Sodium aluminate desiliconization yog ib qho tshuaj lom neeg coagulation -adsorption coprecipitation txheej txheem. Nws cov ntsiab lus xam tsis yog ib qho yooj yim stoichiometric kev sib raug zoo, tab sis yog ib txoj kev engineering raws li kev sim, vam khom rau qhov piv txwv, thiab xav tau kev hloov kho.
I. Desiliconization Mechanism
Hydrolysis: Sodium aluminate (NaAlO₂ lossis NaAl (OH)₄) sai hydrolyzes ntxiv rau dej, tsim cov amorphous aluminium hydroxide (Al(OH)₃) colloids nrog thaj tsam loj tshwj xeeb thiab muaj zog adsorption muaj peev xwm.
NaAlO₂ + 2H₂O → Al(OH)₃↓ + NaOH
Adsorption thiab Coprecipitation: Qhov zoo them Al(OH)₃ colloids neutralize tus nqi ntawm qhov tsis zoo nqi silicon nyob rau hauv dej (xws li HSiO₃⁻, SiO₃²⁻, feem ntau yog sawv cev li SiO₂), thiab los ntawm adsorption thiab complexation, tsim insoluble rau hauv lub complex. co- nag xob nag cua.
Al(OH)₃ + x HSiO₃⁻ → Al(OH)₃·(SiO₂)ₓ (Cov txheej txheem piav qhia, tsis yog- qauv qauv tshuaj tiv thaiv)
Cov txheej txheem no txiav txim siab tias kev siv tshuaj lom neeg sib piv (qhov hnyav piv ntawm sodium aluminate rau silica) tsis yog tus nqi theoretical ruaj khov, tab sis ib qho kev cuam tshuam los ntawm ntau yam.
II. Kev txiav txim siab Chemical Consumption Ratio (R Value)
Tag nrho cov kev suav rov qab nyob ib ncig ntawm tus tub ntxhais empirical piv R:
R=Sodium aluminate ntau npaum li cas (mg/L NaAlO₂) / Tus nqi ntawm silica yuav raug tshem tawm (mg/L SiO₂)
1. Kev txiav txim siab cov ntaub ntawv yooj yim
Raw silica concentration [Si]₀: SiO₂ concentration ntawm cov qauv dej ua ntej kho (mg/L).
Target silica concentration [Si]ₜ: Yuav tsum tau SiO₂ concentration tom qab kho (mg/L).
Tus nqi ntawm silicon yuav raug tshem tawm Δ[Si]: Δ[Si]=[Si]₀ - [Si]ₜ (mg/L SiO₂).
2. Qhov tseem ceeb ntawm qhov piv txwv (R)
Qhov no yog qhov tseem ceeb tshaj plaws rau kev suav thiab yuav tsum tau txais kev sim.
Feem ntau: Kev xyaum ua haujlwm dav dav qhia tau tias tus nqi R feem ntau yog nyob nruab nrab ntawm 8 thiab 20. Qhov ntawd yog, rau txhua txhua 1 mg ntawm SiO₂ tshem tawm, 8 mg rau 20 mg ntawm sodium aluminate yuav tsum tau ntxiv.
Vim li cas thiaj muaj ntau yam? Vim tias tus nqi R muaj kev cuam tshuam loj heev los ntawm cov hauv qab no thiab yuav tsum tau txiav txim siab los ntawm kev sim beaker:
pH tus nqi: Qhov zoo tshaj pH qhov rais rau kev tshem tawm silicon yog nqaim heev, feem ntau ntawm 6.5 thiab 7.5 (tsis muaj zog acidic rau nruab nrab). Yog tias pH tsawg dhau (<6.0), Al(OH)₃ colloids will dissolve into Al³⁺, losing their adsorption capacity; if the pH is too high (>8.0),
Al(OH)₃ yuav yaj mus rau AlO₂⁻, thiab cov colloids yuav tawg. Qhov zoo tshaj pH point txawv me ntsis nyob ntawm seb cov dej zoo. Dej kub: Qhov kub thiab txias nce ntxiv molecular thermal zog, accelerates cov tshuaj tiv thaiv tus nqi, thiab txhawb floc tsim zoo dua, muaj peev xwm txo tus nqi R.
Coexisting ions hauv dej: Hardness (Ca²⁺, Mg²⁺) txhawb flocculation thiab tej zaum yuav txo tus nqi R; Txawm li cas los xij, cov khoom organic sib tw nrog lossis encapsulates colloids, muaj peev xwm nce R tus nqi.
