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Olu phononongo luphanda ngemiphumo yokungcola kwe-NH4+ kunye nomlinganiselo wembewu kwindlela yokukhula kunye nokusebenza kwe-nickel sulfate hexahydrate phantsi kwe-crystallization yokupholisa engaguqukiyo, kwaye luhlola imiphumo yokungcola kwe-NH4+ kwindlela yokukhula, iipropati zobushushu, kunye namaqela asebenzayo e-nickel sulfate hexahydrate. Kwizinga lokungcola eliphantsi, ii-ion ze-Ni2+ kunye ne-NH4+ zikhuphisana ne-SO42− ngokubophelela, okubangela ukwehla kwesivuno sekristale kunye nezinga lokukhula kunye nokwanda kwamandla okusebenza kwekristale. Kwizinga lokungcola okuphezulu, ii-ion ze-NH4+ zifakwa kwisakhiwo sekristale ukwenza ityuwa eyinkimbinkimbi (NH4)2Ni(SO4)2 6H2O. Ukwakheka kwetyuwa eyinkimbinkimbi kubangela ukwanda kwesivuno sekristale kunye nezinga lokukhula kunye nokwehla kwamandla okusebenza kwekristale. Ukubakho kwezinga eliphezulu neliphantsi le-ion ze-NH4+ kubangela ukuphambuka kwe-lattice, kwaye iikristale zizinzile kubushushu ukuya kuthi ga kwi-80 °C. Ukongeza, impembelelo yokungcola kwe-NH4+ kwindlela yokukhula kwekristale inkulu kuneyomlinganiselo wembewu. Xa izinga lokungcola liphantsi, ukungcola kulula ukunamathela kwikristale; xa uxinaniso luphezulu, kulula ukufaka ukungcola kwikristale. Umlinganiselo wembewu unokunyusa kakhulu isivuno sekristale kwaye uphucule kancinci ubumsulwa bekristale.
I-Nickel sulfate hexahydrate (NiSO4 6H2O) ngoku sisixhobo esibalulekileyo esisetyenziswa kumashishini ahlukeneyo, kubandakanya ukwenziwa kweebhetri, i-electroplating, ii-catalysts, kwanakwimveliso yokutya, ioyile, kunye neziqholo. 1,2,3 Ukubaluleka kwayo kukhula ngokukhawuleza ngophuhliso olukhawulezayo lwezithuthi zombane, ezixhomekeke kakhulu kwiibhetri ze-lithium-ion (LiB) ezisekelwe kwi-nickel. Ukusetyenziswa kwee-alloys ze-nickel eziphezulu ezifana ne-NCM 811 kulindeleke ukuba kulawule ngo-2030, nto leyo eyandisa ngakumbi imfuno ye-nickel sulfate hexahydrate. Nangona kunjalo, ngenxa yemida yezixhobo, imveliso isenokungahambelani nemfuno ekhulayo, nto leyo edala umsantsa phakathi kobonelelo kunye nemfuno. Oku kunqongophala kuphakamise iinkxalabo malunga nokufumaneka kwezixhobo kunye nokuzinza kwamaxabiso, nto leyo egxininisa imfuneko yemveliso esebenzayo ye-nickel sulfate ecocekileyo kakhulu, ezinzileyo yebhetri. 1,4
Ukuveliswa kwe-nickel sulfate hexahydrate ngokuqhelekileyo kufezekiswa nge-crystallization. Phakathi kweendlela ezahlukeneyo, indlela yokupholisa yindlela esetyenziswa kakhulu, enezibonelelo zokusetyenziswa kwamandla aphantsi kunye nokukwazi ukuvelisa izinto ezicocekileyo kakhulu. 5,6 Uphando malunga ne-crystallization ye-nickel sulfate hexahydrate kusetyenziswa i-discontinuous cooling crystallization lwenze inkqubela phambili ebalulekileyo. Okwangoku, uninzi lophando lugxile ekuphuculeni inkqubo ye-crystallization ngokuphucula iiparameter ezifana nobushushu, izinga lokupholisa, ubungakanani bembewu kunye ne-pH. 7,8,9 Injongo kukunyusa isivuno sekristale kunye nobunyulu beekristale ezifunyenweyo. Nangona kunjalo, nangona uphando olupheleleyo lwale parameters, kusekho umsantsa omkhulu kwingqwalasela enikwa kwimpembelelo yokungcola, ingakumbi i-ammonium (NH4+), kwiziphumo ze-crystallization.
Ukungcola kwe-ammonium kusenokwenzeka ukuba kukho kwisisombululo se-nickel esisetyenziselwa i-nickel crystallization ngenxa yokubakho kokungcola kwe-ammonium ngexesha lenkqubo yokukhupha. I-Ammonium isetyenziswa kakhulu njenge-saponifying agent, eshiya inani elincinci le-NH4+ kwisisombululo se-nickel. 10,11,12 Nangona kukho ukusasazeka kokungcola kwe-ammonium, iziphumo zabo kwiimpawu zekristale ezifana nesakhiwo sekristale, indlela yokukhula, iimpawu zobushushu, ubumsulwa, njl. azikaqondwa kakuhle. Uphando olulinganiselweyo kwiziphumo zazo lubalulekile kuba ukungcola kunokuthintela okanye kutshintshe ukukhula kwekristale kwaye, kwezinye iimeko, kusebenza njengezithinteli, okuchaphazela utshintsho phakathi kweefom zekristale ezizinzileyo nezizinzileyo. 13,14 Ukuqonda ezi ziphumo ke ngoko kubalulekile kwimbono yemizi-mveliso kuba ukungcola kunokubeka emngciphekweni umgangatho wemveliso.
