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Irhubhululo leli liphenya ngemiphumela yokungcola kwe-NH4+ kanye nesilinganiso sembewu endleleni yokukhula nokusebenza kwe-nickel sulfate hexahydrate ngaphasi kokupholisa okungapheliko, begodu sihlola imiphumela yokungcola kwe-NH4+ endleleni yokukhula, ubujamo bokutjhisa, kanye namaqembu asebenzako we-nickel sulfate hexahydrate. Ekuhlanganisweni okuphasi kokungcola, ama-ayoni we-Ni2+ kanye ne-NH4+ ancintisana ne-SO42− ukubopha, okurholela ekwehleni kwesivuno sekristalu kanye nezinga lokukhula kanye nokukhuphuka kwamandla wokusebenza kwamakristalu. Ekuhlanganisweni okuphezulu kokungcola, ama-ayoni we-NH4+ afakwa esakhiweni sekristalu ukwakha itswayi eliyinkimbinkimbi (NH4)2Ni(SO4)2 6H2O. Ukwakheka kwetswayi eliyinkimbinkimbi kuphumela ekukhuphukeni kwesivuno samakristalu kanye nezinga lokukhula kanye nokwehla kwamandla wokusebenza kwamakristalu. Ukuba khona kwama-ayoni we-NH4+ aphezulu naphasi kubangela ukuhlanekezelwa kwe-lattice, begodu amakristalu azinze ngokutjhisa emazingeni womtjhiso afika ku-80 °C. Ukungezelela, umthelela wokungcola kwe-NH4+ endleleni yokukhula kwekristalu mkhulu kunalowo wesilinganiso sembewu. Lokha ukugxila kokungcola kuphasi, ukungcola kulula ukunamathela kukristalu; lokha ukugxila kuphezulu, ukungcola kulula ukukufaka ngaphakathi kwekristalu. Isilinganiso sembewu singakhuphula khulu isivuno sekristalu begodu sithuthukise kancani ukuhlanzeka kwekristalu.
I-Nickel sulfate hexahydrate (NiSO4 6H2O) njengento eqakathekileko esetjenziswa emabubulweni ahlukahlukeneko, kufaka hlangana ukukhiqiza amabhetri, ukufaka igezi, ama-catalysts, ngitjho nokukhiqizwa kokudla, amafutha, namakha. 1,2,3 Ukuqakatheka kwayo kuyakhula ngokuthuthukiswa okurhabako kweenkoloyi ezisebenzisa umtjhini, ezithembele khulu emabhetri we-nickel-based lithium-ion (LiB). Ukusetjenziswa kwama-alloy ane-nickel ephezulu afana ne-NCM 811 kulindeleke bona kube khulu ngo-2030, okuzokwandisa ukufunwa kwe-nickel sulfate hexahydrate. Kodwana, ngebanga lokutlhogeka kwemithombo, ukukhiqiza kungenzeka kungakhambisani nesidingo esikhulako, okwenza bona kube nesikhala hlangana nokunikelwa nokufunwa. Ukutlhayela lokhu kuphakamise ukutshwenyeka ngokutholakala kwemithombo nokuzinza kwentengo, okuveza itlhogeko yokukhiqiza okuphumelelako kwe-nickel sulfate yezinga eliphezulu, elizinzileko lebhetri. 1,4
Ukukhiqizwa kwe-nickel sulfate hexahydrate kuvamise ukufezwa ngokwenza amakristalu. Hlangana neendlela ezihlukahlukeneko, indlela yokupholisa yindlela esetjenziswa khulu, enezinzuzo zokusetjenziswa kwamandla aphasi nekghono lokukhiqiza izinto ezihlanzekileko. 5,6 Irhubhululo lokwenziwa kwe-nickel sulfate hexahydrate ngokusebenzisa ukupholisa okungapheliko kwenziwe ituthuko ekulu. Njenganje, irhubhululo elinengi ligxile ekwenzeni ngcono ikambiso yokwenza amakristalu ngokuthuthukisa amapharamitha afana nokutjhisa, izinga lokupholisa, ubukhulu bembewu kanye ne-pH. 7,8,9 Umnqopho kukwandisa isivuno samakristalu nokuhlanzeka kwamakristalu atholakeleko. Kodwana, nangaphandle kokufunda okupheleleko kwamapharamitha la, kusese nesikhala esikhulu sokutjheja umthelela wokusilaphazeka, khulukhulu i-ammonium (NH4+), emiphumeleni yokwenza amakristalu.
Ukusilaphazeka kwe-ammonium kungenzeka kube khona esixazululweni se-nickel esisetjenziselwa ukwenza i-nickel ikristalu ngebanga lokuba khona kokungcola kwe-ammonium ngesikhathi senqubo yokukhipha. I-ammonia ivamise ukusetjenziswa njenge-ejenti yokwenza i-saponify, etjhiya inani elincane le-NH4+ esixazululweni se-nickel. 10,11,12 Nanyana ukungcola kwe-ammonium kukhona yoke indawo, imiphumela yayo eentweni ezifana nesakhiwo sekristalu, indlela yokukhula, iimfanelo zokutjhisa, ukuhlanzeka, njll. Irhubhululo elilinganiselweko ngemiphumela yazo liqakathekile ngombana ukungcola kungathikameza nofana kutjhugulule ukukhula kwamakristalu begodu, kwezinye izehlakalo, kusebenza njengeenqabo, kuthinte ukutjhuguluka hlangana namafomu wekristalu azinzileko nezinzileko. 13,14 Ukuzwisisa imiphumela le kuqakathekile ukusuka embonweni webubulo ngombana ukungcola kungaphazamisa ikhwalithi yomkhiqizo.