Initial silica concentration: ntau dua thawj zaug yuav ua rau muaj kev tshem tawm ntau dua ib chav ntawm reagent (tus nqi R yuav zoo li qis dua ntawm qhov ntau).
Cov kev mob tshwm sim: Kev sib xyaw siv, lub sij hawm flocculation, thiab lub sij hawm daws txhua qhov cuam tshuam ncaj qha rau cov nyhuv.
3. Ua kev sim beaker los txiav txim siab R thiab pom pH zoo. Siv cov qauv dej nyoos ntawm qhov sib npaug.
Thawj txheej ntawm kev sim (tso pH, qhov sib txawv ntau npaum li cas): Kho cov pH ntawm tag nrho cov qauv dej mus rau tus nqi preset (piv txwv li, 7.0), thiab ntxiv sodium aluminate cov kev daws teeb meem ntawm cov gradients sib txawv (xws li, ntau npaum li cas xam raws li R=5, 10, 15, 20...). Cov txheej txheem thib ob ntawm kev sim (taw ntau npaum li cas, pH hloov pauv): Ib qho kev siv tshuaj nruab nrab tau xaiv, thiab pH ntawm cov qauv dej tau hloov kho rau cov gradients sib txawv (xws li 6.0, 6.5, 7.0, 7.5, 8.0).
Tag nrho cov qauv dej tau ua raws li txheej txheem nrawm nrawm (sib xyaw), qeeb nplawm (flocculation), thiab teeb tsa.
Qhov seem ntawm SiO₂ concentration tau ntsuas hauv supernatant.
Curve plotting: Ib qho "dosage-residual silicon" nkhaus tau npaj los nrhiav qhov tsawg kawg nkaus uas yuav tsum tau ua kom tiav lub hom phiaj [Si]ₜ. Ib qho "pH-silicon residual" nkhaus tau npaj los nrhiav qhov pH zoo tshaj plaws rau kev tshem tawm silicon.
R- xam tus nqi: Raws li "dosage-residual silicon" nkhaus, qhov ntau npaum C (mg/L NaAlO₂) sib raug rau kev ua tiav lub hom phiaj [Si]ₜ tau pom. Yog li ntawd, R=C/Δ[Si]. 4. Kev Xam Xaj Xwb
Thaum tus nqi R thiab qhov zoo tshaj pH tus nqi tsim nyog rau cov dej zoo tam sim no tau txiav txim siab los ntawm kev sim, kev ua haujlwm niaj hnub ua haujlwm yooj yim heev:
Theoretical Dosage (mg/L)=R × Δ[Si]
Qhov twg, Δ[Si] yog xam raws li qhov tiag -lub sij hawm soj ntsuam silica concentration nyob rau hauv cov dej nyoos thiab lub hom phiaj tus nqi.
III. Auxiliary laij lej thiab kev hloov kho ua haujlwm
1. Alkalinity Consumption thiab pH Kho Kev Ntsuas:
Sodium aluminate hydrolysis tsim NaOH, siv cov acidity (H⁺) hauv dej. Qhov no txhais tau hais tias cov kua qaub ntxiv (xws li sulfuric acid lossis hydrochloric acid) feem ntau yuav tsum tau ua kom ruaj khov pH nyob rau hauv qhov kev pom zoo.
Tus nqi ntawm OH⁻ tsim los ntawm hydrolysis ≈ (mg / L NaAlO₂) / 82) * 1000 (mmol / L)
Qhov yuav tsum tau muaj cov kua qaub ntxiv (raws li 98% H₂SO₄) tuaj yeem kwv yees li: Acid ntxiv (mg/L) ≈ [yuav tsum tau OH⁻ (mmol/L) × 49]/0.98/η
(Qhov twg 49 yog qhov molar loj ntawm H₂SO₄, 0.98 yog qhov purity, thiab η yog qhov ua tau zoo coefficient)
Nco tseg: Qhov no yog qhov kwv yees kwv yees. Qhov tseeb ntawm cov kua qaub ntxiv yuav tsum tau tswj hwm los ntawm kev tawm tswv yim pH hauv online thiab cov kua qaub zaus hloov kho los ntawm PID tswj.
Aluminium residue xam: Tsis yog tag nrho ntxiv aluminium precipitates; ib txhia yuav nyob hauv dej. Cov ntsiab lus ntawm txhuas nyob rau hauv cov effluent yuav tsum tau saib xyuas kom nws ua tau raws li cov qauv dej zoo (feem ntau<0.2mg/L). Overdosing not only wastes reagents but also leads to excessive aluminum levels.