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Dyondzo leyi yi lavisisa mbuyelo wa thyaka ra NH4+ na ratio ya mbewu eka endlelo ro kula na matirhelo ya nickel sulfate hexahydrate ehansi ka discontinuous cooling crystallization, naswona yi kambisisa mbuyelo wa thyaka ra NH4+ eka endlelo ro kula, swivumbeko swa mahiselo, na mintlawa leyi tirhaka ya nickel sulfate hexahydrate. Eka nhlayo yale hansi ya thyaka, ti ions ta Ni2+ na NH4+ ti phikizana na SO42− eka ku boha, leswi endlaka leswaku kuhunguteka mbuyelo wa crystal xikan’we naku kula xikan’we naku tlakuka ka crystallization activation energy. Eka nhlayo yale henhla ya thyaka, ti ions ta NH4+ ti nghenisiwa eka xivumbeko xa crystal kuva ti endla munyu wo rharhangana (NH4)2Ni(SO4)2 6H2O. Ku endliwa ka munyu lowu rharhanganeke swiendla leswaku kuva na ku tlakuka ka mbuyelo wa crystal xikan’we naku kula xikan’we nakuhunguteka ka crystallization activation energy. Kuva kona ka nhlayo yale henhla nale hansi ya NH4+ ion concentrations swivanga ku soholotiwa ka lattice, naswona ti crystals titshamisekile hi mahiselo eka mahiselo lawa yanga fika eka 80 °C. Ku engetela kwalano, nkucetelo wa thyaka ra NH4+ eka endlelo ra kukula ka crystal wukulu kutlula wa ratio ya mbewu. Loko nhlayo ya thyaka yiri ehansi, thyaka ra olova ku ri namarheta eka crystal; loko nhlayo ya kona yi ri ehenhla, thyaka ra olova ku ri nghenisa eka kristala. Nhlayo ya mbewu yinga engetela swinene mbuyelo wa crystal xikan’we naku antswisa nyana ku basa ka crystal.
Nickel sulfate hexahydrate (NiSO4 6H2O) sweswi i nchumu wa nkoka lowu tirhisiwaka eka ti indasitiri to hambana hambana, kukatsa na vumaki bya ti battery, electroplating, catalysts, hambi kuri eka vuhumelerisi bya swakudya, mafurha, na perfume. 1,2,3 Nkoka wa yona wu ya wu kula hi nhluvukiso wa xihatla wa mimovha ya gezi, leyi titshegeke ngopfu hi tibetiri ta lithium-ion (LiB) leti simekiweke eka nickel. Ku tirhisiwa ka ti alloys ta high-nickel tofana na NCM 811 swilanguteriwa kuva swita lawula hi 2030, leswi yaka emahlweni swi engetela xilaveko xa nickel sulfate hexahydrate. Hambiswiritano, hikokwalaho ka swipimelo swa switirhisiwa, vuhumelerisi byinga ha fambisana na xilaveko lexi kulaka, leswi endlaka leswaku kuva na xivandla exikarhi ka mphakelo na xilaveko. Ku pfumaleka loku ku tlakusile ku vilela hi vukona bya switirhisiwa na ku tshamiseka ka nxavo, leswi kombisaka xilaveko xa vuhumelerisi bya kahle bya nickel sulfate ya vutengi bya le henhla, leyi tiyeke ya giredi ya betri. 1,4
Ku endliwa ka nickel sulfate hexahydrate hi xitalo swifikeleriwa hiku crystallization. Exikarhi ka tindlela to hambana hambana, ndlela yo kufumeta i ndlela leyi tirhisiwaka ngopfu, leyingana swipfuno swaku tirhisiwa ka eneji yale hansi xikan’we na vuswikoti byo humelerisa switirhisiwa swa vutengi byale henhla. 5,6 Vulavisisi bya crystallization ya nickel sulfate hexahydrate hiku tirhisa discontinuous cooling crystallization byi endlile nhluvuko lowukulu. Sweswi, vulavisisi byotala byi kongomisa eka ku antswisa maendlelo ya crystallization hiku antswisa ti parameters tofana na mahiselo, cooling rate, vukulu bya mbewu na pH. 7,8,9 Xikongomelo i ku engetela mbuyelo wa ti crystal na ku basa ka ti crystals leti kumiweke. Hambiswiritano, hambi leswi kunga na dyondzo leyi heleleke ya ti parameters leti, kuna xivandla lexikulu eka nyingiso lowu nyikiwaka eka nkucetelo wa thyaka, ngopfu ngopfu ammonium (NH4+), eka mbuyelo wa crystallization.
