Bukatar iskar oxygen ta sinadarai kuma ana kiranta buƙatar iskar oxygen sinadarai (buƙatar oxygen sinadari), ana kiranta da COD. Yana da amfani da sinadarai masu oxidants (kamar potassium permanganate) don oxidize da bazuwar abubuwan da za a iya cirewa a cikin ruwa (kamar kwayoyin halitta, nitrite, gishiri mai ferrous, sulfide, da dai sauransu), sannan a lissafta yawan iskar oxygen bisa adadin ragowar. oxidant. Kamar buƙatun oxygen na biochemical (BOD), alama ce mai mahimmanci na gurɓataccen ruwa. Naúrar COD shine ppm ko mg/L. Karancin ƙimar, ƙarancin gurɓataccen ruwa.
Abubuwan da ke ragewa a cikin ruwa sun haɗa da kwayoyin halitta daban-daban, nitrite, sulfide, gishiri mai ƙarfe, da dai sauransu. Amma babban abu shine kwayoyin halitta. Sabili da haka, ana amfani da buƙatar iskar oxygen (COD) sau da yawa azaman mai nuna alama don auna adadin kwayoyin halitta a cikin ruwa. Mafi girman buƙatar iskar oxygen ɗin sinadarai, mafi munin gurɓacewar ruwa ta kwayoyin halitta. Ƙaddamar da buƙatar oxygen na sinadarai (COD) ya bambanta tare da ƙaddarar rage abubuwa a cikin samfuran ruwa da hanyar ƙaddara. Hanyoyin da aka fi amfani dasu a halin yanzu sune hanyar acidic potassium permanganate oxidation method da kuma hanyar potassium dichromate oxidation. Hanyar potassium permanganate (KMnO4) tana da ƙarancin oxidation, amma yana da sauƙi. Ana iya amfani da shi don ƙayyade ƙimar kwatankwacin kwatankwacin abun ciki na kwayoyin halitta a cikin samfuran ruwa da tsaftataccen ruwan saman da samfuran ruwan ƙasa. Hanyar potassium dichromate (K2Cr2O7) tana da ƙimar iskar oxygen mai girma da haɓaka mai kyau. Ya dace don ƙayyade yawan adadin kwayoyin halitta a cikin samfurori na ruwa a cikin kula da ruwa mai tsabta.
Kwayoyin halitta suna da matukar illa ga tsarin ruwa na masana'antu. Ruwan da ke dauke da adadi mai yawa na kwayoyin halitta zai gurɓata resins na musayar ion lokacin da ke wucewa ta cikin tsarin da ake amfani da shi, musamman resins na musayar anion, wanda zai rage karfin musanya na resin. Ana iya rage kwayoyin halitta da kusan 50% bayan pretreatment (coagulation, bayani da tacewa), amma ba za a iya cire shi a cikin tsarin desalination ba, don haka sau da yawa ana kawo shi cikin tukunyar jirgi ta hanyar ruwan ciyarwa, wanda ya rage darajar pH na tukunyar jirgi. ruwa. Wani lokaci kwayoyin halitta kuma ana iya kawo su cikin tsarin tururi da ruwa mai narkewa, wanda zai rage pH kuma ya haifar da lalata tsarin. Babban abun ciki na kwayoyin halitta a cikin tsarin ruwa mai yawo zai inganta haifuwar ƙananan ƙwayoyin cuta. Don haka, ko don lalata ruwa, ruwan tukunyar jirgi ko tsarin ruwa mai yawo, ƙananan COD, mafi kyau, amma babu ƙayyadaddun ƙayyadaddun ƙididdiga. Lokacin da COD (hanyar KMnO4)> 5mg/L a cikin tsarin ruwa mai sanyaya ruwa, ingancin ruwa ya fara lalacewa.
Bukatar iskar oxygen (COD) shine ma'aunin ma'auni na matakin da ruwa ke da wadata a cikin kwayoyin halitta, kuma yana daya daga cikin mahimman bayanai don auna matakin gurɓataccen ruwa. Tare da haɓaka masana'antu da karuwar yawan jama'a, raƙuman ruwa suna ƙara ƙazanta, kuma ci gaban gano COD ya inganta a hankali.
Ana iya gano asalin gano COD tun a shekarun 1850, lokacin da matsalolin gurɓacewar ruwa suka ja hankalin mutane. Da farko, an yi amfani da COD azaman mai nuna alamun abubuwan sha na acidic don auna yawan abubuwan da ke cikin abubuwan sha. Koyaya, tun da ba a kafa cikakkiyar hanyar aunawa ba a wancan lokacin, an sami babban kuskure a cikin ƙaddarar sakamakon COD.
