Technology of extracting scandium in the comprehensive recovery of red mud-titanium white waste acid
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摘要: 针对赤泥-钛白废酸浸出液中钪及主要杂质的特点, 采用先除杂后萃取的工艺对溶液中钪进行萃取分离.首先, 将一定量的活性炭加入赤泥-钛白废酸浸出液中, 吸附去除浸出液中的硅, 硅的去除率可达96.70%, 而钪的去除率仅为1.25%, 这表明活性炭吸附除杂可在保证浸出液中钪含量基本不损失的情况下除去绝大部分的硅.除硅有效控制了浸出液的胶凝现象, 有利于下一步的钪萃取工艺.在萃取工艺过程中, 具体研究了除杂后液的酸度、萃取剂体积分数、相比、萃取时间对钪萃取率的影响.结果表明, 除杂后液酸度以1.81 mol/L为最佳, 既避免了有机相乳化, 又保证了钪的高萃取率; 相比在1/10~1/30之间时, 钪萃取率达到平衡, 但当相比为1/30时, 发生乳化, 难于分离, 因此, 相比1/25为最佳; 萃取时间为15 min时, 钪的萃取率达到平衡; 萃取剂体积分数为15% P204+ 6% TBP时, 钪的萃取率达到最大值.在最佳的萃取工艺条件下, 钪的萃取率达98.80%.Abstract: In this paper, the extraction technology of scandiumis studied by the process of extraction after removal of impurities according to the property of the leaching solution of red mud-titanium white waste acid.Firstly, a certain amount of activated carbon was added into the leaching solution to remove silicon dioxide (SiO2). The removal rate of SiO2 was 96.70 % and the removal rate of scandium was 1.25 %. It shows that, most of the SiO2 is removed while the Sc3+ content is almost constant after the addition of activated carbon. The removal of SiO2 caneffectively control the gelatinization of leaching solution and facilitate the subsequent extraction process.The effect of acidity of leach solution, extractant volume fraction, phase ratio and extraction time on scandium extraction rate were examined. The results show that the optimal acidity of leaching solution after purification at 1.81 mol/L which can avoid the emulsification of organic phase and ensure high extraction rate of scandium; the extraction rate of scandium reaches equilibrium when the phase ratio is between 1/10~1/30, and the phase ratio of 1/25 is the optimal because the leaching solution is emulsificated when the phase ratio was at 1/30; the extraction rate of scandium reaches equilibrium when the extraction time is 15 min, and reaches the maximum when the extractant volume fraction is 15 % P204 + 6 % TBP. It's found that the extraction rate of scandium is 98.80 % under the optimum extraction conditions.
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Keywords:
- red mud /
- titanium white waste acid /
- scandium /
- purification /
- extraction
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0 引言
某铜矿采用下向进路尾砂胶结充填法采矿，进路空间位置布置的不同是影响采场稳定性的重要因素[1-2].为给矿山提供不同采矿进路布置方案开采稳定性，采用ANSYS和FLAC3D数值模拟软件进行不同采矿进路布置条件下采场稳定性数值模拟分析，进而指导现场施工[3-5].
1 不同采矿进路布置方案
某铜矿矿体赋存条件复杂，其中下盘围岩中等稳固，上盘围岩为强风化岩组，极不稳固.现场施工工程实践表明，采矿进路与矿岩体空间位置关系可分为3种：
（1）方案1：垂直矿体走向与上、下盘接触；
（2）方案2：沿矿体走向与下盘接触；
（3）方案3：沿矿体走向与上盘接触.
不同采矿进路布置示意图见图 1.
2 数值模拟计算模型
2.1 计算模型
本次数值模拟采用ANSYS三维有限元数值模拟软件建立单元模型，然后导入到FLAC3D有限差分数值模拟软件中进行运算分析[6-9].依据工程概况，模型几何尺寸见表 1，计算模型共划分为101 141个单元，共计18 160个节点，计算模型见图 2，隐藏上盘后模型见图 3，开采进路模型见图 4.
表 1 模型几何尺寸
2.2 地应力场及模型边界条件的确定
将模型顶部边界采用自由边界，模型底部边界采用垂直方向的位移约束.模型的前后、左右采用水平方向的位移约束，模型的原岩应力场由自重应力场作用自动生成.
2.3 矿岩力学参数
经相应折减换算后，模拟矿岩及充填体的物理力学参数见表 2.
