摘要
以锂渣在碱溶液中的选择性溶出特性研究为出发点,计算锂渣中的Si、Al和Ca在不同碱-水热环境下的溶出率,分析锂渣在处理前后的物相组成、产物类型和微观形貌,探究碱-水热环境下锂渣的火山灰活性和溶出组分间的反应行为.结果表明:NaOH溶液浓度的提高有利于锂渣中锂辉石等成分溶解和Si、Al与Ca溶出;温度和溶出时间是碱激发锂渣反应进程的主要影响因素;在60 ℃以上的碱-水热环境下,锂渣的火山灰活性能够有效激发,锂渣中各可溶出元素的溶出率显著提高,并伴有大量反应产物生成.
锂渣(lithium slag, LS)是生产碳酸锂过程中产生的一种废渣,每生产1 t碳酸锂会产生8~10 t锂
碱激发胶凝材料是目前最具有发展潜力的绿色胶凝材料之
基于以上背景,本文研究了温度和碱对锂渣活性激发的耦合作用,以及锂渣中活性组分在不同碱-水热环境下的溶出情况和反应行为.
锂渣来源于江苏融达新材料股份有限公司,密度为2.60 g/c
SiO2 | Al2O3 | SO3 | CaO | P2O5 | Fe2O3 | Na2O | K2O | MgO | MnO |
---|---|---|---|---|---|---|---|---|---|
62.40 | 22.10 | 6.73 | 4.53 | 1.12 | 1.06 | 0.89 | 0.52 | 0.49 | 0.06 |

图1 锂渣的基本性能
Fig.1 Basic property of LS
考虑到NaOH溶液在碱激发体系中可直接作为碱激发剂使用或用于不同碱度混合激发剂溶液的配制,本研究选取浓度不同的NaOH溶液来研究锂渣的选择性溶出行为.溶出试验采用去离子水和分析纯NaOH试剂来配制不同浓度的NaOH溶液.
锂渣在碱溶液中的溶出试验研究包括3个部分:(1)锂渣在不同浓度NaOH溶液中的选择性溶出特性;(2)锂渣在相同浓度碱溶液中不同溶出温度下的选择性溶出特性;(3)锂渣在相同碱溶液中不同溶出时间下的选择性溶出特性.溶出试验的具体参数如
Parameter | Value |
---|---|
NaOH concentration/(mol· | 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 |
Temperature/℃ | 20, 30, 40, 50, 60, 70, 80 |
Leaching time/min | 5, 10, 30, 60, 120, 180, 240, 300 |
由于固液比的大小直接影响溶出组分在溶出试剂中的扩散速率,选取足够小的固液比可在最大程度上减少溶出过程中产生的沉淀,以保证溶出液中各溶出元素浓度测定的准确性.本溶出试验将固液比设定为1∶100.锂渣溶出试验流程参照文献[
(1)准确称量1.000 0 g(精确至0.000 1 g)锂渣粉末,与100 mL NaOH溶液混合均匀,密封于250 mL锥形瓶中.
(2)待恒温水浴锅升至溶出试验预设温度后,将密封锥形瓶置于恒温水浴锅中,并用磁力搅拌器在预定温度下以1 000 r/min的转速连续搅拌混合物,开始溶出试验.
(3)按照试验参数完成溶出试验,将锥形瓶中悬浮液抽滤后的滤液用试管装瓶并置于0~4 ℃环境中冷藏保存,所有滤液试样均在24 h内统一完成元素浓度测试;固体滤渣依次用去离子水和乙醇各洗涤3次,然后在60 °C条件下真空干燥24 h,用于后续微观分析.
考虑到碱激发锂渣胶凝材料中的主要产物为水化硅铝酸钠(钙)(N(C)‑A‑S‑H)凝
锂渣及其在不同碱-水热环境下反应产物的XRD图谱如
CaSO4C | (1) |
Ca(OH)2C | (2) |