A farkon karni na 20, tare da ci gaban hanyoyin nazarin sinadarai na zamani, hanyar gano COD ta inganta sannu a hankali. A cikin 1918, masanin kimiyar Jamus Hasse ya ayyana COD a matsayin jimillar adadin kwayoyin halitta da oxidation ke cinyewa a cikin maganin acidic. Daga baya, ya ba da shawarar sabuwar hanyar ƙayyade COD, wanda shine yin amfani da babban maganin chromium dioxide a matsayin mai oxidant. Wannan hanya za ta iya yin amfani da kwayoyin halitta yadda ya kamata a cikin carbon dioxide da ruwa, da kuma auna yawan amfani da oxidants a cikin maganin kafin da bayan hadawan abu da iskar shaka don sanin ƙimar COD.
Duk da haka, gazawar wannan hanyar sun fara bayyana a hankali. Na farko, shirye-shiryen da aiki na reagents suna da rikitarwa, wanda ke ƙara wahala da cin lokaci na gwaji. Na biyu, babban taro na chromium dioxide mafita suna da illa ga muhalli kuma ba su da amfani ga aikace-aikace masu amfani. Sabili da haka, binciken da ya biyo baya ya nemi a hankali hanya mafi sauƙi kuma mafi inganci hanyar tantance COD.
A cikin 1950s, masanin kimiyar Dutch Friis ya ƙirƙira sabuwar hanyar ƙayyade COD, wanda ke amfani da babban abun da ke tattare da persulfuric acid azaman oxidant. Wannan hanyar tana da sauƙi don aiki kuma tana da daidaito mai girma, wanda ke haɓaka haɓakar gano COD sosai. Duk da haka, yin amfani da persulfuric acid shima yana da wasu haɗari na aminci, don haka har yanzu ya zama dole a kula da amincin aiki.
Daga baya, tare da saurin haɓaka fasahar kayan aiki, hanyar ƙayyade COD a hankali ta sami aiki da kai da hankali. A cikin 1970s, na farko COD na'urar nazari ta atomatik ya bayyana, wanda zai iya gane cikakken sarrafawa ta atomatik da gano samfuran ruwa. Wannan kayan aikin ba wai kawai yana inganta daidaito da kwanciyar hankali na ƙaddarar COD ba, amma kuma yana haɓaka ingantaccen aiki sosai.
Tare da haɓaka wayar da kan muhalli da haɓaka buƙatun tsari, hanyar gano COD kuma ana ci gaba da ingantawa. A cikin 'yan shekarun nan, haɓaka fasahar photoelectric, hanyoyin electrochemical da fasahar biosensor sun haɓaka haɓaka fasahar gano COD. Misali, fasahar hoto na iya tantance abubuwan COD a cikin samfuran ruwa ta hanyar canjin siginar hoto, tare da ɗan gajeren lokacin ganowa da aiki mafi sauƙi. Hanyar electrochemical tana amfani da firikwensin lantarki don auna ƙimar COD, wanda ke da fa'idodin babban hankali, saurin amsawa kuma babu buƙatar sakewa. Fasahar Biosensor tana amfani da kayan halitta don gano takamaiman kwayoyin halitta, wanda ke haɓaka daidaito da ƙayyadaddun ƙayyadaddun COD.
Hanyoyin gano COD sun sami ci gaba daga nazarin sinadarai na gargajiya zuwa kayan aikin zamani, fasahar hoto, hanyoyin lantarki da fasahar biosensor a cikin ƴan shekarun da suka gabata. Tare da ci gaban kimiyya da fasaha da haɓaka buƙatu, fasahar gano COD har yanzu ana haɓakawa da haɓakawa. A nan gaba, ana iya hasashen cewa yayin da mutane ke mai da hankali kan lamuran gurɓacewar muhalli, fasahar gano COD za ta ƙara haɓaka kuma ta zama hanyar gano ingancin ruwa cikin sauri, daidai kuma abin dogaro.
A halin yanzu, dakunan gwaje-gwaje galibi suna amfani da hanyoyi biyu masu zuwa don gano COD.
