Removal and Recovery System of Hexavalent Chromium from Waste Water by Tannin Gel Particles
Removal and Recovery System of Hexavalent Chromium from Waste Water by Tannin Gel Particles
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单宁凝胶颗粒去除废水中六价铬的回收系统
DOI：
10.1252/jcej.33.747
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发表时间：
2000
影响因子：
0.8
通讯作者：
M. Konno
中科院分区：
文献类型：
--
作者：
Y. Nakano;Michihito Tanaka;Yasuo Nakamura;M. Konno
通过控制从植物树皮中提取的含羞草单宁的凝胶化，研制出对六价铬具有极高吸附能力的单宁凝胶颗粒。胶凝过程分为两个阶段：通过与甲醛(交联剂)反应使含羞草单宁部分胶凝，以及将部分胶凝溶液分散到十氢呋喃和聚醚非离子表面活性剂的液体混合物中，在剧烈搅拌下造粒。单宁凝胶颗粒的结构由两个阶段的操作条件(如反应时间和温度)的组合控制。反映其结构的单宁凝胶颗粒的水分含量可以从40%到79%(湿基)很大程度上变化，即使在23g含羞草单宁和6ml甲醛(37wt%)的恒定组成下也是如此。研究发现，在不损失机械强度的前提下，增加材料的含水率，并在吸附过程中提供大量的质子，对于获得高吸附容量是非常重要的。在pH≈为2.0时，当含水率为77.6%时，吸附容量最大，为540mg六价铬/(g-单宁干凝胶)。基于这一认识，我们提出了一种新的系统，在去除和回收六价铬方面产生的浪费很少。
Tannin gel particles that have extremely high adsorption capacity for hexavalent chromium Cr(VI) have been developed by controlling gelation of Mimosa tannin extracted from the bark of plants. The gelation process is composed of two stages; partial gelation of Mimosa tannin by reaction with formaldehyde (cross-linking agent) and granulation by dispersing the partially gelated solution into a liquid mixture of decalin and a polyether nonionic surfactant with vigorous stirring. The structure of the tannin gel particles is controlled by a combination of operating conditions such as reaction time and temperature at both stages. The water content of the tannin gel particles that reflects their structure can be widely changed from 40 to 79% (wet basis), even for a constant composition of 23 g Mimosa tannin and 6 ml formaldehyde (37 wt%). It is found that it is very important to increase the water content without losing mechanical strength and supply a large amount of protons during adsorption for achievement of high adsorption capacity. The maximum adsorption capacity, 540 mg-Cr(VI)/(g-dry tannin gel) is obtained at a water content of 77.6% with an acidic solution of pH ≈ 2.0. Based on this knowledge, we propose a new system that generates little waste in removing and recovering hexavalent chromium.