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Lolu cwaningo luhlola imiphumela yokungcola kwe-NH4+ kanye nesilinganiso sembewu endleleni yokukhula kanye nokusebenza kwe-nickel sulfate hexahydrate ngaphansi kwe-crystallization yokupholisa engaphenduki, futhi luhlola imiphumela yokungcola kwe-NH4+ endleleni yokukhula, izakhiwo zokushisa, kanye namaqembu asebenzayo e-nickel sulfate hexahydrate. Ekugxilweni kokungcola okuphansi, ama-ion e-Ni2+ kanye ne-NH4+ ancintisana ne-SO42− ngokubopha, okuholela ekunciphiseni isivuno sekristalu kanye nesilinganiso sokukhula kanye nokwanda kwamandla okusebenza kwekristalu. Ekugxilweni kokungcola okuphezulu, ama-ion e-NH4+ afakwa esakhiweni sekristalu ukuze akhe usawoti oyinkimbinkimbi (NH4)2Ni(SO4)2 6H2O. Ukwakheka kosawoti oyinkimbinkimbi kuphumela ekukhuphukeni kwesivuno sekristalu kanye nesilinganiso sokukhula kanye nokwehla kwamandla okusebenza kwekristalu. Ukuba khona kokubili kokugxilwa kwe-ion ephezulu nephansi ye-NH4+ kubangela ukuphambuka kwe-lattice, futhi amakristalu azinzile ngokushisa emazingeni okushisa afinyelela ku-80 °C. Ngaphezu kwalokho, ithonya lokungcola kwe-NH4+ endleleni yokukhula kwekristalu likhulu kunelesilinganiso sembewu. Lapho ukugxilwa kokungcola kuphansi, ukungcola kulula ukunamathela kukristalu; uma ukuhlushwa kuphezulu, ukungcola kulula ukukufaka kukristalu. Isilinganiso sembewu singakhulisa kakhulu isivuno sekristalu futhi sithuthukise kancane ubumsulwa bekristalu.
I-Nickel sulfate hexahydrate (NiSO4 6H2O) manje iyinto ebalulekile esetshenziswa ezimbonini ezahlukahlukene, okuhlanganisa ukukhiqizwa kwamabhethri, ukufakelwa kwe-electroplating, ama-catalysts, ngisho nasekukhiqizweni kokudla, uwoyela, kanye nephunga elimnandi. 1,2,3 Ukubaluleka kwayo kukhula ngokuthuthukiswa okusheshayo kwezimoto zikagesi, ezithembele kakhulu kumabhethri e-lithium-ion (LiB) asekelwe ku-nickel. Ukusetshenziswa kwama-alloy ane-nickel ephezulu njenge-NCM 811 kulindeleke ukuthi kulawule ngo-2030, okwandisa kakhulu isidingo se-nickel sulfate hexahydrate. Kodwa-ke, ngenxa yemikhawulo yezinsizakusebenza, ukukhiqizwa kungase kungahambisani nesidingo esikhulayo, okudala igebe phakathi kokunikezwa nesidingo. Lokhu kushoda kuphakamise ukukhathazeka mayelana nokutholakala kwezinsizakusebenza kanye nokuzinza kwentengo, kugqamisa isidingo sokukhiqizwa okuphumelelayo kwe-nickel sulfate enezinga lebhethri elizinzile nelihlanzekile. 1,4
Ukukhiqizwa kwe-nickel sulfate hexahydrate ngokuvamile kufezwa ngokukristala. Phakathi kwezindlela ezahlukahlukene, indlela yokupholisa iyindlela esetshenziswa kabanzi, enezinzuzo zokusetshenziswa kwamandla aphansi kanye nekhono lokukhiqiza izinto ezihlanzekile kakhulu. 5,6 Ucwaningo mayelana nokukristala kwe-nickel sulfate hexahydrate kusetshenziswa ukukristala okungapheli kokupholisa luye lwenza intuthuko enkulu. Njengamanje, ucwaningo oluningi lugxile ekuthuthukiseni inqubo yokukristala ngokwenza ngcono amapharamitha afana nokushisa, izinga lokupholisa, usayizi wembewu kanye ne-pH. 7,8,9 Umgomo ukwandisa isivuno sekristalu kanye nobumsulwa bamakristalu atholiwe. Kodwa-ke, naphezu kocwaningo oluphelele lwala mapharamitha, kusenesikhala esikhulu ekunakeni okukhokhelwe ethonyeni lokungcola, ikakhulukazi i-ammonium (NH4+), emiphumeleni yokukristala.
Ukungcola kwe-ammonium kungenzeka kube khona esixazululweni se-nickel esisetshenziselwa ukwakheka kwe-nickel ngenxa yokuba khona kokungcola kwe-ammonium ngesikhathi senqubo yokukhipha. I-Ammonium ivame ukusetshenziswa njenge-saponifying agent, eshiya inani elincane le-NH4+ esixazululweni se-nickel. 10,11,12 Naphezu kokutholakala kokungcola kwe-ammonium, imiphumela yabo ezimpahleni zekristalu ezifana nesakhiwo sekristalu, indlela yokukhula, izakhiwo zokushisa, ubumsulwa, njll. kusalokhu kungaqondwa kahle. Ucwaningo olulinganiselwe ngemiphumela yabo lubalulekile ngoba ukungcola kungaphazamisa noma kushintshe ukukhula kwekristalu futhi, kwezinye izimo, kusebenza njengezithibi, kuthinte ukuguquka phakathi kwamafomu ekristalu azinzile nazinzile. 13,14 Ngakho-ke ukuqonda le miphumela kubalulekile ngokombono wezimboni ngoba ukungcola kungalimaza ikhwalithi yomkhiqizo.