Ngokuya ngombuzo othileko, irhubhululo leli belihlose ukuphenya umphumela wokungcola kwe-ammonium eentweni zamakristalu we-nickel. Ngokuzwisisa umphumela wokusilaphazeka, iindlela ezitjha zingathuthukiswa ukulawula nokunciphisa imiphumela yazo emimbi. Irhubhululo leli liphinde laphenya ukuhlobana hlangana nokugxila kokusilaphazeka nokutjhuguluka kwesilinganiso sembewu. Njengombana imbewu isetjenziswa khulu emsebenzini wokukhiqiza, amapharamitha wembewu asetjenziswe esifundweni lesi, begodu kuqakathekile ukuzwisisa ubudlelwano hlangana nalezi zinto ezimbili. 15 Imiphumela yamapharamitha amabili la yasetjenziselwa ukufunda isivuno sekristalu, indlela yokukhula kwekristalu, isakhiwo sekristalu, ukwakheka, nokuhlanzeka. Ngaphezu kwalokho, ukuziphatha kwe-kinetic, ubujamo bokutjhisa, kanye namaqembu asebenzako wamakristalu ngaphasi kwethonya lokungcola kwe-NH4+ kwaphela kwaphenywa godu.
Iinsetjenziswa ezisetjenziswe esifundweni lesi bekuyi-nickel sulfate hexahydrate (NiSO 6H2O, ≥ 99.8%) enikelwe yi-GEM; i-ammonium sulfate ((NH)SO, ≥ 99%) ethengwe ku-Tianjin Huasheng Co., Ltd.; amanzi ahlanjululweko. Ikristalu yembewu esetjenzisiweko bekuyi-NiSO 6H2O, echotshoziwe begodu yahlungwa ukuthola ubukhulu bezinhlayiya ezifanako ezingu-0.154 mm. Ubunjalo be-NiSO 6H2O butjengiswe kuThebuli 1 kanye noMfanekiso 1.
Umphumela wokungcola kwe-NH4+ kanye nesilinganiso sembewu ekukhiqizeni i-nickel sulfate hexahydrate kwaphenywa kusetjenziswa ukupholisa okuthileko. Zoke iimhloliso zenziwa emazingeni womtjhiso wokuthoma angama-25 °C. 25 °C yakhethwa njengezinga lokutjhisa lokwenza amakristalu ngokucabangela ukulinganiselwa kokulawula izinga lokutjhisa ngesikhathi sokuhlunga. Ukubunjwa kwamakristalu kungenziwa kutjhuguluka kwamazinga womtjhiso ngesikhathi sokuhlunga iinsombululo ezitjhisako kusetjenziswa ifaneli ye-Buchner enomtjhiso ophasi. Ikambiso le ingathinta khulu ukunyakaza, ukuthatha ukungcola, kanye nezakhiwo ezihlukahlukeneko zamakristalu.
Isixazululo se-nickel salungiswa kokuthoma ngokuncibilikisa i-224 g ye-NiSO4 6H2O ngaphakathi kwamanzi ahlanjululweko ayi-200 ml. Ukugxila okukhethiweko kuhambisana nokugcwala okukhulu (S) = 1.109. Ukugcwala okukhulu kwatholwa ngokumadanisa ukuncibilika kwamakristalu we-nickel sulfate ancibilikileko nokuncibilika kwe-nickel sulfate hexahydrate ku-25 °C. Ukugcwala okuphasi kwakhethwa ukukhandela ukukhiqiza okuzenzakalelayo lokha izinga lokutjhisa nalihliswa laya kokuthoma.
Umphumela wokugxila kwe-ayoni ye-NH4+ enqubweni yokwenza amakristalu kwaphenywa ngokufaka i-(NH4)2SO4 esixazululweni se-nickel. I-NH4+ ion concentrations esetjenziswe esifundweni lesi bekuyi-0, 1.25, 2.5, 3.75, kanye ne-5 g/L. Isixazululo safuthunyelwa ku-60 °C isikhathi esingaba mizuzu ema-30 ngesikhathi sivuselelwa nge-300 rpm ukuqinisekisa ukuhlanganiswa okufanako. Isixazululo sapholiswa ukuya emazingeni womtjhiso wokuphendula afunekako. Lokha izinga lokutjhisa nalifikelela ku-25 °C, inani elihlukileko lamakristalu wembewu (amazinga wembewu we-0.5%, 1%, 1.5%, kanye ne-2%) afakwa esixazululweni. Isilinganiso sembewu satholwa ngokumadanisa ubudisi bembewu nobudisi be-NiSO4 6H2O esixazululweni.
