Leachate Treatment by Parkia Speciosa (Petai) pods derived Activated Carbon

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Vivek Laishram, Potsangbam Albino Kumar

Abstract

This study focuses on the employment of a waste derived Parkia Speciosa (Petai) pods activated carbon (PPAC) synthesized with 30% H3P04 at an impregnation ratio of 1:1 for organic ions (COD) uptake from landfill leachate collected from Lamdeng Solid Waste Management Plant, Imphal, Manipur which was pretreated in the previous part of this study. To study the sorption mechanism and rate controlling steps, intra-particle diffusion, Elovich model and non-linear Langmuir and Fruendlich isotherm models were used to test the adsorption data. The adsorption equilibrium was practically reached at 90 min contact time yielding 93% COD removal at an optimum dose of 11g/L PPAC in the previous part of the study. The adsorption kinetic studies revealed that the correlation coefficients (R2) for Elovich model was 0.953 as compared to 0.847 for diffusion model signifying the better fit of the adsorption kinetics data on Elovich model. In the previous part of this study, the linearized Langmuir model fitted better yielding a higher R2 value of 0.998 as compared to 0.497 for the linearized Freundlich isotherm model with lesser Chi-square (χ 2) of 0.56 for Langmuir's isotherm against that of 13.87 for Fruendlich. However, in this part of the study also, the modeling results revealed that the non-linearized Langmuir model (R2=0.971) even fitted the data better than non-linearized Fruendlich model (R2=0.891) with χ 2 value of 0.94 and 4.65 for Langmuir and Fruendlich isotherm respectively. From the observations, the organic ions mainly COD is adsorbed on PPAC (qmax=180.65mg/g), the surface of which is mostly homogeneous. Monolayer adsorption occurs without lateral interactions between the adsorbed molecules suggesting the nature of adsorption to be predominantly chemical adsorption.

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