In this study, a novel hydrothermal gasification process for the simultaneous treatment of simulated aqueous metal effluent (Ni and Zn) and pine needles was designed and investigated. Temperature is the significant parameter that decides the product yields, and the same was varied from 300 to 600 degree celsius to optimize gaseous fraction and solid products. During supercritical water gasification (SCWG) of metal effluent (Ni and Zn) with pine needles, the metal (M) present in wastewater gets dehydrated to form the metal oxide (MO), which further gets reduced to pure metal (M⁽⁰⁾). The result shows that the in-situ generated particles of nanometal act as catalysts and promote the water gas shift reaction and methanation reaction, resulting in increased yield of H₂ and CH₄. The maximum hydrogen 17.2 mmol.g^-1 and total gas yield 25.9 mmol.g^-1 were obtained for Ni-pine needles at supercritical temperature (600 degree celsius), biomass to effluent ratio 1:10 with a reaction time of 60 min and while for Zn-pine needles hydrogen and total gas yield were registered to be 8.9 mmol.g^-1and 19.2 mmol.g^-1respectively. The generated nanometal carbon hybrid (Ni-NCH and Zn-NCH ) was characterized with an X-ray diffractometer (XRD) and X-ray photoelectron spectrometer (XPS) to confirm the transition of metal form M⁽⁺ⁿ⁾to M^(o) and degradation of biomass during in-situ gasification. In addition, the quasi-spherical and cubical-shaped morphology of hybrids were identified by Field scanning electron microscope (FESEM) and Transmission electron microscope (TEM) analysis, while the vibrating sample magnetometer (VSM) analysis was performed to determine the superparamagnetic characteristics of Zn and Ni carbon hybrids.

Pankaj Kumar

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