In Situ Encapsulation of Nanometals in Carbon Matrix from Hazardous Wastewater with Cogeneration of H₂ Using Banana Pseudostem

This study successfully utilized the banana pseudostem (BPS) to remove heavy metals (HMs) from nickel electroplating wastewater (Ni-EPW) while generating H₂-rich gaseous fuel and synthesizing a valuable nanometal carbon matrix (NCM). This study highlights the synergetic effect of HMs promoting the decomposition of lignocellulosic biomass into H₂-rich gaseous fuel, with simultaneous recovery of HMs from the metal effluent in the form of NCM and reduction of formed metal oxide to lower valence metal oxides or metals with an increase in the temperature (300–600 °C). This study also examined how the crucial parameters, like temperature, time, and biomass-to-Ni-EPW ratio, impact the process performance. The maximum H₂ yield (6.8 ± 0.20 mmol·g^–1), total gas yield (TGY) (17.3 ± 0.51 mmol·g^–1), and carbon gasification efficiency (CGE) (36%) were determined at 600 °C and a biomass-to-Ni-EPW ratio of 1:10 for a retention time of 60 min. The use of nickel electroplating wastewater with the banana pseudostem catalyzes the degradation of biomass reaction rate and water gas shift reaction. It improves the TGY, H₂ gas yield, and CGE to 2.2, 1.7, and 2.6 times, respectively, compared with Millipore water (without any metal). The NCM obtained at 600 °C has quasi-spherical morphology with a larger surface area of 146.2 m²·g^–1 and exhibits magnetic saturation (M_s) of ∼3.42 emu·g^–1, which also finds its application in the fabrication of sensors and supercapacitors.