Ngemva kokufaka amakristalu wembewu esixazululweni, ikambiso yokwenza amakristalu yenzeka ngokwemvelo. Ikambiso yokwenza amakristalu yathatha imizuzu ema-30. Isixazululo sahlungwa kusetjenziswa umtjhini wokuhlunga ukuhlukanisa amakristalu abutheleleko esixazululweni. Ngesikhathi senqubo yokuhlunga, amakristalu bekahlanjwa nge-ethanol ukunciphisa amathuba wokuphinda kube namakristalu begodu kunciphise ukunamathelana kokungcola esixazululweni ebusweni bamakristalu. I-ethanol yakhethwa ukuhlanza amakristalu ngombana amakristalu awancibiliki ku-ethanol. Amakristalu ahlungiweko afakwa ngaphakathi kwe-incubator yelabhorethri ku-50 °C. Imingcele yokuhlola esetjenziswe esifundweni lesi itjengiswe kuThebuli 2.
Ukwakheka kwekristalu kwatholwa kusetjenziswa isisetjenziswa se-XRD (SmartLab SE—HyPix-400) begodu ubukhona bamakhompawundi we-NH4+ kwatholakala. Ukuhlukaniswa kwe-SEM (Apreo 2 HiVac) kwenziwa ukuhlaziya ubujamo be-crystal. Iimpawu zokutjhisa zamakristalu zatholwa kusetjenziswa isisetjenziswa se-TGA (TG-209-F1 Libra). Amaqembu asebenzako ahlaziywa nge-FTIR (JASCO-FT/IR-4X). Ukuhlanzeka kwesampula kwatholwa kusetjenziswa isisetjenziswa se-ICP-MS (i-Prodigy DC Arc). Isampula yalungiswa ngokuncibilikisa i-0.5 g yamakristalu ngaphakathi kwe-100 mL yamanzi ahlanjululweko. Ukukhiqizwa kwekristalu (x) kwabalwa ngokuhlukanisa ubudisi bekristalu ephumako ngobukhulu bekristalu engenako ngokuya ngefomula (1).
lapho i-x iyisivuno samakristalu, esuka ku-0 ukuya ku-1, i-mout isisindo samakristalu aphumako (g), i-min isisindo samakristalu afakwako (g), i-msol isisindo samakristalu esixazululweni, begodu i-mseed isisindo samakristalu wembewu.
Ukukhiqizwa kwamakristalu kwaphenywa godu ukuthola ukukhula kwekristalu nokulinganisa inani lamandla wokusebenza. Irhubhululo leli lenziwa ngesilinganiso sokutjala esingu-2% kanye nendlela efanako yokulinga njengangaphambilini. Amapharamitha we-isothermal crystallization kinetics anqunywa ngokuhlola isivuno se-crystal ngeenkhathi ezihlukileko zokukhiqiza (10, 20, 30, kanye ne-40 min) kanye namazinga womtjhiso wokuthoma (25, 30, 35, kanye ne-40 °C). Amazinga akhethiweko emazingeni womtjhiso wokuthoma akhambisana namazinga wokugcwala (S) we-1.109, 1.052, 1, kanye ne-0.953, ngokulandelana. Inani lokugcwala khulu latholakala ngokumadanisa ukuncibilika kwamakristalu we-nickel sulfate ancibilikileko nokuncibilika kwe-nickel sulfate hexahydrate emazingeni womtjhiso wokuthoma. Kulesi sifundo, ukuncibilika kwe-NiSO4 6H2O ku-200 mL yamanzi emazingeni womtjhiso ahlukileko ngaphandle kokusilaphazeka kutjengiswe kuMfanekiso 2.
U-Johnson-Mail-Avrami (ithiyori ye-JMA) isetjenziselwa ukuhlaziya ukuziphatha kwe-isothermal crystallization. Ithiyori ye-JMA ikhethwe ngombana ikambiso yokwenza amakristalu akwenzeki bekube kulapho amakristalu wembewu afakwa esixazululweni. Ithiyori ye-JMA ichazwa ngalendlela:
Lapho i-x(t) imele ukutjhuguluka ngesikhathi t, k imele izinga lokutjhuguluka elihlala njalo, t imele isikhathi sokutjhuguluka, begodu n imele inkomba ye-Avrami. Ifomula 3 isuselwa kufomula (2). Amandla wokwenza amakristalu anqunywa ngokusebenzisa i-equation ye-Arrhenius:
Lapho i-kg ilizinga lokusabela elihlala njalo, i-k0 ilizinga eliqinileko, i-Eg liyi-activation energy yokukhula kwekristalu, i-R liyi-molar gas constant (R=8.314 J/mol K), begodu i-T lilizinga lokutjhisa lokukhiqiza i-isothermal (K).