Thyaka ra ammonium ritala kuva kona eka nickel solution leyi tirhisiwaka eka nickel crystallization hikokwalaho ka vukona bya thyaka ra ammonium hinkarhi wa maendlelo yo humesa. Ammonia yitala kutirhisiwa tani hi saponifying agent, leyi siyaka nhlayo ya NH4+ eka nickel solution. 10,11,12 Hambi leswi thyaka ra ammonium ri nga kona hinkwako, vuyelo bya byona eka swivumbeko swa crystal swo fana na xivumbeko xa crystal, endlelo ro kula, swivumbeko swa ku hisa, ku basa, na swin’wana swa ha twisiseki kahle. Vulavisisi lebyi nga nyawuriki eka vuyelo bya tona i bya nkoka hikuva thyaka ringa sivela kumbe ku cinca kukula ka crystal naswona, eka swiyimo swin’wana, switirha tani hi swisivela, leswi khumbhaka ku cinca exikarhi ka swivumbeko swa metastable na stable crystalline. 13,14 Ku twisisa switandzhaku leswi hikokwalaho i swa nkoka swinene kusuka eka mavonelo ya indasitiri hikuva thyaka ringa kavanyeta khwalithi ya swikumiwa.
Hiku ya hi xivutiso xokarhi, ndzavisiso lowu awu kongomisiwile eka ku lavisisa mbuyelo wa thyaka ra ammonium eka swivumbeko swa ti crystals ta nickel. Hi ku twisisa vuyelo bya thyaka, ku nga endliwa tindlela letintshwa to lawula ni ku hunguta vuyelo bya byona byo biha. Dyondzo leyi yitlhele yi lavisisa ku yelana exikarhi ka nhlayo ya thyaka xikan’we naku cinca ka ratio ya mbewu. Leswi mbewu yi tirhisiwaka ngopfu eka maendlelo ya vuhumelerisi, ti parameters ta mbewu titirhisiwile eka ndzavisiso lowu, naswona swina nkoka kutwisisa vuxaka exikarhi ka swilo leswi swimbirhi. 15 Vuyelo bya ti parameter leti timbirhi byi tirhisiwile ku dyondza mbuyelo wa crystal, ndlela leyi crystal yi kulaka ha yona, xivumbeko xa crystal, morphology na ku basa. Ku engetela kwalano, mahanyelo ya kinetic, swivumbeko swa mahiselo, na mintlawa leyi tirhaka ya ti crystals ehansi ka nkucetelo wa thyaka ra NH4+ ntsena swi lavisisiwile kuya emahlweni.
Switirhisiwa leswi tirhisiweke eka ndzavisiso lowu a ku ri nickel sulfate hexahydrate (NiSO 6H2O, ≥ 99.8%) leyi nyikiweke hi GEM; ammonium sulfate ((NH)SO, ≥ 99%) leyi xaviweke eka Tianjin Huasheng Co., Ltd.; mati lama pfanganisiweke. Crystal ya mbewu leyi tirhisiweke akuri NiSO 6H2O, yi pfotlosiwa naku sefiwa kuva yikuma vukulu bya ti particle lebyi fanaka bya 0.154 mm. Swihlawulekisi swa NiSO 6H2O swi kombisiwile eka Tafula ra 1 na Xifaniso xa 1.
Vuyelo bya thyaka ra NH4+ xikan’we na ratio ya mbewu eka crystallization ya nickel sulfate hexahydrate swikamberiwile hiku tirhisa intermittent cooling. Swikambelo hinkwaswo swiendliwile eka mahiselo yosungula ya 25 °C. 25 °C yi hlawuriwile tani hi mahiselo ya crystallization loko ku tekeriwa enhlokweni swipimelo swa vulawuri bya mahiselo hinkarhi wa filtration. Crystallization yinga hlohleteriwa hiku cinca cinca ka mahiselo hi xitshuketa hinkarhi wa filtration ya ti solutions to hisa hiku tirhisa Buchner funnel ya mahiselo yale hansi. Endlelo leri ringa khumba swinene kinetics, ku tekiwa ka thyaka, na swivumbeko swohambana hambana swa crystal.
Nkatsakanyo wa nickel wusungule ku lulamisiwa hiku n’okisiwa ka 224 g NiSO4 6H2O eka 200 ml ya mati lawa ya distilled. Nhlayo leyi hlawuriweke yi fambelana na supersaturation (S) = 1.109. Supersaturation yikumiwile hiku pimanisa ku n’oka ka ti crystals ta nickel sulfate leti n’okisiweke na ku n’oka ka nickel sulfate hexahydrate eka 25 °C. Supersaturation yale hansi yi hlawuriwile ku sivela spontaneous crystallization loko mahiselo ya hungutiwa kuya eka yosungula.
Vuyelo bya NH4+ ion concentration eka maendlelo ya crystallization byi lavisisiwile hiku chela (NH4)2SO4 eka nickel solution. Nhlayo ya NH4+ ion leyi tirhisiweke eka ndzavisiso lowu a yi ri 0, 1.25, 2.5, 3.75, na 5 g/L. Nkatsakanyo wu hisiwa eka 60 °C kuringana 30 min loko yirikarhi yi hlanganisiwa hi 300 rpm kutiyisisa ku hlanganisiwa loku fanaka. Kutani solution yi titimela kuya eka mahiselo lawa ya lavekaka ya reaction. Loko mahiselo yafika eka 25 °C, nhlayo yohambana hambana ya ti crystals ta mbewu (seed ratios ya 0.5%, 1%, 1.5%, na 2%) yi cheriwile eka solution. Nhlayo ya mbewu yikumiwile hiku pimanisa ntiko wa mbewu na ntiko wa NiSO4 6H2O eka solution.
