Application of novel, low-cost, laterite-based adsorbent for removal of lead from water: Equilibrium, kinetic and thermodynamic studies

ABSTRACT

Contamination of groundwater by carcinogenic heavy metal, e.g., lead is an important issue and possibility of using a natural rock, laterite, is explored in this work to mitigate this problem. Treated laterite (TL- prepared using hydrochloric acid and sodium hydroxide) was successfully utilized for this purpose. The adsorbent was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Fourier Transform Infrared Spectroscopy (FTIR) to highlight its physical and chemical properties. Optimized equilibrium conditions were 1 g L⁻¹ adsorbent concentration, 0.26 mm size and a pH of 7 ± 0.2. Monolayer adsorption capacity of lead on treated laterite was 15 mg/g, 14.5 and 13 mg g⁻¹ at temperatures of 303 K, 313 K and 323 K, respectively. The adsorption was exothermic and physical in nature. At 303 K, value of effective diffusivity of (D_e) and mass transfer co-efficient (K_f) of lead onto TL were 6.5 × 10⁻¹⁰ m²/s and 3.3 × 10⁻⁴ m/s, respectively (solved from shrinking core model of adsorption kinetics). Magnesium and sulphate show highest interference effect on the adsorption of lead by TL. Efficacy of the adsorbent has been verified using real-life contaminated groundwater. Thus, this work demonstrates performance of a cost-effective media for lead removal.

KEYWORDS:

• Effective diffusivity
• lead adsorption
• shrinking core
• treated laterite

Acknowledgment

The authors acknowledge the help of Sourav Mondal, Research scholar from the Department of Chemical Engineering, Kharagpur, India.

Funding

This work is partially supported by a grant from the SRIC, IIT Kharagpur under the scheme no. IIT/SRIC/CHE/SMU/2014-15/40, dated 17-04-2014. Any opinions, findings and conclusions expressed in this article are those of the authors.