1. Hanyar ƙayyade COOD
Potassium dichromate daidaitaccen hanyar, wanda kuma aka sani da hanyar reflux (National Standard of the People's Republic of China)
(I) Ka'ida
Ƙara wani adadin potassium dichromate da mai kara kuzari na azurfa sulfate zuwa samfurin ruwa, zafi da reflux na wani lokaci a cikin matsakaici mai karfi na acidic, wani ɓangare na potassium dichromate yana raguwa ta hanyar abubuwa masu oxidizable a cikin samfurin ruwa, da sauran sauran. potassium dichromate an titrated tare da ammonium ferrous sulfate. Ana ƙididdige ƙimar COD bisa adadin potassium dichromate da aka cinye.
Tun da aka ƙirƙiri wannan ma'auni a cikin 1989, akwai rashin amfani da yawa wajen auna shi tare da ma'auni na yanzu:
1. Yana ɗaukar lokaci mai yawa, kuma kowane samfurin yana buƙatar sake sakewa don 2 hours;
2. The reflux kayan aiki shagaltar da wani babban sarari, yin tsari kayyade wuya;
3. Farashin bincike yana da yawa, musamman ga sulfate na azurfa;
4. A lokacin aiwatar da ƙaddarar, sharar da ruwa na reflux yana da ban mamaki;
5. Gishirin mercury mai guba yana da haɗari ga gurɓataccen gurɓataccen abu;
6. Adadin reagents da aka yi amfani da su yana da girma, kuma farashin kayan amfani yana da yawa;
7. Tsarin gwajin yana da rikitarwa kuma bai dace da haɓakawa ba.
(II) Kayan aiki
1. 250ml duk-gilashin reflux na'urar
2. Na'urar dumama (lantarki tanderu)
3. 25mL ko 50mL acid burette, conical flask, pipette, volumetric flask, da dai sauransu.
(III) Reagents
1. Potassium dichromate daidaitaccen bayani (c1/6K2Cr2O7=0.2500mol/L)
2. Ferrocyanate bayani bayani
3. Ammonium ferrous sulfate misali bayani [c (NH4) 2Fe (SO4) 2 · 6H2O≈0.1mol / L] (calibrate kafin amfani)
4. Sulfuric acid-azurfa sulfate bayani
Potassium dichromate daidaitaccen hanyar
(IV) Matakan ƙaddara
Ammonium ferrous sulfate calibration: Daidai pipette 10.00mL na potassium dichromate daidaitaccen bayani a cikin faifan conical 500ml, tsarma zuwa kusan 110mL da ruwa, a hankali ƙara 30mL na sulfuric acid mai hankali, kuma girgiza sosai. Bayan sanyaya, ƙara digo 3 na maganin ferrocyanate (kimanin 0.15mL) da titrate tare da maganin ammonium ferrous sulfate. Ƙarshen ƙarshen shine lokacin da launi na bayani ya canza daga rawaya zuwa blue-kore zuwa launin ruwan kasa ja.
(V) Ƙaddara
Ɗauki 20ml na samfurin ruwa (idan ya cancanta, ɗauki ƙasa kuma ƙara ruwa zuwa 20 ko tsarma kafin shan), ƙara 10mL na potassium dichromate, toshe cikin na'urar reflux, sa'an nan kuma ƙara 30ml na sulfuric acid da azurfa sulfate, zafi da reflux na 2h . Bayan an sanyaya, kurkure bangon bututun kwandon ruwa da 90.00ml na ruwa sannan a cire flask ɗin conical. Bayan an sake sanyaya maganin, ƙara digo 3 na ferrous acid bayani da kuma titrate tare da daidaitaccen bayani na ammonium ferrous sulfate. Launin maganin yana canzawa daga rawaya zuwa shuɗi-kore zuwa launin ruwan ja, wanda shine ƙarshen ƙarshen. Yi rikodin adadin ammonium ferrous sulfate daidaitaccen bayani. Yayin auna samfurin ruwan, ɗauki 20.00mL na ruwan da aka sake gyara kuma yi gwaji mara kyau bisa ga matakan aiki iri ɗaya. Yi rikodin adadin daidaitaccen maganin ammonium ferrous sulfate da aka yi amfani da shi a cikin titration mara kyau.
Potassium dichromate daidaitaccen hanyar
(VI) Lissafi
CODCR (O2, mg/L) = [8×1000(V0-V1)·C]/V
(VII) Hattara
1. Matsakaicin adadin chloride ion hadaddun tare da 0.4g mercuric sulfate zai iya kaiwa 40mg. Idan an ɗauki samfurin ruwa na 20.00mL, matsakaicin matsakaicin ion chloride na 2000mg/L na iya zama mai rikitarwa. Idan maida hankali na ions chloride yayi ƙasa, ana iya ƙara ƙaramin adadin sulfate na mercuric don kiyaye sulfate na mercuric: ions chloride = 10: 1 (W/W). Idan ƙaramin adadin chloride na mercuric ya yi hazo, ba zai shafi ƙaddarar ba.