Endzhaku ko chela ti crystals ta mbewu eka solution, endlelo ra crystallization rihumelerile hi ntumbuluko. Endlelo ra crystallization ri teke timinete ta 30. Nkatsakanyo lowu wu sefiwile hiku tirhisa filter press kuva wu hambanyisa ti crystals leti hlengeletiweke kusuka eka solution. Hi nkarhi wa maendlelo ya filtration, ti crystals ati tshamela ku hlantswiwa hi ethanol kuva kuhungutiwa ku koteka ka recrystallization xikan’we naku hunguta ku namarhela ka thyaka eka solution eka vuandlalo bya ti crystals. Ethanol yi hlawuriwile ku hlantswa ti crystals hikuva ti crystals ati n’oki eka ethanol. Ti crystals leti sefiweke ti vekiwile eka laboratory incubator eka 50 °C. Vuxokoxoko bya tipharamitha ta swikambelo leti tirhisiweke eka ndzavisiso lowu ti kombisiwile eka Tafula ra 2.
Xivumbeko xa crystal xikumiwile hiku tirhisa xitirhisiwa xa XRD (SmartLab SE—HyPix-400) naswona vukona bya ti NH4+ compounds byi kumiwile. SEM characterization (Apreo 2 HiVac) yi endliwile ku xopaxopa xivumbeko xa crystal. Swihlawulekisi swa mahiselo ya ti crystals swikumiwile hiku tirhisa xitirhisiwa xa TGA (TG-209-F1 Libra). Mintlawa ya ntirho yi kamberiwile hi FTIR (JASCO-FT/IR-4X). Ku basa ka xikombiso swikumiwile hiku tirhisa xitirhisiwa xa ICP-MS (Prodigy DC Arc). Xikombiso xi lulamisiwile hiku n’okisiwa ka 0.5 g ya ti crystals eka 100 mL ya mati ya distilled. Mbuyelo wa crystallization (x) wu hlayiwile hiku avanyisa vukulu bya crystal ya vuhumelerisi hi vukulu bya crystal ya input kuya hi fomula (1).
laha x kunga mbuyelo wa crystal, lowu hambanaka kusuka eka 0 kuya eka 1, mout i ntiko wa ti crystals ta vuhumelerisi (g), min kunga ntiko wa ti crystals leti nghenisiweke (g), msol kunga ntiko wa ti crystals eka solution, naswona mseed i ntiko wa ti crystals ta mbewu.
Mbuyelo wa crystallization wuyile emahlweni ku lavisisiwa ku kumisisa kinetics ya kukula ka crystal xikan’we naku ringanyeta nkoka wa activation energy. Dyondzo leyi yi endliwile hi seeding ratio ya 2% xikan’we na endlelo ro ringeta kufana na khale. Ti parameters ta isothermal crystallization kinetics tikumiwile hiku kambela mbuyelo wa crystal eka minkarhi yohambana hambana ya crystallization (10, 20, 30, na 40 min) na mahiselo yosungula (25, 30, 35, na 40 °C). Ti concentrations leti hlawuriweke eka mahiselo yosungula ti fambelana na supersaturation (S) values ​​ya 1.109, 1.052, 1, na 0.953, hiku landzelelana. Nhlayo ya supersaturation yikumiwile hiku pimanisa ku n’oka ka ti dissolved nickel sulfate crystals na ku n’oka ka nickel sulfate hexahydrate eka mahiselo yosungula. Eka ndzavisiso lowu, ku n’oka ka NiSO4 6H2O eka 200 mL ya mati eka mahiselo yohambana hambana handle ka thyaka swikombisiwile eka Xifaniso xa 2.
Johnson-Mail-Avrami (JMA theory) yitirhisiwa ku xopaxopa mahanyelo ya isothermal crystallization. JMA theory yi hlawuriwile hikuva endlelo ra crystallization ari humeleli kufikela loko ti crystals ta mbewu ti cheriwa eka solution. Tiyori ya JMA yi hlamuseriwa hi ndlela leyi landzelaka:
Laha x(t) yi yimelaka ku cinca hi nkarhi wa t, k yi yimela constant ya mpimo wa ku cinca, t yi yimela nkarhi wa ku cinca, naswona n yi yimela index ya Avrami. Fomula ya 3 yi huma eka fomula ya (2). Eneji ya activation ya crystallization yikumiwa hiku tirhisa Arrhenius equation:
Laha kg ku nga constant rate ya reaction, k0 ku nga constant, Eg i activation energy ya ku kula ka crystal, R ku nga molar gas constant (R=8.314 J/mol K), naswona T i isothermal crystallization temperature (K).