表 2 矿岩及充填体物理力学参数
2.4 介质力学模型与破坏准则
本分析将围岩、矿体及充填体均视为各向同性的弹性连续介质.建立模型后，使用Mohr-Coulomb准则作为岩体的破坏准则，Mohr-Coulomb准则的剪切破坏判据如式（1）、式（2）所示：
(1) 其中，
(2) 式（1）、式（2）中：σ1为最大主应力（压应力为负值）；σ3为最小主应力；c为黏结力（或内聚力）；φ为内摩擦角. f为破坏判断系数，当f≥0时，材料处于塑性流动状态；当f≤0时，材料处于弹性变形阶段.
在模拟过程中，模型变形设置为大变形.
3 模拟过程结果分析
按采矿进路与矿岩体空间位置关系的不同分3种方案进行计算，通过数值模拟得到进路回采后矿岩体及充填体的最大与最小主应力结果，将数值计算结果进行比较.具体模拟结果见图 5~图 7.
通过分析方案1、方案2和方案3的最大及最小主应力云图，见图 5~图 7.从图 5可以看出，进路开挖后应力集中区域为顶板和进路端部.其中顶板主要受拉应力控制，其最大拉应力值为0.078~0.389 MPa，该值小于充填体抗拉强度，说明充填体可以维持开挖后进路顶板的稳定性.进路前后两端及两帮受压应力控制，进路端部压应力集中程度较高，端部底角最大压应力大小为2 MPa，两帮压应力大小为0.75 MPa.
从图 6可以看出顶板中间与充填体侧帮顶角之间的区域受拉应力影响，最大拉应力值为0.1~0.15 MPa，而充填体侧帮受压应力影响，最大受压值为1.4~1.5 MPa.以上数值小于充填体自身强度，这表明进路将处于较安全的环境下[10-12].
分析图 7表明进路开挖后应力主要集中在顶板和进路的强风化侧帮顶角和底角处.顶板最大受拉应力值为0.2~0.36 MPa，软岩侧帮底角最大受拉值为0.4~0.56 MPa.充填体及矿岩体抗压不抗拉，易发生破坏.进路两侧帮出现压应力集中尖点，最大受压值可达10~10.6 MPa，超过充填体及强风化岩体的强度值.在此情况下，采场极可能发生严重片帮，进而可能导致顶板垮塌[13-14].
综合模拟过程中的最大与最小主应力分析可得：采矿进路布置沿矿体走向与上盘接触的开采稳定性程度最低，不宜采用[15].
4 小结
（1）对某铜矿不同采矿进路布置开采方案稳定性的数值模拟分析，可得到针对此矿山不同采矿进路布置方案开采稳定性的程度，避开稳定性程度最差的进路布置开采方案；
（2）通过分析可知数值模拟可以作为一种有效的手段确定此矿山不同采矿进路布置方案开采稳定性，进而指导现场施工.
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图 1 赤泥-钛白废酸浸出液萃取钪工艺流程
Fig 1. Process flow of Sc extraction from leach solution of red mud-titanium white waste acid
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图 3 浸出液酸度对钪、钛、铁、铝萃取率的影响
Fig 3. Influence of leach solution acidity on extraction ratio of Sc, Ti, Fe, Al
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图 6 P204和TBP体积分数对钪萃取率的影响
Fig 6. Influence of volume fraction of P204 and TBP on extraction ratio of scandium
表 1 赤泥-钛白废酸浸出液的主要化学成分/(g·L-1)
Table 1 The main chemical composition of the red mud-titanium white waste acid/(g·L-1)
元素 Al2O3 RExOy Sc2O3 TiO2 Fe2O3 V2O5 ZrO2 SiO2 含量 7.10 0.12 0.016 5.29 41.86 0.22 0.25 3.64 
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表 2 除杂后液的化学成分及除杂率
Table 2 The chemical composition and impurities removal efficiency of the solution after removal of impurities
除杂后液成分 Al2O3 RExOy Sc2O3 TiO2 Fe2O3 V2O5 ZrO2 SiO2 除杂后液/(g·L-1) 6.50 0.115 0.0158 4.86 38.79 0.21 0.24 0.12 除杂率/% 8.45 4.16 1.25 8.13 7.33 4.54 4.00 96.70
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表 3 萃取结果
Table 3 Results of extraction
成分 除杂后液/(g·L-1) 萃余液中含量/(g·L-1) 萃取率/% Sc2O3 0.016 0.000 2 98.80 Al2O3 6.500 6.460 0 0.62 Fe2O3 38.790 34.160 0 1.19 TiO2 4.860 4.460 0 8.23
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