Ngokusekelwe embuzweni othize, lolu cwaningo luhlose ukuphenya umphumela wokungcola kwe-ammonium ezimpahleni zamakristalu e-nickel. Ngokuqonda umphumela wokungcola, izindlela ezintsha zingathuthukiswa ukulawula nokunciphisa imiphumela yazo emibi. Lolu cwaningo luphinde lwahlola ukuhlobana phakathi kokuhlushwa kokungcola kanye noshintsho esilinganisweni sembewu. Njengoba imbewu isetshenziswa kabanzi enkambisweni yokukhiqiza, kusetshenziswe amapharamitha embewu kulolu cwaningo, futhi kubalulekile ukuqonda ubudlelwano phakathi kwalezi zici ezimbili. 15 Imiphumela yalezi pharamitha ezimbili yasetshenziswa ukutadisha isivuno sekristalu, indlela yokukhula kwekristalu, isakhiwo sekristalu, isimo semvelo, kanye nobumsulwa. Ngaphezu kwalokho, ukuziphatha kwe-kinetic, izakhiwo zokushisa, kanye namaqembu asebenzayo amakristalu ngaphansi kwethonya lokungcola kwe-NH4+ kuphela kwacwaningwa kabanzi.
Izinto ezisetshenziswe kulolu cwaningo kwakuyi-nickel sulfate hexahydrate (NiSO 6H2O, ≥ 99.8%) enikezwe yi-GEM; i-ammonium sulfate ((NH)SO, ≥ 99%) ethengwe kwa-Tianjin Huasheng Co., Ltd.; amanzi acwengekile. I-crystal yembewu esetshenzisiwe yayiyi-NiSO 6H2O, echotshoziwe futhi yahlungwa ukuze kutholakale usayizi wezinhlayiya ofanayo ongu-0.154 mm. Izici ze-NiSO 6H2O ziboniswe kuThebula 1 kanye noMfanekiso 1.
Umphumela wokungcola kwe-NH4+ kanye nesilinganiso sembewu ekubunjweni kwe-nickel sulfate hexahydrate kuhlolwe kusetshenziswa ukupholisa ngezikhathi ezithile. Zonke izivivinyo zenziwa ekushiseni kokuqala okungu-25 °C. 25 °C kukhethwe njengokushisa kobucwebe uma kucatshangelwa ukulinganiselwa kokulawula izinga lokushisa ngesikhathi sokuhlunga. Ukwakheka kwe-crystal kungabangelwa ukushintshashintsha kwezinga lokushisa okungazelelwe ngesikhathi sokuhlunga izixazululo ezishisayo kusetshenziswa i-funnel ye-Buchner enokushisa okuphansi. Le nqubo ingathinta kakhulu i-kinetics, ukungcola, kanye nezakhiwo ezahlukahlukene zekristalu.
Isixazululo se-nickel saqala ukulungiswa ngokuncibilikisa amagremu angu-224 e-NiSO4 6H2O emanzini acwecwe angu-200 ml. Ukuhlushwa okukhethiwe kuhambisana nokugcwala okuphezulu (S) = 1.109. Ukugcwala okuphezulu kwanqunywa ngokuqhathanisa ukuncibilika kwamakristalu e-nickel sulfate acwecwekile nokuncibilika kwe-nickel sulfate hexahydrate ku-25 °C. Ukugcwala okuphezulu okuphezulu kwakhethwa ukuvimbela ukuqhekeka okuzenzakalelayo lapho izinga lokushisa lehliswa liye kwelokuqala.
Umphumela wokuhlushwa kwama-ion e-NH4+ enkambisweni yokwenza ikristalu uhlolwe ngokungeza i-(NH4)2SO4 esixazululweni se-nickel. Ukuhlushwa kwama-ion e-NH4+ asetshenziswe kulolu cwaningo kwakuyi-0, 1.25, 2.5, 3.75, kanye ne-5 g/L. Isixazululo sashiswa ku-60 °C imizuzu engama-30 ngenkathi sivunguza ku-300 rpm ukuqinisekisa ukuxubana okufanayo. Isixazululo sabe sesipholiswa ekushiseni kokusabela okufunwayo. Lapho izinga lokushisa lifika ku-25 °C, amanani ahlukene amakristalu embewu (izilinganiso zembewu ezingu-0.5%, 1%, 1.5%, kanye no-2%) zenezelwa esixazululweni. Isilinganiso sembewu sanqunywa ngokuqhathanisa isisindo sembewu nesisindo se-NiSO4 6H2O esixazululweni.