2. Matsakaicin COD da aka ƙayyade ta wannan hanya shine 50-500mg / L. Don samfuran ruwa tare da buƙatar iskar oxygen ƙasa da 50mg/L, 0.0250mol/L potassium dichromate daidaitaccen bayani ya kamata a yi amfani da shi maimakon. 0.01mol/L ammonium ferrous sulfate daidaitaccen bayani yakamata a yi amfani dashi don titration na baya. Don samfuran ruwa tare da COD fiye da 500mg/L, tsoma su kafin ƙaddara.
3. Bayan samfurin ruwa yana mai tsanani kuma ya sake dawowa, ragowar adadin potassium dichromate a cikin maganin ya kamata ya zama 1 / 5-4 / 5 na adadin da aka kara.
4. Lokacin amfani da potassium hydrogen phthalate daidaitaccen bayani don bincika inganci da fasaha na aiki na reagent, tun da CODCr ka'idar kowane gram na potassium hydrogen phthalate shine 1.176g, 0.4251g na potassium hydrogen phthalate (HOOCC6H4COOK) an narkar da shi a cikin ruwa mai ruwa, canjawa wuri zuwa 1000mL volumetric flask, kuma diluted zuwa alamar tare da redistilled ruwa don sa shi 500mg/L CODcr daidaitaccen bayani. Shirya shi sabo ne lokacin amfani.
5. Sakamakon ƙaddarar CODCr yakamata ya riƙe mahimman lambobi huɗu.
6. A yayin kowane gwaji, ammonium ferrous sulfate daidaitaccen bayani na titration ya kamata a daidaita shi, kuma canjin maida hankali ya kamata a ba da kulawa ta musamman lokacin da zafin jiki ya yi girma. (Zaka iya ƙara 10.0ml na potassium dichromate daidaitaccen bayani a cikin blank bayan titration da titrate tare da ammonium ferrous sulfate zuwa ƙarshen batu.)
7. Ya kamata a kiyaye samfurin ruwa sabo kuma a auna shi da wuri-wuri.
Amfani:
Babban daidaito: Reflux titration hanya ce ta ƙayyadaddun COD. Bayan dogon lokaci na haɓakawa da tabbatarwa, an gane daidaitonsa a ko'ina. Zai iya yin daidai daidai da ainihin abun ciki na kwayoyin halitta a cikin ruwa.
Faɗin aikace-aikacen: Wannan hanyar ta dace da nau'ikan samfuran ruwa daban-daban, gami da babban mai da hankali sosai da ƙazantaccen ruwan sharar kwayoyin halitta.
Ƙayyadaddun aiki: Akwai cikakkun matakan aiki da matakai, waɗanda suka dace da masu aiki don ƙwarewa da aiwatarwa.
Rashin hasara:
Cin lokaci: Reflux titration yawanci yana ɗaukar sa'o'i da yawa don kammala ƙayyadaddun samfurin, wanda a fili bai dace da yanayin da ake buƙatar samun sakamako cikin sauri ba.
Yawan amfani da reagent: Wannan hanya tana buƙatar amfani da ƙarin sinadaran reagents, wanda ba kawai tsada ba ne, amma har ma yana gurɓata muhalli zuwa wani yanki.
Hadadden aiki: Mai aiki yana buƙatar samun takamaiman ilimin sinadarai da ƙwarewar gwaji, in ba haka ba yana iya shafar daidaiton sakamakon ƙaddara.
2. Rapid narkewa spectrophotometry
(I) Ka'ida
Ana ƙara samfurin tare da adadin da aka sani na potassium dichromate bayani, a cikin wani karfi sulfuric acid matsakaici, tare da azurfa sulfate a matsayin mai kara kuzari, da kuma bayan high-zazzabi narkewa, da COD darajar ne m da photometric kayan aiki. Tun da wannan hanya yana da ɗan gajeren lokacin ƙaddara, ƙananan gurɓataccen gurɓataccen abu, ƙananan reagent girma da ƙananan farashi, yawancin dakunan gwaje-gwaje a halin yanzu suna amfani da wannan hanya. Koyaya, wannan hanyar tana da babban farashin kayan aiki da ƙarancin amfani, wanda ya dace da dogon lokacin amfani da raka'a COD.
