An eco-friendly composite hydrogel based on covalently crosslinked cellulose/poly (glycerol citrate) for thallium (І) removal from aqueous solutions

Cellulose/poly (glycerol citrate) reinforced with thiol-rich polyhedral oligomeric silsesquioxane and apple peel (POSS-SH@CAG-CEL/AP) was synthesized using gelation method in the presence of glutaraldehyde as a cross linker agent and used as an efficient composite hydrogel for elimination of Tl(CYRILLIC CAPITAL LETTER BYELORUSSIAN-UKRAINIAN I) from aqueous solutions. This composite hydrogel and synthesized thiol-rich polyhedral oligomeric silsesquioxane were characterized by elemental analysis, FT-IR, NMR, TGA, and FE-SEM techniques. The effects of synthetic and environmental parameters on the adsorption capacity of the composite hydrogel were investigated and it was found that thiol-rich polyhedral oligomeric silsesquioxane has improved the hydrogel properties including the Tl(CYRILLIC CAPITAL LETTER BYELORUSSIAN-UKRAINIAN I) uptake and the thermal stability. The maximum adsorption capacity of 352.3 mg g- 1 was obtained within 30 min under optimum reaction conditions. A typical Langmuir adsorption isotherm with was observed for adsorption of Tl(I) onto POSS-SH@CAG-CEL/AP and pseudo-second-order kinetic model provided the best correlation between experimental data. Thermodynamic studies showed that the Tl(I) adsorption was spontaneous process and exothermic. Also, the reusability tests confirmed that the POSS-SH@CAG-CEL/AP can be reused for four times without any remarkable change in its adsorption capacity. Thus, this reusable biobased composite hydrogel can be an ideal candidate for elimination of Tl(I) from aqueous solutions.

Automated summary

In this study, a reusable biobased composite hydrogel was successfully synthesized and used for the removal of Tl(I) from aqueous solutions. The hydrogel exhibited high adsorption capacity and thermal stability, and the adsorption process was found to be thermodynamically spontaneous. The results demonstrated that the hydrogel can be reused multiple times without significant loss of its adsorption capacity.