Umfanekiso 3a utjengisa bona isilinganiso sokutjala kanye nokugxila kwe-dopant kunomthelela ekukhiqizweni kwamakristalu we-nickel. Lokha ukugxila kwe-dopant esixazululweni kukhuphuka kwaba yi-2.5 g/L, isivuno sekristalu sehla ukusuka ku-7.77% ukuya ku-6.48% (isilinganiso sembewu se-0.5%) begodu ukusuka ku-10.89% ukuya ku-10.32% (isilinganiso sembewu se-2%). Ukwanda okungeziweko kwezinga le-dopant kwaholela ekukhuphukeni okufanako kwesivuno sekristalu. Isivuno esiphezulu sifinyelele ku-17.98% lokha isilinganiso sokutjala siyi-2% begodu ukugxila kwe-dopant bekungu-5 g/L. Amatjhuguluko wephetheni yokukhiqiza amakristalu ngokunyuka kokugxila kwe-dopant kungenzeka ahlotjaniswa namatjhuguluko wendlela yokukhula kwamakristalu. Lokha ukugxila kwe-dopant kuphasi, ama-ayoni we-Ni2+ kanye ne-NH4+ aphikisana ngokubophelela ne-SO42−, okurholela ekukhuphukeni kokuncibilika kwe-nickel esixazululweni kanye nokwehla kwesivuno sekristalu. 14 Lokha ukugxila kokungcola kuphezulu, ikambiso yokuncintisana isaqhubeka, kodwana amanye ama-ayoni we-NH4+ asebenzisana nama-ayoni we-nickel kanye ne-sulfate ukwakha itswayi eliphindwe kabili le-nickel ammonium sulfate. 16 Ukwakheka kwetswayi eliphindwe kabili kurholela ekwehleni kokuncibilika kwe-solute, ngaleyo ndlela kukhuphuke isivuno sekristalu. Ukukhuphula izinga lokutjala kungaragela phambili nokuthuthukisa isivuno sekristalu. Imbewu ingathoma ikambiso yokukhula kwenyukliya nokukhula kwamakristalu ngokuzenzakalelako ngokunikela indawo yokuthoma yokuthi ama-ayoni we-solute ahlele begodu enze amakristalu. Njengoba isilinganiso sokutjala sikhula, indawo yokuthoma yokuthi ama-ion ahlele iyakhula, ukwenzela bona kube namakristalu amanengi. Ngalokho-ke, ukwandisa izinga lokutjala kunomthelela oqondileko esilinganisweni sokukhula kwekristalu kanye nokukhiqizwa kwamakristalu. 17
Amapharamitha we-NiSO4 6H2O: (a) ukukhiqizwa kwamakristalu kanye (b) ne-pH yesixazululo se-nickel ngaphambi nangemva kokugonywa.
Umfanekiso 3b utjengisa bona isilinganiso sembewu kanye nokugxila kwe-dopant kuthinta i-pH yesisombululo se-nickel ngaphambi nangemva kokufakwa kwembewu. Umnqopho wokugada i-pH yesixazululo kukuzwisisa amatjhuguluko wokulingana kwamakhemikhali esixazululweni. Ngaphambi kokufaka amakristalu wembewu, i-pH yesisombululo ivamise ukwehla ngebanga lokuba khona kwama-ayoni we-NH4+ akhipha amaphrothoni we-H+. Ukukhuphula ukugxila kwe-dopant kuphumela ekukhutjhweni kwamaphrothoni amanengi we-H+, lokho kwehlisa i-pH yesisombululo. Ngemva kokufaka amakristalu wembewu, i-pH yazo zoke iinsombululo iyakhuphuka. Umkhuba we-pH uhlotjaniswa kuhle nomkhuba wokukhiqizwa kwamakristalu. Inani eliphasi le-pH latholwa ekuhlanganisweni kwe-dopant okungu-2.5 g/L kanye nesilinganiso sembewu esingu-0.5%. Njengoba ukugxila kwe-dopant kukhuphuka kube yi-5 g/L, i-pH yesixazululo iyakhuphuka. Isimanga lesi siyazwisiseka, ngombana ukutholakala kwama-ayoni we-NH4+ esixazululweni kwehla mhlamunye ngebanga lokumunywa, nofana ngebanga lokufakwa, nofana ngebanga lokumuncwa nokufakwa kwama-ayoni we-NH4+ ngamakristalu.
Iimhloliso zokukhiqiza amakristalu nokuhlaziywa kwaragela phambili kwenziwa ukuthola ukuziphatha kwe-kinetic kokukhula kwamakristalu nokubala amandla wokuvuselela ukukhula kwamakristalu. Amapharamitha we-isothermal crystallization kinetics ahlathululwe esigabeni seendlela. Umfanekiso 4 utjengisa iplothi ye-Johnson-Mehl-Avrami (JMA) etjengisa ukuziphatha kwe-kinetic kokukhula kwamakristalu we-nickel sulfate. Iplothi yenziwa ngokuplotha inani le-ln[− ln(1− x(t))] ngokujamelana nenani le-ln t (I-Equation 3). Amanani we-gradient atholakala eplothini ahambelana namanani we-JMA index (n) atjengisa ubukhulu bekristalu ekhulako kanye nendlela yokukhula. Lokha inani lokusika litjengisa izinga lokukhula elijanyelwe yi-ln k engaguqukiko. Amanani we-JMA (n) asuka ku-0.35 ukuya ku-0.75. Inani le-n litjengisa bona amakristalu anokukhula okulinganiselweko begodu alandela indlela yokukhula elawulwa kukusabalala; 0 < n < 1 kutjengisa ukukhula okunehlangothi linye, kuthi n < 1 kutjengisa indlela yokukhula elawulwa kusakazeka. 18 Izinga lokukhula le-k ehlalako lehla ngokukhula kwamazinga womtjhiso, okutjengisa bona ikambiso yokwenza amakristalu yenzeka msinyana emazingeni womtjhiso aphasi. Lokhu kuhlobana nokwanda kokugcwala kwesisombululo emazingeni womtjhiso aphasi.
