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Nano-hydroxyapatite polymeric hydrogels for dye removal

Varaprasad, Kokkarachedu, Nunez, Dariela, Yallapu, Murali Mohan, Jayaramudu, Tippabattini, Elgueta, Elizabeth, Oyarzun, Patricio
RSC advances 2018 v.8 no.32 pp. 18118-18127
absorption, adsorption, calcium, carboxymethylcellulose, chemical precipitation, clams, diffusivity, dyes, electrolytes, gravimetry, hydrogels, kinetics, nanocomposites, polymerization, shell (molluscs), sorbents, water purification
Herein, two kinds of nano-hydroxyapatite were synthesized from Clam and Magellan shell by wet chemical precipitation method. Mainly, carboxymethyl cellulose/acrylamide/nano-hydroxyapatite composite hydrogels were developed via a free-radical polymerization process and investigated as a sorbent for Acid Blue 113 (AB) from aqueous AB solution. The swelled and kinetic behaviours of hydrogels were investigated using a gravimetric method. The swelling properties of the CMC-AM-hydrogels were influenced by the calcium electrolytes (Ca²⁺) content in nano-hydroxyapatites. The diffusion coefficient value increased with the increase of nano-hydroxyapatite content in the CMC-AM/nHA-CS (0.22353–0.27681 cm² s⁻¹) and CMC-AM/nHA-MS (0.22377–0.29737 cm² s⁻¹) hydrogels. The mechanism of water diffusion was found to be anomalous transport. The CMC-AM/nHA-MS hydrogels showed high AB absorption efficiency and adsorption capacities. These results explained that the nano-hydroxyapatites of Magellan shells based hydrogels are attractive nanocomposite hydrogels for the adsorption of dye in the water purification applications.