Production and characterization of a high value-added seaweed-derived biochar: Optimization of pyrolysis conditions and evaluation for sediment treatment

Biochar is a promising material for removing contaminants in sediments. Here, thermal carbonization was carried out to convert a brown seaweed (Sargassum duplicatum) into a high value-added biochar, which was used to activate peroxymonosulfate (PMS) in environmental remediation applications. XRD, FTIR, XPS, C-H-O elemental analysis, and SEM results showed that pyrolysis temperature (300?700 ?C) had a significant influence on the crystal structure, surface functional groups, chemical composition, morphology and porosity of the brown seaweed-derived biochar (BSB). When the biochar samples were tested with PMS for removing polycyclic aromatic hydrocarbons (PAHs, a type of carcinogenic and refractory organic compounds) from marine sediments, pyrolysis temperature also showed crucial effects, and the sample pyrolyzed at 700 ?C was most effective for the oxidative removal of PAHs. Under the optimum conditions (pH0 = 3.0, [BSB] =3.0 g/L, [PMS]:?[PAH] = 1:1, and 10 h reaction time), 77 % of PAHs was eliminated with the maximum degradation rates of 87, 79, 67, 55, and 56 % for the 6-ring, 5-ring, 4-ring, 3-ring, and 2-ring PAHs, respectively. EPR results confirmed that SO4?? and HO? radicals play main roles in the catalytic degradation of PAHs. Based on these results, the sustainably produced BSB has good prospects for the seaweed bioeconomy and remediating organics-contaminated sediments.

Automated summary

Biochar derived from brown seaweed through thermal carbonization showed good potential in oxidatively removing polycyclic aromatic hydrocarbons (PAHs) from marine sediments. Under optimal conditions, the biochar demonstrated effective degradation of PAHs and has promising applications in seaweed bioeconomy and remediating organics-contaminated sediments.