Amaplothi we-Johnson-Mehl-Avrami (JMA) we-nickel sulfate hexahydrate emazingeni womtjhiso ahlukileko: (a) 25 °C, (b) 30 °C, (c) 35 °C kanye (d) 40 °C.
Ukungezelelwa kwama-dopants kutjengise iphetheni efanako yezinga lokukhula kiwo woke amazinga womtjhiso. Lokha ukugxila kwe-dopant bekungu-2.5 g/L, izinga lokukhula kwekristalu lehla, begodu lokha ukugxila kwe-dopant bekuphezulu kune-2.5 g/L, izinga lokukhula kwe-crystal lakhuphuka. Njengombana kutjhiwo ngaphambilini, ukutjhuguluka kwephetheni yezinga lokukhula kwamakristalu kubangelwa kutjhuguluka kwendlela yokusebenzisana hlangana nama-ayoni esixazululweni. Lokha ukugxila kwe-dopant kuphasi, ikambiso yokuncintisana hlangana nama-ayoni esixazululweni ikhuphula ukuncibilika kwe-solute, ngaleyindlela yehlisa izinga lokukhula kwekristalu. 14 Ukungezelela ama-dopants aphezulu kwenza bona ikambiso yokukhula itjhuguluke khulu. Lokha ukugxila kwe-dopant nakudlula i-3.75 g/L, kwakhiwa amanye ama-nuclei we-crystal amatjha, okurholela ekwehleni kokuncibilika kwe-solute, ngaleyindlela kukhuphuke izinga lokukhula kwe-crystal. Ukwakheka kwe-crystal nuclei etja kungatjengiswa ngokwakheka kwe-double salt (NH4)2Ni(SO4)2 6H2O. 16 Lokha nakukhulunywa ngendlela yokukhula kwekristalu, imiphumela ye-X-ray iqinisekisa ukwakheka kwetswayi eliphindwe kabili.
Umsebenzi weplothi ye-JMA wahlolwa godu ukuthola amandla wokwenza amakristalu. Amandla wokusebenza abalwa kusetjenziswa i-equation ye-Arrhenius (etjengiswe ku-Equation (4)). Umfanekiso 5a utjengisa ubudlelwano hlangana nenani le-ln(kg) nenani le-1/T. Bese, amandla wokusebenza abalwa kusetjenziswa inani le-gradient elitholwe esakhiweni. Umfanekiso 5b utjengisa amazinga wamandla wokusebenza wokukhiqiza ngaphasi kwamazinga ahlukileko wokungcola. Imiphumela itjengisa bona amatjhuguluko ekuhlanganisweni kokungcola athinta amandla wokusebenza. Amandla wokuvuselela amakristalu we-nickel sulfate ngaphandle kokungcola angama-215.79 kJ/mol. Lokha ukugxila kokungcola nakufika ku-2.5 g/L, amandla wokusebenza akhuphuka nge-3.99% ukuya ku-224.42 kJ/mol. Ukwanda kwamandla wokusebenza kutjengisa bona isithiyo samandla sendlela yokwenza amakristalu siyakhuphuka, okuzokurholela ekwehleni kwezinga lokukhula kwamakristalu nokukhiqizwa kwamakristalu. Lokha ukugxila kokungcola kungaphezu kwe-2.5 g/L, amandla wokwenza amakristalu ancipha khulu. Ekuhlanganisweni kokungcola okungu-5 g/l, amandla wokusebenza angama-205.85 kJ/mol, okuyi-8.27% ephasi kunamandla wokusebenza ekugxilweni kokungcola okungu-2.5 g/l. Ukwehla kwamandla wokusebenza kutjengisa bona ikambiso yokwenza amakristalu yenziwa lula, okurholela ekukhuphukeni kwezinga lokukhula kwamakristalu nokukhiqizwa kwamakristalu.
(a) Ukulingana kwephlothi ye-ln(kg) ngokuqathaniswa ne-1/T kanye (b) namandla wokusebenza Isib.
