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Okucondooza oku nikucondooza aha bikwatiraine n’obukooko bwa NH4+ n’omubaro gw’embibo aha nkora y’okukura n’okukora kwa nickel sulfate hexahydrate ahansi y’okukyendeeza okukyendeeza okutaine bugarukiro, kandi nikushwijuma ebirikuruga omu bikwatiraine n’obukooko bwa NH4+ aha nkora y’okukura, emitwarize y’okwotsya, n’ebicweka bya sulfate hexahydrate ebirikukora. Omu nkora y’obutafaari bukye, Ni2+ na NH4+ ions nizirwanira SO42− ahabw’okukwatira hamwe, ekirikureetaho okukyendeera omu kutunga ebiriisa n’omubaro gw’okukura n’okwongyera aha maani g’okukora ebiriisa. Omu nkora y’obutafaari bwingi, NH4+ ions nizitaaha omu nkora y’ekibiriiti kubaasa kuhanga omunyugunyu ogugumire (NH4)2Ni(SO4)2 6H2O. Okubaho kw’omunyugunyu ogugumire nikurugamu okweyongyera kw’okutunga ebiriisa n’omubaro gw’okukura n’okukyendeeza aha maani g’okukora ebiriisa. Okubaho kw’ebicweka bya NH4+ ion eby’ahaiguru n’eby’ahansi nikireetaho okuhinduka kw’ebicweka by’omubiri (lattice distortion), kandi ebicupuri nibiguma omu bwire bw’okwotsya aha bwire bw’obutagatsi oburikuhika ahari 80 °C. Okwongyera ahari ekyo, okukwatwaho kw’obukooko bwa NH4+ aha nkora y’okukura kw’ekibiriiti nikukira okw’omubaro gw’enjuma. Obukooko bwaba buri bukye, obukooko nibworoba kukwatira aha kicupuri; okuteerana kwaba kuri ahaiguru, obutashemeire nibworoba kutaaha omu kicupuri. Omubaro gw’enjuma nigubaasa kwongyera munonga aha ntunguuka y’ekibiriiti kandi gutunguureho kakye obushemeire bw’ekibiriiti.
Nickel sulfate hexahydrate (NiSO4 6H2O) hati n’ekintu kikuru ekirikukoresibwa omu makorero gatari gamwe na gamwe, otwariiremu okukora bateri, okuteera amashanyarazi, ebirikureetaho okutunguuka, nangwa n’okukora eby’okurya, amajuta, n’amajuta. 1,2,3 Obukuru bwayo nibweyongyera ahabw‘okutunguuka kw‘ahonaaho kw‘emotoka z‘amashanyarazi, ezirikwesiga munonga battery za lithium-ion (LiB) ezirikukoresa nickel. Okukozesa eby’okurya ebirimu nickel nyingi nka NCM 811 nikuteekateekwaho kuba nikukirayo omu mwaka 2030, ekirikwongyera kwongyera aha kwetenga kwa nickel sulfate hexahydrate. Kwonka ahabw‘okubura eby‘obugaiga, okukora nikubaasa kutagumizamu n‘okweyongyera kw‘okwenda, ekirikureetaho omugaati ahagati y‘okutunga n‘okwenda. Okubura oku kureetsireho okwerarikirira aha kutunga eby’obugaiga n’okugumaho kw’emihendo, ekirikworeka ekyetengo ky’okukora gye ebiriisa bya nickel sulfate eby’omutindo gw’ahaiguru, ebigumire nk’ebya battery. 1,400.
Okukora ebiriisa bya nickel sulfate hexahydrate okutwarira hamwe nikuhikirizibwa omu kuhindura ebiri nk’ebicupuri. Omu miringo etari emwe n’emwe, omuringo gw’okukyendeeza obutagatsi n’omuringo ogurikukoresibwa munonga, oguine oburungi bw’okukoresa amaani makye n’okubaasa kukora ebintu by’obuyonjo bw’ahaiguru. 5,6 Okucondooza aha kuhinduka kw’ekirungo kya nickel sulfate hexahydrate barikukoresa okuhinduka kw’okukyendeeza obutagatsi okutarikugumizamu kukozire entunguuka mpango. Obwahati, okucondooza okurikukirayo nikuta omutima aha kutunguura omuringo gw’okukora ebihimba (crystallization) barikutunguura ebintu nk’obutagatsi, omubaro gw’okukyendeeza, obuhango bw’embibo na pH. 7,8,9 Ekigyendererwa n’okwongyera aha kutunga amaizi g’ebicupuri n’obushemeire bw’ebicupuri ebitungirwe. Kwonka n’obu okucondooza okuhikire aha bikwatiraine n’ebintu ebi kuraabe kwakozirwe, hakiriho omwanya muhango omu kuta omutima aha nkora y’obukooko, namunonga ammonium (NH4+), aha byarugamu omu kuhinduka kw’ebicupuri.
Obukooko bwa ammonium nibubaasa kuba buri omu nkora ya nickel erikukoresibwa omu kuhindura nickel crystallization ahabw’okugira ngu hariho obukooko bwa ammonium omu bwire bw’okushohoza. Ammonia neekira kukozesebwa nk’ekintu ekirikuhindura sabuuni, ekirikusigaho obucweka bukye bwa NH4+ omu nkora ya nickel. 10,11,12 N’obu obukooko bwa ammonium buraabe buri hoona, ebirikurugamu aha mitwarize y’ekibiriiti nk’omutindo gw’ekibiriiti, omuringo gw’okukura, emitwarize y’okwotsya, obushemeire, n’ebindi nibiguma bitarikwetegyerezibwa gye. Okucondooza okukye aha bikwatiraine n‘ebirikurugamu ni kikuru ahabw‘okuba obukooko nibubaasa kuremesa nari kuhindura okukura kw‘ekibiriiti kandi, omu mbeera ezimwe, nibukora nk‘ebirikuzibira, bikakwata aha kuhinduka ahagati y‘emiringo y‘ekibiriiti etarikuhinduka n‘etarikuhinduka. 13,14 Nahabwekyo okwetegyereza ebirugiremu ebi ni kikuru munonga kuruga omu kureeba kw‘amakorero ahabw‘okuba obukooko nibubaasa kushiisha omutindo gw‘ebintu.
