Application of iron-modified kapok fibres for As(V) removal from groundwater using column fixed bed approach

Abstract

Abstract Arsenic pollution of groundwater is a severe problem, particularly for rural residents. This study utilised a simple hydrothermal surface modification technique using iron (Fe-kapok) to create a natural sorbent for As(V) removal from groundwater using a column fixed bed methodology. Specific surface area (BET) isotherms nitrogen adsorption/desorption test, scanning electron microscopy (SEM) imaging, energy-dispersive X-ray (EDS) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to evaluate the properties of the natural adsorbent. Fe-specific kapok's surface area BET (3.272 m2/g) and pore volume (0.032 cm3/g) were greater than those of raw kapok (0.976 m2/g; 0.021 cm3/g), indicating the presence of more As(V) adsorption sites. Even with competing ions such as sulfate, the groundwater chemical parameters did not significantly affect the As(V) adsorption efficiency of the natural sorbents. As(V) adsorption performance decreased as the flow rate and initial concentration of As(V) increased. However, an increase in sorbent dosage results in a rise in As(V) removal efficiency. The adsorption reaction was endothermic, and neutral pH was ideal for As(V) elimination. According to Thomas's model, the adsorption capacity was 6.63 mg/g at 25oC, which was better than Bohart and Adams' prediction of the adsorption curve. After eight adsorption cycles, the regeneration and reusability of the new sorbents were still excellent.