Indlela yokukhula kwekristalu yaphenywa nge-XRD ne-FTIR spectroscopy, begodu ukukhula kwekristalu namandla wokusebenza kwahlaziywa. Umfanekiso 6 utjengisa imiphumela ye-XRD. Idatha iyahambisana ne-PDF #08–0470, etjengisa bona yi-α-NiSO4 6H2O (i-silica ebomvu). Ikristalu ingeyohlelo lwe-tetragonal, isiqhema sesikhala ngu-P41212, amapharamitha weseli yeyunithi ngu-a = b = 6.782 Å, c = 18.28 Å, α = β = γ = 90°, begodu ivolumu ngu-840.8 Å3. Imiphumela le ivumelana nemiphumela eyagadangiswa ngaphambilini ngu-Manomenova et al. 19 Ukungeniswa kwama-ayoni we-NH4+ nakho kurholela ekwakhiweni kwe-(NH4)2Ni(SO4)2 6H2O. Idatha ingeye-PDF No. 31–0062. Ikristalu ingeyohlelo lwe-monoclinic, isiqhema sesikhala P21/a, amapharamitha wamaseli weyunithi a = 9.186 Å, b = 12.468 Å, c = 6.242 Å, α = γ = 90°, β = 106.93°, begodu ivolumu ngu-688 Å33. Imiphumela le ivumelana nesifundo sangaphambilini esibikwe ngu-Su et al.20.
Amaphetheni wokuphambuka kwe-X-ray wamakristalu we-nickel sulfate: (a–b) 0.5%, (c–d) 1%, (e–f) 1.5%, kanye (g–h) 2% isilinganiso sembewu. Isithombe sokudla siyimbono ekhulisiweko yesithombe sokwesokunxele.
Njengombana kutjengisiwe emifanekisweni 6b, d, f kanye ne-h, i-2.5 g/L mkhawulo ophakemeko wokugxila kwe-ammonium esixazululweni ngaphandle kokwakha itswayi elengeziweko. Lokha ukugxila kokungcola kungu-3.75 no-5 g/L, ama-ayoni we-NH4+ afakwa esakhiweni sekristalu ukwakha itswayi eliyinkimbinkimbi (NH4)2Ni(SO4)2 6H2O. Ngokuya ngedatha, ukuqina okuphezulu kwetshwayi eliyinkimbinkimbi kuyakhuphuka njengombana ukugxila kokungcola kukhuphuka ukusuka ku-3.75 ukuya ku-5 g/L, khulukhulu ku-2θ 16.47° no-17.44°. Ukwanda kwesiqongo setshwayi eliyinkimbinkimbi kungenxa yomthetho wokulingana kwamakhemikhali. Kodwana, ezinye iinqongo ezingakajayeleki zibonwa ku-2θ 16.47°, okungabangelwa kuguquguquka kwekristalu. 21 Imiphumela yokuhlukanisa ibuye itjengise bona isilinganiso esiphezulu sokutjala siphumela ekwehleni kwamandla aphezulu wetshwayi eliyinkimbinkimbi. Izinga eliphezulu lembewu lirhabisa ikambiso yokwenza amakristalu, okurholela ekwehleni okukhulu kwe-solute. Kulokhu, ikambiso yokukhula kwekristalu igxile embewini, begodu ukwakheka kweengaba ezitjha kuphazanyiswa kukwehliswa kokugcwala kwesisombululo. Ngokuphikisako, lokha isilinganiso sembewu siphasi, ikambiso yokwenza amakristalu iyaphuza, begodu ukugcwala okukhulu kwesisombululo kuhlala kusezingeni eliphezulu. Isimo lesi sikhuphula amathuba wokubunjwa kwe-nucleation ye-double salt (NH4)2Ni(SO4)2 6H2O. Idatha yokuqina okuphezulu kwetswayi eliphindwe kabili inikelwe kuThebuli 3.
Ukuhlukaniswa kwe-FTIR kwenziwa ukuphenya nanyana ngikuphi ukuphazamiseka nofana amatjhuguluko wesakhiwo ku-host lattice ngebanga lokuba khona kwama-ayoni we-NH4+. Amasampula anesilinganiso sokutjala esingatjhugulukiko se-2% ahlukaniswa. Umfanekiso 7 utjengisa imiphumela ye-FTIR. Iinqhema ezibanzi ezibonwe ku-3444, 3257 kanye ne-1647 cm-1 zibangelwa ziindlela zokulula ze-O-H zamamolekhyuli. Iinqhema ezingu-2370 no-2078 cm-1 zijamele ama-hydrogen bonds hlangana nama-molecule wamanzi. Ibhande elingu-412 cm-1 lihlotjaniswa nokudlidliza kwe-Ni-O. Ukungezelela, ama-ayoni we-SO4− wamahhala atjengisa iindlela ezine ezikulu zokudlidliza ku-450 (υ2), 630 (υ4), 986 (υ1) kanye no-1143 no-1100 cm−1 (υ3). Amatshwayo υ1-υ4 ajamele izakhiwo zeendlela zokuthuthumela, lapho u-υ1 ajamele indlela engawohlokiko (ukugoba okulinganako), u-υ2 ajamele indlela yokuwohloka kabili (ukugoba okulinganako), begodu u-υ3 no-υ4 zijamele iindlela zokuwohloka kathathu (ukugoba okulinganako nokungalinganiko, ngokulandelana). 22,23,24 Imiphumela yokuhlathulula itjengisa bona ukuba khona kwe-ammonium impurities kunikela isiqongo esingezelelweko kunombolo yamagagasi ayi-1143 cm-1 (ephawulwe ngesiyingi esibomvu emfanekisweni). Iqophelo elengeziweko ku-1143 cm-1 litjengisa bona ukuba khona kwama-ayoni we-NH4+, kungakaqalwa ukugxila, kubangela ukuhlanekezelwa kwesakhiwo se-lattice, okurholela ekutjhugulukeni kwemvamisa yokudlidliza kwamamolekhyuli we-sulfate ion ngaphakathi kwekristalu.