Xifaniso xa 3a xikombisa leswaku nhlayo ya ku byala na nhlayo ya dopant swina mbuyelo eka mbuyelo wa ti crystals ta nickel. Loko nhlayo ya dopant eka solution yi tlakukile kuya eka 2.5 g/L, mbuyelo wa crystal wuhunguteke kusuka eka 7.77% kuya eka 6.48% (seed ratio ya 0.5%) na kusuka eka 10.89% kuya eka 10.32% (seed ratio ya 2%). Ku tlakuka kun’wana ka nhlayo ya dopant swiendle leswaku kuva na ku tlakuka loku fambelanaka eka mbuyelo wa crystal. Mbuyelo wale henhla wufike eka 17.98% loko seed ratio yiri 2% naswona dopant concentration yiri 5 g/L. Ku cinca eka xivumbeko xa mbuyelo wa crystal hiku tlakuka ka dopant concentration swinga fambelana na ku cinca eka crystal growth mechanism. Loko nhlayo ya dopant yiri ehansi, ti ions ta Ni2+ na NH4+ ti phikizana hiku boha na SO42−, leswi endlaka leswaku kuva na ku tlakuka ka ku n’oka ka nickel eka solution xikan’we naku hunguteka ka mbuyelo wa crystal. 14 Loko nhlayo ya thyaka yi ri e henhla, endlelo ra mphikizano ra ha humelela, kambe ti ions tin’wana ta NH4+ ti fambisana na ti ions ta nickel na sulfate ku endla munyu lowu phindhiweke kambirhi wa nickel ammonium sulfate. 16 Ku vumbiwa ka munyu lowu phindhiweke kambirhi swi endla leswaku ku hunguteka ka ku n’oka ka solute, xisweswo ku engetela mbuyelo wa crystal. Ku engetela ratio ya seeding swinga ya emahlweni swiantswisa mbuyelo wa crystal. Mbewu yinga sungula endlelo ra nucleation xikan’we naku kula ka crystal hiku tisungulela hiku nyika ndzhawu yosungula yale henhla leswaku ti solute ions ti hlengeleta naku vumba ti crystals. Loko nhlayo ya ku byala yikula, ndzhawu yosungula yale henhla ya ti ions kuva ti hlengeletana ya andza, kutani ti crystals totala tinga vumbiwa. Hikokwalaho, ku engetela mpimo wa ku byala swina mbuyelo wo kongoma eka mpimo wa kukula ka crystal xikan’we na mbuyelo wa crystal. 17
Ti parameter ta NiSO4 6H2O: (a) mbuyelo wa crystal na (b) pH ya nickel solution emahlweni na le ndzhaku ka ku cheriwa.
Xifaniso xa 3b xikombisa leswaku ratio ya mbewu xikan’we na nhlayo ya dopant swi khumba pH ya nickel solution loko kungase cheriwa na endzhaku ka ku cheriwa ka mbewu. Xikongomelo xaku langutisisa pH ya solution iku twisisa ku cinca ka chemical equilibrium eka solution. Loko kungase cheriwa ti crystals ta mbewu, pH ya solution yitala kuhunguteka hikokwalaho ka vukona bya ti ions ta NH4+ leti humesaka ti H+ protons. Ku engetela nhlayo ya dopant swiendla leswaku ku humesiwa ti protons totala ta H+, hindlela yaleyo kuhungutiwa pH ya solution. Endzhaku ko chela ti crystals ta mbewu, pH ya ti solutions hinkwato ya tlakuka. Ntshamiseko wa pH wu fambelanisiwa kahle na ntshamiseko wa mbuyelo wa crystal. Nhlayo yale hansi ya pH yikumeke eka dopant concentration ya 2.5 g/L xikan’we na seed ratio ya 0.5%. Loko nhlayo ya dopant yi tlakuka kuya eka 5 g/L, pH ya solution ya tlakuka. Xiendlakalo lexi xa twisiseka swinene, tani hileswi ku kumeka ka ti ions ta NH4+ eka solution swihungutekaka hikokwalaho ka ku amukeriwa, kumbe hikokwalaho ka ku katsa, kumbe hikokwalaho ka ku amukeriwa naku katsa ti ions ta NH4+ hi ti crystals.
Ti experiment ta mbuyelo wa crystal na nxopaxopo switlhele swi endliwa ku kumisisa mahanyelo ya kinetic ya kukula ka crystal xikan’we naku hlayela activation energy ya kukula ka crystal. Ti parameters ta isothermal crystallization kinetics ti hlamuseriwile eka xiyenge xa ​​Maendlelo. Xifaniso xa 4 xikombisa Johnson-Mehl-Avrami (JMA) plot leyi kombisaka mahanyelo ya kinetic ya kukula ka nickel sulfate crystal. Ploto yi endliwile hi ku plota nhlayo ya ln[− ln(1− x(t))] ku ya hi ntikelo wa ln t (Xiringaniso xa 3). Mimpimo ya gradient leyi kumiweke eka plot yi fambelana na mimpimo ya JMA index (n) leyi kombisaka ti dimensions ta crystal leyi kulaka na endlelo ro kula. Loko nhlayo ya cutoff yi kombisa mpimo wa ku kula lowu yimeriwaka hi constant ln k. Mimpimo ya JMA index (n) yi sukela eka 0.35 ku ya eka 0.75. Nhlayo leyi ya n yikomba leswaku ti crystals tina kukula ka dimension yin’we naswona ti landzelela endlelo ro kula leri lawuriwaka hi diffusion; 0 < n < 1 yi kombisa ku kula ka xiphemu xin’we, kasi n < 1 yi kombisa endlelo ra ku kula leri lawuriwaka hi ku hangalaka. 18 Mpimo wa kukula ka constant k wuhunguteka loko mahiselo ya tlakuka, leswi kombaka leswaku endlelo ra crystallization rihumelela hiku hatlisa eka mahiselo yale hansi. Leswi swi fambelana na ku tlakuka ka supersaturation ya solution eka mahiselo yale hansi.
