Caffeine and Ciprofloxacin Adsorption from Water onto Clinoptilolite: Linear Isotherms, Kinetics, Thermodynamic and Mechanistic Studie

Abstract

In this study, clinoptilolite was used to sequester ciprofloxacin (CIP) and caffeine (CAF), two emergent contaminants, from aqueous solution using batch equilibration method and the effects of contact time, pH, initial contaminant concentration, temperature and adsorbent dosage investigated and herein reported. The adsorption kinetics was described by the pseudo-second-order model (PSO) and pore diffusion was not the sole operative rate-controlling step as depicted by the intraparticle diffusion model. The equilibrium data were modelled using three linear forms of Langmuir equation and Freundlich model and was best fitted by the Lineweaver-Burk linearization of Langmuir equation (type-1). Linearization is shown to induce errors that may lead to discrepancies in parameter values estimation. The derived thermodynamic functions revealed the adsorption processes are exothermic, spontaneous and physical in nature. The adsorption mechanism of CIP is strongly controlled by electrostatic interactions while CAF adsorption is weakly affected by changes in pH. The findings demonstrate that clinoptilolite in its unmodified form is a potential low-cost and eco-friendly adsorbent for removal of pharmaceutically active ingredients from water.

Mechanism and behavior of caffeine sorption: affecting factors

“…It was found that increasing the reaction temperature from 298 K to 338 K decreased the adsorption efficiency from 86.05% to 59.75%. 53 In the article published by Anastopoulos and Pashalidis in 2019, in the adsorption studies performed during the adsorption of caffeine on oxidized carbon derived from Luffa cylindrica, the highest adsorption capacity was 298 K, q max ¼ 59.9 mg g À1 , and the lowest adsorption capacity was 323 K they also obtained q max ¼ 49.3 mg g À1 . These results conrm that the adsorption is exothermic.…”

“…40,41,53 There are studies in the literature that show that when caffeine is physically absorbed, its capacity for adsorption diminishes with temperature. 41,53,64,65 When the surface is highly functionalized with oxygen, however, the adsorption capacity may increase with temperature due to chemical absorption of caffeine. 37,40 Temperature has a signicant impact on both selectivity and adsorption capacity.…”

Adsorption Isotherm, Kinetic and Thermodynamic Modelling of <i>Bacillus subtilis</i> ATCC13952 Mediated Adsorption of Arsenic in Groundwaters of Selected Gold Mining Communities in the Wassa West Municipality of the Western Region of Ghana

“…Therefore, linearizing them would undermine the assumptions upon which they were developed and can result in a flawed outcome [14]. Linearization of isotherms has been applied in several studies to determine the fit of an isotherm to an adsorption data because its interpretation is simple [12] [13]. The linear forms of the isotherms use the coefficient of determination (R 2 ) to predict the fit of the isotherm to the experimental data [14].…”

Enhanced ciprofloxacin removal from aqueous solution using a chemically modified biochar derived from bamboo sawdust: Adsorption process optimization with response surface methodology

“…Various adsorbents such as montmorillonite (Wu et al, 2010), clinoptilolite (Ngeno et al, 2019), metal-organic framework (Gadipelly et al, 2018), graphene hydrogel (Yu et al, 2019), activated bentonite (Maged, 2020), iron oxide nanoparticle (Lin and Lee, 2020), titanate nanotubes (Ji et al, 2021), silica-xerogels (Kaya et al, 2021), nanocomposite (Elessawy et al, 2020), chitosan (Nazraz et al, 2019) and biochar (Luo et al, 2019;Li et al, 2018;Huang et al, 2018) have been applied for CIP removal. Magnetic nanoparticles such as magnetic core-shell MnFe 2 O 4 @TiO 2 nanoparticles (Chang et al, 2021), humic acid, and levulinic acid-coated Fe 3 O 4 nanoparticles are efficient in removing CIP from water (Mahmoud et al, 2021).…”