Ngemva kokufaka amakristalu embewu esixazululweni, inqubo yokwenza amakristalu yenzeke ngokwemvelo. Inqubo yokwenza amakristalu yahlala imizuzu engama-30. Isixazululo sahlungwa kusetshenziswa umshini wokuhlunga ukuze kuhlukaniswe amakristalu aqongelelwe esixazululweni. Ngesikhathi senqubo yokuhlunga, amakristalu ayehlanzwa njalo nge-ethanol ukuze kuncishiswe amathuba okuphinda kufakwe amakristalu futhi kuncishiswe ukunamathela kokungcola esixazululweni ebusweni bamakristalu. I-ethanol yakhethwa ukugeza amakristalu ngoba amakristalu awancibiliki ku-ethanol. Amakristalu ahlungiwe afakwa ku-incubator yelabhorethri ku-50 °C. Imingcele yokuhlola eningiliziwe esetshenziswe kulolu cwaningo iboniswe kuThebula 2.
Isakhiwo sekristalu sinqunywe kusetshenziswa ithuluzi le-XRD (SmartLab SE—HyPix-400) futhi kwatholakala ukuba khona kwama-NH4+ compounds. Ukuchazisisa kwe-SEM (i-Apreo 2 HiVac) kwenziwa ukuze kuhlaziywe isimo sekristalu. Izakhiwo zokushisa zamakristalu zinqunywe kusetshenziswa ithuluzi le-TGA (TG-209-F1 Libra). Amaqembu asebenzayo ahlaziywe yi-FTIR (JASCO-FT/IR-4X). Ubumsulwa besampula bunqunywe kusetshenziswa ithuluzi le-ICP-MS (i-Prodigy DC Arc). Isampula yalungiswa ngokuncibilikisa amakristalu angu-0.5 g ku-100 mL wamanzi acwecwe. Isivuno sekristalu (x) sabalwa ngokuhlukanisa isisindo sekristalu ephumayo ngobuningi bekristalu efakiwe ngokwefomula (1).
lapho u-x eyinzuzo yekristalu, ehluka kusuka ku-0 kuya ku-1, i-mout iyisisindo samakristalu okukhiphayo (g), i-min iyisisindo samakristalu okufakayo (g), i-msol iyisisindo samakristalu esixazululweni, kanti i-mseed iyisisindo samakristalu embewu.
Isivuno se-crystallization siphinde sahlolwa ukuze kutholakale i-kinetics yokukhula kwe-crystal futhi kulinganiswe inani lamandla okusebenza. Lolu cwaningo lwenziwe ngesilinganiso sokuhlwanyela esingu-2% kanye nenqubo efanayo yokuhlola njengangaphambili. Amapharamitha e-kinetics e-isothermal crystallization anqunywa ngokuhlola isivuno se-crystal ngezikhathi ezahlukene ze-crystallization (10, 20, 30, kanye nemizuzu engu-40) kanye namazinga okushisa okuqala (25, 30, 35, kanye no-40 °C). Amazinga akhethiwe ekushiseni kokuqala ahambisana namanani e-supersaturation (S) angu-1.109, 1.052, 1, kanye no-0.953, ngokulandelana. Inani le-supersaturation linqunywa ngokuqhathanisa ukuncibilika kwamakristalu e-nickel sulfate ancibilikisiwe nokuncibilika kwe-nickel sulfate hexahydrate ekushiseni kokuqala. Kulolu cwaningo, ukuncibilika kwe-NiSO4 6H2O ku-200 mL wamanzi emazingeni okushisa ahlukene ngaphandle kokungcola kuboniswe kuMfanekiso 2.
I-Johnson-Mail-Avrami (ithiyori ye-JMA) isetshenziselwa ukuhlaziya ukuziphatha kwe-isothermal crystallization. Ithiyori ye-JMA ikhethwa ngoba inqubo ye-crystallization ayenzeki kuze kube yilapho amakristalu embewu engeziwe esixazululweni. Ithiyori ye-JMA ichazwa kanje:
Lapho u-x(t) emele ukuguquka ngesikhathi u-t, u-k umele izinga lokuguquka elingaguquki, u-t umele isikhathi sokuguquka, kanti u-n umele inkomba ye-Avrami. Ifomula 3 isuselwa kufomula (2). Amandla okusebenza kwe-crystallization anqunywa kusetshenziswa i-Arrhenius equation:
Lapho i-kg ingukuguquguquka kwesilinganiso sokusabela, i-k0 ingukuguquguquka, i-Eg amandla okusebenza okukhula kwekristalu, i-R ingukuguquguquka kwegesi ye-molar (R=8.314 J/mol K), kanti i-T ingukushisa kwe-isothermal crystallization (K).
