Barium sulfate aggregates with an average size of 0.5μm were synthesized at pH 7, directed by ethylenediaminetetraacetic acid （EDTA） anions. The particle morphology, chemical composition, and size distribution of the BaSO4 aggregates were characterized. The as-synthesized BaSO4 particles were spherical and comprised many interconnected nanoballs, of which the surface properties were affected by the EDTA anions. The adsorption of EDTA anions reversed the charge and weakened the surface polarity of BaSO4, instigating the formation of aggregates by a self-assembly and transformation process. The resulting BaSO4 particles at pH 9-10 were ellipsoidal and featured smooth surfaces. Based on the zeta potential of BaSO4, variations in the morphology induced by changes in pH were closely related to the adsorption of mono- and multi-valent anions onto the electrical double layer of BaSO4.