(II) Kayan aiki
An haɓaka kayan aikin waje a baya, amma farashin yana da yawa, kuma lokacin ƙaddara yana da tsayi. Farashin reagent gabaɗaya ba zai yuwu ga masu amfani da shi ba, kuma daidaito bai yi yawa ba, saboda ka'idodin sa ido na kayan aikin waje sun bambanta da na ƙasata, musamman saboda matakin kula da ruwa da tsarin kula da ƙasashen waje sun bambanta da na nawa. kasa; Hanyar spectrophotometry mai saurin narkewa ta dogara ne akan hanyoyin gama gari na kayan aikin gida. Ƙayyadaddun ƙayyadaddun hanzari na hanyar COD shine ma'aunin ƙirƙira na wannan hanyar. An ƙirƙira shi tun farkon shekarun 1980. Bayan fiye da shekaru 30 na aikace-aikacen, ya zama ma'auni na masana'antar kare muhalli. An yi amfani da kayan aikin gida na 5B sosai a cikin binciken kimiyya da sa ido na hukuma. An yi amfani da kayan aikin gida ko'ina saboda fa'idar farashinsu da sabis na tallace-tallace akan lokaci.
(III) Matakan ƙaddara
Ɗauki samfurin 2.5ml--ƙara reagent--narke na minti 10-- sanyi na minti 2--zuba cikin tasa mai launi--nunin kayan aiki yana nuna ƙaddamarwar COD na samfurin.
(IV) Kariya
1. Ya kamata samfuran ruwa masu girma-chlorine suyi amfani da reagent high-chlorine.
2. Ruwan sharar yana kusan 10ml, amma yana da yawan acidic kuma yakamata a tattara a sarrafa shi.
3. Tabbatar cewa saman mai watsa haske na cuvette yana da tsabta.
Amfani:
Gudun sauri: Hanyar sauri yawanci yana ɗaukar ƴan mintuna zuwa fiye da mintuna goma don kammala ƙaddamar da samfurin, wanda ya dace da yanayin da ake buƙatar samun sakamako cikin sauri.
Karancin amfani da reagent: Idan aka kwatanta da hanyar reflux titration, hanyar sauri tana amfani da ƙarancin reagents na sinadarai, yana da ƙarancin farashi, kuma yana da ƙarancin tasiri akan muhalli.
Aiki mai sauƙi: Matakan aiki na hanya mai sauri suna da sauƙin sauƙi, kuma mai aiki baya buƙatar samun ilimin sinadarai da yawa da ƙwarewar gwaji.
Rashin hasara:
Ƙananan daidaito: Tunda saurin hanyar yawanci yana amfani da wasu sauƙaƙan halayen sinadarai da hanyoyin aunawa, daidaiton sa na iya zama ƙasa kaɗan fiye da hanyar reflux titration.
Iyakance na aikace-aikace: Hanyar sauri ta fi dacewa da ƙayyadaddun ƙayyadaddun ruwan sharar yanayi. Domin ruwan sharar ƙasa mai girma, sakamakon ƙaddararsa na iya yin tasiri sosai.
Abubuwan da ke haifar da tsangwama: Hanyar gaggawa na iya haifar da manyan kurakurai a wasu lokuta na musamman, kamar lokacin da akwai wasu abubuwa masu tsaka-tsaki a cikin samfurin ruwa.
A taƙaice, hanyar reflux titration da saurin hanya kowanne yana da nasa fa'ida da rashin amfani. Wace hanya za a zaɓa ya dogara da takamaiman yanayin aikace-aikacen da buƙatun. Lokacin da ake buƙatar babban daidaito da fa'ida mai fa'ida, za a iya zaɓar titration na reflux; lokacin da ake buƙatar sakamako mai sauri ko kuma ana sarrafa adadi mai yawa na samfuran ruwa, hanyar sauri shine zaɓi mai kyau.
Lianhua, a matsayin mai kera na'urorin gwajin ingancin ruwa na tsawon shekaru 42, ta ƙera minti 20.COD saurin narkewa spectrophotometryhanya. Bayan babban adadin kwatancen gwaji, ya sami damar cimma kuskuren ƙasa da 5%, kuma yana da fa'idodin aiki mai sauƙi, sakamako mai sauri, ƙarancin farashi da ɗan gajeren lokaci.
Lokacin aikawa: Juni-07-2024