Ngokusekelwe kumbuzo othile, olu phononongo lujolise ekuphononongeni impembelelo yokungcola kwe-ammonium kwiimpawu zeekristale ze-nickel. Ngokuqonda impembelelo yokungcola, iindlela ezintsha zinokuphuhliswa ukulawula nokunciphisa iziphumo zazo ezimbi. Olu phononongo lukwaphande ulwalamano phakathi koxinzelelo lokungcola kunye notshintsho kumlinganiselo wembewu. Ekubeni imbewu isetyenziswa kakhulu kwinkqubo yemveliso, iiparameter zembewu zisetyenzisiwe kolu phononongo, kwaye kubalulekile ukuqonda ubudlelwane phakathi kwezi zinto zimbini. 15 Iziphumo zezi parameter zimbini zisetyenzisiwe ekufundeni isivuno sekristale, indlela yokukhula kwekristale, ulwakhiwo lwekristale, imo, kunye nobunyulu. Ukongeza, ukuziphatha kwe-kinetic, iipropati zobushushu, kunye namaqela asebenzayo eekristale phantsi kwempembelelo yokungcola kwe-NH4+ kuphela kuphandwe ngakumbi.
Izinto ezisetyenzisiweyo kolu phononongo yayiyi-nickel sulfate hexahydrate (NiSO 6H2O, ≥ 99.8%) enikwe yi-GEM; i-ammonium sulfate ((NH)SO, ≥ 99%) ethengwe kwiTianjin Huasheng Co., Ltd.; amanzi acociweyo. I-crystal yembewu esetyenzisiweyo yayiyi-NiSO 6H2O, yatyunyuzwa yaza yahluzwa ukuze kufunyanwe ubungakanani obufanayo be-0.154 mm. Iimpawu ze-NiSO 6H2O ziboniswe kwiTheyibhile 1 kunye noMfanekiso 1.
Isiphumo sokungcola kwe-NH4+ kunye nomlinganiselo wembewu kwi-crystallization ye-nickel sulfate hexahydrate siphandwe kusetyenziswa ukupholisa okungapheliyo. Zonke iimvavanyo zenziwe kubushushu bokuqala obuyi-25 °C. Ama-25 °C akhethwe njengobushushu be-crystallization kuthathelwa ingqalelo imida yolawulo lobushushu ngexesha lokuhluza. I-crystallization inokubangelwa kukutshintshatshintsha kobushushu ngequbuliso ngexesha lokuhluza izisombululo ezishushu kusetyenziswa i-Buchner funnel enobushushu obuphantsi. Le nkqubo inokuchaphazela kakhulu i-kinetics, ukungcola, kunye neepropati ezahlukeneyo zekristale.
Isisombululo se-nickel salungiswa okokuqala ngokunyibilikisa i-224 g ye-NiSO4 6H2O emanzini acwecweyo angama-200 ml. Uxinzelelo olukhethiweyo luhambelana ne-supersaturation (S) = 1.109. I-supersaturation yafunyanwa ngokuthelekisa ukunyibilika kweekristale ze-nickel sulfate ezinyibilikisiweyo kunye nokunyibilika kwe-nickel sulfate hexahydrate kuma-25 °C. I-supersaturation esezantsi yakhethwa ukuthintela i-spontaneous crystallization xa ubushushu buncitshiswa ukuya kobokuqala.
Isiphumo soxinzelelo lwe-NH4+ ion kwinkqubo yokwenza ikristale siphandwe ngokongeza i-(NH4)2SO4 kwisisombululo se-nickel. Uxinzelelo lwe-NH4+ ion olusetyenzisiweyo kolu phononongo yayiyi-0, 1.25, 2.5, 3.75, kunye ne-5 g/L. Isisombululo sifudunyezwe kwi-60 °C kangangemizuzu engama-30 ngelixa sixutywa kwi-300 rpm ukuqinisekisa ukuxubana okufanayo. Isisombululo sapholiswa kubushushu obufunekayo bokusabela. Xa ubushushu bufikelele kwi-25 °C, izixa ezahlukeneyo zeekristale zembewu (umlinganiselo wembewu we-0.5%, 1%, 1.5%, kunye ne-2%) zongezwa kwisisombululo. Umlinganiselo wembewu umiselwe ngokuthelekisa ubunzima bembewu nobunzima be-NiSO4 6H2O kwisisombululo.
