Isidingo somoya-mpilo wamakhemikhali sibuye sibizwe ngesidingo somoya-mpilo wamakhemikhali (isidingo se-oksijini samakhemikhali), esibizwa nge-COD. Kuwukusetshenziswa kwama-chemical oxidants (afana ne-potassium permanganate) ukuze kufakwe i-oxidize futhi kubolise izinto ezi-oxidizable emanzini (njengezinto eziphilayo, i-nitrite, usawoti oyinsimbi, i-sulfide, njll.), bese kubala ukusetshenziswa komoya-mpilo ngokusekelwe enanini lensalela. i-oxidant. Njengesidingo se-biochemical oxygen (BOD), iyinkomba ebalulekile yokungcoliswa kwamanzi. Iyunithi ye-COD ingu-ppm noma mg/L. Uma inani lincane, ukungcoliswa kwamanzi kuba lula.
Izinto ezinciphisayo emanzini zihlanganisa izinto ezihlukahlukene eziphilayo, i-nitrite, i-sulfide, usawoti oyinsimbi, njll. Kodwa okuyinhloko yizinto eziphilayo. Ngakho-ke, i-chemical oxygen demand (COD) ivame ukusetshenziswa njengenkomba yokukala inani lezinto eziphilayo emanzini. Uma sikhulu isidingo somoya-mpilo ngamakhemikhali, kuba kubi nakakhulu ukungcoliswa kwamanzi yizinto eziphilayo. Ukunqunywa kwesidingo somoya-mpilo wamakhemikhali (COD) kuyahlukahluka ngokunqunywa kokunciphisa izinto kumasampula amanzi kanye nendlela yokunquma. Izindlela ezisetshenziswa kakhulu njengamanje i-asidi ye-potassium permanganate oxidation nendlela ye-potassium dichromate oxidation. Indlela ye-potassium permanganate (KMnO4) inezinga eliphansi le-oxidation, kodwa ilula kakhulu. Ingasetshenziselwa ukunquma inani elihlobene lokuqhathanisa lokuqukethwe kwemvelo kumasampula amanzi namanzi ahlanzekile angaphezulu kanye namasampula amanzi angaphansi komhlaba. Indlela ye-potassium dichromate (K2Cr2O7) inezinga eliphezulu le-oxidation kanye nokuzala okuhle. Ilungele ukunquma inani eliphelele lezinto eziphilayo kumasampula amanzi ekuqaphelweni kwamanzi angcolile.
Izinto eziphilayo ziyingozi kakhulu ezinhlelweni zamanzi zezimboni. Amanzi aqukethe inani elikhulu lezinto eziphilayo azongcolisa ama-resin exchange ion lapho edlula ohlelweni lokukhipha usawoti emanzini, ikakhulukazi ama-anion exchange resins, okuzonciphisa amandla okushintshanisa inhlaka. Izinto eziphilayo zingancishiswa cishe ngamaphesenti angu-50 ngemva kokwelashwa kwangaphambili (i-coagulation, ukucaciswa nokuhlunga), kodwa azikwazi ukukhishwa ohlelweni lokukhipha usawoti emanzini, ngakho-ke kuvame ukungeniswa kubhayela ngamanzi okuphakelayo, okunciphisa inani le-pH lebhayela. amanzi. Ngezinye izikhathi izinto eziphilayo zingase zilethwe ohlelweni lwesitimu bese amanzi e-condensate, okuzonciphisa i-pH futhi kubangele ukugqwala kwesistimu. Okuqukethwe okuphezulu kwezinto eziphilayo ohlelweni lwamanzi ajikelezayo kuzokhuthaza ukuzalana kwama-microbial. Ngakho-ke, kungakhathaliseki ukuthi i-desalination, amanzi e-boiler noma uhlelo lwamanzi ajikelezayo, i-COD ephansi, ingcono, kodwa ayikho inkomba yokukhawulela ehlanganisiwe. Uma i-COD (indlela ye-KMnO4) > 5mg/L ohlelweni lwamanzi okupholisa ajikelezayo, ikhwalithi yamanzi isiqalile ukuwohloka.
