I-Chemical oxygen demand (COD): irula elingabonakali lekhwalithi yamanzi enempilo

Endaweni esihlala kuyo, ukuphepha kwekhwalithi yamanzi kuyisixhumanisi esibalulekile. Nokho, izinga lamanzi alibonakali ngaso sonke isikhathi, futhi lifihla izimfihlo eziningi esingakwazi ukuzibona ngokuqondile ngamehlo ethu enqunu. Isidingo somoya-mpilo wekhemikhali (COD), njengepharamitha eyinhloko ekuhlaziyeni izinga lamanzi, sifana nerula engabonakali engasisiza ukuba silinganise futhi sihlole okuqukethwe kokungcoliswa kwemvelo emanzini, ngaleyo ndlela kwembule isimo sangempela sekhwalithi yamanzi.
Cabanga nje uma indle ekhishini lakho ivinjiwe, kuzoba nephunga elibi? Lelo phunga empeleni likhiqizwa ukuvutshelwa kwento ephilayo endaweni engenawo umoya-mpilo. I-COD isetshenziselwa ukukala ukuthi ingakanani i-oxygen edingekayo uma lezi zinto eziphilayo (kanye nezinye izinto ezingafakwa oksijini, njenge-nitrite, usawoti oxakile, i-sulfide, njll.) kufakwa i-oxidized emanzini. Kalula nje, ukuphakama kwenani le-COD, kulapho umzimba wamanzi ungcoliswa izinto eziphilayo.
Ukutholwa kwe-COD kunokubaluleka okungokoqobo okubaluleke kakhulu. Ingenye yezinkomba ezibalulekile zokulinganisa izinga lokungcoliswa kwamanzi. Uma inani le-COD liphezulu kakhulu, kusho ukuthi umoya-mpilo oncibilikisiwe emanzini uzosetshenziswa ngobuningi. Ngale ndlela, izinto eziphilayo zasemanzini ezidinga umoya-mpilo ukuze ziphile (njengezinhlanzi nezimfanzi) zizobhekana nenkinga yokusinda, futhi zingase ziholele ngisho nasentweni “yamanzi afile”, okubangela ukuwohloka kwendawo yonke. Ngakho-ke, ukuhlola okuvamile kwe-COD kufana nokuhlola ikhwalithi yamanzi, ukuthola nokuxazulula izinkinga ngesikhathi.
Ungalithola kanjani inani le-COD lamasampula amanzi? Lokhu kudinga ukusetshenziswa “kwezikhali” ezithile zochwepheshe.
Indlela esetshenziswa kakhulu yi-potassium dichromate. Kuzwakala kuyinkimbinkimbi, kodwa isimiso empeleni silula kakhulu:
Isigaba sokulungiselela: Okokuqala, sidinga ukuthatha inani elithile lesampula lamanzi, bese sengeza i-potassium dichromate, “i-super oxidant”, bese sengeza i-silver sulfate njenge-catalyst ukwenza ukusabela kucace kakhudlwana. Uma kukhona i-chloride ion emanzini, kufanele ivikelwe nge-mercuric sulfate.
Heating reflux: Okulandelayo, shisisa lezi zingxube ndawonye futhi uzivumele zisabele ekubiliseni i-sulfuric acid. Le nqubo ifana nokunikeza isampula yamanzi "i-sauna", eveza ukungcola.
Ukuhlaziywa kwe-Titration: Ngemva kokuphela kokusabela, sizosebenzisa i-ammonium ferrous sulfate, “i-ejenti yokunciphisa”, ukuze sihlanganise i-potassium dichromate esele. Ngokubala ukuthi ingakanani i-ejenti yokunciphisa esetshenzisiwe, singakwazi ukwazi ukuthi ingakanani i-oxygen eyasetshenziswa ukuze kufakwe ukungcola emanzini.
Ngaphandle kwendlela ye-potassium dichromate, kunezinye izindlela ezifana nendlela ye-potassium permanganate. Zinezinzuzo zazo, kodwa inhloso iyafana, okuwukulinganisa ngokunembile inani le-COD.
Njengamanje, indlela ye-spectrophotometry yokugaya ngokushesha isetshenziswa kakhulu ukuthola i-COD emakethe yasekhaya. Lena indlela esheshayo yokuthola i-COD esekelwe endleleni ye-potassium dichromate, futhi isebenzisa izinga lenqubomgomo elithi “HJ/T 399-2007 Ukunqunywa Kwekhwalithi Yamanzi Ye-Chemical Oxygen Demand Rapid Digestion Spectrophotometry”. Kusukela ngo-1982, uMnu. Ji Guoliang, umsunguli we-Lianhua Technology, usungule i-COD yokugaya ukudla okusheshayo kwe-spectrophotometry kanye nezinsimbi ezihlobene. Ngemva kweminyaka engaphezu kwengu-20 yokukhuthazwa nokuduma, yagcina isiyindinganiso kazwelonke yezemvelo ngo-2007, okwaletha ukutholwa kwe-COD enkathini yokutholwa ngokushesha.
I-COD ye-spectrophotometry yokugaya okusheshayo eyakhiwe yi-Lianhua Technology ingathola imiphumela ye-COD enembile phakathi nemizuzu engama-20.
1. Thatha u-2.5 ml wesampula, engeza i-reagent D ne-reagent E, bese unyakazisa kahle.
2. Shisisa i-COD digester ibe yi-165 degrees, bese ufaka isampula futhi ugaye imizuzu eyi-10.
3. Ngemuva kokuthi isikhathi sesiphelile, khipha isampula bese uyipholisa imizuzu emi-2.
4. Faka u-2.5 ml wamanzi acwengekile, unyakazise kahle bese uwapholisa emanzini imizuzu emi-2.
5. Faka isampula ku-I-COD photometerngoba colorimetry. Asikho isibalo esidingekayo. Imiphumela iboniswa ngokuzenzakalelayo futhi iphrintwe. Kuyasiza futhi kuyashesha.