Abiotic sorption experiments were conducted with four carbon substrates (glucose, glutamic acid, oxalic acid, para-hydroxybenzoic acid) on four clay minerals (kaolinite, feldspar, ferrihydrite, amorphous aluminum hydroxide) after sterilization by gamma irradiation. The adsorption isotherms were carried across a range of substrate carbon concentrations (0, 20, 100, and 500 mg carbon per L) and pH conditions (approximately 5 – 9) in a background of 10 mM NaCl for 48 hours. The data release contains measured pH values and carbon concentrations before and after the sorption experiments. The release provides derived values of carbon sorption (e.g., carbon sorbed per mineral surface area) as well as characterization of the minerals (e.g., surface area, x-ray diffraction patterns). Users can calculate the derived values independently with ancillary data in the release (e.g., masses, volumes, surface areas). The file "data_dictionary" provides descriptions, valid ranges, and units for all fields in the data files.