The data set contains information about the TEM images of hydrochar alone, with phosphate (b), and with montmorillonite (c) at a pH of 6.0; SEM images of hydrochar alone (a, b), with montmorillonite (c, d), and with a combination of montmorillonite and phosphate (e, f) and the corresponding EDX spectra (g, h) at a pH of 6.0 (a, c, e, g) and 9.0 (b, d, f, h); .Capillary pressure curves (a,b) and pore size distribution determined by means of mercury intrusion porosimetry (MIP) (c,d) for the hydrochar samples prepared at pH 6.0 (a,c) and 9.0 (b,d); .FTIR spectra of the synthesized hydrochar in solutions with different pH values; Zeta potentials of hydrochar with and without montmorillonite (M) and/or phosphate (P), quartz sand and aluminum oxide-coated sand in a 10 mM NaCl solution as a function of the pH (a) and the concentrations of NaCl solution at pH 6.0 (b) and 9.0 (c); .Hydrodynamic radius of hydrochar with and without montmorillonite (M) in the absence or presence of phosphate (P) under different NaCl concentrations at pH 6.0 (a) and 9.0 (b); Observed (dots) and fitted (lines) breakthrough curves (BTCs) of 0.2 g L-1 hydrochar under different NaCl concentrations in uncoated sand (a, b) and aluminum oxide-coated sand (c, d) at pH 6.0 (a, c) and 9.0 (b, d), respectively. This dataset is associated with the following publication: 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(26): 32842-32855, (2020).