Okurugirira aha kibuuzo ekimwe, okucondooza oku kukaba kugyendereire kucondooza aha nkora y’obukooko bwa ammonium aha mitwarize y’ebicupuri bya nickel. Omu kwetegyereza oku obukooko burikukora, emiringo mirungi neebaasa kukorwa kubaasa kukyebera n‘okukyendeeza aha kabi akarikurugamu. Okucondooza oku kukacondooza n’aha nkoragana eri ahagati y’okutaho obukooko n’empindahinduka omu nkora y’embibo. Ahabw’okugira ngu embibo neekoresibwa munonga omu nkora y’okuhinga, ebipimo by’embibo bikakoresibwa omu kucondooza oku, kandi ni kikuru kwetegyereza akakwate akari ahagati y’ebintu ebi bibiri. 15 Ebirugire omu bipimo ebi bibiri bikakoresibwa kwega aha nkora y’okukura kw’ebicupuri, omuringo gw’okukura kw’ebicupuri, enkora y’ebicupuri, enkora y’ebicupuri, n’obushemeire. Okwongyera ahari ekyo, emitwarize y’okugyendera, emitwarize y’okwotsya, n’ebicweka by’emirimo y’ebicupuri ebiri ahansi y’okutegyekwa obukooko bwa NH4+ bwonka bikagaruka byacondoozibwa.
Ebikoreso ebyakozesiibwe omu kucondooza oku bikaba biri eby’okurya ebirimu ebiriisa by’omubiri (NiSO 6H2O, ≥ 99.8%) ebyabaire biheebwayo GEM; ebiriisa by’omubiri ((NH)SO, ≥ 99%) ebyaguzirwe kuruga omu kampuni ya Tianjin; amaizi agateirwemu ebiriisa. Ekirungo ky’enjuma ekyakozesiibwe kikaba kiri NiSO 6H2O, kyacwekyerezibwa kandi kyasendwa kutunga obuhango bw’ebicweka ebirikushushana ebya mm 0.154. Emitwarize ya NiSO 6H2O neeyorekwa omu kipande 1 n’ekishushani 1.
Ekirikubaho ahabw’obukooko bwa NH4+ n’omubaro gw’embibo aha kuhinduka kw’ekirungo kya nickel sulfate hexahydrate kikacondoozibwa barikukoresa okukyendeeza kw’obwire bukye. Okucondooza kwona kukakorwa aha bwire bw’okubanza obw’obutagatsi bwa 25 °C. 25 °C ekatooranwa nk’obutagatsi bw’okuhinduka ekicupuri barikuteekateeka aha bugarukiro bw’okutegyeka obutagatsi omu bwire bw’okushwijuma. Okuhinduka kw’ebicupuri nikubaasa kureetwa okuhinduka kw’obutagatsi okwa ahonaaho omu bwire bw’okushwijuma ebirungo ebirikwotsya orikukoresa omuhanda gwa Buchner ogw’obutagatsi bukye. Enkora egi neebaasa kukwata munonga aha nkora y’okutambura, okutwara obukooko, n’emitwarize y’ekibiriiti etari emwe n’emwe.
Omubazi gwa nickel gukabanza gwatebeekanisibwa barikusheenya 224 g NiSO4 6H2O omu miriyoni 200 z’amaizi agateirwemu ebiriisa. Okuteekateeka okutoorainwe nikuhikaana n‘okujwara munonga (S) = 1.109. Okujwara munonga kukamanyirwa aha kugyeragyeranisa okushohoza kw’ebicupuri bya nickel sulfate ebishohoziibwe n’okushohoza kw’ebicupuri bya nickel sulfate hexahydrate ahari 25 °C. Supersaturation y’ahansi ekatooranwa kuzibira okuhinduka kw’amaizi (crystallization) okwetunguura obu obutagatsi bwagarurwa ahansi kuhika aha bw’okubanza.
Ekirikubaho ahabw’okuteerana kwa NH4+ ion aha nkora y’okuhindura amaizi g’ebicupuri kikacondoozibwa barikuteeka (NH4)2SO4 omu nkora ya nickel. Ebicweka bya NH4+ ebyakozesiibwe omu kucondooza oku bikaba biri 0, 1.25, 2.5, 3.75, na 5 g/L. Omubazi gukaheebwa omuriro aha 60 °C kumara edakiika 30 obwo gurikuteerwa aha 300 rpm kureeba ngu gwatabura omu muringo gumwe. Omubazi ogwo gukaheza gukyendeezibwa kuhika aha bwire bw’okugarukamu oburikwetengyesa. Ebirikuba biriho ku byahikire ahari 25 °C, ebihimba by’embibo ebitari bimwe na bimwe (embibo z’ebihimba bya 0.5%, 1%, 1.5%, na 2%) bikateebwa omu nshonga. Omubaro gw’embibo gukamanyirwa aha kugyeragyeranisa oburemeezi bw’embibo n’oburemeezi bwa NiSO4 6H2O omu nshonga.
