Abstract
Porous carbon materials derived from biopolymers are attractive sorbents for the removal of emerging pollutants from water, due to their high specific surface area, high porosity, tunable surface chemistry, and reasonable cost. However, carrageenan biopolymers were scarcely investigated as a carbon source to prepare porous carbon materials. Herein, hydrochars (HCs) and porous activated carbons (ACs) derived from natural occurring polysaccharides with variable sulfate content (κ-, ι- and λ-carrageenan) were prepared and investigated in the uptake of ciprofloxacin, which is an antibiotic detected in water sources and that poses serious hazards to public health. The materials were prepared using hydrothermal carbonization and subsequent chemical activation with KOH to increase the available surface area. The activated carbons were markedly microporous, presenting high specific surface area, up to 2800 m2/g. Activated carbons derived from κ- and λ-carrageenan showed high adsorption capacity (422 and 459 mg/g, respectively) for ciprofloxacin and fast adsorption kinetics, reaching the sorption equilibrium in approximately 5 min. These features place the ACs investigated here among the best systems reported in the literature for the removal of ciprofloxacin from water.
Highlights
Emerging pollutants are a vast series of man-made chemicals such as cosmetics, pesticides and pharmaceuticals that are essential to modern society and whose production has increased dramatically over the last century
The spherical shape of the hydrochars HC-ι and HC-λ was preserved after KOH activation, in agreement with previous findings reported for spherical-activated carbons prepared from carrageenan using identical KOH activation conditions [37]
Hydrochars and porous-activated carbons prepared from three distinct carrageenan polysaccharides, κ, ι- and λ-carrageenan, have been reported here
Summary
Emerging pollutants are a vast series of man-made chemicals such as cosmetics, pesticides and pharmaceuticals that are essential to modern society and whose production has increased dramatically over the last century. Environment and aquatic ecosystems are still poorly studied, but may include endocrinal disruption, promotion of antibiotic resistance, and chronic toxicity [3,4]. Wastewater treatment plants (WWTP) are currently unable to completely remove most of these compounds [5,6] This is the case of ciprofloxacin (CIP, Scheme 1), an antibiotic that belongs to the class of quinolones and is used to treat several bacterial infections in animals and humans [7]. The detected amount of CIP in wastewaters discharged from hospitals and drug production units is much higher, up to 150 μg/L and 30 mg/L, respectively, which is potentially harmful to human health and ecosystems [9,10,11]. The presence of CIP in water sources poses serious hazards to public health because it can promote antimicrobial resistance in certain pathogenic microorganisms [12,13,14]
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