I-Chemical oxygen demand (COD) iyinkomba yokulinganisa yezinga amanzi anothe ngalo ezintweni eziphilayo, futhi ingenye yezinkomba ezibalulekile zokulinganisa izinga lokungcoliswa kwamanzi. Ngokuthuthuka kwezimboni kanye nokwanda kwenani labantu, imizimba yamanzi iya ngokuya ingcoliswa, futhi ukuthuthukiswa kokutholwa kwe-COD kuye kwaba ngcono kancane kancane.
Umsuka wokutholwa kwe-COD ungalandelelwa emuva kuma-1850s, lapho izinkinga zokungcoliswa kwamanzi zazidonse ukunaka kwabantu. Ekuqaleni, i-COD yayisetshenziswa njengenkomba yeziphuzo ezine-asidi ukukala ukugcwala kwezinto eziphilayo eziphuzweni. Nokho, njengoba indlela yokulinganisa ephelele yayingakasungulwa ngaleso sikhathi, kwaba nephutha elikhulu emiphumeleni yokunquma ye-COD.
Ekuqaleni kwekhulu lama-20, ngokuthuthuka kwezindlela zesimanje zokuhlaziya amakhemikhali, indlela yokuthola i-COD yathuthukiswa kancane kancane. Ngo-1918, usokhemisi waseJalimane u-Hasse wachaza i-COD njengesamba senani lezinto eziphilayo ezidliwa i-oxidation kwisixazululo esine-asidi. Ngokulandelayo, uphakamise indlela entsha yokunquma i-COD, okuwukusebenzisa isisombululo se-chromium dioxide esinezinga eliphezulu njenge-oxidant. Le ndlela ingakwazi ukukhipha izinto eziphilayo zibe yi-carbon dioxide nasemanzini, futhi ilinganise ukusetshenziswa kwama-oxidants esixazululweni ngaphambi nangemuva kwe-oxidation ukuze kunqunywe inani le-COD.
Nokho, ukushiyeka kwale ndlela kuye kwavela kancane kancane. Okokuqala, ukulungiswa nokusebenza kwama-reagents kuyinkimbinkimbi, okwandisa ubunzima kanye nokuchitha isikhathi sokuhlolwa. Okwesibili, izixazululo ze-chromium dioxide ezigxilile kakhulu ziyingozi emvelweni futhi azihambisani nokusetshenziswa okungokoqobo. Ngakho-ke, izifundo ezalandela ziye zafuna kancane kancane indlela yokunquma ye-COD elula nenembe kakhudlwana.
Ngawo-1950, usokhemisi ongumDashi uFriis wasungula indlela entsha yokunquma i-COD, esebenzisa i-persulfuric acid ene-concentration ephezulu njenge-oxidant. Le ndlela ilula ukuyisebenzisa futhi inokunemba okuphezulu, okuthuthukisa kakhulu ukusebenza kahle kokutholwa kwe-COD. Kodwa-ke, ukusetshenziswa kwe-persulfuric acid nakho kunezingozi ezithile zokuphepha, ngakho-ke kusadingeka ukunaka ukuphepha kokusebenza.
Kamuva, ngokuthuthuka okusheshayo kobuchwepheshe be-instrumentation, indlela yokunquma ye-COD kancane kancane izuze i-automation kanye nobuhlakani. Ngawo-1970, kwavela uhlaziyo lokuqala oluzenzakalelayo lwe-COD, olukwazi ukubona ukucubungula okuzenzakalelayo nokutholwa kwamasampula amanzi. Leli thuluzi alithuthukisi nje kuphela ukunemba nokuzinza kokunqunywa kwe-COD, kodwa futhi lithuthukisa kakhulu ukusebenza kahle komsebenzi.
Ngokuthuthukiswa kokuqwashisa ngemvelo kanye nokuthuthukiswa kwezidingo zokulawula, indlela yokuhlonza i-COD nayo ithuthukiswa ngokuqhubekayo. Eminyakeni yamuva, ukuthuthukiswa kobuchwepheshe be-photoelectric, izindlela ze-electrochemical kanye nobuchwepheshe be-biosensor kukhuthaze ukusungulwa kobuchwepheshe bokutholwa kwe-COD. Isibonelo, ubuchwepheshe be-photoelectric bunganquma okuqukethwe kwe-COD kumasampuli wamanzi ngokushintsha amasignali e-photoelectric, ngesikhathi sokuthola esifushane kanye nokusebenza okulula. Indlela ye-electrochemical isebenzisa izinzwa ze-electrochemical ukukala amanani e-COD, anezinzuzo zokuzwela okuphezulu, ukuphendula okusheshayo futhi asikho isidingo sama-reagents. Ubuchwepheshe be-Biosensor busebenzisa izinto zebhayoloji ukuthola ngokuqondile izinto eziphilayo, okuthuthukisa ukunemba nokucaciswa kokunqunywa kwe-COD.
