Macroporous chitosan/polyvinyl alcohol composite adsorbents based on activated carbon substrate

In current work, granular activated carbon (AC) was impregnated with different blends of chitosan (CS) and polyvinyl alcohol (PVA), (1:1, 1:2 and 2:1 w/w) polymers. Batch adsorption of methylene blue from water was studied using composite adsorbents. Isotherms and kinetics of adsorption on pristine, acidified and composite ACs were investigated and compared. FTIR, SEM, synthesis yield, swelling ratio and abrasion hardness analyses were selected for characterizing the adsorbents. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were employed to study the adsorption kinetics and, the pseudo-first-order model provided a better fit. Equilibrium results revealed that both Langmuir and Freundlich isotherms could well describe the adsorption equilibrium. Activated carbon/chitosan adsorbent suggested the highest adsorption capacity (468.7 mg/g) which was around 33 mg/g larger than that of the pristine activated carbon (435.2 mg/g). Moreover, AC/CS/PVA composites demonstrated the superior uptake rate and swelling degree in spite of having inferior yield of production. The hardness value was improved as a result of the polymer coating especially with the blends of CS and PVA due to developed interconnected network of the resultant coating layer. Generally, the results indicated that the role of CS was more highlighted in elevation of adsorption capacity while PVA was more effective in kinetic rate enhancement.