Chitosan based adsorbent aerogels for water remediation purposes.

MELINA KLOSTER; M. A. MOSIEWICKI; N. E. MARCOVICH

Congreso; WCCE11 - 11th World Congress of Chemical Engineering. XXX Congreso Interamericano de Ingeniería Química. CAIQ2023 - XI Congreso Argentino de Ingeniería Química. CIBIQ- 2do Congreso IberoAmericano de Ingeniería Química; 2023

Water pollution is one of the most important problems around the world therefore, the objective of this work is to designbioadsorbents with proper adsorption capacity for water remediation. Gels were prepared by mixing an acid chitosan (C) solution with an aqueous glutaraldehyde (G) solution. The mixture was casted in molds and left at room temperature for 24 h to let the crosslinking reaction occur. Samples were frozen and subsequently lyophilized, resulting in aerogels named C-3-G-5 and C-4-G-5 based on C mass and G content (Fig. 1a). These samples were characterized by swelling degree (SD), porosity (P) and apparent density (D). Congo red (CR) was used as model adsorbate for adsorption tests which were carried out adding 0.06 g of adsorbent to flasks containing 40 mL of 100 m/L CR solutions and the whole system was submitted to orbital shaken at 100 rpm at 25±1 °C. Different contact times were evaluated and the final concentration of CR solutions was measured by UV-vis spectrophotometry.D, P, SD are 0.056 g/mL, 71.2 % and 31.8 gH2O/g for C-3-G-5 and 0.063 g/mL, 50.2 % and 22.8 gH2O/g for C-4-G-5, respectively. Comparing both samples, C-3-G-5, which was synthesized with the lower CH content in the initial solution,has a lower density that is related with its larger porosity and greater swelling degree.Adsorption results were theoretically modeled with the pseudo-second order model (PSO): qt=kqe2t/(1+ kqet) (Fig. 1b);where qe and qt are the adsorption capacity at equilibrium and time t, respectively, and k is the rate constant. qe=41.2mg/g and k=5.4 10-4 min-1for C-3-G-5 (R2=0.998) and qe=35.5 mg/g and k=1.8 10-4 min-1for C-4-G-5 (R2=0.966). PSO is based on the assumption that the rate-limiting step is chemisorption [1] and predicts the equilibrium capacity even if it had not been reached. The adsorption capacity depends on the C concentration for the same percentage of G. The deviation of results from theoretical model is thought to be due to heterogeneous porous formed by ice crystals during the freezing step. Summarizing, different bioadsorbent materials with good physical properties and sorption capacitywere obtained using a natural polymer.