Valorization of lignocellulosic solid waste obtained from essential oil industry for bio-oil production and dye removal

Abstract This research underscores the potential of utilizing carrot seed waste and its derived biochar as effective solutions for waste management and wastewater treatment applications. This waste is thoroughly characterized for its chemical, thermal, and morphological properties. It is found to be rich in carbon and cellulose, proved suitable for pyrolysis, yielding 25% biochar and 45% bio-oil, with the latter containing carboxylic acids and hydrocarbons. Biochar, characterized by a high surface area of around 300 m2/g, micro- and mesopores, and the presence of metal oxides, demonstrated outstanding adsorption properties. Biochar shows superior performance compared to raw carrot seed waste, mainly in the context of methylene blue dye removal, obtaining an impressive removal efficiency of 99%. Subsequently, optimization of pH, adsorbent dosage, dye concentration, and reaction temperature is carried out using biochar as the adsorbent to maximize dye removal and adsorption capacity, whereas adsorption kinetics follows pseudo-first-order kinetics.