Effectiveness of termite hill as an economic adsorbent for the adsorption of alizarin red dye

Abstract

The adsorption of alizarin red (AR) dye onto termite hill sample (THs) was investigated. Prior to the adsorption studies, the elemental, morphological, surface and structural properties of THs were examined by modern analytical methods. Instrumental analysis showed that the homogenous micro-structured THs are comprised of iron oxide, silica oxide, and alumina as major components. Experiments showed that the adsorption capacity of AR decreases with increasing pH and initial AR concentrations, and increases with increasing contact time, stirring speed and temperature. The equilibrium study obeyed the Langmuir adsorption model and the kinetics followed the pseudo-second-order model. About 95.0% AR reduction (1.425 mg/g) was achieved when 0.8 g of THs was mixed with 30 mL of 40 mg/L AR solution for 120 min at 400 rpm and a pH of 2. Thermodynamic study suggested that AR adsorption onto THs is spontaneous at higher temperatures of 323 K and above (ΔGo values are negative). However, ΔGo are positive at lower temperatures of 293–313 K, which implies that the adsorption process is not spontaneous at these temperatures. This study showed that THs could be used as alternative, low-cost, natural adsorbents for the removal of dyes from wastewater.

Keywords

• adsorption models
• alizarin red dye
• remediation process
• termite mound
• wastewater treatment