Bwanyima y’okutaho ebirungo by’enjuma omu nshonga, omuringo gw’okuhinduka ebirungo gukabaho omu buhangwa. Omuringo gw’okukora ekibiriiti gukamara edakiika 30. Omubazi gukasendwa barikukoresa ekikwato ky’okushwijuma (filter press) kwongyera kutaanisa ebicupuri ebyabaire biteeraine kuruga omu mubazi. Omu bwire bw’okushwijuma, ebicupuri bikaba biguma nibiyozibwa n’ethanol kukyendeeza aha kubaasa kw’okugaruka kuhinduka ebicupuri n’okukyendeeza aha kukwatira hamwe kw’obukooko oburi omu nshonga aha mutwe gw’ebicupuri. Ethanol ekatooranwa kwozya ebicupuri ahabwokuba ebicupuri tibirikushohora omu ethanol. Ebicupuri ebyashwijumirwe bikateebwa omu kishengye ky’okukyebera aha 50 °C. Ebirikugyezesibwa omu bwijwire ebyakozesiibwe omu kucondooza oku nibyorekwa omu kipande kya 2.
Omuringo gw’ekibiriiti gukamanyirwa aha kukozesa ekikwato kya XRD (SmartLab SE—HyPix-400) kandi okubaho kw’ebirungo bya NH4+ kukashangwa. Okucondooza kwa SEM (Apreo 2 HiVac) kukakorwa kukyebera enkora y‘ekibiriiti. Ebintu by’okwotsya eby’ebicupuri bikamanyirwa aha kukoresa ekikwato kya TGA (TG-209-F1 Libra). Ebibiina by‘emirimo bikakyeberwa omu nkora ya FTIR (JASCO-FT/IR-4X). Obushemeire bw’eky’okureeberaho bukamanyirwa aha kukoresa ekikwato kya ICP-MS (Prodigy DC Arc). Eky’okureeberaho kikatebeekanisibwa barikusheenya 0.5 g y’ebicupuri omu 100 mL y’amaizi agateirwemu ebiriisa. Ekirugire omu kuhinduka kw’ekibiriiti (x) kikabarwa barikugabanisa oburemeezi bw’ekibiriiti ekirikurugamu n’oburemeezi bw’ekibiriiti ekirikutaaha kurugiirira aha nkora (1).
aho x eri ekirungo ky’ekibiriiti, ekirikuhinduka kuruga ahari 0 kuhika ahari 1, mout n’oburemeezi bw’ebibiriiti ebirikurugamu (g), min n’oburemeezi bw’ebibiriiti ebirikutaaha (g), msol n’oburemeezi bw’ebibiriiti ebiri omu nshonga, kandi mseed n’oburemeezi bw’ebibiriiti by’enjuma.
Ekirugire omu kuhinduka kw’ekibiriiti kikongyerwa kucondoozibwa kubaasa kumanya oku ekibiriiti kirikukura n’okutebereza omuhendo gw’amaani g’okukora. Okucondooza oku kukakorwa n’omubaro gw’okubyara ogwa 2% n’omuringo gw’okugyezesa nk’ogwabandize. Ebipimo by’okugyendera aha nkora y’okusheeshasheesha kw’eitaka bikamanyirwa aha kucondooza aha nkora y’okusheeshasheesha omu bwire bw’okusheeshasheesha obutari bumwe na bumwe (edakiika 10, 20, 30, na 40) n’obutagatsi bw’okubanza (25, 30, 35, na 40 °C). Ebicweka ebyatoorainwe aha bwire bw’obwire bw’okubanza bikahikaana n’emihendo ya supersaturation (S) eya 1.109, 1.052, 1, na 0.953, nk’oku biri. Omuhendo gw’okujwara munonga gukamanyirwa aha kugyeragyeranisa okushohoza kw’ebicupuri bya nickel sulfate ebishohoziibwe n’okushohoza kwa nickel sulfate hexahydrate aha bwire bw’obwire bw’okubanza. Omu kucondooza oku, okushohoza kwa NiSO4 6H2O omu maizi 200 mL aha bwire bw’obwire obutari bumwe na bumwe hatariho obukooko nikworekwa omu kishushani 2.
Johnson-Mail-Avrami (enteekateeka ya JMA) neekoresibwa kucondooza aha mitwarize y’okuhindura ebiri omu itaka. Enteekateeka ya JMA neetooranwa ahabw’okuba omuringo gw’okuhindura amaizi g’ebicupuri tigurikubaho kuhitsya obu amaizi g’ebicupuri g’embibo garikugambwaho omu nshonga. Enteekateeka ya JMA neeshoboororwa omu muringo ogu:
Aha x(t) erikworeka okuhinduka omu bwire t, k neejwekyera omubaro gw’okuhinduka ogutarikuhinduka, t neejwekyera obwire bw’okuhinduka, kandi n neejwekyera omubaro gwa Avrami. Enkora ya 3 neeruga omu nkora ya (2). Amaani g’okukora g’okuhinduka kw’ebintu nigamanyirwa aha kukoresa ekibaro kya Arrhenius:
Aha kg n’omubaro gw’okugarukamu ogutarikuhinduka, k0 n’omubaro gw’okugarukamu, Eg n’amaani g’okukora g’okukura kw’ekibiriiti, R n’omubaro gw’omuyaga gwa molar (R=8.314 J/mol K), kandi T n’obutagatsi bw’okuhinduka kw’ekibiriiti (K).