Isithombe 3a sibonisa ukuthi isilinganiso sokuhlwanyela imbewu kanye nokuhlushwa kwe-dopant kunomthelela ekuvuneni kwamakristalu e-nickel. Lapho ukuhlushwa kwe-dopant esixazululweni kukhuphukela ku-2.5 g/L, ukuhlushwa kwekristalu kwehle kusuka ku-7.77% kuya ku-6.48% (isilinganiso sembewu esingu-0.5%) kanye nokusuka ku-10.89% kuya ku-10.32% (isilinganiso sembewu esingu-2%). Ukwanda okwengeziwe kokuhlushwa kwe-dopant kwaholela ekwandeni okuhambisanayo kokuhlushwa kwekristalu. Isivuno esiphezulu sifinyelele ku-17.98% lapho isilinganiso sokuhlwanyela imbewu sasingu-2% kanti ukuhlushwa kwe-dopant kwakungu-5 g/L. Izinguquko kuphethini yokuhlushwa kwekristalu ngokwanda kokuhlushwa kwe-dopant zingase zihlobane nezinguquko endleleni yokukhula kwekristalu. Lapho ukuhlushwa kwe-dopant kuphansi, ama-ion e-Ni2+ kanye ne-NH4+ ancintisana ngokubopha ne-SO42−, okuholela ekwandeni kokuncibilika kwe-nickel esixazululweni kanye nokwehla kokuhlushwa kwekristalu. 14 Uma ukugcwala kokungcola kuphezulu, inqubo yokuncintisana isaqhubeka, kodwa amanye ama-ion e-NH4+ ahlangana nama-ion e-nickel ne-sulfate ukuze akhe usawoti ophindwe kabili we-nickel ammonium sulfate. 16 Ukwakheka kosawoti ophindwe kabili kuholela ekunciphiseni kokuncibilika kwe-solute, ngaleyo ndlela kwandise isivuno sekristalu. Ukwandisa isilinganiso sokuhlwanyela kungathuthukisa njalo isivuno sekristalu. Imbewu ingaqalisa inqubo ye-nucleation kanye nokukhula kwekristalu okuzenzakalelayo ngokunikeza indawo yokuqala yobuso bama-ion ancibilikayo ukuze ahlele futhi akhe amakristalu. Njengoba isilinganiso sokuhlwanyela sikhula, indawo yokuqala yobuso bama-ion ukuze ahlele iyanda, ngakho-ke kungakhiwa amakristalu amaningi. Ngakho-ke, ukwandisa isilinganiso sokuhlwanyela kunomthelela oqondile esilinganisweni sokukhula kwekristalu kanye nesivuno sekristalu. 17
Amapharamitha e-NiSO4 6H2O: (a) isivuno sekristalu kanye (b) i-pH yesisombululo se-nickel ngaphambi nangemva kokugonywa.
Isithombe 3b sibonisa ukuthi isilinganiso sembewu kanye nokuhlushwa kwe-dopant kuthinta i-pH yesisombululo se-nickel ngaphambi nangemva kokufakwa kwembewu. Inhloso yokuqapha i-pH yesisombululo ukuqonda izinguquko ekulinganisweni kwamakhemikhali esixazululweni. Ngaphambi kokufaka amakristalu embewu, i-pH yesisombululo ivame ukwehla ngenxa yokuba khona kwama-ion e-NH4+ akhipha ama-proton e-H+. Ukwandisa ukuhlushwa kwe-dopant kuholela ekukhishweni kwama-proton e-H+ amaningi, ngaleyo ndlela kunciphisa i-pH yesisombululo. Ngemva kokufaka amakristalu embewu, i-pH yazo zonke izixazululo iyanda. Ukuthambekela kwe-pH kuhlobene kahle nokuthambekela kokukhiqizwa kwekristalu. Inani le-pH eliphansi kakhulu litholakale ekuhlushweni kwe-dopant okungu-2.5 g/L kanye nesilinganiso sembewu esingu-0.5%. Njengoba ukuhlushwa kwe-dopant kukhuphuka kufika ku-5 g/L, i-pH yesisombululo iyanda. Lesi simo siyaqondakala impela, njengoba ukutholakala kwama-ion e-NH4+ esixazululweni kuncipha ngenxa yokumuncwa, noma ngenxa yokufakwa, noma ngenxa yokumuncwa nokufakwa kwama-ion e-NH4+ ngamakristalu.
Ukuhlolwa kwe-crystal yield kanye nokuhlaziywa kwenziwa ukuze kutholakale ukuziphatha kwe-kinetic kokukhula kwe-crystal nokubala amandla okusebenza kokukhula kwe-crystal. Amapharamitha e-isothermal crystallization kinetics achazwe esigabeni seMethods. Isithombe 4 sibonisa i-Johnson-Mehl-Avrami (JMA) plot ekhombisa ukuziphatha kwe-kinetic kokukhula kwe-nickel sulfate crystal. I-plot yakhiqizwa ngokuhlela inani le-ln[− ln(1− x(t))] ngokumelene nenani le-ln t (Isibalo 3). Amanani e-gradient atholakale ku-plot ahambisana namanani e-JMA index (n) ​​abonisa ubukhulu be-crystal ekhulayo kanye nendlela yokukhula. Ngenkathi inani le-cutoff libonisa izinga lokukhula elimelelwa yi-ln k engaguquki. Amanani e-JMA index (n) asukela ku-0.35 kuya ku-0.75. Leli nani le-n libonisa ukuthi amakristalu anokukhula kobukhulu obulodwa futhi alandela indlela yokukhula elawulwa ukusabalala; 0 < n < 1 ikhombisa ukukhula kobukhulu obulodwa, kuyilapho i-n < 1 ikhombisa indlela yokukhula elawulwa ukusabalala. 18 Izinga lokukhula kwe-k engaguquki liyancipha ngokushisa okwandayo, okubonisa ukuthi inqubo yokwakheka kwekristalu yenzeka ngokushesha emazingeni okushisa aphansi. Lokhu kuhlobene nokwanda kokugcwala kwesisombululo emazingeni okushisa aphansi.
