Experimental and theoretical study for removal of trimethoprim from wastewater using organically modified silica with pyrazole-3-carbaldehyde bridged to copper ions

Background: Human and veterinary antibiotics are typically discharged as parent chemicals in urine or feces and are known to be released into the environment via wastewater treatment plants (WWTPs). Several research investigations have recently been conducted on the removal and bioremediation of pharmaceutical and personal care products (PPCPs) disposed of in wastewater. Results: SiNP-Cu, a chelating matrix, was produced by delaying and slowing 1.5-dimethyl-1H-pyrazole-3-carbaldehyde on silica gel from functionalized with 3-aminopropyltrimethoxysilane. The prepared sorbent material was characterized using several techniques including BET surface area, FT-IR spectroscopy, Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and nitrogen adsorption-desorption isotherm. The pseudo-second-order model provided the best correlation due to the big match between the experimental and theoretical of different adsorption coefficients. The Langmuir and Freundlich adsorption models were used and the study showed a better match with the Freundlich model with a capacity of removal reached up to 420 mg g(-1). The removal capacity was dependent on pH and increased by increasing pH. The removal percentage reached 91;5% at pH= 8. The adsorbent demonstrated a high percentage removal of TMP, reaching more than 94% when increased pH. The sample was simply regenerated by soaking it for a few minutes in 1 N HCl and drying it. The sorbent was repeated five times with no discernible decrease in removal capacity. The thermodynamic study also showed endothermic, increasing randomness and not spontaneous. The free energy was 2.71 kJ/mol at 320 K. The findings of the DFT B3LYP/6-31 +g (d, p) local reactivity descriptors revealed that nitrogen atoms and pi-electrons of the benzene and pyrimidine rings in the TMP are responsible for the adsorption process with the SiNP surface. The negative values of the adsorption energies obtained by molecular dynamic simulation indicated the spontaneity of the adsorption process. Conclusion: The global reactivity indices prove that TMP is stable and it can be removed from wastewater using SiNP surface. The results of the local reactivity indices concluded that the active centers for the adsorption process are the nitrogen atoms and the Tr-electrons of the pyrimidine and benzene rings. Furthermore, the positive value of the maximum charge transfer number (Delta N) proves that TMP has a great tendency to donate electrons to SiNP surface during the process of adsorption.

Automated summary

SiNP-Cu, a chelating matrix, was used to efficiently remove TMP from wastewater, with a better fit to the Freundlich model. The removal capacity was pH-dependent, with higher pH values resulting in higher removal rates. Thermodynamic analysis indicated that the adsorption process was endothermic, increased randomness, and not spontaneous. DFT B3LYP/6-31+g (d, p) local reactivity descriptors showed that the nitrogen atoms and pi-electrons of the benzene and pyrimidine rings were responsible for the adsorption process with the SiNP surface.