Ngokuya ngemiphumela ye-XRD ne-FTIR ehlobene nokuziphatha kwe-kinetic yokukhula kwamakristalu namandla wokusebenza, Umfanekiso 8 utjengisa isikimu senqubo yokwenza amakristalu we-nickel sulfate hexahydrate ngokungezwa kwe-NH4+ impurities. Nakungabikho ukusilaphazeka, ama-ayoni we-Ni2+ azokusabelana ne-H2O ukwakha i-nickel hydrate [Ni(6H2O)]2−. Bese, i-nickel hydrate ihlangana ngokuzenzakalelako nama-ayoni we-SO42− ukwakha i-Ni(SO4)2 6H2O nuclei bese ikhula ibe makristalu we-nickel sulfate hexahydrate. Lokha nakufakwa izinga eliphasi lokungcola kwe-ammonium (2.5 g/L nofana ngaphasi) esixazululweni, [Ni(6H2O)]2− kuba budisi ukuyihlanganisa ngokupheleleko nama-ayoni we-SO42− ngombana i-[Ni(6H2O)]2− kanye nama-ayoni we-NH4+ ancintisana ngokuhlanganiswa nama-ayoni we-SO42−, nanyana kusese nama-ayoni we-sulfate aneleko ukusabela nawo womabili ama-ayoni. Isimo lesi kurholela ekukhuphukeni kwamandla wokwenza amakristalu kanye nokukhula kwekristalu. 14,25 Ngemva kobana ama-nickel sulfate hexahydrate nuclei akhiwe begodu akhule abe makristalu, ama-ayoni amanengi we-NH4+ kanye ne-(NH4)2SO4 adonswa phezu kwekristalu. Lokhu kuchaza bona kubayini isiqhema esisebenzako se-SO4− ion (inomboro yegagasi 1143 cm−1) kumasampula we-NSH-8 ne-NSH-12 sihlala sakhiwe ngaphandle kwenqubo yokufaka. Lokha ukugxila kokungcola kuphezulu, ama-ayoni we-NH4+ athoma ukufakwa esakhiweni sekristalu, enza amatswayi amabili. 16 Isimanga lesi senzeka ngebanga lokutlhogeka kwama-ayoni we-SO42− esixazululweni, begodu ama-ayoni we-SO42− abophelela kuma-nickel hydrates msinya ukudlula ama-ayoni we-ammonium. Indlela le ikhuthaza ukwakheka nokukhula kwamatswayi amabili. Ngesikhathi senqubo yokuhlanganisa, i-Ni(SO4)2 6H2O kanye ne-(NH4)2Ni(SO4)2 6H2O iinyukliya zakhiwa ngasikhathi sinye, okurholela ekwandeni kwenani leenyukliya ezitholwako. Ukwanda kwenani lama-nuclei kukhuthaza ukurhaba kokukhula kwamakristalu kanye nokwehla kwamandla wokusebenza.
Ukusabela kwamakhemikhali kokuncibilikisa i-nickel sulfate hexahydrate emanzini, ukungezelela inani elincani nelinengi le-ammonium sulfate, bese kwenziwa ikambiso yokwenza ikristalu kungavezwa ngalendlela elandelako:
Imiphumela ye-SEM itjengiswe kuMfanekiso 9. Imiphumela yokuhlathulula itjengisa bona inani letswayi le-ammonium elingezelelweko kanye nesilinganiso sokutjala akuthinti khulu ijamo lekristalu. Ubukhulu bamakristalu akhiweko buhlala bunjalo, nanyana amakristalu amakhulu avela kwezinye iindawo. Nanyana kunjalo, kusatlhogeka ukuhlathulula okungeziweko ukuthola umphumela wokugxila kwetswayi le-ammonium kanye nesilinganiso sokutjala ebukhuluni obuphakathi bamakristalu akhiweko.
I-crystal morphology ye-NiSO4 6H2O: (a–e) 0.5%, (f–j) 1%, (h–o) 1.5% kanye (p–u) 2% isilinganiso sembewu esitjengisa ukutjhuguluka kwe-NH4+ ukugxila ukusuka phezulu ukuya phasi, okuyi-0, 1.25, 2.5, 3.75/L, ngokulandelana.