Emva kokongeza iikristale zembewu kwisisombululo, inkqubo yokwenza ikristale yenzeke ngokwendalo. Inkqubo yokwenza ikristale yahlala imizuzu engama-30. Isisombululo sahluzwa kusetyenziswa i-filter press ukuze kwahlulwe ngakumbi iikristale eziqokelelweyo kwisisombululo. Ngexesha lenkqubo yokucoca, iikristale zazihlanjwa rhoqo nge-ethanol ukunciphisa amathuba okuphinda kusetyenziswe kwaye kuncitshiswe ukunamathela kokungcola kwisisombululo kumphezulu weekristale. I-ethanol yakhethwa ukuhlamba iikristale kuba iikristale azinyibiliki kwi-ethanol. Iikristale ezihluziweyo zafakwa kwi-incubator yelabhoratri kuma-50 °C. Iiparameter zovavanyo ezineenkcukacha ezisetyenzisiweyo kolu phononongo ziboniswe kwiTheyibhile 2.
Ulwakhiwo lwekristale luchongiwe kusetyenziswa isixhobo se-XRD (SmartLab SE—HyPix-400) kwaye kwafunyaniswa ubukho beekhompawundi ze-NH4+. Ukuchazwa kwe-SEM (Apreo 2 HiVac) kwenziwe ukuhlalutya imo yekristale. Iipropati zobushushu beekristale zichongiwe kusetyenziswa isixhobo se-TGA (TG-209-F1 Libra). Amaqela asebenzayo ahlalutywe yi-FTIR (JASCO-FT/IR-4X). Ubunyulu besampuli buchongiwe kusetyenziswa isixhobo se-ICP-MS (Prodigy DC Arc). Isampuli ilungiselelwe ngokunyibilikisa i-0.5 g yeekristale kwi-100 mL yamanzi acocekileyo. Isivuno sekristale (x) sibalwa ngokwahlula ubunzima bekristale ephumayo ngobunzima bekristale engenisiweyo ngokwefomula (1).
apho u-x yimveliso yekristale, eyahluka ukusuka ku-0 ukuya ku-1, i-mout bubunzima beekristale eziphumayo (g), i-min bubunzima beekristale ezifakwayo (g), i-msol bubunzima beekristale ezikwisisombululo, kwaye i-mseed bubunzima beekristale zembewu.
Isivuno sekristale siphandwe ngakumbi ukuze kuchongwe i-kinetics yokukhula kwekristale kunye nokuqikelela ixabiso lamandla okusebenza. Olu phononongo lwenziwe ngomlinganiselo wembewu we-2% kunye nenkqubo efanayo yovavanyo njengangaphambili. Iiparameter ze-kinetics zekristale ye-isothermal zichongiwe ngokuvavanya isivuno sekristale ngamaxesha ahlukeneyo ekristale (10, 20, 30, kunye ne-40 min) kunye namaqondo obushushu okuqala (25, 30, 35, kunye ne-40 °C). Amanqanaba akhethiweyo kubushushu bokuqala ahambelana namaxabiso e-supersaturation (S) e-1.109, 1.052, 1, kunye ne-0.953, ngokulandelanayo. Ixabiso le-supersaturation lichongiwe ngokuthelekisa ukunyibilika kweekristale ze-nickel sulfate ezinyibilikisiweyo kunye nokunyibilika kwe-nickel sulfate hexahydrate kubushushu bokuqala. Kolu phononongo, ukunyibilika kwe-NiSO4 6H2O kwi-200 mL yamanzi kumaqondo obushushu ahlukeneyo ngaphandle kokungcola kuboniswe kuMfanekiso 2.
Ithiyori yeJohnson-Mail-Avrami (ithiyori yeJMA) isetyenziselwa ukuhlalutya indlela yokuziphatha kwe-isothermal crystallization. Ithiyori yeJMA ikhethwa kuba inkqubo ye-crystallization ayenzeki de kongezwe iikristale zembewu kwisisombululo. Ithiyori yeJMA ichazwa ngolu hlobo lulandelayo:
Apho u-x(t) emele utshintsho ngexesha u-t, u-k umele i-transition rate constant, u-t umele ixesha lotshintsho, kwaye u-n umele i-Avrami index. I-Formula 3 ithathwe kwi-formula (2). Amandla okusebenza kwe-crystallization amiselwa kusetyenziswa i-Arrhenius equation:
Apho i-kg ikwizinga lokusabela elingaguqukiyo, i-k0 yi-constant, i-Eg yi-activation energy yokukhula kwekristale, i-R yi-molar gas constant (R=8.314 J/mol K), kwaye i-T yi-isothermal crystallization temperature (K).
