Nitrogen-doped porous biochar derived from marine algae for efficient solid-phase microextraction of chlorobenzenes from aqueous solution

Highlights: • Marine algae were utilized to fabricate nitrogen-doped porous biochar. • Nitrogen-doped porous biochar possessed developed pore structure, high graphitization degree and strong hydrophobicity. • Nitrogen-doped porous biochar-coated fiber exhibited higher extraction efficiency than commercial fibers. • A sensitive method was developed to rapidly determine trace chlorobenzenes in aqueous solution. Nitrogen-doped porous biochar (NPB) with a large specific surface area, wide pore size distribution, graphitized structure, nitrogen doping, and hydrophobicity was fabricated by high-temperature modification of algal biochar with potassium carbonate. This NPB was then uniformly coated on stainless steel wire as a novel solid-phase microextraction (SPME) fiber. The extraction efficiency of NPB-coated fiber for seven chlorobenzenes (CBs) was excellent; it was 1.0–112.2 times higher than that of commercial SPME fibers. A trace determination method was developed for seven CBs in water with the optimized extraction conditions by NPB-coated fiber and gas chromatography–electron capture detector, which showed wide linear ranges (1–1000 ng L⁻¹), low detection limits (0.007–0.079 ng L⁻¹), great repeatability (2.5–6.5% for intra-day, and 3.1–6.8% for inter-day), and excellent reproducibility (3.5–6.3%, n = 5). The practicality of the developed method was evaluated using real water samples and showed great recoveries (89.55–105.19%). This study showed that low-cost biomass wastes could be converted to advanced biochar materials by a facile method, and displayed excellent performance in SPME applications.