# Activated Carbons as Effective Adsorbents of Non-Steroidal Anti-Inflammatory Drugs
###### Abstract  
In this study, the adsorption of naproxen sodium, ibuprofen sodium, and diclofenac sodium on activated carbon is investigated. Comprehensive studies of adsorption equilibrium and kinetics were performed using UV-Vis spectrophotometry. Thermal analysis and zeta potential measurements were also performed for pure activated carbon and hybrid materials (activated carbon-drug) obtained after adsorption of naproxen sodium, ibuprofen sodium, and diclofenac sodium. The largest amount and rate of adsorption was demonstrated for naproxen sodium. A significant impact of temperature on the adsorption of the tested salts of non-steroidal anti-inflammatory drugs was also indicated. Faster kinetics and larger amounts of adsorption were recorded at higher temperatures. Thermodynamic parameters were also determined, based on which it was indicated that adsorption in the tested experimental systems is an endothermic, spontaneous, and thermodynamically privileged process of a physical nature. The generalized Langmuir isotherm was used to study the equilibrium data. The adsorption rate data were analyzed using numerous adsorption kinetics equations, including FOE, SOE, MOE, f-FOE-, f-SOE, f-MOE, and m-exp.  
buprofen sodium; diclofenac sodium; naproxen sodium; activated carbon; adsorption equilibrium and kinetics; temperature effect +
Footnote †: journal: Applied sciences  
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Footnote †: journal: Applied sciences  
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Footnote 0: _Applied Sciences_  
Currently, adsorption methods based on activated carbon as an adsorbent find applications in water and sewage treatment processes [8]. Carbon materials are characterized by high sorption capacity toward many pollutants, in particular, aromatic organic compounds, and demonstrate high chemical and thermal resistance. Moreover, they are characterized by non-toxicity, a highly developed porous structure, and low production costs, which encourage their use. Of course, the efficiency of removing pollutants from aqueous solutions is influenced by a number of factors that relate not only to the properties of the adsorbent but also to the characteristics of the adsorbate (e.g., solubility, particle diameter, pKa, and charge) as well as the adsorption conditions (e.g., pH, temperature, mixing speed, and the presence of accompanying substances) [8; 9; 10; 11; 12; 13; 14; 15].  
The aim of the presented manuscript is to investigate the adsorption of sodium salts in non-steroidal anti-inflammatory drugs, i.e., naproxen sodium, ibuprofen sodium, and diclofenac sodium, on activated carbon. As part of a comprehensive analysis, equilibrium and adsorption kinetics measurements were conducted using UV-vis spectrophotometry. The adsorption processes were carried out at different temperatures: 15, 25, and 35 \({}^{\circ}\)C and 25 and 35 \({}^{\circ}\)C for equilibrium and adsorption rates, respectively. The equilibrium data were analyzed using the generalized Langmuir isotherm, which describes adsorption on energetically heterogeneous solids. Adsorption rate data were analyzed using simple kinetic equations: first- (FOE) and second- (SOE) order, 1,2-mixed-order MOE, fractal-like MOE (f-MOE), fractal-like FOE (f-FOE), fractal-like SOE (f-SOE), and multi-exponential (m-exp). Thermal analysis and zeta potential measurements were also performed for pure activated carbon and hybrid materials (activated carbon-drug) obtained after adsorption of naproxen sodium, ibuprofen sodium, and diclofenac sodium. Obtaining high-quality adsorption amount and rate data (kinetic curves consisting of at least seventy experimental points) and their detailed analysis using multiple equations and models of adsorption equilibrium and kinetics, as well as additional studies of thermal stability and electrokinetic potential enabled detailed information on the mechanism of adsorption of non-steroidal anti-inflammatory drugs on activated carbon.