Transportation Research Part D: Transport and Environment
Transportation Research Part D: Transport and Environment
4 years ago

Thermal air oxidation changes surface and adsorptive properties of black carbon (char/biochar)

Thermal air oxidation changes surface and adsorptive properties of black carbon (char/biochar)
In this study, we systematically investigated the effects of thermal air oxidation on the properties of biomass-derived black carbon (BC) made at carbonization temperatures (HTTs) of 300–700°C. BC produced by including air in the carbonization step was found to have a low surface area and underdeveloped pore structure. Substantial changes of BC were observed after post-pyrolysis thermal air oxidation (PPAO). Well-carbonized BC samples made anoxically at relatively high HTTs (600 and 700°C) showed, after PPAO, significant increases in N2 BET surface area (SA) (up to 700 times), porosity (<60Å) (up to 95 times), and adsorptivity (up to 120 times) of neutral organic species including two triazine herbicides and one natural estrogen. Partially carbonized BC made at a lower HTT (300 or 400°C) showed moderate increases in these properties after PPAO, but a large increase in the intensity of Fourier transform infrared spectroscopy bands corresponding to various oxygen-containing functional groups. Well-carbonized BC samples, on the other hand, were deficient in surface oxygen functionality even after the PPAO treatment. Adsorption of the test organic compounds on BC generally trended with BET SA when it was less than 300m2/g, but BET SA was poorly predictive of adsorption when it was greater than 300m2/g. Overall, our results suggest that thermal reactions between molecular oxygen and BC 1) increase surface oxygen functionality more effectively for low-HTT than for high-HTT BC samples; 2) increase SA and porosity (<60Å) especially for high-HTT BC samples; and 3) create new adsorption sites and/or relieve steric restriction of organic molecules to micropores, thereby enhancing the adsorptivity of BC. These results will prove useful not only for understanding the fate of environmental BC but also in devising strategies for improving the practical performance of the engineered form of BC (i.e., biochar).

Publisher URL: www.sciencedirect.com/science

DOI: S0048969717330693

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.