An eco-friendly cellulose support functionalized with tin titanate nanoparticles for the fast removal of clonazepam drug from the drinking water: adsorption mechanisms

This research studied the performance of tin titanate (SnTiO₃, SnT) and cellulose-based composites for the removal of clonazepam (CZP) drug by physical adsorption. The cellulose was extracted from a plant named tithonia tubaeformis, which is considered as weed in the crop fields of Mexico. The analysis by microscopy revealed that the SnTiO₃ powders are formed by a mixture of coalesced grains and nanotubes with lengths in the range of 97-633 nm. Furthermore, the X-ray diffraction analysis indicated that the SnT powders present a mixture of cassiterite and rutile phases. Experiments for the CZP removal from drinking water were carried out, and several parameters such as initial drug concentration (1-10 mg/L), amount of SnT adsorbent per liter of contaminated solution (10-50 mg/L), and pH (3-10) were varied in order to study their influence on the CZP removal percentage. Essentially, we found that the SnT dosage of 50 mg/L produced the most efficient and fastest CZP removal, since 94.3% of CZP was removed after only 10 min of reaction. Moreover, a piece of cellulose (Cell) was decorated with 50 mg of SnT powder to form the Cell+SnT composite, and this was able to remove a maximum of 80.5% of CZP after 180 min of reaction. If the amount of SnT powder deposited on the Cell+SnT composite is raised up to 100 mg, the composite can remove 95.5% of CZP. The adsorption capacity was also calculated for the SnT powders and Cell+SnT composite and found that it was 6.3 times higher for the SnT powders. Furthermore, the Raman spectra recorded for the Cell+SnT composites demonstrated the presence of surface defects, which acted as adsorption centers for the CZP molecules. The results of this investigation demonstrate that eco-friendly and low-cost floatable composites can be used for the removal of pharmaceutical contaminants, which is an advantage over adsorbent powders.