Caffeine Adsorption onto Bentonite Clay in Suspension and Immobilized

Abstract

This study describes the use of bentonite in suspension for the caffeine adsorption (pollutant of emerging concern) by taking different conditions of the pH, adsorbent mass, adsorbent calcination temperature and interferents into account. The results were compared with those obtained using bentonite immobilized in alginate beads. The acid medium has a greater efficiency for the caffeine adsorption and the adsorbent calcination temperature exerts, due to structural changes. Caffeine removal higher than 90% was obtained at optimized conditions. The Langmuir model indicated a better fit of the data and the adsorption capacity of caffeine onto bentonite. The bentonite immobilized led to a slower adsorption process in relation to the suspended.

Mechanism and behavior of caffeine sorption: affecting factors

“…This study shows that caffeine is adsorbed more efficiently in an acidic environment, revealing that pH 2 is the best pH for the adsorption process. 52 In the study published by W. A. Cabrera-Lafaurie et al in 2012; investigated the effect of clays functionalized with transition metals and calcination on the caffeine removal, and as seen in Table 3, when the caffeine adsorption of different adsorbents at different pH conditions was evaluated, it was concluded that better efficiency was achieved in an acidic or neutral environment. 50 Anastopoulos et al, in their optimization study of caffeine adsorption with oxidized biochar obtained from pine needles in 2020, conrmed that the adsorption capacity increases with increases up to 4 in solution pH, and then begins to decrease aer 4.…”

“…41 Caffeine adsorption with 773 K bentonite reached equilibrium in 1440 minutes, according to Lenzi et al They also looked into the effect of calcined bentonite in calcium alginate on the adsorption process, and discovered that compared to bentonite in suspension, caffeine adsorption was reduced by 19%. 52 The adsorption equilibrium time was 40 hours, according to Oliveira et al, who used thermally modied Verdo-lodo bentonite as an adsorbent. The adsorption kinetics showed the best agreement with the pseudo second-order model.…”

“…This study shows that caffeine is adsorbed more efficiently in an acidic environment, revealing that pH 2 is the best pH for the adsorption process. 52 …”

“…Caffeine adsorption with 773 K bentonite reached equilibrium in 1440 minutes, according to Lenzi et al They also looked into the effect of calcined bentonite in calcium alginate on the adsorption process, and discovered that compared to bentonite in suspension, caffeine adsorption was reduced by 19%. 52 …”