Umfanekiso 3a ubonisa ukuba umlinganiselo wokutyala imbewu kunye noxinzelelo lwe-dopant zinefuthe kwisivuno seekristale ze-nickel. Xa uxinano lwe-dopant kwisisombululo lunyuke lwaya kwi-2.5 g/L, isivuno sekristale sehla ukusuka kwi-7.77% ukuya kwi-6.48% (umlinganiselo wembewu we-0.5%) kunye nokusuka kwi-10.89% ukuya kwi-10.32% (umlinganiselo wembewu we-2%). Ukwanda okungakumbi koxinzelelo lwe-dopant kukhokelele ekwandeni okufanayo kwesivuno sekristale. Isivuno esiphezulu sifikelele kwi-17.98% xa umlinganiselo wokutyala imbewu wawuyi-2% kwaye uxinano lwe-dopant lwaluyi-5 g/L. Utshintsho kwipateni yokuvelisa ikristale kunye nokwanda koxinzelelo lwe-dopant lunokunxulunyaniswa notshintsho kwindlela yokukhula kwekristale. Xa uxinano lwe-dopant luphantsi, ii-ion ze-Ni2+ kunye ne-NH4+ zikhuphisana ngokubopha ne-SO42−, nto leyo ekhokelela ekwandeni kokunyibilika kwe-nickel kwisisombululo kunye nokwehla kwesivuno sekristale. 14 Xa uxinano lokungcola luphezulu, inkqubo yokhuphiswano iyaqhubeka, kodwa ezinye ii-ion ze-NH4+ zihambelana nee-ion ze-nickel kunye ne-sulfate ukuze zenze ityuwa ephindwe kabini ye-nickel ammonium sulfate. 16 Ukwenziwa kwetyuwa ephindwe kabini kukhokelela ekunciphiseni ukunyibilika kwe-solute, ngaloo ndlela kwandisa isivuno sekristale. Ukwandisa umlinganiselo wokuhlwayela imbewu kunokuqhubeka nokuphucula isivuno sekristale. Imbewu inokuqalisa inkqubo ye-nucleation kunye nokukhula kwekristale okuzenzekelayo ngokubonelela ngendawo yokuqala yomphezulu wee-ion ezinyibilikayo ukuze zihlele kwaye zenze iikristale. Njengoko umlinganiselo wokuhlwayela imbewu usanda, indawo yokuqala yomphezulu wee-ion ezilungelelanisiweyo iyanda, ngoko ke iikristale ezininzi zinokwenziwa. Ke ngoko, ukwandisa umlinganiselo wokuhlwayela imbewu kunempembelelo ngqo kwizinga lokukhula kwekristale kunye nesivuno sekristale. 17
Iiparameter zeNiSO4 6H2O: (a) i-crystal yield kunye (b) ne-pH yesisombululo se-nickel ngaphambi nasemva kokuyinonga.
Umfanekiso 3b ubonisa ukuba umlinganiselo wembewu kunye noxinzelelo lwe-dopant luchaphazela i-pH yesisombululo se-nickel ngaphambi nasemva kokongezwa kwembewu. Injongo yokujonga i-pH yesisombululo kukuqonda utshintsho kulinganiso lweekhemikhali kwisisombululo. Ngaphambi kokongeza iikristale zembewu, i-pH yesisombululo idla ngokuncipha ngenxa yokubakho kwee-ion ze-NH4+ ezikhupha iiproton ze-H+. Ukwandisa uxinzelelo lwe-dopant kubangela ukuba kukhutshwe iiproton ze-H+ ezingaphezulu, ngaloo ndlela kunciphisa i-pH yesisombululo. Emva kokongeza iikristale zembewu, i-pH yazo zonke izisombululo iyanda. Umgaqo we-pH uhambelana kakuhle nomgaqo we-crystal yield. Ixabiso le-pH eliphantsi lifunyenwe kuxinzelelo lwe-dopant lwe-2.5 g/L kunye nomlinganiselo wembewu we-0.5%. Njengoko uxinano lwe-dopant lunyuka luye kwi-5 g/L, i-pH yesisombululo iyanda. Le nto iyaqondakala, kuba ukufumaneka kwee-ion ze-NH4+ kwisisombululo kuncipha nokuba kungenxa yokufunxwa, okanye ngenxa yokufakwa, okanye ngenxa yokufunxwa kunye nokufakwa kwee-ion ze-NH4+ ngeekristale.
Uvavanyo lwe-crystal yield kunye nohlalutyo lwenziwe ngakumbi ukuze kuchongwe indlela esebenza ngayo i-crystal growth kunye nokubala amandla okusebenza kokukhula kwe-crystal. Iiparameter ze-isothermal crystallization kinetics zichazwe kwicandelo leeMethods. Umfanekiso 4 ubonisa i-Johnson-Mehl-Avrami (JMA) plot ebonisa indlela esebenza ngayo i-nickel sulfate crystal growth. I-plot yenziwe ngokudwelisa ixabiso le-ln[− ln(1− x(t))] ngokuchasene nexabiso le-ln t (Equation 3). Amaxabiso e-gradient afunyenwe kwi-plot ahambelana namaxabiso e-JMA index (n) abonisa ubungakanani be-crystal ekhulayo kunye nendlela yokukhula. Ngelixa ixabiso le-cutoff libonisa izinga lokukhula elimelwa yi-ln k engaguqukiyo. Amaxabiso e-JMA index (n) aqala kwi-0.35 ukuya kwi-0.75. Eli xabiso le-n libonisa ukuba ii-crystals zinokukhula okunemilinganiselo enye kwaye zilandela indlela yokukhula elawulwa yi-diffusion; 0 < n < 1 ibonisa ukukhula okunemilinganiselo enye, ngelixa i-n < 1 ibonisa indlela yokukhula elawulwa yi-diffusion. 18 Izinga lokukhula kwe-constant k liyancipha xa ubushushu busanda, nto leyo ebonisa ukuba inkqubo ye-crystallization yenzeka ngokukhawuleza xa ubushushu buphantsi. Oku kunxulumene nokwanda kwe-supersaturation yesisombululo xa ubushushu buphantsi.
