Charge properties ofmixtures ofminerals with variable and constant surface charge

Surface charge of mixtures of lepidocrocite and i\lite determined by adsorption of potentia l-determining and electrolyte ions is studied as a functi on of pH and NaCI concentration. Deviations between results oblained by both methods were a fu nction of the ill ile content of the mixtures, and can be mainly attributed lO coatings of hydroxyalum inium compl exes on the constant charge surfaces of the clay mineral , which can reacl wit h H + ion s or re lease exchange siles by precipi lat ion of well-formed hydroxides. These coatings of aluminium complexes can cause H+ consum ptions similar to those due to lepidocrocite. Sorne ideas a re pul forwa rd for modell ing charge properties of mixed systems.