Abstract
This study aimed to understand the adsorption process of cephalexin (CPX) from aqueous solution by a biochar produced from the fiber residue of palm oil. Scanning electron microscopy, Fourier transform infrared spectroscopy, Boehm titration, and the point of zero charge were used to characterize the morphology and surface functional groups of the adsorbent. Batch tests were carried out to evaluate the effects of the solution pH, temperature, and antibiotic structure. The adsorption behavior followed the Langmuir model and pseudo-second-order model with a maximum CPX adsorption capacity of 57.47 mg g−1. Tests on the thermodynamic behavior suggested that chemisorption occurs with an activation energy of 91.6 kJ mol−1 through a spontaneous endothermic process. Electrostatic interactions and hydrogen bonding represent the most likely adsorption mechanisms, although π–π interactions also appear to contribute. Finally, the CPX removal efficiency of the adsorbent was evaluated for synthetic matrices of municipal wastewater and urine. Promising results were obtained, indicating that this adsorbent can potentially be applied to purifying wastewater that contains trace antibiotics.
Highlights
Antibiotics are indispensable products for human life, and their consumption has increased to combat the spread of infectious diseases in humans and animals [1]
FZn has the highest CPX removal efficiency at 74.1%, while SZn and FHA had similar removal efficiencies of 17.5% and 17.4%, respectively. This behavior can be associated with the nature of the prepared adsorbent and is characterized by the pH at point of of zero zero charge (PZC), which is a parameter for identifying the variation in the surface charge of the adsorbent with the pH
All adsorbents had the potential for electrostatic interaction. This indicates that pH at PZC (pHPZC) by itself does not explain the behavior of adsorbents during the CPX adsorption process
Summary
Antibiotics are indispensable products for human life, and their consumption has increased to combat the spread of infectious diseases in humans and animals [1]. 30–90% of consumed antibiotics are not metabolized in the body and are discharged into aquatic systems as active compounds [2]. The discharge of contaminated water from pharmaceutical facilities, hospitals, homes, and agro-industrial facilities containing pharmaceuticals such as CPX into the environment can have adverse impacts on human health, increase antibiotic resistance, and inhibit the growth of algae and beneficial microorganisms in the environment [5]. Adsorption is a promising and available technique for removing many contaminants in water. Several oxygenated functional groups on its surface, including alcohols, carboxylic acids, phenols, and ethers, allow interactions such as π–π electron donor–acceptor interactions, electrostatic interactions, and hydrogen bonding that have been established as major adsorption mechanisms between antibiotics and biochar [6]
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