Izindlela zokuthola i-COD zenze inqubo yokuthuthukiswa kusukela ekuhlaziyweni kwamakhemikhali omdabu kuya ekusetshenzisweni kwezinsimbi zesimanje, ubuchwepheshe bezithombe zikagesi, izindlela ze-electrochemical kanye nobuchwepheshe be-biosensor emashumini ambalwa eminyaka adlule. Ngokuthuthuka kwesayensi nobuchwepheshe kanye nokwanda kwesidingo, ubuchwepheshe bokuthola i-COD busathuthukiswa futhi buyenziwa izinto ezintsha. Ngokuzayo, kungabonwa kusengaphambili ukuthi njengoba abantu benaka kakhulu izindaba zokungcoliswa kwemvelo, ubuchwepheshe bokuthola i-COD buzothuthuka futhi bube indlela esheshayo, enembayo futhi enokwethenjelwa yokuthola ikhwalithi yamanzi.
Njengamanje, amalabhorethri asebenzisa izindlela ezimbili ezilandelayo ukuthola i-COD.
1. Indlela yokunquma ye-COD
Indlela ejwayelekile ye-Potassium dichromate, eyaziwa nangokuthi indlela ye-reflux (Izinga Likazwelonke Le-People's Republic of China)
(I) Isimiso
Engeza inani elithile le-potassium dichromate kanye ne-catalyst silver sulfate kusampula lamanzi, ukushisa kanye ne-reflux isikhathi esithile endaweni ene-asidi eqinile, ingxenye ye-potassium dichromate incishiswa yizinto ezi-oxidizable kusampula yamanzi, futhi okusele. I-potassium dichromate ihlanganiswa ne-ammonium ferrous sulfate. Inani le-COD libalwa ngokusekelwe enanini le-potassium dichromate esetshenzisiwe.
Njengoba leli zinga lakhiwe ngo-1989, kuningi okungalungile ekulilinganiseni ngezinga elikhona manje:
1. Kuthatha isikhathi esiningi, futhi isampula ngayinye idinga ukukhishwa kabusha amahora ama-2;
2. Imishini ye-reflux ithatha indawo enkulu, okwenza ukuzimisela kweqoqo kube nzima;
3. Izindleko zokuhlaziya ziphezulu, ikakhulukazi isiliva sulfate;
4. Phakathi nenqubo yokunquma, ukuchithwa kwamanzi e-reflux kuyamangalisa;
5. Usawoti we-mercury onobuthi uvame ukungcoliswa okwesibili;
6. Inani lama-reagents asetshenzisiwe likhulu, futhi izindleko zezinto ezisetshenziswayo ziphezulu;
7. Inqubo yokuhlola iyinkimbinkimbi futhi ayifaneleki ukukhushulwa.
(II) Izisetshenziswa
1. 250mL idivayisi ye-reflux yengilazi yonke
2. Idivayisi yokushisisa (isithando somlilo)
3. I-25mL noma i-50mL ye-asidi burette, i-conical flask, i-pipette, i-volumetric flask, njll.
(III) Ama-reagents
1. Isixazululo esijwayelekile se-Potassium dichromate (c1/6K2Cr2O7=0.2500mol/L)
2. Isixazululo senkomba ye-Ferrocyanate
3. Isixazululo esijwayelekile se-Ammonium ferrous sulfate [c(NH4)2Fe(SO4)2·6H2O≈0.1mol/L] (linganisa ngaphambi kokusetshenziswa)
4. Isixazululo se-sulfuric acid-silver sulfate
Indlela ejwayelekile ye-potassium dichromate
(IV) Izinyathelo zokunquma
I-Ammonium ferrous sulfate calibration: I-pipette enembile engu-10.00mL yesisombululo esijwayelekile se-potassium dichromate ibe yifulaski eyikhonikhi engu-500mL, hlambulula ibe cishe ku-110mL ngamanzi, kancane wengeze u-30mL we-sulfuric acid egxilile, bese unyakazisa kahle. Ngemva kokupholisa, engeza amaconsi ama-3 esisombululo senkomba ye-ferrocyanate (cishe u-0.15mL) kanye ne-titrate ngesisombululo se-ammonium ferrous sulfate. Iphuzu lokugcina yilapho umbala wesixazululo ushintsha usuka kophuzi uye koluhlaza okwesibhakabhaka ukuya kunsundu ngokubomvu.
