Novel nano-biosorbent materials from thermal catalytic degradation of green pea waste for cationic and anionic dye decolorization

The recycling of waste materials in wastewater decontamination has been an attractive discipline in zero discharge and energy recovery. Biochar/zeolite nanocomposite has been successfully synthesized as a cheap and eco-friendly material from a solid fraction obtained from the thermos-catalytic conversion of green pea agriculture waste (Pisum sativum). A dark-whitish solid was obtained from thermal pyrolysis at 450 °C with a heating rate of 27 °C/min for 15 min that was further subjected to alkaline chemical activation. The synthesized composites have been examined using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), transmission emission microscopy (TEM), and Brunauer-Emmet-Teller (BET) analyses. The successful preparation of biochar/zeolite nanocomposite was evident from characterization results with an average particle size of 30–40 nm with a high surface area of 15.3 m²/g. The material was evaluated as an eco-friendly adsorbent for decolorization of both cationic methylene blue dye (MB) and Congo red anionic dye (CR) using the batch technique. The influence of dosage, pH, temperature, initial dye concentration, and contact time were studied against the dye adsorption process. It was indicated that the material recorded maximum dye decolorization efficiencies of 87.5% at pH of 12 and 84.1% at pH of 2 for MB and CR, respectively. The optimum material dosage and contact time for dye decolorization were 5 g/l and 60 min, respectively. Thermodynamic parameters were calculated from the sorption process and revealed a negative charge of Gibbs free energy (Δ G^o) an indication of spontaneity and thermodynamic favorability. Positive enthalpy and entropy demonstrated the endothermic behavior and the disorderliness. Equilibrium adsorption results best fitted to the Langmuir isotherm model, while MB and CR adsorption kinetics were pseudo-second-order reactions.