As(V) Adsorption Kinetics of Humic Acid-Coated Magnetite Particles

Abstract

The discharge of arsenic (As) ions into water is a serious issue which needs to be curbed effectively due to the hazards of As exposure. Hence, a simple, cheap and effective removal procedure is required in order to meet water quality standards. In this research, magnetite (Fe3O4) particles coated with humic acid were investigated for its efficacy in adsorbing As. The particles were synthesised by varying the temperature (70, 80 and 90°C) and concentration of humic acid (1%, 2% and 3%) to study the corresponding changes in terms of size, structure and As adsorption performance. The phase and size were characterised with X-ray Diffraction and Dynamic Light Scattering technique, respectively. The performance of the synthesised particles in removing As (V) was quantitatively analysed using the colorimetric method with the assistance of a double-beam Ultraviolet-Visible Spectrophotometry. XRD analysis confirms the formation of magnetite while samples coated with 2% and 3% humic acid exhibited less crystallised structures. From the DLS analysis, Fe3O4 was found to have an average size of 2238nm while humic acid coated-Fe3O4 had increased particle sizes of between 2400nm to 3712nm. All the synthesised magnetite particles were able to remove certain percentages of As (V) from water. The highest adsorption capacity obtained was 1.984 mg/g and the lowest was 1.376 mg/g for a contact times of 40 minutes and 20 minutes, respectively.