Ama-Johnson-Mehl-Avrami (JMA) ama-slots e-nickel sulfate hexahydrate emazingeni okushisa ahlukene e-crystallization: (a) 25 °C, (b) 30 °C, (c) 35 °C kanye (d) 40 °C.
Ukwengezwa kwama-dopants kubonise iphethini efanayo yesilinganiso sokukhula kuwo wonke amazinga okushisa. Lapho ukuhlushwa kwe-dopant kungu-2.5 g/L, izinga lokukhula kwekristalu lehla, futhi lapho ukuhlushwa kwe-dopant kuphakeme kuno-2.5 ​​g/L, izinga lokukhula kwekristalu lenyuka. Njengoba kushiwo ngaphambili, ushintsho kuphethini yesilinganiso sokukhula kwekristalu lubangelwa ushintsho endleleni yokusebenzisana phakathi kwama-ion esixazululweni. Lapho ukuhlushwa kwe-dopant kuphansi, inqubo yokuncintisana phakathi kwama-ion esixazululweni ikhulisa ukuncibilika kwe-solute, ngaleyo ndlela kunciphisa izinga lokukhula kwekristalu. 14 Ngaphezu kwalokho, ukwengezwa kwamazinga aphezulu ama-dopants kubangela ukuthi inqubo yokukhula ishintshe kakhulu. Lapho ukuhlushwa kwe-dopant kudlula u-3.75 g/L, kwakheka ama-nuclei amasha ekristalu, okuholela ekunciphiseni ukuncibilika kwe-solute, ngaleyo ndlela kwandisa izinga lokukhula kwekristalu. Ukwakheka kwama-nuclei amasha ekristalu kungabonakaliswa ngokwakhiwa kosawoti ophindwe kabili (NH4)2Ni(SO4)2 6H2O. 16 Uma kuxoxwa ngendlela yokukhula kwekristalu, imiphumela ye-X-ray diffraction iqinisekisa ukwakheka kosawoti ophindwe kabili.
Umsebenzi we-JMA plot uphinde wahlolwa ukuze kutholakale amandla okusebenza e-crystallization. Amandla okusebenza abalwa kusetshenziswa i-Arrhenius equation (eboniswe ku-Equation (4)). Isithombe 5a sibonisa ubudlelwano phakathi kwenani le-ln(kg) kanye nenani le-1/T. Ngemuva kwalokho, amandla okusebenza abalwa kusetshenziswa inani le-gradient elitholwe ku-plot. Isithombe 5b sibonisa amanani amandla okusebenza e-crystallization ngaphansi kwamazinga ahlukene okungcola. Imiphumela ikhombisa ukuthi izinguquko ekugxilweni kokungcola zithinta amandla okusebenza. Amandla okusebenza e-crystallization yamakristalu e-nickel sulfate ngaphandle kokungcola angama-215.79 kJ/mol. Lapho ukugxilwa kokungcola kufinyelela ku-2.5 g/L, amandla okusebenza anda ngo-3.99% kuya ku-224.42 kJ/mol. Ukwanda kwamandla okusebenza kubonisa ukuthi isithiyo samandla senqubo ye-crystallization siyanda, okuzoholela ekwehleni kwesilinganiso sokukhula kwekristalu kanye nokuvunwa kwekristalu. Lapho ukugxilwa kokungcola kungaphezu kuka-2.5 g/L, amandla okusebenza e-crystallization ancipha kakhulu. Uma kugxilwe ekungcoleni okungu-5 g/l, amandla okusebenza angu-205.85 kJ/mol, okungaphansi ngo-8.27% kunamandla okusebenza uma kugxilwe ekungcoleni okungu-2.5 g/l. Ukwehla kwamandla okusebenza kubonisa ukuthi inqubo yokwenza ikristalu ilula, okuholela ekwandeni kwesilinganiso sokukhula kwekristalu kanye nokukhiqizwa kwekristalu.
(a) Ukufakwa kwesakhiwo se-ln(kg) uma kuqhathaniswa ne-1/T kanye (b) namandla okusebenza Isib. Ukukristala ekujuleni okuhlukene kokungcola.
