Heavy metal remediation from automobile effluent by thermally treated montmorillonite-rice husk composite

Abstract

The adsorption capacities of montmorillonite for heavy metals from effluents have been improved by acid and alkaline treatments. However, the use of these chemicals is expensive, noxious to the environment and results in secondary contamination, hence the need for alternatives. This study exploits the use of calcined montmorillonite-rice husk combo (CM-RHC) for sequestration of heavy metals from automobile effluent. The CM-RHC was characterised by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analysis. The influence of effluent pH, sorbent dose, particle size, contact time and temperature was studied. Equilibrium and kinetic models were evaluated using regression (R²) and chi-square (χ²) statistics. The Freundlich model presented a better fit for the sorption process than the Langmuir, Tempkin and Dubinin–Radushkevich models. The trend of metal ions adsorbed on CM-RHC was Zn > Cu > Mn > Cd > Pb > Ni. The pseudo-second order model and liquid film diffusion mechanism were found to be suitable for the sorption process. Thermodynamics revealed a feasible, spontaneous physisorption process. The results indicated that CM-RHC could be a promising candidate for attenuation of heavy metals from contaminated effluents due to its low cost, eco-friendly characteristics, easy preparation as well as high removal efficiency.

Keywords:

• calcined montmorillonite
• rice husk
• automobile effluent
• remediation
• heavy metals