(V) Ukuzimisela
Thatha u-20mL wesampula wamanzi (uma kunesidingo, thatha kancane bese wengeza amanzi ku-20 noma uhlambulule ngaphambi kokuthatha), engeza u-10mL we-potassium dichromate, uxhume idivayisi ye-reflux, bese wengeza u-30mL we-sulfuric acid ne-silver sulfate, ukushisa kanye ne-reflux amahora angu-2. . Ngemuva kokupholisa, hlambulula udonga lweshubhu ye-condenser ngamanzi angu-90.00mL bese ususa i-conical flask. Ngemuva kokuthi ikhambi selipholile futhi, engeza amaconsi ama-3 esisombululo senkomba ye-ferrous acid kanye ne-titrate ngesisombululo esijwayelekile se-ammonium ferrous sulfate. Umbala wesixazululo uyashintsha usuka ophuzi uye koluhlaza okwesibhakabhaka ukuya kunsundu ngokubomvu, okuyindawo yokugcina. Rekhoda inani lesixazululo esijwayelekile se-ammonium ferrous sulfate. Ngenkathi ukala isampula lamanzi, thatha u-20.00mL wamanzi acwecwe kabusha futhi wenze isilingo esingenalutho ngokuya ngezinyathelo ezifanayo zokusebenza. Rekhoda inani lesixazululo esijwayelekile se-ammonium ferrous sulfate elisetshenziswe ku-titration engenalutho.
Indlela ejwayelekile ye-potassium dichromate
(VI) Ukubala
CODCr(O2, mg/L)=[8×1000(V0-V1)·C]/V
(VII) Izinyathelo zokuqapha
1. Inani eliphezulu le-ion ye-chloride ehlanganiswe ne-0.4g ye-mercuric sulfate ingafinyelela ku-40mg. Uma isampula lamanzi elingu-20.00mL lithathwa, ubuningi be-ion ye-chloride engu-2000mg/L ingahlanganiswa. Uma i-concentration ye-chloride ion iphansi, inani elincane le-mercuric sulfate lingangezwa ukugcina i-mercuric sulfate: i-chloride ion = 10:1 (W/W). Uma inani elincane le-mercuric chloride lishisa, akuthinti ukuzimisela.
2. Ububanzi be-COD obunqunywe yile ndlela ngu-50-500mg/L. Kumasampuli amanzi anesidingo sekhemikhali komoyampilo esingaphansi kuka-50mg/L, esikhundleni salokho kufanele kusetshenziswe isisombululo esijwayelekile se-potassium dichromate esingu-0.0250mol/L. Isixazululo esijwayelekile se-ammonium ferrous sulfate esingu-0.01mol/L kufanele sisetshenziselwe ukubuyisela emuva. Kumasampuli amanzi ane-COD angaphezu kuka-500mg/L, wahlukanise ngaphambi kokunqunywa.
3. Ngemuva kokuthi isampula samanzi sishiswe futhi sihlanjululwe kabusha, inani elisele le-potassium dichromate kusixazululo kufanele libe yi-1/5-4/5 yenani elingeziwe.
4. Uma usebenzisa isixazululo esijwayelekile se-potassium hydrogen phthalate ukuhlola ikhwalithi nokusebenza kobuchwepheshe be-reagent, njengoba i-CODCr yethiyori yegremu ngayinye ye-potassium hydrogen phthalate ingu-1.176g, 0.4251g we-potassium hydrogen phthalate (HOOCC6H4COOK) ichitheka emanzini aphinde agaywe kabusha, idluliselwe ku-1000mL ye-volumetric flask, futhi ihlanjululwe kumaki ngamanzi aphinde acwecwe ukuze alenze isixazululo esijwayelekile se-CODcr esingu-500mg/L. Yilungiselele isisha uma isetshenziswa.