Johnson-Mehl-Avrami (JMA) plots ya nickel sulfate hexahydrate eka mahiselo yohambana hambana ya crystallization: (a) 25 °C, (b) 30 °C, (c) 35 °C na (d) 40 °C.
Ku engeteriwa ka ti dopants swikombe xivumbeko lexi fanaka xa mpimo wa kukula eka mahiselo hinkwawo. Loko nhlayo ya dopant yiri 2.5 g/L, mpimo wa kukula ka crystal wuhunguteke, naswona loko nhlayo ya dopant yiri e henhla kutlula 2.5 g/L, nhlayo ya kukula ka crystal yi tlakukile. Tani hilaha swinga boxiwaka hakona ekusunguleni, ku cinca ka xivumbeko xa crystal growth rate swivangiwa hiku cinca ka mechanism ya interaction exikarhi ka ions eka solution. Loko nhlayo ya dopant yiri ehansi, endlelo ra mphikizano exikarhi ka ti ions eka solution ri engetela ku n’oka ka solute, leswi endlaka leswaku kuhungutiwa mpimo wa kukula ka crystal. 14 Ku tlula kwalaho, ku engeteriwa ka nhlayo ya le henhla ya ti- dopant swi endla leswaku endlelo ro kula ri cinca swinene. Loko nhlayo ya dopant yi tlula 3.75 g/L, ku endliwa ti crystal nuclei tintshwa leti engetelekeke, leswi endlaka leswaku kuhunguteka ku n’oka ka solute, leswi endlaka leswaku ku engeteleriwa mpimo wa kukula ka crystal. Ku endliwa ka ti crystal nuclei tintshwa swinga kombisiwa hiku vumbiwa ka double salt (NH4)2Ni(SO4)2 6H2O. 16 Loko ku buriwa hi ndlela leyi kristala yi kulaka ha yona, vuyelo bya X-ray diffraction byi tiyisekisa ku vumbiwa ka munyu lowu nga ni swiphemu swimbirhi.
Ntirho wa JMA plot wu tlhele wu kamberiwa ku kumisisa activation energy ya crystallization. Enerji ya activation yi hlayiwile hiku tirhisa Arrhenius equation (leyi kombisiweke eka Equation (4)). Xifaniso xa 5a xi kombisa vuxaka exikarhi ka nhlayo ya ln(kg) na nhlayo ya 1/T. Kutani, matimba ya activation ya hlayiwile hiku tirhisa gradient value leyi kumiweke kusuka eka plot. Xifaniso xa 5b xi kombisa mimpimo ya eneji ya activation ya crystallization ehansi ka ti concentrations to hambana ta thyaka. Mbuyelo wukombisa leswaku ku cinca eka nhlayo ya thyaka swi khumba matimba ya activation. Eneji ya activation ya crystallization ya ti crystals ta nickel sulfate handle ka thyaka i 215.79 kJ/mol. Loko nhlayo ya thyaka yifika eka 2.5 g/L, activation energy yi tlakuka hi 3.99% kuya eka 224.42 kJ/mol. Ku tlakuka ka activation energy swikomba leswaku energy barrier ya crystallization process ya tlakuka, leswinga ta endla leswaku kuva na kuhunguteka ka crystal growth rate xikan’we na crystal yield. Loko nhlayo ya thyaka yi tlula 2.5 g/L, activation energy ya crystallization ya hunguteka swinene. Eka nhlayo ya thyaka ya 5 g/l, activation energy i 205.85 kJ/mol, leswinga ehansi hi 8.27% kutlula activation energy eka nhlayo ya thyaka ya 2.5 g/l. Kuhunguteka ka activation energy swikomba leswaku maendlelo ya crystallization ya olovisiwa, leswi endlaka leswaku kuva na ku tlakuka ka crystal growth rate xikan’we na mbuyelo wa crystal.
(a) Ku ringanela ka plot ya ln(kg) ku hambana na 1/T na (b) activation energy Xikombiso xa crystallization eka ti concentrations to hambana ta thyaka.