Iiploti zeJohnson-Mehl-Avrami (JMA) ze-nickel sulfate hexahydrate kumaqondo obushushu ahlukeneyo e-crystallization: (a) 25 °C, (b) 30 °C, (c) 35 °C kunye (d) 40 °C.
Ukongezwa kwee-dopants kubonise indlela efanayo yokukhula kwesantya kuwo onke amaqondo obushushu. Xa uxinano lwe-dopant lwaluyi-2.5 g/L, izinga lokukhula kwekristale lehla, kwaye xa uxinano lwe-dopant lwaluphezulu kune-2.5 g/L, izinga lokukhula kwekristale landa. Njengoko bekutshiwo ngaphambili, utshintsho kwipateni yokukhula kwekristale lubangelwa kukutshintsha kwendlela yokusebenzisana phakathi kwee-ions kwisisombululo. Xa uxinano lwe-dopant luphantsi, inkqubo yokhuphiswano phakathi kwee-ions kwisisombululo yonyusa ukunyibilika kwe-solute, ngaloo ndlela kunciphisa izinga lokukhula kwekristale. 14 Ngaphezu koko, ukongezwa kwamanqanaba aphezulu e-dopants kubangela ukuba inkqubo yokukhula itshintshe kakhulu. Xa uxinano lwe-dopant ludlula i-3.75 g/L, kwakheka ii-nuclei ezintsha zekristale, nto leyo ekhokelela ekunciphiseni ukunyibilika kwe-solute, ngaloo ndlela kwandisa izinga lokukhula kwekristale. Ukwakheka kwee-nuclei ezintsha zekristale kunokubonakaliswa ngokwenziwa kwetyuwa ephindwe kabini (NH4)2Ni(SO4)2 6H2O. 16 Xa kuxoxwa ngendlela yokukhula kwekristale, iziphumo ze-X-ray diffraction ziqinisekisa ukwakheka kwetyuwa ephindwe kabini.
Umsebenzi we-JMA plot uvavanywe ngakumbi ukuze kuchongwe amandla okusebenza e-crystallization. Amandla okusebenza abalwe kusetyenziswa i-Arrhenius equation (eboniswe kwi-Equation (4)). Umfanekiso 5a ubonisa ubudlelwane phakathi kwexabiso le-ln(kg) kunye nexabiso le-1/T. Emva koko, amandla okusebenza abalwe kusetyenziswa ixabiso le-gradient elifunyenwe kwi-plot. Umfanekiso 5b ubonisa amaxabiso amandla okusebenza e-crystallization phantsi kwamanqanaba ahlukeneyo okungcola. Iziphumo zibonisa ukuba utshintsho kuxinzelelo lokungcola luchaphazela amandla okusebenza. Amandla okusebenza e-crystallization yeekristale ze-nickel sulfate ngaphandle kokungcola yi-215.79 kJ/mol. Xa uxinzelelo lokungcola lufikelela kwi-2.5 g/L, amandla okusebenza ayanda nge-3.99% ukuya kwi-224.42 kJ/mol. Ukwanda kwamandla okusebenza kubonisa ukuba umqobo wamandla wenkqubo ye-crystallization uyanda, nto leyo eya kukhokelela ekunciphiseni izinga lokukhula kwekristale kunye nesivuno sekristale. Xa uxinzelelo lokungcola lungaphezulu kwe-2.5 g/L, amandla okusebenza e-crystallization ayancipha kakhulu. Kwi-concentration yokungcola eyi-5 g/l, amandla okusebenza angama-205.85 kJ/mol, aphantsi nge-8.27% kunamandla okusebenza kwi-concentration yokungcola eyi-2.5 g/l. Ukwehla kwamandla okusebenza kubonisa ukuba inkqubo yokwenza i-crystallization ilula, nto leyo ekhokelela ekwandeni kwesantya sokukhula kwe-crystal kunye ne-crystal viety.
(a) Ukufakwa kweploti ye-ln(kg) ngokuchasene ne-1/T kunye (b) namandla okuvula Umz. we-crystallization kumanqanaba ahlukeneyo okungcola.
