Biochar from the co-pyrolysis of Saccharina japonica and goethite as an adsorbent for basic blue 41 removal from aqueous solution

The effects of utilizing goethite (5%, 10%, and 20%) in co-pyrolysis with low-lignin macroalgae, Saccharina japon-ica, on the carbon sequestration potential, magnetic, physicochemical, and dye (basic blue 41, BB41) removal properties of the resulting biochar were investigated. Biochars exhibited more aromaticity, better magnetic prop-erties, and insignificant alterations to their point of zero charges (11.07 +/- 0.03 to 10.59 +/- 0.01) with goethite increment. Optimum conditions for high organic matter conversion and carbon preservation occurred using 5% goethite. Adsorption experiments showed that BB41 adsorption was highly pH-dependent, equilibrated later (from 12 h to 24 h) after goethite modification, and was best fitted to the pseudo-second-order model (higher R-2 and lower SSE values). Langmuir monolayer adsorption capacity for BB41 was the highest amongst carbona-ceous adsorbents in the literature [1494 mg/g (pristine); 1216 mg/g (5% goethite)]; initial BB41 concentration of 2000 mg/L at 30 degrees C and pH 8. The main governing mechanisms involved ion exchanges, hydrogen bonding, pi-pi interaction and pore-filling. Overall, low goethite amount (5%), co-pyrolyzed with macroalgae, offers an econom-ically and environmentally effective way to produce magnetic biochar with enhanced carbon sequestration po-tential and superb cationic dye removal performance for environmental remediation applications. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Utilizing goethite in co-pyrolysis with low-lignin macroalgae can enhance the properties of resulting biochar, improving its carbon sequestration potential and dye removal efficiency. Optimal conditions were found with 5% goethite, leading to biochars with increased aromaticity, magnetic properties, and superior adsorption of the dye BB41.