The behavior and structure of supercritical fluid (SCF) mixtures in contact with an adsorptive solid surface have been determined by the nonuniform Ornstein-Zernike integral equations for the molecular distributions. In this work, we examine the behavior of attractive and repulsive mixtures (A = SCF and B = solute) with respect to adsorption on planar substrates. Properties and fluid structures in the vicinity of the wall (W) are explored. The behavior of a dilute solute B adsorbed to wall W from solvent A (i.e. system AS B/W) is described for the cases where ASB form either an attractive SCF mixture or a repulsive SCF mixture for a temperature where the solvent A is slightly supercritical and for density conditions where A is subcritical, critical, and supercritical. We examine the degree of preferential adsorption of B vis-g-vis the competitive interactions with A and W. This shows the relative adsorptions, while covering a range of states. We find evidence of solute rejection by the SCF toward the wall, when the mixture A + B changes character from ＇attractive＇ to ＇repulsive＇. The numerical work is very demanding in computer memory and time. Thus, full numerical convergence has not been achieved in the calculations reported here. We have attained partial convergence. However, the qualitative trends are considered unaltered. The mechanisms of solute adsorption in SCF have been demonstrated at a fundamental molecular level.