اندازه گيري اكسيژن خواهي شيميايي ( COD ) در محيط هاي شور با استفاده از روش اسپكتروفتومتري

Measurement of chemical oxygen demand (COD) in saline environments using spectrophotometric method

ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﻣﺰاﺣﻤﺖﻫﺎي ﯾﻮنﻫﺎي ﮐﻠﺮاﯾﺪ در ﻣﺤﯿﻂﻫﺎي ﺷﻮر، ﺳﻨﺠﺶ اﮐﺴﯿﮋن ﺧﻮاﻫﯽ ﺷﯿﻤﯿﺎﯾﯽ )COD( ﺑﺎ روشﻫﺎي اﺳﺘﺎﻧﺪارد ﻣﻮﺟﻮد ﻧﻈﯿﺮ اﮐﺴﯿﺪاﺳﯿﻮن اﺳﯿﺪي ﺑﺎ ديﮐﺮوﻣﺎت ﭘﺘﺎﺳﯿﻢ ﻣﻤﮑﻦ ﻧﯿﺴﺖ ﻟﺬا ﯾﺎﻓﺘﻦ ﺳﺎﯾﺮ روشﻫﺎ ﮐﻪ ﻣﺰاﺣﻤﺖﻫﺎي ﻋﻨﻮانﺷﺪه در اﻧﺪازهﮔﯿﺮي COD ﺗﺄﺛﯿﺮي ﻧﺪاﺷﺘﻪ ﺑﺎﺷﺪ ﻣﯽﺗﻮاﻧﺪ راﻫﮕﺸﺎ ﺑﺎﺷﺪ. ﻣﻘﺎﻟﻪ ﺣﺎﺿﺮ ﺑﻪ اراﺋﻪ روش اﺳﭙﮑﺘﺮوﻓﺘﻮﻣﺘﺮي ﺟﻬﺖ ﺳﻨﺠﺶ COD ﭘﺮداﺧﺘﻪ اﺳﺖ. ﺟﻬﺖ ﺗﻬﯿﻪ ﻣﺤﻠﻮلﻫﺎي ﮐﺎﻟﯿﺒﺮاﺳﯿﻮن COD ﻣﻄﺎﺑﻖ روش اﺳﺘﺎﻧﺪارد از ﭘﺘﺎﺳﯿﻢ ﻫﯿﺪروژن ﻓﺘﺎﻟﺎت اﺳﺘﻔﺎده ﺷﺪ. ﻣﺤﻠﻮلﻫﺎ در دو ﻣﺤﯿﻂ آب ﻣﻘﻄﺮ و آب ﺷﻮر ﺗﻬﯿﻪ ﮔﺮدﯾﺪ. ﺑﺮ اﺳﺎس ﻧﺘﺎﯾﺞ اﯾﻦ ﺗﺤﻘﯿﻖ، ﺷﻮري آب ﺑﺮ ﺟﺬب ﻧﻮري در ﻃﻮل ﻣﻮج 254 ﻧﺎﻧﻮﻣﺘﺮ ﺗﺄﺛﯿﺮي ﻧﺪاﺷﺘﻪ اﺳﺖ. ﺑﻪ ﻣﻨﻈﻮر ﻣﻘﺎﯾﺴﮥ روش اراﺋﻪﺷﺪه در ﻣﻄﺎﻟﻌﮥ ﺣﺎﺿﺮ ﺑﺎ روش اﺳﺘﺎﻧﺪارد اﮐﺴﯿﺪاﺳﯿﻮن اﺳﯿﺪي ﺑﺎ ديﮐﺮوﻣﺎت ﭘﺘﺎﺳﯿﻢ ﻫﺮ دو روش ﺑﺮ روي 33 ﻧﻤﻮﻧﻪ ﻓﺎﺿﻠﺎب اﺟﺮا ﺷﺪ. ﺑﺮ اﺳﺎس ﯾﺎﻓﺘﻪﻫﺎي ﺣﺎﺻﻞ از اﯾﻦ ﺗﺤﻘﯿﻖ، ﺑﺮازش ﻣﻨﺎﺳﺒﯽ ﺑﯿﻦ دو روش ﻋﻨﻮانﺷﺪه وﺟﻮد دارد )0/98 =R2(، ﻟﺬا ﭘﯿﺸﻨﻬﺎد ﻣﯽﮔﺮدد ﻣﻌﺎدﻟﮥ ﺳﻨﺠﺶ COD ﺑﺮ اﺳﺎس ﺟﺬب ﻧﻮري در ﻃﻮل ﻣﻮج 254 ﻧﺎﻧﻮﻣﺘﺮ ﺑﺮاي ﻣﺤﯿﻂﻫﺎي ﺷﻮر و ﻏﯿﺮ ﺷﻮر ﻣﻮرد اﺳﺘﻔﺎده ﻗﺮار ﮔﯿﺮد و ازآﻧﺠﺎﯾﯽﮐﻪ در روش ﭘﯿﺸﻨﻬﺎدي ﺗﺤﻘﯿﻖ ﺣﺎﺿﺮ، ﻣﻮاد ﺷﯿﻤﯿﺎﯾﯽ آﻟﺎﯾﻨﺪه ﺧﺼﻮﺻﺎً ﺗﺮﮐﯿﺒﺎت ﺟﯿﻮه و ﻧﻘﺮه ﺑﮑﺎر ﺑﺮده ﻧﻤﯽﺷﻮد، ﺑﻪ ﻋﻨﻮان روش دوﺳﺘﺪار ﻣﺤﯿﻂزﯾﺴﺖ ﻣﻌﺮﻓﯽ ﮔﺮدد.

Due to the interference of chloride ions in saline environments, chemical oxygen demand (COD) is not possible with existing standard methods such as acid oxidation with potassium dichromate. Therefore, finding a method for COD that do not has the effect of the interfering, it can be helpful. The present research aims to provide spectrophotometric method for COD measurement. Potassium hydrogen phthalate was used to prepare COD calibration solutions according to the standard method. The solutions were prepared in distilled water and saline water. Based on the results of this study, water salinity did not affect absorption at 254 nm. In order to compare the method presented in this study, the standard method of oxidation of acid with potassium dichromate was carried out on 33 samples of wastewater. According to the findings, there is a good fit between the two methods (R2 = 0.98), therefore, it is suggested that the COD measurement equation based on absorption at 254 nm wavelength for saline and fresh environment. Because the proposed method of the present study does not used Chemicals, especially mercury and silver compounds, it can be suggested as an environmentally friendly method.