Seaweed-Derived Biochar for Effective Treatment of Dye-Contaminated Wastewater

Freshwater scarcity is a growing concern, exacerbated by industrial effluents containing dyes and other pollutants that endanger aquatic ecosystems. This study explores the potential of biochar sorbents, derived from renewable seaweed biomass, as a sustainable solution for water decontamination. Seaweed biomass (sargaço), collected from Portuguese seashores, was carbonized at 300 °C and 400 °C to produce biochar. Adsorption experiments with methylene blue (MB) revealed that carbonization at 400 °C, followed by ball milling, significantly enhanced adsorption performance. Langmuir isotherm analysis demonstrated a maximum adsorption capacity of 500 mg MB/g sorbent for the optimized biochar (400 °C, ball milled), with adsorption efficiency improving at elevated temperatures and pH levels up to 12. Infrared reflectance spectra of fresh and post-adsorption biochars confirmed the involvement of π–π interactions and hydrogen bonding in the adsorption mechanism. These findings highlight the potential of seaweed-derived biochar as an effective and eco-friendly solution for water purification.