Indlela yokukhula kwekristalu ihlolwe nge-XRD kanye ne-FTIR spectroscopy, kwahlaziywa i-kinetics yokukhula kwekristalu kanye namandla okusebenza. Isithombe 6 sibonisa imiphumela ye-XRD. Imininingwane ihambisana ne-PDF #08–0470, ekhombisa ukuthi iyi-α-NiSO4 6H2O (i-silica ebomvu). Ikristalu ingeyesistimu ye-tetragonal, iqembu lesikhala yi-P41212, amapharamitha weseli leyunithi yi-a = b = 6.782 Å, c = 18.28 Å, α = β = γ = 90°, kanti ivolumu yi-840.8 Å3. Le miphumela ihambisana nemiphumela eyanyatheliswa ngaphambilini nguManomenova et al. 19 Ukwethulwa kwama-ion e-NH4+ kuholela ekwakhekeni kwe-(NH4)2Ni(SO4)2 6H2O. Imininingwane ingeye-PDF No. 31–0062. Ikristalu ingeyesistimu ye-monoclinic, iqembu lesikhala P21/a, amapharamitha weseli leyunithi angu-a = 9.186 Å, b = 12.468 Å, c = 6.242 Å, α = γ = 90°, β = 106.93°, kanti ivolumu ingu-684 Å3. Le miphumela ihambisana nocwaningo lwangaphambilini olubikwe nguSu et al.20.
Amaphethini okusabalalisa kwe-X-ray amakristalu e-nickel sulfate: (a–b) 0.5%, (c–d) 1%, (e–f) 1.5%, kanye (g–h) 2% isilinganiso sembewu. Isithombe sesokudla siwumbono okhulisiwe wesithombe sesobunxele.
Njengoba kuboniswe kuZithombe 6b, d, f kanye ne-h, u-2.5 g/L uwumkhawulo ophezulu kakhulu wokuhlushwa kwe-ammonium esixazululweni ngaphandle kokwenza usawoti owengeziwe. Lapho ukuhlushwa kokungcola kungu-3.75 kanye no-5 g/L, ama-ion e-NH4+ afakwa esakhiweni sekristalu ukuze akhe usawoti oyinkimbinkimbi (NH4)2Ni(SO4)2 6H2O. Ngokusho kwedatha, ukuqina okuphezulu kosawoti oyinkimbinkimbi kuyanda njengoba ukuhlushwa kokungcola kukhuphuka kusuka ku-3.75 kuya ku-5 g/L, ikakhulukazi ku-2θ 16.47° kanye no-17.44°. Ukwanda kokuphezulu kosawoti oyinkimbinkimbi kungenxa nje yesimiso sokulingana kwamakhemikhali. Kodwa-ke, ezinye iziqongo ezingavamile zibonwa ku-2θ 16.47°, okungabangelwa ukuguquguquka kwe-elastic kwekristalu. 21 Imiphumela yokuchaza ikhombisa nokuthi isilinganiso sokuhlwanyela esiphezulu siphumela ekwehleni kokuhlushwa okuphezulu kosawoti oyinkimbinkimbi. Isilinganiso sembewu esiphezulu sisheshisa inqubo yokwenza ikristalu, okuholela ekwehleni okukhulu kwe-solute. Kulesi simo, inqubo yokukhula kwekristalu igxile embewini, futhi ukwakheka kwezigaba ezintsha kuphazanyiswa ukwehla kokugcwala kwesisombululo. Ngokuphambene nalokho, lapho isilinganiso sembewu siphansi, inqubo yokugcwala kwekristalu ihamba kancane, futhi ukugcwala kwesisombululo kuhlala kusezingeni eliphezulu. Lesi simo sandisa amathuba okuthi kube khona i-nucleation kasawoti ophindwe kabili ongancibiliki kalula (NH4)2Ni(SO4)2 6H2O. Idatha yobukhulu obuphezulu kasawoti ophindwe kabili inikezwe kuThebula 3.
Ukucaciswa kwe-FTIR kwenziwa ukuze kuhlolwe noma yikuphi ukuphazamiseka noma izinguquko zesakhiwo ku-lattice yomsingathi ngenxa yokuba khona kwama-ion e-NH4+. Amasampula anesilinganiso sokuhlwanyela esingaguquki esingu-2% abonisiwe. Isithombe 7 sibonisa imiphumela yokucaciswa kwe-FTIR. Iziqongo ezibanzi ezibonwe ku-3444, 3257 kanye no-1647 cm−1 zibangelwa izindlela zokwelula ze-O–H zama-molecule. Iziqongo ku-2370 kanye no-2078 cm−1 zimelela izibopho ze-hydrogen eziphakathi kwama-molecule amanzi. Ibhendi ku-412 cm−1 ihlotshaniswa nokudlidliza kokwelula kwe-Ni–O. Ngaphezu kwalokho, ama-ion e-SO4− amahhala abonisa izindlela ezine ezinkulu zokudlidliza ku-450 (υ2), 630 (υ4), 986 (υ1) kanye no-1143 kanye no-1100 cm−1 (υ3). Izimpawu υ1-υ4 zimelela izakhiwo zezindlela zokudlidliza, lapho u-υ1 emelela imodi yokungadlidlizi (ukwelula okulinganayo), u-υ2 umelela imodi yokudlidliza okuphindwe kabili (ukugoba okulinganayo), kanye no-υ3 no-υ4 bamelela izindlela zokudlidliza okuphindwe kathathu (ukwelula okulinganayo kanye nokugoba okulinganayo, ngokulandelana). 22,23,24 Imiphumela yokuchaza ikhombisa ukuthi ukuba khona kokungcola kwe-ammonium kunikeza inani eliphakeme kakhulu kunombolo ye-wave engu-1143 cm-1 (ephawulwe ngombuthano obomvu esithombeni). Inani eliphakeme kakhulu ku-1143 cm-1 libonisa ukuthi ukuba khona kwama-ion e-NH4+, kungakhathaliseki ukuthi kugxilwe kangakanani, kubangela ukuphambuka kwesakhiwo se-lattice, okuholela ekushintsheni kwemvamisa yokudlidliza kwama-molecule e-ion e-sulfate ngaphakathi kwekristalu.