Ndlela ya kukula ka crystal yi lavisisiwile hi XRD na FTIR spectroscopy, naswona kinetics ya kukula ka crystal na activation energy swikamberiwile. Xifaniso xa 6 xi kombisa mbuyelo wa XRD. Data yi fambisana na PDF #08–0470, leswi kombisaka leswaku i α-NiSO4 6H2O (red silica). Crystal yi wela eka tetragonal system, ntlawa wa space i P41212, ti parameter ta unit cell i a = b = 6.782 Å, c = 18.28 Å, α = β = γ = 90°, naswona volume i 840.8 Å3. Mimbuyelo leyi yi fambisana na mbuyelo lowu nga kandziyisiwa khale hi Manomenova et al. 19 Ku nghenisiwa ka ti-ion ta NH4+ swi tlhela swi yisa eka ku vumbiwa ka (NH4)2Ni(SO4)2 6H2O. Data leyi i ya PDF No. 31–0062. Crystal yi wela eka sisiteme ya monoclinic, ntlawa wa xibakabaka P21/a, ti parameter ta sele ya yuniti i a = 9.186 Å, b = 12.468 Å, c = 6.242 Å, α = γ = 90°, β = 106.93°, naswona vholumo i 684 Å3. Mimbuyelo leyi yi fambisana na ndzavisiso wa khale lowu vikiweke hi Su et al.20.
Tiphetheni ta X-ray diffraction ta ti crystals ta nickel sulfate: (a–b) 0.5%, (c–d) 1%, (e–f) 1.5%, na (g–h) 2% wa mpimo wa mbewu. Xifaniso xa xinene i xivono lexi kurisiweke xa xifaniso xa ximatsi.
Tani hilaha swikombisiweke hakona eka Swifaniso swa 6b, d, f na h, 2.5 g/L i mpimo wa le henhla wa nhlayo ya ammonium eka solution handle ko endla munyu wo engetela. Loko nhlayo ya thyaka yiri 3.75 na 5 g/L, ti ions ta NH4+ ti nghenisiwa eka xivumbeko xa crystal kuva ti endla munyu wo rharhangana (NH4)2Ni(SO4)2 6H2O. Kuya hi data, nhlohlorhi ya matimba ya munyu lowu rharhanganeke ya tlakuka loko nhlayo ya thyaka yi tlakuka kusuka eka 3.75 kuya eka 5 g/L, ngopfu ngopfu eka 2θ 16.47° na 17.44°. Ku tlakuka ka nhlohlorhi ya munyu lowu rharhanganeke swi vangiwa ntsena hi nsinya wa nawu wa ku ringanisela ka tikhemikhali. Hambiswiritano, tinhlohlorhi tin’wana letinga tolovelekangiki ti voniwa eka 2θ 16.47°, leswinga vangiwa hi elastic deformation ya crystal. 21 Mbuyelo wa swihlawulekisi wu tlhela wu kombisa leswaku mpimo wa le henhla wa ku byala wu endla leswaku ku va na ku hunguteka ka matimba ya nhlohlorhi ya munyu lowu rharhanganeke. Nhlayo yale henhla ya mbewu yi hatlisisa maendlelo ya crystallization, leswi endlaka leswaku kuva na kuhunguteka lokukulu eka solute. Eka xiyimo lexi, endlelo ro kula ra crystal ri kongomisiwile eka mbewu, naswona ku endliwa ka swiphemu leswintshwa swi kavanyetiwa hi kuhunguteka ka supersaturation ya solution. Kuhambana na sweswo, loko ratio ya mbewu yiri ehansi, maendlelo ya crystallization ya nonoka, naswona supersaturation ya solution yitshama yiri eka levele yale henhla swinene. Xiyimo lexi xi engetela ku koteka ka nucleation ya munyu lowu nga nyawuriki ngopfu (NH4)2Ni(SO4)2 6H2O. Data ya peak intensity ya double salt yi nyikiwile eka Tafula ra 3.
FTIR characterization yi endliwile ku lavisisa xiphiqo xin’wana na xin’wana kumbe ku cinca ka xivumbeko eka host lattice hikokwalaho ka vukona bya NH4+ ions. Tisampulu letingana constant seeding ratio ya 2% ti hlawuriwile. Xifaniso xa 7 xi kombisa mbuyelo wa swihlawulekisi swa FTIR. Tinhlohlorhi to anama leti voniweke eka 3444, 3257 na 1647 cm−1 ti vangiwa hi tindlela to ololoka ta O–H ta ti molecule. Tinhlohlorhi eka 2370 na 2078 cm−1 tiyimela swihlanganisi swa hayidirojeni swa intermolecular exikarhi ka ti molecules ta mati. Band eka 412 cm−1 yi vangiwa hi Ni–O stretching vibrations. Ku engetela kwalano, ti free SO4− ions ti kombisa mune wa tindlela letikulu ta ku rhurhumela eka 450 (υ2), 630 (υ4), 986 (υ1) na 1143 na 1100 cm−1 (υ3). Swikombiso swa υ1-υ4 swi yimela swihlawulekisi swa tindlela ta ku rhurhumela, laha υ1 yi yimelaka movha lowu nga onhakiki (ku ololoka ka symmetric), υ2 yi yimela movha lowu onhakeke kambirhi (ku gombonyoka ka symmetric), naswona υ3 na υ4 yi yimela tindlela leti onhakeke kanharhu (ku ololoka ka asymmetric na ku gombonyoka ka asymmetric, hi ku landzelelana). 22,23,24 Mimbuyelo ya swihlawulekisi yi kombisa leswaku vukona bya thyaka ra ammonium byi nyika nhlohlorhi yo engetela eka nhlayo ya magandlati ya 1143 cm-1 (leyi funghiweke hi xirhendzevutana xo tshwuka eka xifaniso). Nhlohlorhi yo engetelela eka 1143 cm-1 yikomba leswaku vukona bya ti ions ta NH4+, kunga khathariseki nhlayo ya yona, swivanga ku soholotiwa ka xivumbeko xa lattice, leswi tisaka ku cinca eka frequency ya vibration ya ti molecules ta sulfate ion endzeni ka crystal.
