This study was focused on the removal of Cr(VI) ions from electroplating wastewater by ultrasound-assisted adsorption onto activated carbon obtained from melon seed husk. The activated carbon was produced by carbonization of crushed melon seed husk at a temperature of 500 °C for 15 min and further activation using 1.0 M concentration of potassium chloride (KCl) at a temperature of 500 °C for 90 min in a muffle furnace. The obtained adsorption isotherm data were better fitted to the Langmuir

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... l than Freundlich model for adsorption both in the presence and absence of ultrasound (US). The adsorbent maximum adsorption capacity for Cr(VI) ion obtained from the Langmuir isotherms, were 5.059 mg/g and 2.031 mg/g both in the presence of ultrasound and its absence, respectively. The adsorption process in the presence and absence of ultrasound obeyed the pseudo-second-order kinetics. The SEM image of activated carbon before adsorption of metal ion revealed that the surface of activated carbon contains pores with different sizes and shapes, and also showed a significant change on the surface of activated carbon after interaction with Cr(VI) ions.