Dra. Elgueta-Herrera, Elizabeth

The adsorption capacity of hydrogels derived from modified xylan hemicellulose has been tested in order to develop new bio-based adsorbent materials useful for removing metal ions pollutants, such as Cd(II), Cu(II) and Pb(II) from an aqueous solution. Xylan was extracted from bleached kraft pulp of eucalyptus and subsequently modified with different proportions of functional sulfonic acid groups (HA3–HA7) and sulfonate groups (HS30–HS70) to generate hydrogels. The results showed that all the synthesized hydrogels were capable of adsorbing metal ions, being the hydrogels with 30% and 50% xylan the ones that presented the highest adsorption capacity. Maximum capacity studies at different initial concentrations revealed that at an initial concentration of 300 mg·L−1, the HA3 hydrogel presented an adsorption capacity of 193 mg Pb(II), 182 mg Cd(II), and 66 mg Cu(II) per g hydrogel. The HA5 hydrogel presented a capacity of 185 mg Pb(II), 113 mg Cd(II), and 48 mg Cu(II) per g hydrogel. The HS30 hydrogel exhibited an adsorption of 205 mg Pb(II), 174 mg Cd(II), and 71 mg Cu(II) per g hydrogel, and HS50 hydrogel exhibited an adsorption capacity of 273 mg Pb(II), 143 mg Cd(II), and 45 mg Cu(II) per g hydrogel. These results show that modified Xylan hemicellulose is a promising adsorbent for removal Cd(II), Cu(II), and Pb(II) ions from aqueous solutions.

Industrialization and human activities have exacerbated water pollution, demanding effective pollutant removal methods. Bio-based hydrogels, with their high porosity and extensive surface area, hold promise for this purpose. Cellulose is a suitable biopolymer for gel fabrication; however, the adsorption capacity of unmodified raw cellulose fibers often falls short of performance expectations due to the lack of strong binding sites. Therefore, this study investigates how different cellulose fiber types, chemical treatments, and solvent systems influence hydrogel properties for adsorption applications. Hydrogels were prepared from phosphorylated and unphosphorylated unbleached kraft pulps (UKP) derived from eucalyptus and pine using NMMO and IL solvent systems. Phosphorylation increased the surface charge of UKP from ~ 0.05 to ~ 2.3 mmol/g. However, the surface charge of phosphorylated samples decreased to 0.5–0.72 mmol/g after coagulation into hydrogels. Hydrogels prepared from phosphorylated UKP exhibited superior properties compared to the unphosphorylated counterparts, including increased specific surface area (12–64 m2/g to 53–95 m2/g), swelling capacity (1930–2800% to 3400–4800%), and higher MB adsorption capacity (13–30 mg/g to 156–291 mg/g). When comparing solvent systems, the NMMO-based hydrogel showed enhanced surface area and pore characteristics, while the IL-based hydrogel exhibited increased MB adsorption capacity (291 mg/g vs. 233 mg/g). Although pine-derived hydrogels had lower MB adsorption than eucalyptus-derived ones (156 mg/g vs. 291 mg/g), both showed comparable adsorption performance for Cu2+ ions (~ 40 mg/g). Overall, the IL-derived hydrogel from phosphorylated eucalyptus UKP proved most effective for removing MB and Cu2+ from aqueous solutions. These findings contribute to advancing cellulose-based hydrogels for efficient adsorption in wastewater treatment.