Indlela yokukhula kwekristale iphandwe yi-XRD kunye ne-FTIR spectroscopy, kwaye i-kinetics yokukhula kwekristale kunye namandla okusebenza ahlalutyiwe. Umfanekiso 6 ubonisa iziphumo ze-XRD. Idatha iyahambelana nePDF #08–0470, ebonisa ukuba yi-α-NiSO4 6H2O (i-silica ebomvu). Ikristale yeyenkqubo ye-tetragonal, iqela lesithuba yi-P41212, iiparameter zeyunithi yeseli yi-a = b = 6.782 Å, c = 18.28 Å, α = β = γ = 90°, kwaye ivolumu yi-840.8 Å3. Ezi ziphumo ziyahambelana neziphumo ezipapashwe ngaphambili nguManomenova et al. 19 Ukwaziswa kwee-ion ze-NH4+ kukhokelela ekwakhiweni kwe-(NH4)2Ni(SO4)2 6H2O. Idatha yeyePDF No. 31–0062. Ikristale yeyomhlelo we-monoclinic, iqela lesithuba P21/a, iiparameter zeyunithi yeseli ziyi-a = 9.186 Å, b = 12.468 Å, c = 6.242 Å, α = γ = 90°, β = 106.93°, kwaye ivolumu yi-684 Å3. Ezi ziphumo ziyahambelana nophando lwangaphambili olubikwe nguSu et al.20.
Iipateni ze-X-ray diffraction zeekristale ze-nickel sulfate: (a–b) 0.5%, (c–d) 1%, (e–f) 1.5%, kunye (g–h) 2% umlinganiselo wembewu. Umfanekiso osekunene ngumbono omkhulu womfanekiso osekhohlo.
Njengoko kubonisiwe kwiMifanekiso 6b, d, f kunye ne-h, i-2.5 g/L yeyona mda iphezulu yoxinzelelo lwe-ammonium kwisisombululo ngaphandle kokwenza ityuwa eyongezelelweyo. Xa uxinzelelo lokungcola luyi-3.75 kunye ne-5 g/L, ii-ion ze-NH4+ zifakwa kwisakhiwo sekristale ukuze zenze ityuwa eyinkimbinkimbi (NH4)2Ni(SO4)2 6H2O. Ngokwedatha, ubunzulu bencochoyi yetyuwa eyinkimbinkimbi buyanda njengoko ubunzulu bokungcola bunyuka ukusuka kwi-3.75 ukuya kwi-5 g/L, ngakumbi kwi-2θ 16.47° kunye ne-17.44°. Ukwanda kwencochoyi yetyuwa eyinkimbinkimbi kungenxa yomgaqo wokulingana kweekhemikhali. Nangona kunjalo, ezinye iincochoyi ezingaqhelekanga zibonwa kwi-2θ 16.47°, ezinokubangelwa kukuguquguquka kwe-elastic kwekristale. 21 Iziphumo zokuchazwa zibonisa nokuba umlinganiselo ophezulu wokuhlwayela ubangela ukwehla kobunzulu bencochoyi yetyuwa eyinkimbinkimbi. Umlinganiselo ophezulu wembewu ukhawulezisa inkqubo yekristale, ekhokelela ekunciphiseni okukhulu kwe-solute. Kule meko, inkqubo yokukhula kwekristale igxile kwimbewu, kwaye ukwakheka kwamanqanaba amatsha kuthintelwa kukuncipha kokugcwala kwesisombululo. Ngokwahlukileyo koko, xa umlinganiselo wembewu uphantsi, inkqubo yokuqhekeka kwekristale icotha, kwaye ukugcwala kwesisombululo kuhlala kwinqanaba eliphezulu. Le meko yonyusa amathuba okuba ityuwa engaphantsi kwenyibilikayo (NH4)2Ni(SO4)2 6H2O ikhule. Idatha yobunzulu betyuwa ephindwe kabini inikwe kwiTheyibhile 3.
Ukuchazwa kwe-FTIR kwenziwe ukuze kuphandwe naluphi na utshintsho kwi-lattice yomsingathi ngenxa yokubakho kwee-ion ze-NH4+. Iisampuli ezine-constant seeding ratio ye-2% zichaziwe. Umfanekiso 7 ubonisa iziphumo zokuchazwa kwe-FTIR. Iincopho ezibanzi ezibonwe kwi-3444, 3257 kunye ne-1647 cm−1 zibangelwa ziindlela zokolula ze-O–H zeemolekyuli. Iincopho kwi-2370 kunye ne-2078 cm−1 zimele ii-intermolecular hydrogen bonds phakathi kweemolekyuli zamanzi. Ibhendi kwi-412 cm−1 ibangelwa kukungcangcazela kokungcangcazela kwe-Ni–O. Ukongeza, ii-ion ze-SO4− zasimahla zibonisa iindlela ezine ezinkulu zokungcangcazela kwi-450 (υ2), 630 (υ4), 986 (υ1) kunye ne-1143 kunye ne-1100 cm−1 (υ3). Iimpawu υ1-υ4 zimele iipropati zeendlela zokungcangcazela, apho u-υ1 emele imo yokungaphuhli (ukunwebeka okulinganayo), u-υ2 umele imo yokuphuhla okuphindwe kabini (ukugoba okulinganayo), kwaye u-υ3 kunye no-υ4 bamele iindlela zokuphuhla okuphindwe kathathu (ukunwebeka okulinganayo kunye nokugoba okulinganayo, ngokulandelelana). 22,23,24 Iziphumo zokuchazwa zibonisa ukuba ubukho bokungcola kwe-ammonium bunika incochoyi eyongezelelweyo kwinani lamaza eliyi-1143 cm-1 (eliphawulwe ngesangqa esibomvu kumfanekiso). Incochoyi eyongezelelweyo kwi-1143 cm-1 ibonisa ukuba ubukho bee-ion ze-NH4+, nokuba zingakanani na uxinzelelo, bubangela ukugqwetheka kwesakhiwo se-lattice, okukhokelela kutshintsho kwi-frequency yokungcangcazela kwee-molecules ze-ion ze-sulfate ngaphakathi kwekristale.
