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Batch mode experiments were conducted to study the removal of hexavalent chromium (Cr(Ⅵ)) from aqueous solutions using ultrasound-assisted aqueous solution ball milling.The results show that the reduction rate of Cr(Ⅵ) by ultrasound-assisted aqueous solution ball milling was significantly faster than that by ball milling or ultrasound treatment alone,and an initial Cr(Ⅵ) concentration of 166 mg/L could be decreased to 0.35 mg/L at 120 min.The decisive factors,including initial concentration of Cr(Ⅵ),pH value,ultrasonic frequency and filling gas,were studied.It was found that the optimal ultrasonic frequency for ultrasound-assisted aqueous solution ball milling device was 20 kHz,and the rate of Cr(Ⅵ)reduction as a function of filling gas followed the order:Ar ＞ air ＞ N2 ＞ O2.Samples were characterized by X-ray diffraction,fluorescence measurements,atomic absorption and the diphenylcarbazide colorimetric method.The Cr(Ⅵ) transformed into a precipitate that could be removed from the contaminated water,after which the water could be reused.