Umfanekiso 10a utjengisa amajika we-TGA wamakristalu anamazinga ahlukileko wokungcola. Ukuhlaziywa kwe-TGA kwenziwa emasampula ngesilinganiso sokutjala esingu-2%. Ukuhlaziywa kwe-XRD nakho kwenziwa kusampula ye-NSH-20 ukuthola amakhompawundi akhiweko. Imiphumela ye-XRD etjengiswe kuMfanekiso 10b iqinisekisa amatjhuguluko esakhiweni sekristalu. Iinlinganiso ze-thermogravimetric zitjengisa bona woke amakristalu akhiweko atjengisa ukuzinza kokutjhisa ukuya ku-80°C. Ngemva kwalokho, ubudisi bekristalu behla ngama-35% lokha izinga lokutjhisa nalikhuphukela ku-200°C. Ukulahlekelwa budisi kwamakristalu kubangelwa yindlela yokubola, ebandakanya ukulahlekelwa kwamamolekhyuli wamanzi amahlanu ukwakha i-NiSO4 H2O. Lokha izinga lokutjhisa nalikhuphukela ku-300 ukuya ku-400°C, ubudisi bamakristalu bebubuye behle godu. Ukulahlekelwa budisi kwamakristalu bekungaba ma-6.5%, ngesikhathi ukulahlekelwa budisi kwesampula yamakristalu we-NSH-20 bekuphezulu kancani, ngqo ama-6.65%. Ukubola kwama-ayoni we-NH4+ abe yigesi ye-NH3 kusampula ye-NSH-20 kwabangela ukunciphisa okuphezulu kancani. Njengoba amazinga womtjhiso akhuphuka ukusuka ku-300 ukuya ku-400°C, ubudisi bamakristalu behla, okwenza bona woke amakristalu abe nesakhiwo se-NiSO4. Ukukhuphula izinga lokutjhisa ukusuka ku-700°C ukuya ku-800°C kwenze bona isakhiwo sekristalu sitjhuguluke sibe yi-NiO, okwenza bona kukhutjhwe amagesi we-SO2 ne-O2.25,26
Ukuhlanzeka kwamakristalu we-nickel sulfate hexahydrate kwatholakala ngokuhlola ukugxila kwe-NH4+ kusetjenziswa isisetjenziswa se-DC-Arc ICP-MS. Ukuhlanzeka kwamakristalu we-nickel sulfate kwatholwa kusetjenziswa ifomula (5).
Lapho i-Ma isisindo sokusilaphazeka ekristalini (mg), i-Mo isisindo sekristalu (mg), i-Ca ibukhulu bokungcola esixazululweni (mg/l), i-V iyivolumu yesixazululo (l).
Umfanekiso 11 utjengisa ukuhlanzeka kwamakristalu we-nickel sulfate hexahydrate. Inani lokuhlanzeka linani eliphakathi leemfanelo ezi-3. Imiphumela itjengisa bona izinga lokutjala kanye nokugxila kokungcola kuthinta ngqo ukuhlanzeka kwamakristalu we-nickel sulfate akhiweko. Ukugxila okuphezulu kokungcola, ukumuncwa okukhulu kokungcola, okuholela ekuhlanzekeni okuphansi kwamakristalu akhiwe. Kodwana, iphetheni yokumunywa kokusilaphazeka ingatjhuguluka ngokuya ngokugxila kokungcola, begodu igrafu yomphumela itjengisa bona ukumunywa kokungcola okupheleleko ngamakristalu akutjhuguluki khulu. Ukungezelela, imiphumela le iveza nokuthi isilinganiso esiphezulu sokutjala singathuthukisa ukuhlanzeka kwamakristalu. Isimanga lesi kungenzeka ngombana lokha inengi lama-nuclei we-crystal akhiweko naligxile e-nickel nuclei, amathuba wokubuthelela ama-ion we-nickel phezu kwe-nickel aphezulu. 27
Irhubhululo litjengise bona ama-ayoni we-ammonium (NH4+) athinta khulu ikambiso yokwenza amakristalu kanye nezakhiwo zekristalu zamakristalu we-nickel sulfate hexahydrate, begodu iveze nomthelela wesilinganiso sembewu ehlelweni lokwenza amakristalu.
Ekuhlanganisweni kwe-ammonium okungaphezu kwe-2.5 g/l, isivuno sekristalu kanye nezinga lokukhula kwekristalu liyancipha. Ekuhlanganisweni kwe-ammonium okungaphezu kwe-2.5 g/l, ukukhiqizwa kwekristalu kanye nezinga lokukhula kwekristalu kuyakhuphuka.
Ukungezelelwa kokungcola esixazululweni se-nickel kwandisa ukuncintisana hlangana nama-ayoni we-NH4+ kanye ne-[Ni(6H2O)]2− we-SO42−, okurholela ekukhuphukeni kwamandla wokusebenza. Ukwehla kwamandla wokusebenza ngemva kokufaka ukungcola okuphezulu kungenxa yokungena kwama-ayoni we-NH4+ esakhiweni sekristalu, ngaleyo ndlela kwakha itswayi eliphindwe kabili (NH4)2Ni(SO4)2 6H2O.
Ukusebenzisa isilinganiso esiphezulu sokutjala kungathuthukisa isivuno sekristalu, izinga lokukhula kwamakristalu kanye nokuhlanzeka kwekristalu ye-nickel sulfate hexahydrate.
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