Ekishushani 3a nikyoreka ngu omubaro gw’okubyara n’okutaho ebiriisa biine eki birikukora aha kutunga ebirungo bya nickel. Omubaro gw’ebiriisa omu nshonga ku gwayeyongyeire kuhika ahari 2.5 g/L, okutunga ebiriisa bya crystal kukakyendeera kuruga ahari 7.77% kuhika ahari 6.48% (omubaro gw’enjuma 0.5%) kandi kuruga ahari 10.89% kuhika ahari 10.32% (omubaro gw’enjuma 2%). Okwongyera kweyongyera kw’okutaho ebiriisa (dopant concentration) kukareetera okweyongyera okurikuhikaana n’okutunga ebiriisa by’ekibiriiti. Okuhinga okurikukirayo kukahika ahari 17.98% obu omubaro gw’okubyara gwabaire guri 2% kandi omubaro gw’ebiriisa (dopant concentration) gukaba guri 5 g/L. Empindahinduka omu nkora y‘okutunga ebiriisa n‘okwongyera aha nkora y‘okutaho ebiriisa nibibaasa kuba nibikwatagana n‘empindahinduka omu nkora y‘okukura kw‘ebiriisa. Ekirungo kya dopant kyaba kiri kikye, Ni2+ na NH4+ ions nizirwanira okukwatira hamwe na SO42−, ekirikureetaho okweyongyera kw’okushohoza kwa nickel omu nshonga n’okukyendeera omu kutunga kw’ekibiriiti. 14 Obutafaari bwaba buri ahaiguru, omuringo gw’okuhakanisa nigugumaho, kwonka emwe aha ions za NH4+ nizikwatanisa na ions za nickel na sulfate kuhanga omunyugunyu gwa kabiri ogwa nickel ammonium sulfate. 16 Okubaho kw’omunyugunyu gw’emirundi ebiri nikureetera okukyendeera kw’okushohoza kw’ekintu ekirikushuuma, reero kiyongyere aha kutunga ekirungo ky’ekirungo. Okwongyera aha nkora y’okubyara nikibaasa kuguma nikitunguura ebiriisa by’ekibiriiti. Enjuma nizibaasa kutandikaho omuringo gw’okukora nucleation n’okukura kw’ebicupuri okwekundiire obwo zirikuha omwanya gw’okubanza aha mutwe gw’ebicupuri (solute ions) kutebeekanisa n’okukora ebicupuri. Omubaro gw’okubyara ku gurikweyongyera, omwanya gw’okubanza ogw’okutebeekanisamu ayoni nigweyongyera, n’ahabw’ekyo ebicupuri bingi nibibaasa kuhangwa. Nahabwekyo, okwongyera aha nkora y’okubyara nikikwata butunu aha kukura kw’ebihimba n’okutunga ebihimba. 17
Ebirikumanyisa NiSO4 6H2O: (a) okurugamu kw’ekibiriiti na (b) pH y’omubazi gwa nickel gutakatandikire n’enyima y’okukyebera.
Ekishushani 3b nikyoreka ngu omubaro gw’embibo n’okutaho ebiriisa nibikwata aha pH y’omubazi gwa nickel embibo etakatandikire n’enyima y’okutaho. Ekigyendererwa ky’okureeberera pH y’omubazi n’okwetegyereza empindahinduka omu nkora y’eby’obuhangwa omu mubazi. Otakagiiremu ebirungo by’enjuma, pH y’omubazi neekira kukyendeera ahabw’okugira ngu hariho NH4+ ions ezirikurekura H+ protons. Okwongyera aha nkora ya dopant nikirugamu okurekura kwa purotoni nyingi eza H+, obwo nikikyendeeza pH y’omubazi. Bwanyima y’okutaho ebirungo by’enjuma, pH y’ebirungo byona neeyeyongyera. Omuze gwa pH nigukwatagana gye n’omuze gw’okutunga ebiriisa by’ekibiriiti. Omuhendo gwa pH oguri ahansi munonga gukatunga aha nkora ya dopant 2.5 g/L n’omubaro gw’embibo 0.5%. Omubaro gw’ekiriisa kya dopant ku gurikweyongyera kuhika ahari 5 g/L, pH y’omubazi neeyeyongyera. Ekintu eki nikyetegyerezibwa gye, ahabw’okuba okubaho kwa NH4+ ions omu nshonga nikukyendeera ahabw’okunywa, nari ahabw’okutaho, nari ahabw’okunywa n’okutaho NH4+ ions ahabw’ebicupuri.
Okugyezesa n’okushwijuma eby’okurya by’ebicupuri bikagaruka byakorwa kubaasa kumanya emitwarize y’okukura kw’ebicupuri n’okubara amaani g’okukora g’okukura kw’ebicupuri. Ebirikugyenderwaho omu nkora y‘okuhindura ebiri omu isothermal crystallization kinetics bikashoboororwa omu kicweka ky‘emiringo y‘okukora. Ekishushani 4 nikyoreka puroguraamu ya Johnson-Mehl-Avrami (JMA) erikworeka emitwarize y‘okugyendera aha kukura kw‘ekibiriiti ky‘omubiri. Puloti ekakorwa omu kuhandiika omuhendo gwa ln[− ln(1− x(t))] aha muheendo gwa ln t (Ekibaro 3). Emihendo y‘okukura (gradient) erikutunga kuruga omu puroguraamu neehikaana n‘emihendo ya JMA index (n) erikworeka obuhango bw‘ekibiriiti ekirikukura n‘omuringo gw‘okukura. Obwire obu omuhendo gw‘okusharaho gurikworeka omubaro gw‘okukura ogurikworekwa n‘ekintu ekitarikuhinduka ln k. Omubaro gwa JMA (n) niguruga ahari 0.35 kuhika ahari 0.75. Omuhendo ogu n nigworeka ngu ebicupuri biine okukura kw’omuringo gumwe kandi nibikuratira omuringo gw’okukura ogurikutegyekwa okujanjaara; 0 < n < 1 neeyoreka okukura kw‘omuringo gumwe, kandi n < 1 neeyoreka omuringo gw‘okukura ogurikutegyekwa okujanjaara. 18 Omubaro gw’okukura kw’ekintu ekitarikuhinduka k nigukyendeera n’okweyongyera kw’obutagatsi, ekirikworeka ngu omuringo gw’okukora ekibiriiti nigubaho juba aha bwire bw’obutagatsi oburi ahansi. Eki nikikwatagana n’okwongyera aha supersaturation y’omubazi aha bwire bw’obwire bw’ahansi.