Ngokusekelwe emiphumeleni ye-XRD kanye ne-FTIR ehlobene nokuziphatha kwe-kinetic kokukhula kwekristalu kanye namandla okusebenza, Isithombe 8 sibonisa i-schematic yenqubo yokwenza ikristalu ye-nickel sulfate hexahydrate ngokungezwa kokungcola kwe-NH4+. Uma kungekho ukungcola, ama-ion e-Ni2+ azosabela ne-H2O ukwakha i-nickel hydrate [Ni(6H2O)]2−. Ngemuva kwalokho, i-nickel hydrate ihlangana ngokuzenzakalelayo nama-ion e-SO42− ukwakha i-nuclei ye-Ni(SO4)2 6H2O futhi ikhule ibe amakristalu e-nickel sulfate hexahydrate. Lapho ukugcwala okuphansi kokungcola kwe-ammonium (2.5 g/L noma ngaphansi) kufakwa esixazululweni, i-[Ni(6H2O)]2− kunzima ukuyihlanganisa ngokuphelele nama-ion e-SO42− ngoba ama-ion e-[Ni(6H2O)]2− kanye ne-NH4+ ancintisana ngokuhlanganiswa nama-ion e-SO42−, yize kusekhona ama-ion e-sulfate anele okusabela ngawo womabili ama-ion. Lesi simo siholela ekwandeni kwamandla okusebenza okwenza ikristalu kanye nokwehla kokukhula kwekristalu. 14,25 Ngemva kokuba ama-nuclei e-nickel sulfate hexahydrate akhiwe futhi akhule abe amakristalu, ama-ion amaningi e-NH4+ kanye ne-(NH4)2SO4 ayamuncwa ebusweni bekristalu. Lokhu kuchaza ukuthi kungani iqembu elisebenzayo le-SO4− ion (inombolo ye-wave engu-1143 cm−1) kumasampula e-NSH-8 kanye ne-NSH-12 lihlala lakhiwe ngaphandle kwenqubo yokukhipha i-doping. Lapho ukugcwala kokungcola kuphezulu, ama-ion e-NH4+ aqala ukufakwa esakhiweni sekristalu, akha usawoti ophindwe kabili. 16 Lesi simo senzeka ngenxa yokuntuleka kwama-ion e-SO42− esixazululweni, kanti ama-ion e-SO42− abopha kuma-nickel hydrate ngokushesha kunama-ion e-ammonium. Le ndlela ikhuthaza i-nucleation kanye nokukhula kwama-salts aphindwe kabili. Ngesikhathi senqubo yokuhlanganisa, ama-nuclei e-Ni(SO4)2 6H2O kanye ne-(NH4)2Ni(SO4)2 6H2O akhiwa ngasikhathi sinye, okuholela ekwandeni kwenani lama-nuclei atholiwe. Ukwanda kwenani lama-nuclei kukhuthaza ukusheshisa kokukhula kwekristalu kanye nokwehla kwamandla okusebenza.
Ukusabela kwamakhemikhali kokuncibilikisa i-nickel sulfate hexahydrate emanzini, ukwengeza inani elincane kanye nenani elikhulu le-ammonium sulfate, bese kwenziwa inqubo yokwenza i-crystallization kungavezwa kanje:
Imiphumela yokuchaza i-SEM iboniswe kuMfanekiso 9. Imiphumela yokuchaza ikhombisa ukuthi inani likasawoti we-ammonium elingeziwe kanye nesilinganiso sokuhlwanyela imbewu akuthinti kakhulu ukuma kwekristalu. Usayizi wamakristalu akhiwe uhlala ungaguquki, yize amakristalu amakhulu avela kwezinye izindawo. Kodwa-ke, kusadingeka ukucacisa okwengeziwe ukuze kutholakale umphumela wokuhlushwa kukasawoti we-ammonium kanye nesilinganiso sokuhlwanyela imbewu kusayizi ojwayelekile wamakristalu akhiwe.
Ukwakheka kwekristalu kwe-NiSO4 6H2O: (a–e) 0.5%, (f–j) 1%, (h–o) 1.5% kanye ne-(p–u) 2% isilinganiso sembewu esibonisa ushintsho lokuhlushwa kwe-NH4+ kusuka phezulu kuya phansi, okungu-0, 1.25, 2.5, 3.75 kanye no-5 g/L, ngokulandelana.