5. Umphumela wokunquma we-CODCr kufanele ugcine amadijithi amane abalulekile.
6. Phakathi nokuhlolwa ngakunye, isisombululo se-ammonium ferrous sulfate esijwayelekile kufanele silinganiswe, futhi ukuguqulwa kokugxilisa ingqondo kufanele kunakwe ngokukhethekile lapho izinga lokushisa legumbi liphezulu. (Ungengeza futhi u-10.0ml wesixazululo esijwayelekile se-potassium dichromate endaweni engenalutho ngemva kokufakwa kwe-titration kanye ne-titrate nge-ammonium ferrous sulfate kuze kube sekugcineni.)
7. Isampula lamanzi kufanele ligcinwe lisha futhi likalwe ngokushesha ngangokunokwenzeka.
Izinzuzo:
Ukunemba okuphezulu: I-Reflux titration iyindlela yakudala yokunquma ye-COD. Ngemva kwesikhathi eside sokuthuthukiswa nokuqinisekiswa, ukunemba kwayo kuye kwaqashelwa kabanzi. Ingabonisa ngokunembe kakhudlwana okuqukethwe kwangempela kwezinto eziphilayo emanzini.
Ukusetshenziswa okubanzi: Le ndlela ifaneleka ezinhlotsheni ezahlukene zamasampula amanzi, okuhlanganisa ukugxilwa okuphezulu kanye namanzi angcolile ezinto eziphilayo angagxili kakhulu.
Imininingwane yokusebenza: Kunamazinga nezinqubo ezinemininingwane zokusebenza, ezilungele opharetha ukuze bazi kahle futhi bazisebenzise.
Ububi:
Kudla isikhathi: I-Reflux titration ivamise ukuthatha amahora ambalwa ukuqedela ukunquma kwesampula, okusobala ukuthi ayisihambisi isimo lapho imiphumela idinga ukutholwa ngokushesha.
Ukusetshenziswa okuphezulu kwe-reagent: Le ndlela idinga ukusetshenziswa kwama-reagents amakhemikhali amaningi, angabizi nje kuphela, kodwa futhi angcolisa imvelo ngezinga elithile.
Ukusebenza okuyinkimbinkimbi: Umsebenzisi udinga ukuba nolwazi oluthile lwamakhemikhali namakhono okuhlola, ngaphandle kwalokho kungase kuthinte ukunemba kwemiphumela yokunquma.
2. I-spectrophotometry yokugaya ngokushesha
(I) Isimiso
Isampula yengezwe ngenani elaziwayo lesisombululo se-potassium dichromate, endaweni eqinile ye-sulfuric acid medium, ne-silver sulfate njenge-catalyst, futhi ngemva kokugaya okunezinga lokushisa eliphezulu, inani le-COD linqunywa imishini ye-photometric. Njengoba le ndlela inesikhathi esifushane sokuzimisela, ukungcola okuncane kwesibili, umthamo omncane we-reagent kanye nezindleko eziphansi, ama-laboratories amaningi asebenzisa le ndlela okwamanje. Kodwa-ke, le ndlela inezindleko eziphezulu zensimbi kanye nezindleko eziphansi zokusebenzisa, ezifanele ukusetshenziswa kwesikhathi eside kwamayunithi e-COD.
(II) Izisetshenziswa
Imishini yangaphandle yathuthukiswa ngaphambili, kodwa intengo iphezulu kakhulu, futhi isikhathi sokuzimisela side. Intengo ye-reagent ngokuvamile ayikwazi ukuthengeka kubasebenzisi, futhi ukunemba akukho phezulu kakhulu, ngoba izindinganiso zokuqapha izinsimbi zangaphandle zihlukile kwalezo zezwe lami, ikakhulukazi ngenxa yokuthi izinga lokuhlanza amanzi kanye nesistimu yokuphatha yamazwe angaphandle kwehlukile kweyami. izwe; indlela ye-spectrophotometry yokugaya ngokushesha isekelwe ezindleleni ezivamile zezinsimbi zasekhaya. Ukunqunywa okusheshayo kwe-catalytic yendlela ye-COD izinga lokwakhiwa kwale ndlela. Yasungulwa ekuqaleni kwawo-1980. Ngemva kweminyaka engaphezu kwengu-30 yokufakwa kwesicelo, isibe indinganiso yemboni yokuvikela imvelo. Ithuluzi lasekhaya le-5B lisetshenziswe kabanzi ocwaningweni lwesayensi nokuqapha okusemthethweni. Izinsimbi zasekhaya zisetshenziswe kakhulu ngenxa yezinzuzo zazo zentengo kanye nesevisi efika ngesikhathi yangemva kokuthengisa.