Johnson-Mehl-Avrami (JMA) puroti z’eby’okurya ebirimu ebiriisa by’omubiri aha bwire bw’obwire bw’okuhinduka kw’amaizi obutarikushushana: (a) 25 °C, (b) 30 °C, (c) 35 °C na (d) 40 °C.
Okwongyeraho ebirungo (dopants) kukooreka omuringo nigwo gumwe gw’okukura kw’omubaro gw’obwire bwona. Omubaro gw’ekiriisa kya dopant ku gwabaire guri 2.5 g/L, omubaro gw’okukura kw’ekibiriiti gukaba nigukyendeera, kandi omubaro gw’ekiriisa kyaba guri ahaiguru ya 2.5 g/L, omubaro gw’okukura kw’ekibiriiti gukaba gweyongyera. Nkoku kyagambirweho enyima, empindahinduka omu nkora y’okukura kw’ekibiriiti neereetwa empindahinduka omu nkora y’okukoragana ahagati y’ebicweka by’omubiri ebiri omu nshonga. Ekirungo kya dopant kyaba kiri kikye, omuringo gw’okuhakanisa ahagati ya ayoni omu nshonga nigweyongyera aha kushohora kw’ekirungo, obwo nikikyendeeza aha kukura kw’ekirungo. 14 Ekindi, okwongyeraho ebiriisa bingi ebirikuhwera omu kukura nikireetera omuringo gw’okukura kuhinduka munonga. Ekirungo kya dopant kyaba nikirenga 3.75 g/L, ebicweka bisya by’ekibiriiti nibibaho, ekirikureetaho okukyendeera kw’okushohoza kw’ekirungo, obwo n’okwongyera aha kukura kw’ekirungo. Okuhangwa kw’ebicweka bisya by’ekibiriiti nikubaasa kworekwa ahabw’okuhangwa kw’omunyugunyu gw’emirundi ebiri (NH4)2Ni(SO4)2 6H2O. 16 Twaba nitugamba aha muringo ogu amaizi g’omubiri garikukuramu, ebyarugamu omu kucondooza kwa X-ray nibihamya ngu hariho omunyugunyu gw’emirundi ebiri.
Omurimo gwa plot ya JMA gukagaruka gwakyeberwa kubaasa kumanya amaani g‘okukora g‘okukora kw‘ekibiriiti. Amaani g‘okukora gakabarwa barikukoresa enkora ya Arrhenius (eyorekwa omu nkora (4)). Ekishushani 5a nikyoreka akakwate akari ahagati y‘omuhendo gwa ln(kg) n‘omuhendo gwa 1/T. Bwanyima, amaani g‘okukora gakabarwa barikukoresa omuhendo gw‘okutunguuka ogwatungirwe kuruga omu puroguraamu. Ekishushani 5b nikyoreka emihendo y‘amaani g‘okukora g‘okuhinduka kw‘ebintu ahansi y‘ebicweka by‘obukooko ebitarikushushana. Ebirugiremu nibyoreka ngu empindahinduka omu nkora y‘okutaho obutashemeire nizikwata aha maani g‘okukora. Amaani g’okukora g’okuhindura ebicupuri bya nickel sulfate bitaine buzibu ni 215.79 kJ/mol. Obutafaari bw’omubiri bwahika ahari 2.5 g/L, amaani g’okukora nigayongyera n’ebicweka 3.99% kuhika ahari 224.42 kJ/mol. Okwongyera aha maani g‘okukora nikworeka ngu omuzigo gw‘amaani gw‘omuringo gw‘okukora amaizi nigweyongyera, ekirikuza kureetera okukyendeera kw‘omubaro gw‘okukura kw‘amaizi n‘okutunga amaizi. Obutafaari bw’omubiri bwaba buri ahaiguru ya 2.5 g/L, amaani g’okukora g’okuhinduka kw’ebintu nigakyendeera munonga. Aha nkora y‘obutashemeire bwa 5 g/l, amaani g‘okukora ni 205.85 kJ/mol, ekirikumanyisa 8.27% ahansi y‘amaani g‘okukora aha nkora y‘obutashemeire bwa 2.5 g/l. Okukyendeera kw’amaani g’okukora nikworeka ngu omuringo gw’okukora ekibiriiti nigukora gye, ekirikureetaho okweyongyera kw’omubaro gw’okukura kw’ekibiriiti n’okutunga ekibiriiti.
(a) Okuhikaana kwa puroguraamu ya ln(kg) n‘okugyeragyeranisa na 1/T na (b) amaani g‘okukora Eg y‘okuhinduka kw‘ekibiriiti aha nkora z‘obutashemeire zitari zimwe na zimwe.
