Environmental Technology & Innovation 17 (2020) 100620 Contents lists available at ScienceDirect Environmental Technology & Innovation journal homepage: www.elsevier.com/locate/eti Synthesis and evaluation of CMC-g-AMPS/Fe/Al/AC composite hydrogel and their use in fluoride removal from aqueous solution Vibha Sinha ∗ , Sumedha Chakma Department of Civil Engineering, Indian Institute of Technology, Delhi 110016, India article info Article history: Received 30 October 2019 Received in revised form 7 January 2020 Accepted 7 January 2020 Available online 10 January 2020 Keywords: Hydrogel Fluoride removal CMC-g-AMPS/Fe/Al/AC polymer Plackett–Burman design Isotherm modeling abstract Cellulose based hydrogels are emerging adsorbents for treating aqueous pollutants due to their modifiable surface characteristics and superabsorbent properties. This study investigates the sorption of fluoride (F − ) on CMC-g-AMPS/Fe/Al composite hydrogel impregnated with activated charcoal. Statistically valid Plackett–Burman design of ex- periments was employed for determination of most significant factors affecting F − removal. The maximum defluoridation efficiency of metal oxide incorporated HG (CMC- g-AMPS/Fe/Al/AC) was found to be 84.67% at pH 6 at an initial F − concentration of 5 mg/L which is significantly higher compared to control HG (CMC-g-AMPS/AC). Analysis of variance (ANOVA) revealed the effect of pH followed by contact time as the most significant parameter (P value < 0.05) affecting F − removal. The experimental data fitted well with the Langmuir isotherm model, with the maximum F − adsorption of 67.114 mg/g. The modification mechanism and adsorption process on HGs were examined with equilibrium degree of swelling (EDS), FT-IR spectra, SEM, EDX and XRD analysis. Characterization analysis of CMC-g-AMPS/Fe/Al/AC HG confirms a parallel hydrolysis reaction on fibrous polycrystalline lattice along with the desired metal incorporation and higher gel strength making it an excellent anionic polymer with high F − binding capacity. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Fresh water constitutes about 2.66% of the total water resources, out of that only 0.6% is fit for drinking water (Singh et al., 2018). The permitted limit of fluoride in the drinking water is considered to be between 0.5 to 1.5 mg/l as per WHO guidelines (Wasana et al., 2017). Fluoride being one of the most abundant contaminant, if present in more than the allowed concentration, possesses health risk in many aspects (Podgorski et al., 2018). In India, waste discharge mainly from glass and ceramic plants, electroplating and metallurgical operations, chemical fertilizers plants, sewage, sludge, coal-fired power stations, etc. results in higher F − concentration in groundwater affecting environmental sustainability and human health (Kanagaraj and Elango, 2019; Khurshid, 2019; Rao et al., 2017; Jadhav et al., 2015). Hence these industrial effluents containing fluoride-spiked wastewater, needs to be treated at point source of discharge. Existing technologies reported for excess F − removal includes ion exchange, membrane separation, reverse osmosis, electrolytic defluoridation, filtration via nanomaterials, and ultrafiltration that limits their usage due to higher capital cost, lesser selectivity and less efficiency at lower concentrations (Mukherjee and Singh, 2018). ∗ Corresponding author. E-mail addresses: vibhas@civil.iitd.ac.in (V. Sinha), chakma@civil.iitd.ac.in (S. Chakma). https://doi.org/10.1016/j.eti.2020.100620 2352-1864/© 2020 Elsevier B.V. All rights reserved.