Magnetic mesoporous sodium citrate modified lignin for improved adsorption of calcium ions and methylene blue from aqueous solution

A novel magnetic lignin-based adsorbent modified with sodium citrate (L-SC@Fe3O4) was simply manufactured by one-step hydrothermal method to eliminate calcium ions and methylene blue from aqueous solution. Various characterization methods were applied to explore the structural morphological features of the obtained sample. The as-designed adsorbent possessed high specific surface area, rough surface and rich mesoporous structure. Adsorption experimental data accorded with the Langmuir isotherm with maximum adsorption amount of 339.4 mg/g and 281.4 mg/g for calcium ions and methylene blue, respectively. Kinetic data fitted well with the pseudo-second-order model. Furthermore, the adsorption mass transfer process of calcium ions and methylene blue was predicted by the pore volume diffusion model, virtually governed by intraparticle resistance. The adsorbent showed considerable efficiency toward calcium ions and methylene blue within a broad pH range of 4–8 and 4–10, separately. The resulting adsorbent also exhibited strong anti-salts interference and possessed good regenerability with magnetic separation feasibility. Altogether, the tailor-made magnetic adsorbent is promising as an efficient and sustainable adsorbent for calcium ions and methylene blue removal, illuminating the future design of competent adsorbents for scavenging metal ions and dyes from real complex waste liquid. [Display omitted] •L-SC@Fe3O4 was simply prepared by hydrothermal method to clear Ca2+ and MB.•L-SC@Fe3O4 had maximum uptaken amount of 339.4 and 281.4 mg/g for Ca2+/MB.•L-SC@Fe3O4 enabled high efficiency for Ca2+ /MB within pH range of 4–8 / 4–10.•The pore volume diffusion model predicted Ca2+/MB mass transfer process well.