Enkora y’okukura kw’ekibiriiti ekacondoozibwaho XRD na FTIR spectroscopy, kandi okukura kw’ekibiriiti n’amaani g’okukora bikakyeberwa. Ekishushani 6 nikyoreka ebyarugamu omu XRD. Ebihandiiko nibikwatagana na PDF #08–0470, ekirikworeka ngu ni α-NiSO4 6H2O (silika erikutukura). Ekibiriiti kiri omu nkora y’ebicweka bina, ekibiina ky’omwanya ni P41212, ebipimo by’obutafaari bw’ekicweka ni a = b = 6.782 Å, c = 18.28 Å, α = β = γ = 90°, kandi obuhango ni 840.8 Å3. Ebirugire omu kucondooza oku nibikwatagana n‘ebyarugamu ebyabaire bishohoziibwe enyimaho na Manomenova na bagyenzi be. 19 Okutaho ayoni za NH4+ nakyo nikireetaho okukora kwa (NH4)2Ni(SO4)2 6H2O. Ebihandiiko ebi biri aha PDF namba 31–0062. Ekibiriiti eki kiri omu nkora y’ekicweka kimwe, ekibiina ky’omu mwanya P21/a, ebipimo by’obutafaari bw’ekicweka ni a = 9.186 Å, b = 12.468 Å, c = 6.242 Å, α = γ = 90°, β = 106.93°, kandi obuhango bwakyo ni 638 Å. Ebirugiremu ebi nibikwatagana n‘okucondooza okwabandize okwagambirweho Su et al.20.
Enkora y’okutambura kwa X-ray ey’ebicupuri bya nickel sulfate: (a–b) 0.5%, (c–d) 1%, (e–f) 1.5%, na (g–h) 2% omubaro gw’embibo. Ekishushani kya buryo n’ekishushani ekihango eky’aha bumosho.
Nkoku kirikworekwa omu bishushani 6b, d, f na h, 2.5 g/L n’ekikomo ky’ahaiguru munonga eky’okuteerana kwa ammonium omu nshonga hatariho kuhanga omunyugunyu ogundi. Obutafaari bwaba buri 3.75 na 5 g/L, NH4+ ions nizitaaha omu nkora y’ekibiriiti kubaasa kuhanga omunyugunyu ogugumire (NH4)2Ni(SO4)2 6H2O. Okurugirira aha bihandiiko, enshonga y’amaani g’omunyugunyu ogugumire neeyeyongyera nk’oku obutashemeire burikweyongyera kuruga ahari 3.75 kuhika ahari 5 g/L, namunonga ahari 2θ 16.47° na 17.44°. Okwongyera aha mutwe gw’omunyugunyu ogugumire nikureetwaho omusingye gw’okuringana kw’eby’obuhangwa gwonka. Kwonka, enshonga ezimwe ezitari za buriijo nizireebeka ahari 2θ 16.47°, ekirikubaasa kuba nikireetwaho okuhinduka kw’omubiri (elastic deformation) kw’ekibiriiti. 21 Ebirugire omu kucondooza aha mitwarize nabyo nibyoreka ngu omubaro gw’okubyara oguri ahaiguru nigurugamu okukyendeera kw’amaani g’enshonga y’omunyugunyu ogugumire. Omubaro gw’embibo oguri ahaiguru nigutunguura omuringo gw’okuhinduka amaizi, ekirikureetaho okukyendeera kw’amaani omu kirungo. Omu muringo ogu, omuringo gw’okukura kw’ekibiriiti niguta omutima aha mbuto, kandi okukora emiringo mirungi nikuremesibwa okukyendeera omu kujwara munonga kw’omubazi. Okutaana n’ekyo, omubaro gw’embibo gwaba guri mukye, omuringo gw’okuhinduka ekibiriiti nigugyenda mpora, kandi okujwara kw’ekirungo (supersaturation) kw’omubazi nikuguma aha rurengo rwahaiguru munonga. Embeera egi neeyongyera aha kubaasa kw’okuhinduka kw’omunyugunyu gw’emirundi ebiri (NH4)2Ni(SO4)2 6H2O ogutarikubaasa kusheesheka munonga. Ebihandiiko by‘amaani g‘ahaiguru eby‘omunyugunyu gw‘emirundi ebiri nibiheebwa omu kipande kya 3.
FTIR characterization ekakorwa kucondooza aha buremeezi bwona nari empindahinduka omu nkora y‘omugyenyi ahabw‘okugira ngu hariho NH4+ ions. Sampuli eziine omubaro gw’okubyara ogutarikuhinduka ogwa 2% zikamanyisibwa. Ekishushani 7 nikyoreka ebyarugamu omu kucondooza kwa FTIR. Enshonga z’ahaiguru ezirikureebeka ahari 3444, 3257 na 1647 cm−1 nizireetwa emiringo y’okutambatambura kwa O–H ey’ebicweka by’omubiri. Enshonga eziri aha 2370 na 2078 cm−1 nizijwekyera enkoragana y’ebicweka by’amaizi ebiri ahagati y’ebicweka by’amaizi. Ekipande ekiri aha 412 cm−1 nikigambwaho ahabw’okutengeeta kw’okutambatambura kwa Ni–O. Okwongyera ahari ekyo, ebiriisa bya SO4− eby’obuntu nibyoreka emiringo ena y’okutengeeta emikuru ahari 450 (υ2), 630 (υ4), 986 (υ1) na 1143 na 1100 cm−1 (υ3). Obumanyiso υ1-υ4 nibujwekyera emitwarize y‘emiringo y‘okutengeeta, ahu υ1 erikweshushaniriza omuringo ogutarikusheesheka (okutambatambura okurikushushana), υ2 neejwekyera omuringo gw‘okugaruka kusheesheka emirundi ebiri (okusheesheka okurikushushana), kandi υ3 na υ4 nizijwekyera emiringo y‘okusheesheka emirundi eshatu nk‘okusheesheka okurikushushana n‘okusheesheka (asymmetric be-asymmetric). 22,23,24 Ebirugire omu kucondooza nibyoreka ngu okubaho kw’obukooko bwa ammonium nikuha enshonga y’okwongeraho aha wavenumber ya 1143 cm-1 (ehandiikirwe n’enziga erikutukura omu kishushani). Enshonga y’okwongyeraho ahari 1143 cm-1 neeyoreka ngu okubaho kwa NH4+ ions, hatariho kugyendera aha nkora, nikireetaho okuhindura omu nkora ya lattice, ekirikureetaho empindahinduka omu mirundi y’okutengeeta kw’ebicweka bya sulfate ion omunda y’ekibiriiti.
