Cysteine- and glycine-functionalized mesoporous silica as adsorbents for removal of paracetamol from aqueous solution

Abstract

ABSTRACT The presence of pharmaceutical compounds in the environment is problem for human health worldwide. Paracetamol is one of the pharmaceutical compounds that is widely used as a pain reliever and fever reducer, and it has been discharged in water via industrial and domestic wastewater. This study aimed to improve the removal of paracetamol from aqueous solutions using two different amino-acid-modified mesoporous silica nanoparticles (MSNs). Two types of adsorbents were used: the surfaces of epoxy-modified MSNs were modified with glycine (MSN-Gly) and cysteine (MSN-Cys). Topographical images indicated that the size of fabricated nanoparticles ranged between 220 and 360 nm, with a pore size of ~5 nm. IR spectra confirmed the successful attachment of amino acids on MSN surfaces as a peak appeared at ~1720 cm−1, indicating a carbonyl group. A series of experiments were performed using the batch adsorption method to investigate the effects of contact time, initial concentration of the adsorbate, and pH on the removal of paracetamol from the aqueous solution. The adsorption capacity of paracetamol was higher in acidic media for both adsorbents. The maximum adsorbed amount of paracetamol was 300 mg/g for MSN-Gly compared with 250 mg/g for MSN-Cys. For both adsorbents and at all pH values, the experimental data were well matched with the pseudo-second order and the adsorption isotherm was fitted using a Temkin model.