分离硫酸选择性结晶用双 - iminoguanidinium配体
Summary
一种在双（iminoguanidinium）配位体及其在硫酸盐的选择性分离利用原位水性合成协议提出。
Abstract
A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), is demonstrated. The ligand is synthesized as the chloride salt (BBIG-Cl) by in situ imine condensation of terephthalaldehyde with aminoguanidinium chloride in water, followed by crystallization as the sulfate salt (BBIG-SO4). Alternatively, BBIG-Cl is synthesized ex situ in larger scale from ethanol. The sulfate separation ability of the BBIG ligand is demonstrated by selective and quantitative crystallization of sulfate from seawater. The ligand can be recycled by neutralization of BBIG-SO4 with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into BBIG-Cl with aqueous HCl and reused in another separation cycle. Finally, 35S-labeled sulfate and β liquid scintillation counting are employed for monitoring the sulfate concentration in solution. Overall, this protocol will instruct the user in the necessary skills to synthesize a ligand, employ it in the selective crystallization of sulfate from aqueous solutions, and quantify the separation efficiency.
Introduction
从有竞争力的水溶液的亲水oxoanions（ 例如 ，硫酸盐，铬酸盐，磷酸盐）的选择性分离代表具有相关性环境整治，能源生产，和人类健康的基本挑战。1,2-硫酸盐，特别是很难从水中提取，由于其固有磁阻摆脱其水化球和迁移到极性较小的环境中。3使硫酸水溶液萃取更有效，通常需要复杂的受体是困难和冗长合成和纯化，通常涉及有毒的试剂和溶剂。4,5-
选择性结晶提供从水中硫酸盐分离一个简单而有效的替代方案。6-9虽然某些金属阳离子如钡2+，铅离子或Ra 2+形式非常不溶性硫酸盐，其在硫酸的分离使用并不总是实用由于其高TOXI城市，有时低的选择性。采用有机配体硫酸盐沉淀利用结构的多样性和顺从的设计特性的有机分子。硫酸水溶液结晶的理想有机配体应是可溶于水，但形成在相对短的时间，并在高浓度的竞争离子的存在的不溶性硫酸盐或复合物。另外，它应该是容易合成和回收。一个这样的配体，1,4-苯-二（iminoguanidinium）（BBIG），自组装从两种市售的前体，对苯和aminoguanidinium酰氯原位 ，最近被发现在硫酸水溶液分离非常有效。10的配体是水溶性的氯化物形式，并用硫酸选择性结晶成一个极其不溶性盐可以从通过简单的过滤溶液中容易地除去。该BBIG配体随后可以通过去质子与回收queous NaOH和中性双 – iminoguanidine，它可以被转换回用HCl水溶液的氯化物形式，并再利用在另一分离循环的结晶。这种配位体在从水中除去硫酸盐的功效是如此之大，监测溶液中的剩余的硫酸浓度不再是一个简单的任务，需要更先进的技术，其允许的阴离子痕量精确测量。为了这个目的，在以β液体闪烁计数结合的放射性标记的35号硫酸盐示踪剂采用一种技术在液-液萃取分离通常使用，并在最近证明是有效的监测硫酸盐结晶。8
这个协议表明在 BBIG配位体的原位合成及其作为从水溶液硫酸盐结晶的单罐。配体11 易地合成也提出作为合作为生产更大量的BBIG-CL，它可以被存储在结晶形式中待用nvenient方法。然后使用预先制备BBIG-氯配体海水硫酸盐除去是证明。最后，使用35 S-标记的硫酸盐和用于测量海水中硫酸盐浓度β液体闪烁计数的是证明。该协议旨在为那些在探讨水性阴离子分离使用选择性结晶的广泛兴趣提供的教程。
Protocol
Representative Results
Discussion
这种技术是相当耐受从书面程序，这使得它相当健壮许多偏差。然而有两块必须遵循的关键步骤。第一，BBIG-氯配位体需要是尽可能纯。杂质不仅会影响结晶，将所得的硫酸盐的溶解度，同时也将使得难以计算从溶液定量硫酸除去所需的时间量。其次，在β液体闪烁计数节中的所有步骤都要精心其次，因为这种技术可能是微妙的变化非常敏感。
由于结晶技术的简单性，将最有?…
Divulgazioni
The authors have nothing to disclose.
Acknowledgements
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. We thank the University of North Carolina Wilmington for providing the seawater.
Materials
| Terephthalaldehyde | Sigma | T2207 | |
| Aminoguanidinium Chloride | Sigma | #396494 | |
| Sodium Sulfate | Sigma | #239313 | |
| Barium Chloride | Sigma | #342920 | Highly Toxic |
| Ethanol | Any | Reagent Grade (190 proof) | |
| Sodium Hydroxide | EMD | SX0590-1 | |
| Hydrochloric Acid | Sigma | #258148 | |
| Filter Paper | Any | – | Any qualitative or analytical filter paper will work |
| Syringe Filter (0.22 um) | Any | – | Nylon filter |
| 35S Labeled Sulfate | Perkin Elmer | NEX041005MC | |
| Ultima Gold Scintillation Cocktail | Perkin Elmer | #6013329 | |
| Polypropylene Vials | Any | – | |
| Disposable Syringe (2-3 mL) | Any | – | Any disposable plastic syringe works |
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