Removal of chemical oxygen demand from landfill leachate using cow-dung ash as a low-cost adsorbent

• Very first application of activated cow dung ash for the removal of organic contaminants (COD) from landfill leachate.
• 79% load of COD was reduced using ACA at 30 °C (pH 6.0 using 20 g/L dose).
• Freundlich and Langmuir adsorption isotherms indicate good fits to the experimental data.
• SEM image shows that activated carbon particles make the surface of ACA more porous, leading to high adsorption efficiency.
• Comparatively ACA proves to be cost-effective as it has high COD removal efficiency from the wastewater.

The application of cow dung ash was assessed for the removal of organic contamination from the wastewater using landfill leachate of known Chemical Oxygen Demand (COD) concentration in batch mode. The effect of various parameters like adsorbents dose, time, pH and temperature was investigated. Results indicate that upto 79% removal of COD could be achieved using activated cow dung ash (ACA) at optimum temperature of 30 °C at pH 6.0 using 20 g/L dose in 120 min, whereas cow dung ash (CA) shows 66% removal at pH 8.0 using 20 g/L dose, also in 120 min. Data also shows that ACA exhibited 11–13% better removal efficiency than CA. COD removal efficiency of various adsorbents was also compared and it was found that ACA offers significantly higher efficiency. Freundlich and Langmuir adsorption isotherms were also applied, which depicts good correlations (0.921 and 0.976) with the experimental data. Scanning electron microscope (SEM) images shows that after the activation, carbon particles disintegrate and surface of particles become more rough and porous, indicating the reason for high adsorption efficiency of ACA. Hence, ACA offers a cost-effective solution for the removal of organic contaminants from the wastewater and for the direct treatment of landfill leachate.

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