Caffeine removal by chitosan/activated carbon composite beads: Adsorption in tap water and synthetic hospital wastewater

• Published in: Chemical engineering research & design 2022-08, Vol.184, p.1-12
• Main Authors: Quesada, Heloise Beatriz, de Araújo, Thiago Peixoto, Cusioli, Luís Fernando, de Barros, Maria Angélica Simões Dornellas, Gomes, Raquel Guttierres, Bergamasco, Rosângela
• Format: Article
• Language: English
• Subjects: Biopolymers; Chichá-do-cerrado; Fixed-bed adsorption; Immobilization; Pharmaceuticals
• ISSN: 0263-8762
• DOI: 10.1016/j.cherd.2022.05.044

Caffeine in water resources has been reported, indicating the need for alternative treatments. Activated carbons (ACs) are efficient adsorbents; however, they present issues that immobilization in chitosan hydrogel (CH) can overcome. Despite the importance of both aspects, adsorption in continuous systems and different aqueous matrices are understudied. The present study developed and characterized chitosan/AC composites to improve the adsorbent properties and fill the research gap presented. The adsorbent was applied to adsorb caffeine in batch and fixed-bed experiments, using distilled and tap water and synthetic hospital wastewater. Chicha-do-cerrado shells were used to develop two different ACs (KAC and CAC) and composite beads (CH-KAC and CH-CAC). KAC and CH-KAC showed high surface area (1082 and 240 m² g−1), and FTIR indicated that CH assigned new functional groups to the composites. Batch studies revealed a maximum adsorption capacity of 391.00, 139.61, 121.90, and 39.53 mg g−1 for KAC, CAC, CH-KAC, and CH-CAC, respectively. The ions effect in tap water did not occur for the composites due to the bridging phenomenon. In treating the synthetic hospital wastewater, the addition of AC increased the removal efficiency. The fixed-bed maximum adsorption capacity was 83.88 mg g−1 for CH-KAC, and the column was reused three times. The importance of both CH and ACs has been successfully proven. •The addition of chitosan to the activated carbon enriched the adsorbent’s structure•KOH activated carbon/chitosan composite obtained a high surface area (240 m² g−1).•The adsorption of caffeine in tap water was evaluated.•The ions effect did not occur in tap water due to the bridging phenomenon.•The adsorbents treated a synthetic hospital wastewater.