Enhanced Removal of Non-Steroidal Inflammatory Drugs from Water by Quaternary Chitosan-Based Magnetic Nanosorbents

Abstract

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most common pharmaceuticals used worldwide. They are widely detected in natural waters due to their persistence in wastewater treatment, and their removal is desirable in wastewater management. As a contribution to tackle this challenge, this study explores magnetic quaternary chitosan-based nanosorbents for the effective magnetically assisted removal of three NSAIDs (diclofenac, naproxen, and ketoprofen) from water. Toward this goal, silane groups were grafted onto the backbone of trimethyl chitosan through the reaction with an epoxide functionalized silane. Once silanized, the modified chitosan was employed to coat Fe3O4 nanoparticles. The prepared materials were characterized using FTIR spectroscopy and solid-state 29Si and 13C NMR spectroscopy, which confirmed the encapsulation of Fe3O4 nanoparticles with a hybrid siliceous material enriched in trimethyl chitosan. The effect of the initial NSAIDs concentration, pH, and contact time in the adsorption behavior was investigated. The kinetic data were well described by the pseudo-second-order kinetic model, indicating a chemisorption mechanism. The maximum adsorption capacities estimated from the Langmuir model were 188.5 mg/g (0.5925 mmol/g), 438.1 mg/g (1.7371 mmol/g), and 221.5 mg/g (0.8710 mmol/g) for diclofenac, naproxen, and ketoprofen, respectively. These adsorption capacities are higher than those of most reported sorbents, indicating the potential of these biosorbents to remove the selected NSAIDs using low-energy magnetically assisted separation.

Assessing the Performance of Environmentally Friendly-Produced Zerovalent Iron Nanoparticles to Remove Pharmaceuticals from Water

“…Ali et al [88] reported increased removal efficiencies of IBU with an increase in the adsorbent's dose but this was only up to a maximum point, after which additional material could not lead to higher removal efficiencies. The same conclusion was reached by Soares et al [82] regarding DCF, KTP and NPX, using a chitosan-based magnetic nano adsorbent. In this study, the use of R-nFe at 15 g L −1 was the maximum dose investigated and the effect was positive, meaning that the full extent of the material's capacity regarding these compounds was not reached.…”

“…The maximum specific removal capacity of R-nFe achieved in our work was 0.17 µg g −1 for the total mass of the pollutants. In comparison with the aforementioned studies [82,88], which utilized other types of iron nano adsorbents, this capacity does not seem to be substantial, suggesting that larger doses of R-nFe should be investigated and that the employment of R-nFe in Fenton processes could be more cost-effective than utilizing R-nFe as a stand-alone process.…”

“…Regarding the effect of pH, acidic conditions favor the removal of targeted NSAIDs with R-nFe (Figure 6). The dominant role of pH on the degradation of NSAIDs has been reported in several studies; usually, it affects NSAID removal through adsorption [80][81][82][83]. For example, Al Othman et al [84] showed that the maximum adsorption of DCF was achieved at a pH = 5 (85%) due to the carboxylic group in its molecule, resulting in the anionic form of the compound.…”

“…All in all, the removal of all targeted compounds in our study was maximized at the lower pH value investigated (pH = 3), which may be attributed to adsorption via electrostatic interactions. The reason is that the pKa of all targeted NSAIDs ranges between 4.14 and 4.59; thus, at lower pH values, those compounds that are characterized as weak acids are neutrally charged and, at higher pH values, they exist in the anionic form [82], whereas resin and nZVI has a positive surface charge at pH values < 7 [85,86]. Other mechanisms of adsorption, such as hydrophobic interactions, π-cation interaction, and hydrogen bonding in combination with Fenton reactions in the presence of oxygen and nZVI may be also responsible for the removal rates obtained.…”

Removal of naproxen from wastewater using chitosan–aerogel–activated carbon biocomposites: Theory, equilibrium, kinetics, thermodynamics, and process optimization

“…Among them, adsorption process can easily and effectively be adapted to conventional water treatment systems. It is also more environmentally friendly, sustainable, and economical compared with other removal methods (Soares et al, 2021). The pore distribution and surface area of adsorbent are the main factors that should be considered in adsorption.…”