Ngokusekelwe kwiziphumo ze-XRD kunye ne-FTIR ezinxulumene nokuziphatha kwe-kinetic kokukhula kwekristale kunye namandla okusebenza, Umfanekiso 8 ubonisa isicwangciso senkqubo yokwenza ikristale ye-nickel sulfate hexahydrate ngokongezwa kokungcola kwe-NH4+. Xa kungekho kungcola, ii-ion ze-Ni2+ ziya kusabela ne-H2O ukwenza i-nickel hydrate [Ni(6H2O)]2−. Emva koko, i-nickel hydrate idibana ngokuzenzekelayo nee-ion ze-SO42− ukwenza ii-nuclei ze-Ni(SO4)2 6H2O kwaye ikhula ibe ziikristale ze-nickel sulfate hexahydrate. Xa uxinzelelo oluphantsi lokungcola kwe-ammonium (2.5 g/L okanye ngaphantsi) longezwa kwisisombululo, i-[Ni(6H2O)]2− kunzima ukuyidibanisa ngokupheleleyo nee-ion ze-SO42− kuba ii-ion ze-[Ni(6H2O)]2− kunye ne-NH4+ ziyakhuphisana ngokudityaniswa nee-ion ze-SO42−, nangona kusekho ii-ion ze-sulfate ezaneleyo zokusabela nee-ion zombini. Le meko ikhokelela ekwandeni kwamandla okusebenza kwekristale kunye nokucotha kokukhula kwekristale. 14,25 Emva kokuba iinuclei ze-nickel sulfate hexahydrate zenziwe zaza zakhula zaba ziikristale, ii-ion ezininzi ze-NH4+ kunye ne-(NH4)2SO4 ziyafunxwa kumphezulu wekristale. Oku kuchaza isizathu sokuba iqela elisebenzayo le-SO4− ion (inombolo ye-wavenumber 1143 cm−1) kwiisampulu ze-NSH-8 kunye ne-NSH-12 lihlala lenziwe ngaphandle kwenkqubo yokuxuba. Xa uxinzelelo lokungcola luphezulu, ii-ion ze-NH4+ ziqala ukufakwa kwisakhiwo sekristale, zenze iityuwa ezimbini. 16 Le nto yenzeka ngenxa yokunqongophala kwee-ion ze-SO42− kwisisombululo, kwaye ii-ion ze-SO42− zibopha kwi-nickel hydrates ngokukhawuleza kunee-ion ze-ammonium. Le ndlela ikhuthaza i-nucleation kunye nokukhula kweetyuwa ezimbini. Ngexesha lenkqubo yokudibanisa, ii-nuclei ze-Ni(SO4)2 6H2O kunye ne-(NH4)2Ni(SO4)2 6H2O zenziwa ngaxeshanye, nto leyo ekhokelela ekwandeni kwenani leenuclei ezifunyenweyo. Ukwanda kwenani leenuclei kukhuthaza ukukhawuleziswa kokukhula kwekristale kunye nokuncipha kwamandla okusebenza.
Impendulo yamakhemikhali yokunyibilikisa i-nickel sulfate hexahydrate emanzini, ukongeza inani elincinci kunye nenani elikhulu le-ammonium sulfate, uze emva koko wenze inkqubo ye-crystallization ingabonakaliswa ngolu hlobo lulandelayo:
Iziphumo zokuchazwa kwe-SEM ziboniswe kuMfanekiso 9. Iziphumo zokuchazwa zibonisa ukuba ubungakanani betyuwa ye-ammonium eyongeziweyo kunye nomlinganiselo wembewu azichaphazeli kakhulu imo yekristale. Ubungakanani beekristale ezenziweyo buhlala bufana, nangona iikristale ezinkulu zivela ngamanye amaxesha. Nangona kunjalo, kusafuneka ukuchazwa okungakumbi ukuze kuchongwe isiphumo soxinzelelo lwetyuwa ye-ammonium kunye nomlinganiselo wembewu kubungakanani obuqhelekileyo beekristale ezenziweyo.
Imo yekristale yeNiSO4 6H2O: (a–e) 0.5%, (f–j) 1%, (h–o) 1.5% kunye (p–u) 2% umlinganiselo wembewu obonisa utshintsho loxinzelelo lwe-NH4+ ukusuka phezulu ukuya ezantsi, oluyi-0, 1.25, 2.5, 3.75 kunye ne-5 g/L, ngokulandelelana.
