Soils contain many kinds of inorganic and organic particles with at least one dimension in the nanoscale or colloidal range (<100 nm). Well-known examples are clay minerals, metal (hydr)oxides, and humic substances, while allophane and imogolite are abundant in volcanic soils. Apparently, only a small proportion of nanoparticles in soil occur as discrete entities. Organic colloids in soil, for example, are largely associated with their inorganic counterparts or form coatings over mineral surfaces. For this reason, individual nanoparticles are difficult to separate and collect from the bulk soil, and extraction yields are generally low. By the same token, the characterization of soil nanoparticles often requires advanced analytical and spectroscopic techniques. Because of their large surface area and the presence of surface defects and dislocations, nanoparticles in soil are very reactive towards external solute molecules. The focus of research in recent years has been on the interactions of nanoparticles with environmental pollutants and on their impact on the movement, fate, and bioavailability of contaminants.
1 January 2017 in Science of The Total Environment
Waste residues produced by agricultural and forestry industries can generate energy and are regarded as a promising source of sustainable fuels. Pyrolysis, where waste biomass is heated under low-oxygen conditions, has recently attracted attention as a means to add value to these residues. The material is carbonized and yields a solid product known as biochar. In this study, eight types of biomass were evaluated for their suitability as raw material to produce biochar. Material was pyrolyzed at either 350 °C or 500 °C and changes in ash content, volatile solids, fixed carbon, higher heating value (HHV) and yield were assessed. For pyrolysis at 350 °C, significant correlations (p < 0.01) between the biochars’ ash and fixed carbon content and their HHVs were observed. Masson pine wood and Chinese fir wood biochars pyrolyzed at 350 °C and the bamboo sawdust biochar pyrolyzed at 500 °C were suitable for direct use in fuel applications, as reflected by their higher HHVs, higher energy density, greater fixed carbon and lower ash contents. Rice straw was a poor substrate as the resultant biochar contained less than 60% fixed carbon and a relatively low HHV. Of the suitable residues, carbonization via pyrolysis is a promising technology to add value to pecan shells and Miscanthus.