Hi ku ya hi mbuyelo wa XRD na FTIR lowu fambelanaka na mahanyelo ya kinetic ya ku kula ka crystal na eneji ya activation, Xifaniso xa 8 xi kombisa xikimi xa endlelo ra crystallization ra nickel sulfate hexahydrate hi ku engeteriwa ka thyaka ra NH4+. Loko kungari na thyaka, ti ions ta Ni2+ tita endla reaction na H2O kuva ti endla nickel hydrate [Ni(6H2O)]2−. Kutani, nickel hydrate yi hlangana hiku tisungulela na SO42− ions kuva yi endla Ni(SO4)2 6H2O nuclei naswona yikula kuva ti crystals ta nickel sulfate hexahydrate. Loko nhlayo yale hansi ya thyaka ra ammonium (2.5 g/L kumbe ehansi) yi cheriwa eka solution, [Ni(6H2O)]2− swa tika ku hlanganisa hiku hetiseka na ti ions ta SO42− hikuva ti ions ta [Ni(6H2O)]2− na NH4+ ti phikizana hiku hlanganisiwa na ti ions ta SO42−, hambi leswi kungana ti ions ta sulfate leti ringaneleke kuva ti endla na ti ions leti hatimbirhi. Xiyimo lexi xi endla leswaku kuva na ku tlakuka ka activation energy ya crystallization xikan’we naku hunguteka ka kukula ka crystal. 14,25 Endzhaku kaloko ti nuclei ta nickel sulfate hexahydrate ti vumbiwile no kula ti va ti crystals, ti ions to tala ta NH4+ na (NH4)2SO4 ti adsorbed eka vuandlalo bya crystal. Leswi swi hlamusela leswaku hikokwalaho ka yini ntlawa lowu tirhaka wa SO4− ion (wavenumber 1143 cm−1) eka tisampulu ta NSH-8 na NSH-12 wu tshama wu vumbiwile handle ka endlelo ra doping. Loko nhlayo ya thyaka yiri e henhla, ti ions ta NH4+ tisungula ku nghenisiwa eka xivumbeko xa crystal, ku endla ti double salts. 16 Xiendlakalo lexi xi humelela hikokwalaho ka ku pfumaleka ka ti SO42− ions eka solution, naswona ti SO42− ions ti boha eka ti nickel hydrates hiku hatlisa kutlula eka ti ammonium ions. Endlelo leri ri hlohletela nucleation na kukula ka ti double salts. Hi nkarhi wa maendlelo ya alloying, Ni(SO4)2 6H2O na (NH4)2Ni(SO4)2 6H2O nuclei swivumbiwa hi nkarhi wun’we, leswi endlaka leswaku kuva na ku tlakuka ka nhlayo ya ti nuclei leti kumiweke. Ku tlakuka ka nhlayo ya ti nuclei swi hlohletela ku hatlisa ka kukula ka crystal xikan’we nakuhunguteka ka activation energy.
Ku cinca ka tikhemikhali ka ku n’okisiwa ka nickel sulfate hexahydrate ematini, ku cheriwa nhlayo yitsongo na nhlayo leyikulu ya ammonium sulfate, ivi ku endliwa endlelo ra crystallization swi nga kombisiwa hi ndlela leyi landzelaka:
Mbuyelo wa swihlawulekisi swa SEM wu kombisiwile eka Xifaniso xa 9. Mbuyelo wa swihlawulekisi wu kombisa leswaku nhlayo ya munyu wa ammonium lowu engeteriweke na mpimo wa ku byala a swi khumbi ngopfu xivumbeko xa crystal. Vukulu bya tikristale leti vumbiweke byi tshama byi nga cinci, hambileswi tikristale letikulu ti humelelaka eka tindhawu tin’wana. Hambiswiritano, ku ya emahlweni ka swihlawulekisi swa ha laveka ku kumisisa mbuyelo wa nhlayo ya munyu wa ammonium na mpimo wa ku byala eka vukulu bya xikarhi bya ti crystals leti vumbiweke.
Crystal morphology ya NiSO4 6H2O: (a–e) 0.5%, (f–j) 1%, (h–o) 1.5% na (p–u) 2% seed ratio leswi kombisaka ku cinca ka nhlayo ya NH4+ kusuka ehenhla kuya ehansi, leswinga 0, 1.25, 2.5, 3.75 na 5 g/L, hiku landzelelana.
