Adsorption of amlodipine on surface-modified activated carbon derived from Delonix <i>regia</i> seed pod

Abstract

In this study, seed pods of Delonix regia was used to produce activated carbon (DRAC) whose efficiency as an adsorbent in removing amlodipine (AML) from aqueous solution was examined. Adsorbent's characterization was carried out via Fourier infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Boehm titration (BT), and pH point of zero charge (pHpzc). Results obtained from FTIR showed notable peaks attributed to various functional groups present on the DRAC's surface which must have contributed to the effective adsorptive removal of AML. Images obtained from the SEM analysis revealed that the surface of DRAC possesses various pore sites which enhances the uptake of AML to the adsorbent's surface. Results obtained from the Boehm titration showed the total value of the acidic group on the surface of the DRAC to be 0.99 ± 0.02 and 0.28 ± 0.01 for the total basic group; this implies that the DRAC's surface is predominantly acidic as further supported by the value obtained for the pHpzc which was 4.2 ± 0.2. At 303K, a maximum adsorption capacity of 56.5 ± 0.3 mg/g was obtained. It was observed that the Langmuir adsorption model best describes the adsorption data obtained and the data fitted the Pseudo-Second Order kinetics most. Analysis of adsorption thermodynamics showed that the sorption process was exothermic and physisorption defines the nature of the sorption mechanism (Ea< 40 kJmol−1). The cost analysis revealed that producing DRAC is 10 times cheaper as compared to buying commercially-available activated carbon. Hence, the adsorption of AML from aqueous solution using DRAC is efficient as well as cost-effective.