The chronic exposure to the pharmaceuticals and personal care products contaminants in water represent a serious public health problem to man and animal. We studied the removal of aspirin (Asp) as an example to these hazardous materials from an aqueous solution using functionalized (FMCNT) and pristine multiwall carbon nanotubes (PMCNT). The characterization of synthetic sorbents was examined with scanning electron energy-dispersive microscopy and transmission electron microscopy. The effects of adsorption time, sorbent mass, solution pH, ionic strength, and temperature were optimized. The functionalization increased the surface area from 151 to 181 m² g⁻¹. Consequently, the adsorption capacity increased from 41 mg g⁻¹ to 58 mg g⁻¹ for PMCNT and FMCNT, respectively. The results showed that the adsorption kinetic follows the pseudo-second-order model with very good agreement. Whereas, the adsorption mechanism study showed a partial agreement with the liquid-film diffusion model on PMCNT and FMCNT at 25 °C and 35 °C, respectively, with acceptable linear regression coefficients. The adsorption isotherm results revealed that the adsorption fits the Freundlich model. The thermodynamic study revealed that, Asp adsorption on both sorbents is exothermic, spontaneous and favorable. FMCNT showed relatively high removal efficiency when compared with the PMCNT when used for most of the conditions investigated.

In December 2019, a new coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) led to the outbreak of a pulmonary disease called COVID-19, which killed thousands of people worldwide. Therefore, the necessity to find out the potential therapeutic pharmaceuticals is imperious. This study investigates the inhibitory effect of SARS-CoV-2 3-chymotrypsin-like protease (3CL^pro) using caffeine and caffeine-containing pharmaceuticals (3CPs) based on molecular dynamics simulations and free energy calculations by means of molecular mechanics-Poisson–Boltzmann surface area (MMPBSA) and molecular mechanics-generalized-Born surface area (MMGBSA). Of these 3CPs, seven drugs approved by the US-Food and Drug Administration have shown a good binding affinity to the catalytic residues of 3CL^pro of His⁴¹ and Cys¹⁴⁵: caffeine, theophylline, dyphylline, pentoxifylline, linagliptin, bromotheophylline and istradefylline. Their binding affinity score ranged from –4.9 to –8.6 kcal/mol. The molecular dynamic simulation in an aqueous solution of docked complexes demonstrated that the 3CPs conformations bound to the active sites of 3CL^pro during 200 ns molecular dynamics simulations. The free energy of binding also confirms the stability of the 3CPs–3CL^pro complexes. To our knowledge, this in silico study shows for the first time very inexpensive drugs available in large quantities that can be potential inhibitors against 3CL^pro. In particular, the repurposing of linagliptin, and caffeine are recommended for COVID-19 treatment after in vitro, in vivo and clinical trial validation. Communicated by Ramaswamy H. Sarma