The unique chemical and physical properties of gold are increasingly being sought for use in a growing number of industrial and medical applications. The agricultural residue spent buckwheat hulls (60 mesh) modified with organodiphosphonic acid (denoted as ODPA-BH) was successfully developed and characterized, and cellulose with an organodiphosphonic acid group was calculated at the B3LYP/6-31G(d) level. ODPA-BH was employed to adsorb Au(III) ions in both spiked samples and industrial wastewater samples, and the relevant adsorption kinetics and isotherms were investigated. A better interpretation for the experimental data was obtained with the Langmuir isotherm equation, and the maximum adsorption capacity for Au(III) was found to be 465.16 mg/g at 35 degrees C. The adsorption kinetics were modeled by a pseudo-second-order rate equation, and the thermodynamic parameters Delta G, Delta H, and Delta S were determined to be -8.89 kJ.mol(-1), 70.93 kJ.mol(-1), and 257.25 J.K-1.mol(-1), respectively.