Science Inventory

Surface Heterogeneity Mediated Transport of Hydrochar Nanoparticles in Heterogeneous Porous Media

Citation:

Yang, J., M. Chen, H. Yang, N. Xu, G. Feng, Z. Li, C. Su, AND D. Wang. Surface Heterogeneity Mediated Transport of Hydrochar Nanoparticles in Heterogeneous Porous Media. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH. Ecomed Verlagsgesellschaft AG, Landsberg, Germany, 27:32842-32855, (2020). https://doi.org/10.1007/s11356-020-09482-w

Impact/Purpose:

Hydrochar may be used as a soil amendment or adsorbent for environmental remediation. Information is lacking about the effects of phosphate and clay minerals on fate and transport of hydrochar. This research shows that the reversible deposition of hydrochar was significantly different between pH 6.0 and pH 9.0, which can be attributed to the distinct surface characteristics of hydrochar at pH7.0. The deposition of hydrochar was much greater in Al-coated sand than in uncoated sand, especially at higher NaCl concentrations and lower pH. However, in Al-coated sand, deposition of hydrochar was alleviated appreciably due to the preferential attachment of M to the Al oxide coating. Interestingly, M substantially increased the hydrochar retention on uncoated sand by the formation of nanoaggregates between hydrochar and M. The facilitated transport of hydrochar by P depended on solution pH, regardless of the collector’s heterogeneity (uncoated and Al-coated sand). Numerical simulations using the commonly used two-site kinetic attachment model (TSKAM) suggested that a combination of the first-order reversible retention coefficients (k1d/k1) and the first-order irreversible retention coefficient (k2) can be used to describe the hydrochar transport behavior in the presence of M and/or P. Overall, our findings indicate that cautions should be taken when using hydrochar to clean-up contaminated sites particularly in the presence of clays and phosphate, potentially due to hydrochar-facilitated transport of contaminants in the subsurface. The results can be used by program offices, states, and industries for evaluating environmental risks of biochar.

Description:

Hydrochar has recently showed great potential for soil amendment, bioenergy production, and wastewater treatment. Thus, unravelling the mechanisms controlling the mobility of hydrochar in the subsurface is a high priority research frontier. Herein, the effects of phosphate (P) and clay particles (montmorillonite, M) on the transport behaviors of hydrochar in water-saturated porous media (uncoated and aluminum (Al) oxide-coated sands) were explored at environmentally-relevant concentrations (1-50 mM) of NaCl. Our results showed that the reversible deposition of hydrochar was significantly different between pH 6.0 and pH 9.0, which can be attributed to the distinct surface characteristics of hydrochar at pH7.0. The deposition of hydrochar was much greater in Al-coated sand than in uncoated sand, especially at higher NaCl concentrations and lower pH. However, in Al-coated sand, deposition of hydrochar was alleviated appreciably due to the preferential attachment of M to the Al oxide coating. Interestingly, M substantially increased the hydrochar retention on uncoated sand by the formation of nanoaggregates between hydrochar and M. The facilitated transport of hydrochar by P depended on solution pH, regardless of the collector’s heterogeneity (uncoated and Al-coated sand). Numerical simulations using the commonly used two-site kinetic attachment model (TSKAM) suggested that a combination of the first-order reversible retention coefficients (k1d/k1) and the first-order irreversible retention coefficient (k2) can be used to describe the hydrochar transport behavior in the presence of M and/or P. Overall, our findings indicate that cautions should be taken when using hydrochar to clean-up contaminated sites particularly in the presence of clays and phosphate, potentially due to hydrochar-facilitated transport of contaminants in the subsurface.

Record Details:

Record Type: DOCUMENT ( JOURNAL/ PEER REVIEWED JOURNAL)
Product Published Date: 09/01/2020
Record Last Revised: 09/09/2020
OMB Category: Other
Record ID: 349636