(III) Izinyathelo zokunquma
Thatha isampula engu-2.5ml—–engeza i-reagent—–gaya imizuzu engu-10—–pholile imizuzu engu-2—–uthele esitsheni esinemibala—–isibonisi semishini sibonisa ngokuqondile ukugxiliswa kwe-COD kwesampula.
(IV) Izinyathelo zokuqapha
1. Amasampula amanzi ane-chlorine ephezulu kufanele asebenzise i-high-chlorine reagent.
2. Uketshezi olulahlwayo lungaba ngu-10ml, kodwa lune-acidic kakhulu futhi kufanele luqoqwe futhi lucutshungulwe.
3. Qinisekisa ukuthi indawo edlulisa ukukhanya ye-cuvette ihlanzekile.
Izinzuzo:
Isivinini esisheshayo: Indlela esheshayo ivamise ukuthatha amaminithi ambalwa ukuya ngaphezu kwemizuzu eyishumi ukuqedela ukunqunywa kwesampula, efaneleka kakhulu ezimeni lapho imiphumela idinga ukutholwa ngokushesha.
Ukusetshenziswa kwe-reagent encane: Uma kuqhathaniswa nendlela ye-reflux titration, indlela esheshayo isebenzisa ama-reagents amakhemikhali ambalwa, inezindleko eziphansi, futhi inomthelela omncane emvelweni.
Ukusebenza okulula: Izinyathelo zokusebenza zendlela esheshayo zilula uma kuqhathaniswa, futhi u-opharetha akudingeki abe nolwazi lwamakhemikhali oluphakeme kakhulu namakhono okuhlola.
Ububi:
Ukunemba okuphansi kancane: Njengoba indlela esheshayo ivamise ukusebenzisa ukusabela kwamakhemikhali okwenziwe lula nezindlela zokulinganisa, ukunemba kwayo kungase kube ngaphansi kancane kunendlela ye-reflux titration.
Ububanzi obunomkhawulo bokusebenzisa: Indlela esheshayo ifaneleka ngokuyinhloko ukunqunywa kwamanzi angcolile ezinto eziphilayo angagxili kakhulu. Ngamanzi angcolile anezinga eliphezulu, imiphumela yawo yokuzimisela ingase ithinteke kakhulu.
Ithintwa izici zokuphazamiseka: Indlela esheshayo ingase ikhiqize amaphutha amakhulu kwezinye izimo ezikhethekile, njengalapho kunezinto ezithile eziphazamisayo kusampula yamanzi.
Kafushane, indlela ye-reflux titration kanye nendlela esheshayo ngayinye inezinzuzo zayo kanye nokubi. Iyiphi indlela ongayikhetha incike esimeni sohlelo oluthile kanye nezidingo. Uma ukunemba okuphezulu nokusebenza okubanzi kuyadingeka, i-reflux titration ingakhethwa; lapho imiphumela esheshayo idingeka noma inani elikhulu lamasampula amanzi licutshungulwa, indlela esheshayo iyisinqumo esihle.
I-Lianhua, njengomkhiqizi wezinsimbi zokuhlola izinga lamanzi iminyaka engu-42, isungule imizuzu engama-20.I-COD yokugaya ngokushesha i-spectrophotometryindlela. Ngemuva kwenani elikhulu lokuqhathaniswa kokuhlolwa, liye lakwazi ukufeza iphutha elingaphansi kuka-5%, futhi linezinzuzo zokusebenza okulula, imiphumela esheshayo, izindleko eziphansi nesikhathi esifushane.
Isikhathi sokuthumela: Jun-07-2024
