pH‐Dependent Boron Adsorption by Na‐Montmorillonite

Abstract A simple phenomenological equation was derived and applied to boron adsorption by Na‐montmorillonite as a function of pH and boron concentration in solution. The equation, which is based on the assumption that B(OH) 3 , B(OH) 4 ‐ , and OH ‐ are all competing for the same adsorption sites, includes constants related to the binding energy K HB , K B , and K OH for the three species as well as the total boron adsorption capacity factor, T . Results of boron adsorption at three pH's were used to estimate the values of these parameters. Estimated values of T , K HB , K B , and K OH were 6.02 × 10 −6 mol/g, 194, 1,745, and 25,803 liters/mol, respectively. It was found that these values for the parameters could in turn be used to predict boron adsorption on Na‐montmorillonite systems at other pH values and boron concentrations. Results found for Na‐montmorillonite were consistent with those found by others in that boron adsorption varied with both pH and boron concentration, with maximum adsorption occurring at pH 9.3.