图2 锂渣及其在不同碱-水热环境下反应产物的XRD图谱
Fig.2 XRD patterns of LS and reaction products in different alkali‑hydrothermal environments
由
由
4SiO2+Al2O3+2NaOH+H2O=Na2O·Al2O3·4SiO2·2H2O | (3) |
3SiO2+Al2O3+Ca(OH)2+2H2O=CaO·Al2O3·3SiO2·3H2O | (4) |
此外,需要注意的是,锂渣在60 ℃条件下溶出300 min时的XRD图谱中发现了半水石膏衍射峰(

图3 锂渣及其在不同碱-水热环境下反应产物的FTIR图谱
Fig.3 FTIR spectra of LS and reaction products in different alkali‑hydrothermal environments

图4 锂渣中Si、Al和Ca在不同碱-水热环境下的溶出率
Fig.4 Leaching ratios of Si, Al and Ca obtained in different alkali‑hydrothermal environments
采用FTIR可有效了解碱激发胶凝材料的激发前驱物和反应产物中化学键的变化情况.锂渣及其在不同碱-水热性环境下反应产物的FTIR图谱如
Adsorption band/c | Assignment | Interpretation |
---|---|---|
3 643 | O—H | Ca(OH)2 |
3 546 | O—H | CaSO4·2H2O |
3 448, 3 438, 3 435, 3 408 | O—H | N‑(C)‑A‑S‑H |
2 501 | O—H | CaSO4·2H2O |
1 655, 1 637, 1 624 | δ H—O—H | N‑(C)‑A‑S‑H |
1 620 | O—H | CaSO4·0.5H2O |
1 458, 1 450, 1 448, 1 444 | C—O | Na2CO3/CaCO3 |
1 200-950 | Si—O—Si, Al | N‑(C)‑A‑S‑H |
881, 866 | C—O | Na2CO3/CaCO3 |
796 | Si—O—Si | SiO2 |
689, 694 | C—O | Na2CO3/CaCO3 |
600, 669 | O—H | CaSO4·0.5H2O |
565-555 | δ Si—O—Si/Si—O—Al | N‑(C)‑A‑S‑H |
453-430 | δ Si—O | N‑(C)‑A‑S‑H |
426 | δ Si—O—Si/O—Si—O | Si‑rich glass or SiO2 |
Note: represents stretching vibration; δ represents deformation vibration.
(1)3 448、3 438、3 435 c
(2)1 458、1 450、1 448、1 444、881、866、689、694 c
(3)3 546、2 501 c
(4)锂渣的碱-水热激发过程导致其组分结构重组,碱激发锂渣的反应过程可以通过吸收频率为1 200~950 c
锂渣中Si、Al和Ca在不同碱-热环境下的溶出率如
由
由
由
锂渣及其在不同碱-水热性环境下溶出后滤渣的SEM照片如

图5 锂渣及其在不同碱-水热环境下溶出后滤渣的SEM照片
Fig.5 SEM images of LS and residues obtained in different alkali‑hydrothermal environments
由
由
由
(1)锂渣中二水石膏和半水石膏相在碱-水热环境下极易溶解,锂渣中迅速溶出的Ca除部分参与凝胶产物的生成外,其余在强碱环境中主要以Ca(OH)2的形式存在.
(2)提高NaOH溶液浓度可以加速锂渣颗粒的表面侵蚀和锂辉石等物相的溶解.当NaOH溶液浓度为1~6 mol/L时,锂渣中Si和Al的溶出率随着NaOH溶液浓度的升高而显著增加;当NaOH溶液浓度高于6 mol/L时,锂渣中Si和Al的溶出率增长趋势明显减缓.
(3)当溶出温度高于60 ℃时,锂渣的活性显著提高,锂渣中活性Si、Al和Ca的溶出、扩散与转移速率明显加速,N‑A‑S‑H与C‑A‑S‑H混合凝胶相产物显著增多.
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