIHIO (269.61 m 2 g -1 ) relative to HIO (165.6 m 2 g -1 ) is noticeable. CIHIO particles are estimated to be ~ 50 nm from AFM and TEM analyses. Although the pH optimized for arsenite and fluoride adsorptions are different, the efficiencies of CIHIO towards their adsorption are very good at pH 6.5 (pH zpc ). The adsorption kinetics and equilibrium data of either tested species agree well, respectively, with pseudo-second order model and Langmuir monolayer adsorption phenomenon. Langmuir capacities (mg g -1 at 303 K) estimated are 29.07 and 25.57, respectively, for arsenite and fluoride. The spontaneity of adsorption reactions (ΔG 0 = - 18.02 to - 20.12 kJ mol -1 for arsenite; - 0.2523 to - 3.352 kJ mol -1 for fluoride) are the consequence of entropy parameter. The phosphate ion (1 mM) compared to others influenced adversely the arsenite and/or fluoride adsorption reactions. CIHIO (2.0 g L -1 ) is capable to abstract arsenite or fluoride above 90% from their solution (0 to 5.0 mg L -1 ). Mechanism assessment revealed that the adsorption of arsenite occurs via chelation, while of fluoride occurs with ion-exchange. Keywords Adsorption . Arsenite . Ca 2+ -incorporated ferric oxide . Characterization . Fluoride Introduction The constant rapid growth of population, urban civilization, and industrialization in the world has been dramatically dete- riorating the global climate and natural ecosystem owing to waste generation, which contain various pollutants including heavy metal ions (Moghaddam et al.2016), toxic organic com- pounds, pharmaceuticals, organic and inorganic dyes, and dis- solved inorganic solids (Taghavi et al. 2018a, b). Among the inorganic pollutants, arsenic and fluoride have attracted great attention towards the secure drinking water predominantly due to two major reasons. One is their chronic deadly effects on human health caused by high intake and the other is their natural abundance in drinkable water sources. Smedley and Kinniburgh (2002) had reported the abundance of high arsenic concentration (100–5000 μg L -1 ) in surface and groundwater in sulfide mineralization areas. Underground aquifers in south eastern Asia (India, Bangladesh, Philippines, China), South and North South Responsible editor: Tito Roberto Cadaval Jr Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-018-3872-3) contains supplementary material, which is available to authorized users. * Krishna Biswas kbiswas202@gmail.com * Uday Chand Ghosh ucghosh@yahoo.co.in 1 Department of Chemistry, Maharaja Manindra Chandra College, Kolkata, India 2 Department of Chemistry, Presidency University, 86/1 College Street, Kolkata 700073, India 3 School of Ecology and Environmental Studies, Nalanda University, Rajgir, Bihar, India 4 Department of Chemistry, National Institute of Technology, Durgapur, India 5 CSIR-Central Mechanical Engineering research institute, Durgapur, India Environmental Science and Pollution Research https://doi.org/10.1007/s11356-018-3872-3