Okurugirira aha byarugamu bya XRD na FTIR ebiine akakwate n‘emitwarize y‘okugyendera aha kukura kw‘ekibiriiti n‘amaani g‘okukora, ekishushani 8 nikyoreka enteekateeka y‘omuringo gw‘okukura kw‘ekibiriiti kya nickel sulfate hexahydrate n‘okwongyeraho obukooko bwa NH4+. Omu kubura obukooko, ayoni za Ni2+ niziija kukwatagana na H2O kuhanga amaizi ga nickel [Ni(6H2O)]2−. Bwanyima, amaizi ga nickel nigakwatanisa n’eby’okurya bya SO42− ions kubaasa kuhanga Ni(SO4)2 6H2O nuclei kandi gakura gahinduka amaizi g’ekirungo kya nickel sulfate hexahydrate. Omubaro gw’ebintu ebikye (2.5 g/L nari ahansi) gwateebwa omu nshonga, [Ni(6H2O)]2− nikiguma kwegaita kimwe n’eby’okurya bya SO42− ahabw’okuba [Ni(6H2O)]2− n’eby’okurya bya NH4+ nibirwanira okwegaita n’eby’okurya bya SO42− bikiriho n’eby’okurya bya sulfa. Embeera egi neereetaho okweyongyera kw‘amaani g‘okukora (activation energy) g‘okuhinduka kw‘ebicupuri n‘okukyendeera omu kukura kw‘ebicupuri. 14,25 Bwanyima y’ebicweka by’omubiri ebirikwetwa nickel sulfate hexahydrate nuclei kuhangwa kandi bikakura bikahinduka ebicupuri, ions nyingi eza NH4+ na (NH4)2SO4 nizikwatwa aha mutwe gw’ekicupuri. Eki nikishoboorora ahabwenki ekibiina ky‘emirimo kya SO4− ion (wavenumber 1143 cm−1) omu sampo za NSH-8 na NSH-12 nikiguma kihangirwe hatariho nkora y‘okutaho ebiriisa. Obutafaari bwaba buri bwingi, NH4+ ions nizitandika kutaaha omu nkora y’ekibiriiti, zikora eminyoro ebiri. 16 Ekintu eki nikibaho ahabw’okubura ions za SO42− omu nshonga, kandi ions za SO42− nizikwatanisa na nickel hydrates juba kukira ions za ammonium. Enkora egi neehwera omu kureetaho okuteerana n’okukura kw’eminyoro ebiri. Omu nkora y’okuteerana, obutafaari bwa Ni(SO4)2 6H2O na (NH4)2Ni(SO4)2 6H2O nibuhangwa omurundi gumwe, ekirikureetaho okweyongyera kw’omubaro gw’obutafaari oburikutunga. Okwongyera aha mubaro gw’ebicweka by’omubiri ebirikukora nk’ebicupuri nikureetaho okukura kw’ebicupuri n’okukyendeera kw’amaani g’okukora.
Eby’obuhangwa ebirikukora aha kusheenya nickel sulfate hexahydrate omu maizi, okwongyeraho akacweka kakye n’akacweka kakye ka ammonium sulfate, reero okakora omuringo gw’okusheenya nickel sulfate nikibaasa kworekwa omu muringo ogu:
Ebirugire omu kucondooza kwa SEM nibyorekwa omu kishushani 9. Ebirugire omu kucondooza nibyoreka ngu omuhendo gw’omunyugunyu gwa ammonium ogurikwongyerwamu n’omubaro gw’okuhinga tibirikukwata munonga aha nkora y’ekibiriiti. Obuhango bw’ebicupuri ebihangirwe nibuguma nibushushana, n’obu ebicupuri ebihango biraabe nibireebeka omu bicweka ebimwe. Kwonka, okweyongyera aha mitwarize y’ebintu nikyetengyesa kubaasa kumanya oku okuteerana kw’omunyugunyu gwa ammonium n’omubaro gw’okuhinga birikukora aha bugabe bwa purayimare bw’ebicupuri ebihangirwe.
Enkora y’ebicupuri bya NiSO4 6H2O: (a–e) 0.5%, (f–j) 1%, (h–o) 1.5% na (p–u) 2% omubaro gw’embibo ogurikworeka empindahinduka omu nkora ya NH4+ kuruga ahaiguru kuza ahansi, ekiri 0, 1.25, 2.5, 3/5.