Isithombe 10a sibonisa amajika e-TGA amakristalu anokuhlushwa okuhlukile kokungcola. Ukuhlaziywa kwe-TGA kwenziwa kumasampula anesilinganiso sokuhlwanyela esingu-2%. Ukuhlaziywa kwe-XRD kwenziwa futhi kusampula ye-NSH-20 ukuthola ama-compounds akhiwe. Imiphumela ye-XRD eboniswe ku-Figure 10b iqinisekisa izinguquko esakhiweni sekristalu. Ukulinganiswa kwe-Thermogravimetric kubonisa ukuthi wonke amakristalu ahlanganisiwe abonisa ukuzinza kokushisa kuze kufike ku-80°C. Ngemva kwalokho, isisindo sekristalu sehle ngo-35% lapho izinga lokushisa lenyuka laya ku-200°C. Ukulahlekelwa isisindo kwamakristalu kungenxa yenqubo yokubola, ehilela ukulahlekelwa ama-molecule amanzi angu-5 ukuze akhe i-NiSO4 H2O. Lapho izinga lokushisa lenyuka laya ku-300–400°C, isisindo samakristalu sehla futhi. Ukulahlekelwa isisindo kwamakristalu kwakungaba ngu-6.5%, kanti ukulahlekelwa isisindo kwesampula yekristalu ye-NSH-20 kwakuphakeme kancane, ncamashi ngo-6.65%. Ukuwohloka kwama-ion e-NH4+ abe yigesi ye-NH3 kusampula ye-NSH-20 kuholele ekunciphiseni okuncane. Njengoba izinga lokushisa landa kusuka ku-300 kuya ku-400°C, isisindo samakristalu sehla, okwaholela ekutheni wonke amakristalu abe nesakhiwo se-NiSO4. Ukwandisa izinga lokushisa kusuka ku-700°C kuya ku-800°C kwabangela ukuthi isakhiwo sekristalu siguquke sibe yi-NiO, okwabangela ukukhishwa kwamagesi e-SO2 ne-O2.25,26
Ubumsulwa bamakristalu e-nickel sulfate hexahydrate bunqunywe ngokuhlola ukuhlushwa kwe-NH4+ kusetshenziswa ithuluzi le-DC-Arc ICP-MS. Ubumsulwa bamakristalu e-nickel sulfate bunqunywe kusetshenziswa ifomula (5).
Lapho i-Ma iyisisindo sokungcola kukristalu (mg), i-Mo iyisisindo sekristalu (mg), i-Ca iyisilinganiso sokungcola kusixazululo (mg/l), i-V iyivolumu yesisombululo (l).
Isithombe 11 sibonisa ubumsulwa bamakristalu e-nickel sulfate hexahydrate. Inani lobumsulwa liyinani elimaphakathi lezici ezi-3. Imiphumela ikhombisa ukuthi isilinganiso sokuhlwanyela kanye nokuhlushwa kokungcola kuthinta ngqo ubumsulwa bamakristalu e-nickel sulfate akhiwe. Uma ukuhlushwa kokungcola kuphakeme, kulapho ukumuncwa kokungcola kukhulu, okuholela ekuhlanzekeni okuphansi kwamakristalu akhiwe. Kodwa-ke, iphethini yokumuncwa kokungcola ingashintsha kuye ngokuthi ukuhlushwa kokungcola kungakanani, futhi igrafu yomphumela ikhombisa ukuthi ukumuncwa kokungcola okuphelele ngamakristalu akushintshi kakhulu. Ngaphezu kwalokho, le miphumela ikhombisa nokuthi isilinganiso sokuhlwanyela esiphezulu singathuthukisa ubumsulwa bamakristalu. Lesi simo singenzeka ngoba lapho iningi lama-nuclei e-crystal akhiwe ligxile kuma-nuclei e-nickel, amathuba okuba ama-ion e-nickel aqoqeke kuma-nickel aphezulu. 27
Ucwaningo lubonise ukuthi ama-ion e-ammonium (NH4+) athinta kakhulu inqubo yokwenza ikristalu kanye nezakhiwo zekristalu zamakristalu e-nickel sulfate hexahydrate, futhi aveze nethonya lesilinganiso sembewu enqubweni yokwenza ikristalu.
Uma amazinga e-ammonium engaphezu kuka-2.5 g/l, isivuno sekristalu kanye nesilinganiso sokukhula kwekristalu kuyehla. Uma amazinga e-ammonium engaphezu kuka-2.5 g/l, isivuno sekristalu kanye nesilinganiso sokukhula kwekristalu kuyenyuka.
Ukwengezwa kokungcola esixazululweni se-nickel kwandisa ukuncintisana phakathi kwama-ion angu-NH4+ kanye nama-ion angu-[Ni(6H2O)]2− e-SO42−, okuholela ekwandeni kwamandla okusebenza. Ukwehla kwamandla okusebenza ngemva kokwengeza amazinga aphezulu okungcola kungenxa yokungena kwama-ion angu-NH4+ esakhiweni sekristalu, ngaleyo ndlela kwakha usawoti ophindwe kabili (NH4)2Ni(SO4)2 6H2O.
Ukusebenzisa isilinganiso esiphezulu sokuhlwanyela imbewu kungathuthukisa isivuno sekristalu, izinga lokukhula kwekristalu kanye nobumsulwa bekristalu be-nickel sulfate hexahydrate.
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