Xifaniso xa 10a xi kombisa ti TGA curves ta ti crystals letingana nhlayo yohambana hambana ya thyaka. Nxopaxopo wa TGA wu endliwile eka swikombiso leswingana seeding ratio ya 2%. Nxopaxopo wa XRD wutlhele wu endliwa eka xikombiso xa NSH-20 ku kumisisa ti compounds leti vumbiweke. Mbuyelo wa XRD lowu kombisiweke eka Xifaniso xa 10b wu tiyisisa ku cinca eka xivumbeko xa kristala. Mipimo ya thermogravimetric yikombisa leswaku ti crystals hinkwato leti endliweke ti kombisa ku tiya ka mahiselo kuya fika eka 80°C. Endzhaku ka sweswo, ntiko wa crystal wuhunguteke hi 35% loko mahiselo ya tlakuka kuya eka 200°C. Ku lahlekeriwa hi ntiko wa ti crystals swivangiwa hi maendlelo ya decomposition, leswi katsaka ku lahlekeriwa hi 5 wa ti molecules ta mati kuva ti endla NiSO4 H2O. Loko mahiselo ya tlakuka kuya eka 300–400°C, ntiko wa ti crystals wuhunguteke nakambe. Ku lahlekeriwa hi ntiko wa ti crystals akuri kwalomu ka 6.5%, kasi ku lahlekeriwa hi ntiko wa xikombiso xa crystal ya NSH-20 akuri e henhla nyana, kahle kahle 6.65%. Ku bola ka ti ions ta NH4+ kuya eka gasi ya NH3 eka xikombiso xa NSH-20 swiendle leswaku kuva na kuhunguteka lokukulu nyana. Loko mahiselo ya tlakuka kusuka eka 300 kuya eka 400°C, ntiko wa ti crystals wuhunguteke, leswinga endla leswaku ti crystals hinkwato tiva na xivumbeko xa NiSO4. Ku tlakuka ka mahiselo kusuka eka 700°C kuya eka 800°C swiendle leswaku xivumbeko xa crystal xi hundzuka NiO, leswinga endla leswaku ku humesiwa tigasi ta SO2 na O2.25,26
Ku basa ka ti crystals ta nickel sulfate hexahydrate swikumiwile hiku kambela nhlayo ya NH4+ hiku tirhisa xitirhisiwa xa DC-Arc ICP-MS. Ku basa ka ti crystals ta nickel sulfate ku kumiwile hiku tirhisa formula (5).
Laha Ma ku nga ntiko wa thyaka eka kristala (mg), Mo ku nga ntiko wa kristala (mg), Ca ku nga nhlayo ya thyaka eka xitofu (mg/l), V i vholumo ya xitofu (l).
Xifaniso xa 11 xi kombisa ku basa ka ti crystals ta nickel sulfate hexahydrate. Nhlayo ya vutengi i nhlayo ya xikarhi ya swihlawulekisi swa 3. Mbuyelo wukombisa leswaku mpimo wa ku byala na nhlayo ya thyaka swi khumba hiku kongoma ku basa ka ti crystals ta nickel sulfate leti vumbiweke. Loko thyaka riri ehenhla, ku amukeriwa lokukulu ka thyaka, leswi endlaka leswaku kuva na ku basa ka le hansi ka ti crystals leti vumbiweke. Hambiswiritano, xivumbeko xa ku amukeriwa ka thyaka xinga cinca kuya hi nhlayo ya thyaka, naswona girafu ya mbuyelo yikombisa leswaku ku amukeriwa hinkwako ka thyaka hi ti crystals aswi cinci ngopfu. Ku engetela kwalano, mbuyelo lowu wutlhela wukombisa leswaku nhlayo yale henhla ya mbewu yinga antswisa ku basa ka ti crystals. Xiendlakalo lexi xa koteka hikuva loko vunyingi bya ti crystal nuclei leti vumbiweke ti hlanganisiwile eka ti nickel nuclei, ku koteka ka ti nickel ions leti hlengeletaneke eka nickel swile henhla. 27.
Dyondzo yi kombisile leswaku ti ammonium ions (NH4+) ti khumba swinene maendlelo ya crystallization xikan’we na swivumbeko swa crystalline swa ti crystals ta nickel sulfate hexahydrate, naswona yitlhele yi paluxa nkucetelo wa ratio ya mbewu eka maendlelo ya crystallization.
Eka nhlayo ya ammonium yale henhla ka 2.5 g/l, mbuyelo wa crystal xikan’we naku kula ka crystal swihunguteka. Eka nhlayo ya ammonium yale henhla ka 2.5 g/l, mbuyelo wa crystal xikan’we naku kula ka crystal swikula.
Ku engeteriwa ka thyaka eka solution ya nickel swi engetela mphikizano exikarhi ka NH4+ na [Ni(6H2O)]2− ions eka SO42−, leswi yisaka eka ku tlakuka ka activation energy. Kuhunguteka ka activation energy endzhaku ko chela nhlayo yale henhla ya thyaka swivangiwa hiku nghena ka NH4+ ions eka xivumbeko xa crystal, xisweswo swi endla double salt (NH4)2Ni(SO4)2 6H2O.
Ku tirhisa ratio yale henhla ya seeding swinga antswisa mbuyelo wa crystal, crystal growth rate xikan’we na ku basa ka crystal ya nickel sulfate hexahydrate.
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