Investigation of citric acid–glycerol based pH-sensitive biopolymeric hydrogels for dye removal applications: A green approach

•Synthesis of pH-sensitive citric acid based hydrogels via solventless greener approach.•Synthesized biopolymeric hydrogels have shown excellent dye removing capacity.•Thermally stable and environment friendly hydrogels.

Hydrogels are three dimensional polymeric structure with segments of hydrophilic groups. The special structure of hydrogels facilitates the diffusion of solutes into the interior network and possess numerous ionic and non-ionic functional groups, which can absorb or trap ionic dyes from waste water. The present investigation was devoted to the synthesis of a series of citric acid and glycerol based pH sensitive biopolymeric hydrogels using a solventless green approach via condensation polymerization in the presence of acidic medium. The formations of hydrogels were confirmed using various spectral investigations viz., FT-IR, 1H and 13C NMR. The thermal properties of various hydrogels have been studied using TGA, DTA and DSC analysis. The rationalized relationship was noticed with increasing of pH from 4.0 to 10.0. The surface morphologies of hydrogels were analyzed using SEM technique which was well supported from the results of swelling studies. Methylene blue has been selected as a cationic dye for its removal from various environmental sources using pH-sensitive biopolymeric hydrogels. The results of dye removal revealed that glycerol based biopolymeric hydrogels have shown an excellent dye removal capacity. Hence, the synthesized pH sensitive biopolymeric hydrogels have an adaptability with pH tuned properties might have greater potential opening in various environmental applications viz., metal ion removal, agrochemical release, purification of water, dye removal etc.

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