Ekishushani 10a nikyoreka ebicweka bya TGA eby‘ebicupuri ebiine obukooko obutari bumwe na bumwe. Okushwijuma kwa TGA kukakorwa aha sampo eziine omubaro gw’okubyara ogwa 2%. Okushwijuma kwa XRD nakwo kukakorwa aha sampo ya NSH-20 kubaasa kumanya ebirungo ebyahangirwe. Ebirugire omu XRD ebirikworekwa omu kishushani 10b nibihamya empindahinduka omu nkora y‘ekibiriiti. Ebipimo bya thermogravimetric nibyoreka ngu ebicupuri byona ebikozirwe nibyoreka okugumaho kw’okwotsya kuhika ahari 80°C. Okurugirira ahari ekyo, oburemeezi bw’ekibiriiti bukakyendeera n’ebicweka 35% obu obutagatsi bwayeyongyera kuhika ahari 200°C. Okukyendeeza aha buremeezi bw’ebicupuri nikureetwaho omuringo gw’okuvunda, ogurimu okufeerwa kw’ebicweka 5 by’amaizi kubaasa kuhanga NiSO4 H2O. Ebirikuba biriho ku byayeyongyeire kuhika ahari 300–400°C, oburemeezi bw’ebicupuri bukagaruka bwakyendeera. Okukyendeeza aha buremeezi bw’ebicupuri kukaba kuri nka 6.5%, obwo okukyendeeza aha buremeezi bw’eky’okureeberaho ky’ebicupuri bya NSH-20 kukaba kuri ahaiguru kakye, 6.65% byonka. Okuvunda kwa NH4+ ions omu gaasi ya NH3 omu sampo ya NSH-20 kukarugamu okukyendeeza kw’ahaiguru kakye. Ebiriisa byayeyongyera kuruga ahari 300 kuhika ahari 400°C, oburemeezi bw’ebicupuri bukakyendeera, ekyarugiremu ebicupuri byona kugira omutindo gwa NiSO4. Okwongyera aha bwire bw’obwire kuruga ahari 700°C kuhika ahari 800°C kikareetera omubiri gw’ekibiriiti kuhinduka NiO, ekyareetera okurekura kwa SO2 na O2.25,26.
Obushemeire bw’ebicupuri bya nickel sulfate hexahydrate bukamanyirwa aha kucondooza aha nkora ya NH4+ barikukoresa ekikwato kya DC-Arc ICP-MS. Obushemeire bw’ebicupuri bya nickel sulfate bukamanyirwa aha kukoresa enkora (5).
Aho Ma ari oburemeezi bw’ebintu ebitari birungi ebiri omu kicupuri (mg), Mo ni oburemeezi bw’ekicupuri (mg), Ca ni okuteerana kw’ebintu ebitari birungi omu kirungo (mg/l), V ni obuhango bw’ekirungo (l).
Ekishushani 11 nikyoreka obushemeire bw’ebicupuri bya nickel sulfate hexahydrate. Omuhendo gw‘obushemeire n‘omuhendo gwa purayimare gw‘emitwarize 3. Ebirugiremu nibyoreka ngu omubaro gw’okubyara n’okutaho obutashemeire nibikwata butosha aha bushemeire bw’ebicupuri bya nickel sulfate ebihangirwe. Oku obukooko burikweyongyera, nikwo obukooko burikweyongyera kunywa, ekirikureetaho obuyonjo bukye bw’ebicupuri ebihangirwe. Kwonka omuringo gw’okunywa obukooko nigubaasa kuhinduka kurugiirira aha nkora y’obukooko, kandi giraafu y’ebirugiremu neeyoreka ngu okunywa obukooko kwona okurikukorwa ebishushani by’ebicupuri tikurikuhinduka munonga. Okwongyera ahari ekyo, ebyarugamu ebi nabyo nibyoreka ngu okubyara kw’embibo kwingi nikubaasa kutunguura obushemeire bw’ebihimba. Eki nikibaasika ahabw’okuba ebicweka ebikuru eby’ekibiriiti ebihangirwe byaba birikuteerana aha bikwato bya nickel, omugisha gw’okuteerana ions za nickel aha nickel niguba guri ahaiguru. 27
Okucondooza oku kukooreka ngu ammonium ions (NH4+) nizikwata munonga aha nkora y’okuhindura amaizi g’ebicupuri n’emitwarize y’ebicupuri bya nickel sulfate hexahydrate crystals, kandi n’okushohoza oku omubaro gw’enjuma gurikukora aha nkora y’okuhinduka amaizi g’ebicupuri.
Aha nkora ya ammonium eri ahaiguru ya 2.5 g/l, okuruga kw’ekibiriiti n’omubaro gw’okukura kw’ekibiriiti nibikyendeera. Aha nkora ya ammonium eri ahaiguru ya 2.5 g/l, okutunga amaizi g’ekibiriiti n’omubaro gw’okukura kw’ekibiriiti nibyeyongyera.
Okwongyeraho obukooko omu nkora ya nickel nikwongera okurwanagana ahagati ya NH4+ na [Ni(6H2O)]2− ions ahabwa SO42−, ekirikureetaho okweyongyera kw’amaani g’okukora. Okukyendeera kw’amaani g’okukora bwanyima y’okwongyeraho obukooko bwingi nikureetwaho okutaaha kwa NH4+ ions omu nkora y’ekibiriiti, obwo nibukora omunyugunyu gw’emirundi ebiri (NH4)2Ni(SO4)2 6H2O.
Okukozesa omubaro gw’okuhinga oguri ahaiguru nikibaasa kutunguura okukura kw’ebishaka, omubaro gw’okukura kw’ebishaka n’obushemeire bw’ebishaka bya nickel sulfate hexahydrate.
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