Modification of carbon black using polyethylenimine (PEI) for aspirin removal

Abstract

Aspirin is the most common drug consumed by humans and animals, so there must be high demand on the production of this drug. Aspirin may bring adverse impact to humans and the environment even at low concentrations. This study was conducted to modify the carbon black by polyethylenimine (PEI) and characterize the modified carbon black (TC-PEI), to study the effect of various parameters during the adsorption process; as well as to analyse isotherm, kinetics, and thermodynamic behaviour of the adsorption. The carbon black obtained from the pyrolysis of tire waste provides an incentive to be used as a precursor to low-cost adsorbents due to its high carbon content. At first, the carbon black was treated by nitric acid to remove ash or sulphur content. Then, the impregnation of treated carbon black in PEI was done by varying the impregnation ratio, impregnation temperature and impregnation time. The best impregnation conditions are with one to two weight ratios of carbon black and PEI at 4 hours and 50°C. Next, the TC-PEI was used for adsorption studies. The TC-PEI was characterized in terms of surface morphology, surface area and functional group using field emission scanning electron microscopy, Brunauer-Emmett-Teller and Fourier transform infrared spectroscopy and point of zero charge, respectively. The kinetic, isotherm and thermodynamic studies were also performed. The adsorption process was seen fitted to the pseudo second-order and Langmuir isotherms. For thermodynamic studies, the adsorption gave an exothermic reaction, an increase in randomness and a spontaneous reaction. The regeneration study suggested two cycles for the adsorption of TC-PEI onto aspirin with 40% removal. From the results obtained, it gave the maximum capacity at 29.40 mg/g, which contributed to 60% aspirin removal within 120 minutes, at room temperature with pH 3 and 0.1 g of TC-PEI. In conclusion, the modified of TC by PEI can be used as an adsorbent for aspirin removal from pharmaceutical effluents.