In this work, carboxymethyl cellulose (CMC), a biobased polymer, and Carbopol 940, a synthetic polymer, and their blends were used for the creation of novel adsorbents. Briefly, hydrogels of CMC, Carbopol, blends of CMC and Carbopol 25/75, 50/50 and 75/25 m/m, and citric acid, as crosslinker, were freeze-dried and heated at 438 K for 7 min. The resulting cryogels were characterized by compression tests, FTIR, TGA, SEM, water swelling and X-ray microtomography (XRM). The density decreased from (0.034 ± 0.002) g/cm3 for pure CMC to (0.027 ± 0.002) g/cm3 for blends, as depicted in the 3D images from XRM for pure CMC (Figure a) and 50/50 blends (Figure b). The surface area for pure CMC and 50/50 blends amounted to 1.278 m2/g and 1.762 m2/g, respectively. The highest compression modulus (141 ± 3 kPa) was observed for 50/50 blends. Pure CMC cryogels presented swelling ratio of 300 %, whereas for the blends it was 180%. The crosslinking of CMC and Carbopol chains mediated by citric acid was evidenced by FTIR and TGA. All aerogels were tested for the removal of methylene blue (MB) dye in the concentration range of 0.5 to 4.0 mg/mL by means of spectrophotometry at 660 nm. Under equilibrium conditions, the retention ratio increased with the MB concentration achieving the maximal removal values of (83 ± 2)% for blends and of (42 ± 3)% for pure CMC. Probably, the strong hydration of pure CMC represents a barrier for the adsorption of MB. Inside a syringe, under gravitational flow, the retention of 90 % MB took place in two minutes, after that, aerogels were rinsed with HCl 2.4 mol/L and a new aliquot of 2 mL MB solution was injected for reuse. After the 2nd reuse, the retention capacity decreased to ~ 70% and this level was kept up to 5 recycles. Thus, the 50/50 blend aerogels displayed (i) improved mechanical properties in comparison to all other, possibly due to the balance between hydrophobic interaction among the alkyl side chains and electrostatic interaction among the carboxylate groups, and (ii) the possibility to be applied as efficient adsorbents for methylene blue. The application of blend aerogels for water/oil separation is in progress.

Novel hybrid polymeric adsorbents for wastewater treatment

255th National Meeting (2018)

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