DOI: https://doi.org/10.55373/mjchem.v25i2.98

Keywords: Adsorbent; cadmium(II); comparison; mechanism; silane-functionalised carbon nanotubes

Abstract

Silane-functionalized carbon nanotubes (Si-CNTs) as an adsorbent for cadmium(II) removal was investigated. The method included adsorbent preparation, adsorption study, comparison study, existing model evaluation, and characterization study. The 50 % removal at 2 mg of Si-CNTs was selected as the optimum amount of adsorbent used in order to minimize time and chemical/ materials. The optimum pH and contact time were unadjusted pH 5.61 and 30 minutes, respectively. The removal and uptake of Si-CNT exhibited a double better performance than resin and activated charcoal. For the isotherm study, the Langmuir corresponded to Freundlich with maximum Langmuir uptake at 120 mg/g. Meanwhile, the pseudo-second-order kinetic is a better fit than the pseudo-first-order, thus indicating that chemisorption is the rate-limiting step. Thermodynamic study reveals that cadmium(II) adsorption is a non-spontaneous endothermic in nature and forms an irreversible binding. Such findings suggest ion exchange and complexation mechanisms. The morphology of Si-CNT changed from a rough rope-like surface into dotted patches attached to the surface of Si-CNTs. EDX confirms the attachment of cadmium(II) on the surface of Si-CNTs. Fourier Transform Infrared Spectroscopy analysis reveals functional groups such as hydroxyl, amide, carbonyl and silica oxide. The characterization results support ion exchange and complexation mechanisms. In conclusion, the Si-CNTs are a potential adsorbent for cadmium(II) removal. This study plays a main role in large-scale pilot application studies as well as modelling and digital platform studies.