Valorization of Parthenium hysterophorus weed into biochar for adsorptive removal of industrial dyes from multi-pollutant aqueous systems

The invasive weed Parthenium hysterophorus poses global ecological, economic and agricultural challenges. Meanwhile, industrial dye effluents threaten waterbodies, prompting human health and environmental concerns. Therefore, to tackle problems related to Parthenium hysterophorus and dye effluents, this study aims to investigate performance of biochars derived from Parthenium hysterophorus- hydrochloric acid biochar (HPC) and sodium hydroxide biochar (NPC). These biochars were evaluated for removal of rhodamine-B (RB) and methyl orange (MO) dyes in mono-pollutant (MO/RB) and multi-pollutant (MO + RB) systems. The study examines influence of time (0 to 180 min), dose (0.1–3 g/L), pH (2 to 12) and concentration (1–100 mg/L) on dyes removal. Various kinetic and equilibrium models were used to fit adsorption data. Additionally, synergistic or antagonistic nature of sorption process was explored in multi-component system. HPC and NPC exhibited crystalline nature with pH_pzc of 7.2 and 8.6, respectively. HPC showed BET surface area of 186.16 m²/g, while NPC had 156.62 m²/g. At optimal conditions (60 min, 1 g/L dose and pH 6), HPC exhibited maximum sorption capacity of 14.10 mg/g (RB) and 16.67 mg/g (MO), and NPC showed 12.64 mg/g (RB) and 18.28 mg/g (MO). Results showed Langmuir isotherm and pseudo-second-order kinetic models best-fit for RB and MO dyes on both HPC and NPC. HPC and NPC demonstrated synergistic effect for removal of MO and RB dyes from multi-pollutant system. Overall, valorization of invasive weed into biochar and their effective application for simultaneous removal of industrial dyes presents sustainable solution for safeguarding aqueous environment and management of invasive weeds.