Fabrication of Mg-Doped Sargassum Biochar for Phosphate and Ammonium Recovery

Biochars prepared from macro-algae have a lower C/N ratio compared to lignocellulosic biochar, which is advantageous for direct nutrition. In particular, Sargassum, a marine macro-algae, has a high Mg content; hence, it can be expected to adsorb P and N simultaneously. In this study, Sargassum horneri biochar (SB), pyrolyzed at 400, 500, and 600 & DEG;C, was doped with innate Mg through water leaching, and nutrient recovery from the wastewater-mimicking solution was confirmed. The biochar pyrolyzed at 600 & DEG;C showed maximum Mg adsorption during water leaching, and the efficiency of K and Na removal was also high, at 92.7% and 91.9%, respectively. The addition of MgCl2 during pyrolysis and high ion exchange did not show distinct advantages for surface modification and nutrient adsorption. X-ray photoelectron spectroscopy analysis confirmed the participation of biochar in the surface adsorption of Mg and PO4 recovery. The PO4 sorption capacity of biochar reached > 120 mg & BULL;g(-1), while the sorption capacity for NH4 was low, at 22.8-28.2 mg & BULL;g(-1), suggesting that Mg-surface-doped SB presented excellent phosphorus recovery. Hence, upgrading an adsorbent as a wastewater-treatment material and soil ameliorant that recovers nutrients using innate Mg from Sargassum is possible through appropriate surface modification.

Automated summary

The study found that water leaching can recover nutrients from wastewater by incorporating innate magnesium into the biochar pyrolyzed from marine algae. Biochar pyrolyzed at 600°C exhibited the highest magnesium adsorption capacity and efficient removal of K and Na. The addition of MgCl2 during pyrolysis and high ion exchange did not show significant advantages in terms of surface modification and nutrient adsorption.