Carbon aerogels derived from sodium lignin sulfonate embedded in carrageenan skeleton for methylene-blue removal

We reported an ecofriendly and cost-effective way to prepare carbon aerogels that were derived from sodium lignin sulfonate using κ-carrageenan as a skeleton for efficient dye adsorption. The scanning electron microscopy, nitrogen adsorption and desorption methods were used to analyze the surface configuration and porous structure of the samples. The specific surface area of the as-prepared carbon aerogels based on the Brunauer-Emmet-Teller method reached 594.6 m²/g and the average pore diameter based on the Barrett-Joyner-Halenda method was 2.2118 nm. X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy were used to analyze the elements and functional groups in the samples. The interaction between the as-prepared carbon aerogels and methylene blue (MB) involved π-π electron-donor-acceptor interaction, hydrogen bonding, and electrostatic interaction. The adsorption data at different conditions fitted the pseudo-second-order and Freundlich models well. ∆S° data demonstrated the increased randomness during adsorption. ∆H° and ∆G° data indicated that the interaction between MB and carbon aerogel was endothermic and spontaneous. The adsorption capacity of the as-prepared carbon aerogels for MB removal reached 421.94 mg/g. This work is promising for multi-valued use of lignin sulfonate from pulping wastewater and MB dye wastewater treatment.