Umfanekiso 10a ubonisa ii-TGA curves zeekristale ezinezinga lokungcola ezahlukeneyo. Uhlalutyo lwe-TGA lwenziwe kwiisampuli ezine-seeding ratio ye-2%. Uhlalutyo lwe-XRD lwenziwe nakwisampuli ye-NSH-20 ukufumanisa iikhompawundi ezenziweyo. Iziphumo ze-XRD eziboniswe kuMfanekiso 10b ziqinisekisa utshintsho kwisakhiwo sekristale. Ukulinganiswa kwe-Thermogravimetric kubonisa ukuba zonke iikristale ezidityanisiweyo zibonisa uzinzo lobushushu ukuya kuthi ga kwi-80°C. Emva koko, ubunzima bekristale behle ngama-35% xa ubushushu bunyuka ukuya kwi-200°C. Ukulahleka kobunzima beekristale kungenxa yenkqubo yokubola, ebandakanya ukulahleka kweemolekyuli zamanzi ezi-5 ukwenza i-NiSO4 H2O. Xa ubushushu bunyuke ukuya kwi-300–400°C, ubunzima beekristale behla kwakhona. Ukulahleka kobunzima beekristale bekumalunga ne-6.5%, ngelixa ukulahleka kobunzima besampuli yekristale ye-NSH-20 bekuphezulu kancinci, kanye nge-6.65%. Ukuqhekeka kwee-ion ze-NH4+ kwigesi ye-NH3 kwisampulu ye-NSH-20 kubangele ukuncitshiswa okuphezulu kancinci. Njengoko ubushushu bunyuka ukusuka kwi-300 ukuya kwi-400°C, ubunzima beekristale buyehla, nto leyo ebangele ukuba zonke iikristale zibe nesakhiwo se-NiSO4. Ukunyusa ubushushu ukusuka kwi-700°C ukuya kwi-800°C kubangele ukuba isakhiwo sekristale siguquke sibe yi-NiO, nto leyo ebangele ukukhululwa kweegesi ze-SO2 kunye ne-O2.25,26
Ubunyulu beekristale ze-nickel sulfate hexahydrate bumiselwe ngokuvavanya uxinaniso lwe-NH4+ kusetyenziswa isixhobo se-DC-Arc ICP-MS. Ubunyulu beekristale ze-nickel sulfate bumiselwe kusetyenziswa ifomula (5).
Apho u-Ma bubunzima bokungcola kwikristale (mg), u-Mo bubunzima bekristale (mg), u-Ca bubuninzi bokungcola kwisisombululo (mg/l), u-V bubungakanani besisombululo (l).
Umfanekiso 11 ubonisa ubunyulu beekristale ze-nickel sulfate hexahydrate. Ixabiso lobunyulu lixabiso eliphakathi leempawu ezi-3. Iziphumo zibonisa ukuba umlinganiselo wokuhlwayela imbewu kunye noxinzelelo lokungcola luchaphazela ngokuthe ngqo ubunyulu beekristale ze-nickel sulfate ezenziweyo. Okukhona uxinano lokungcola luphezulu, kokukhona ukufunxwa kokungcola kukhulu, nto leyo ebangela ubunyulu obuphantsi beekristale ezenziweyo. Nangona kunjalo, indlela yokufunxwa kokungcola inokutshintsha ngokuxhomekeke kuxinano lokungcola, kwaye igrafu yesiphumo ibonisa ukuba ukufunxwa kokungcola ngokubanzi ziikristale akutshintshi kakhulu. Ukongeza, ezi ziphumo zikwabonisa ukuba umlinganiselo ophezulu wokufunxwa kwembewu unokuphucula ubunyulu beekristale. Le nto inokwenzeka kuba xa uninzi lwee-nuclei zekristale ezenziweyo zigxile kwi-nuclei ye-nickel, amathuba okuba ii-ion ze-nickel ziqokelele kwi-nickel aphezulu. 27
Olu phononongo lubonise ukuba ii-ion ze-ammonium (NH4+) zichaphazela kakhulu inkqubo yokwenza ikristale kunye neempawu zekristale ze-nickel sulfate hexahydrate crystals, kwaye zikwabonise nempembelelo yomlinganiselo wembewu kwinkqubo yokwenza ikristale.
Xa i-ammonium ingaphezulu kwe-2.5 g/l, i-crystal income kunye ne-crystal growth rate ziyehla. Xa i-ammonium ingaphezulu kwe-2.5 g/l, i-crystal income kunye ne-crystal growth rate ziyenyuka.
Ukongezwa kokungcola kwisisombululo se-nickel kwandisa ukhuphiswano phakathi kwe-NH4+ kunye ne-[Ni(6H2O)]2− ions ze-SO42−, nto leyo ekhokelela ekwandeni kwamandla okusebenza. Ukuncipha kwamandla okusebenza emva kokongeza ubuninzi bokungcola kungenxa yokungena kwee-NH4+ ions kwisakhiwo sekristale, ngaloo ndlela kwakheka ityuwa ephindwe kabini (NH4)2Ni(SO4)2 6H2O.
Ukusebenzisa umlinganiselo ophezulu wokutyala imbewu kunokuphucula isivuno sekristale, izinga lokukhula kwekristale kunye nobumsulwa bekristale ye-nickel sulfate hexahydrate.
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