en تخصصي Special مقاله اصیل Original Article <div style="text-align: justify;">Background: Considering the carcinogenic effects of heavy metals, such as chromium, it is essential to remove these elements from water and wastewater. Direct osmosis is a new membrane technology, which can be a proper alternative to conventional chromium removal processes.<br> Methods: The wastewater samples were collected from an electroplating unit, located in Alborz industrial city, Qazvin, Iran. Magnesium chloride was used as the draw solution, and a semipermeable membrane (Aquaporin) was used in this study. The experiments were designed, using response surface methodology (RSM) and central composite design (CCD) with draw solution concentration (0.5- 1.5 M), feed solution concentration (4-12 mg/L), and experiment time (30-90 minutes) as variable factors. The chromium concentration and water flux were also measured, based on atomic absorption spectrophotometry and water flux equation, respectively.<br> Results: Direct osmosis was highly efficient in chromium removal and water recycling. Water flux and chromium removal efficiency were 15.6 LMH and 85.58%, respectively, under optimal conditions (draw solution = 1.27 mol/L, feed solution = 4 mg/L, and experiment time = 90 min). In terms of validity,<br> the results predicted by the quadratic polynomial model were in good agreement with the responses reported in the laboratory.<br> Conclusion: In direct osmosis, the use of magnesium chloride as the draw solution resulted in the acceptable chromium removal from electroplating wastewater. Using this method, chromium concentration in wastewater reduced to a level lower than the discharge standards, established by Iran&rsquo;s<br> Department of Environment.</div> Direct osmosis, Chromium removal, Electroplating, Optimization 113 120 http://ehemj.com/browse.php?a_code=A-10-407-7&slc_lang=en&sid=1 Zohreh Naghdali z.naghdali@gmail.com 10031947532846005318 10031947532846005318 No Student Research Committee, Qazvin University of Medical Sciences, Qazvin, Iran Soleyman Sahebi soleysahebi@gmail.com 10031947532846005319 10031947532846005319 No Research and Technology Center of Membrane Processes (RTCMP), School of Chemical, Petroleum and Gas Engineering, Iran University of Science and Technology (IUST), Tehran, Iran Reza Ghanbari ghanbari33@gmail.com 10031947532846005320 10031947532846005320 No Department of Environmental Health Engineering, School of Health, Qazvin University of Medical Sciences, Qazvin, Iran Milad Mousazadeh m.milad199393@gmail.com 10031947532846005321 10031947532846005321 No Student Research Committee, Qazvin University of Medical Sciences, Qazvin, Iran Hamzeh Ali Jamali jamalisadraei@yahoo.com 10031947532846005322 10031947532846005322 Yes Corresponding author: Department of Environmental Health Engineering, School of Health, Qazvin University of Medical Sciences, Qazvin, Iran