The present study focuses on the adsorption of organic matter mainly COD from pretreated landfill leachate of Lamdeng Khunou Solid Waste Management Plant, Manipur, India through the employment of H3PO4 treated activated carbon derived from Parkia speciosa (Petai) pods (PPAC). The adsorbent was analyzed for morphological and surface characterization by various methods including, Field emission scanning electron microscopy (FESEM), Energy Dispersive X-Ray Analysis (EDAX), Brunauer–Emmett–Teller (BET) surface area and pH at zero point charges ( pHZPC). The impacts of adsorption processes such as initial pH, temperature, equilibrium time and dose of adsorbent were considered to evaluate the performance of PPAC. At 20 °C, PPAC showed maximum COD removal of 93% within 90 min contact time, at optimum pH 2. Adsorption kinetic was able to explain by Lagergren’s pseudo-second-order equation and intraparticular diffusion models suggesting the combined behavior of both the physical and chemical adsorption of COD on PPAC. Through thermodynamics and isotherm studies, the adsorption of COD on PPAC is revealed to be exothermic with maximum monolayer coverage of 200 mg COD/g PPAC. The performance of the PPAC adsorbent is also compared with other existing reported adsorbents for treating leachate.

    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Synthesis of adsorbent
        2.2 Leachate sample collection and analysis
        2.3 Batch experiment and analysis
        2.4 Methodology
    3 Results and discussion
        3.1 Characterization of alum pretreated stabilized leachate
        3.2 Adsorbent characterization
        3.3 Surface morphology of PPAC adsorbent by FESEM analysis
        3.4 Elemental composition of PPAC adsorbent by EDAX analysis
        3.5 Point of zero charge of PPAC
        3.6 Influence of pH on COD removal by PPAC adsorption
        3.7 Effects of contact time on COD adsorption by PPAC
        3.8 Kinetic adsorption modeling
        3.9 Temperature effects on COD removal
        3.10 Thermodynamics part of temperature effect
        3.11 Effects of PPAC dosage on COD removal
        3.12 Adsorption isotherm study on COD removal
        3.13 Influence of PPAC dosage on TDS, total iron and colour removal
        3.14 Regeneration and reuse of spent adsorbent
    4 Conclusion
    References

• Vivek Laishram(Department of Civil Engineering, National Institute of Technology Manipur)
• Potsangbam Albino Kumar(Department of Civil Engineering, National Institute of Technology Manipur)