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A cellulose nanofibers reinforced starch-graft-poly(acrylic acid) (St-g-P(AA)) nanocomposite hydrogel was developed as a bio adsorbent to remove chromium ions [Cr(VI)] using a fix-bed adsorption column (FBC). The influence of several factors on adsorption column efficiency was investigated in this study, including pH, starting concentration of Cr(VI) ions, and solution input flow rate. Following the first study, the appropriate pH, starting concentration, and flow rate ranges were determined to be 4-6, 20-60 mg/L, and 5-15 mL/min, respectively. The surface response approach based on the Box-Behnken model was used to statistically examine the influence of each independent parameter on response performance (removal efficiency) and anticipate the optimal result. The findings showed that the pH of the solution had the most significant impact. The maximum removal efficiency of the nanocomposite hydrogel was 50.26 percent at pH = 6, an initial concentration of 20 mg/L, and a flow velocity of 10 mL/min. The Langmuir isotherm model successfully matched the results, and the maximum adsorption capacity was calculated to be 23.47 mg/g.

To prepare superabsorbent hydrogels, starch-graft-poly(acrylic acid) reinforced by cellulose nanofibers (CNF), was synthesized through free radical graft polymerization. The results of its biocompatibility tests exhibited that by increasing incubation time from 1 to 5 days, the numbers of living cells were increased on both reinforced and unreinforced hydrogels. However, the fraction of cells on the surfaces of the reinforced hydrogel is comparable to unreinforced samples. The swelling amounts in NaCl, CaCl2, and AlCl3 solutions were 193 ± 9, 110 ± 8, and 99 ± 7 (gwater/gabsorbent) for 5 wt% CNF-reinforced hydrogels and 109 ± 8, 62 ± 7, and 56 ± 6 (gwater/gabsorbent) for unreinforced hydrogels, respectively. Compressive strength and Young’s modulus of 5 wt% CNF-assisted hydrogels were also 63.3 and 31.6 kPa corresponding to 69% and 140% improvements compared with unreinforced one. The graft polymerization of acrylic acid monomer was controlled by monomer content and cross-linking percentage, in order to achieve the highest swelling capacity for hydrogels. Hydrogel swelling in water was 312 gwater/gabsorbent for unreinforced hydrogel and 523 gwater/gabsorbent for 5 wt% CNF-reinforced sample and water absorption kinetics results was in agreement with the pseudo-second-order model. The prepared CNF-reinforced starch-graft-poly(acrylic acid) hydrogels can be used in a wide range of medical application due to the enhanced hydrophilicity, mechanical strength, and biocompatibility.

Ag doped Sn

Removal of pollutants by bio-superadsorbent is currently in the limelight due to their low cost and biocompatibility with the environment. This research, we investigated the potential of cellulose nanofibers (CNFs) treated starch-g-poly(acrylic acid) (St-g-PAA) superadsorbent hydrogels in removing Cu2+ ions from water. It was found that CNFs-incorporated starch-g-poly(acrylic acid) hydrogel exhibit the highest amount of Cu2+ uptake in a solution containing 0.1 g/L Cu2+ ions, and that adsorption capacity rises significantly with the increase in Cu2+ concentration from 0.1 to 0.6 g/L. The influence of CNFs on the adsorption of Cu2+ ions was studied by Langmuir and Freundlich adsorption isotherm models, the graphs verged on linearity in Langmuir model while the maximum monolayer adsorption capacity was found to be 0.736 g/g for the untreated St-g-PAA hydrogels and 0.957 g/g for the CNFs-treated hydrogels in 0.6 g/L Cu2+ solution at pH 5. In this study, the adsorption capacity was enhanced by increasing the contact time between the bio-adsorbent and solution up to 5 h while longer contact time resulted in reduced adsorption and desorption phenomenon. In addition, desorption results showed that maximum adsorbent recovery for pH near to 1–2. This study confirms that the starch-based hydrogel is promising to be used for removal of pollutants from water efficiently.