New Wet Treatment Process of Barite (BaSO_4) using EDTA

重晶石是每一种钡化合物的主要原料，在1000-1200℃的温度下，在焦炭或沥青的存在下煅烧，转化成含硫化钡的黑灰。然而，这个过程需要处理硫化物作为副产品。因此，开发一种节能、对环境影响小的重晶石处理新工艺是值得期待的。研究了EDTA溶液中温浸出重晶石，水热条件下沉淀硫酸钡的新工艺。含有Ba (edta)^<2->络合物的浸出液可以在控制形貌和粒度分布的情况下直接制备钡盐，而不会产生麻烦的硫化氢。工艺运行在80 ~ 250℃之间，可以利用低温余热，沉淀中释放的EDTA可以循环利用。[EDTA溶液浸出重晶石]对重晶石工艺进行了动力学研究。随着温度的升高，浸出率显著提高，在60-90℃时，450 ~ 1100rpm的搅拌转速对浸出率影响不大。当颗粒大小减半时，速率增加了两倍。随着浸出过程的进行，重晶石颗粒上形成了许多较深的裂纹，因此即使在1小时内也不能用收缩核模型来分析其机理。修正后的模型为表观活化能为16kcal/mol。因此，速率过程由任何化学反应控制。以[edta]/[重晶石]摩尔比为1，在90℃下浸出10h，制备了含有0.024M [Ba^<2+>]_T和0.08M [edta]_T的[重晶石的沉淀]Ba (edta)^<2->溶液。在等体积的Ba (edta)^<2->溶液中加入10 ml 0.2或0.4 M硫酸钠溶液，将得到的溶液放入玻璃管（Duran）中，在180-200ºC的空气浴中加热0-10h。钡离子沉淀成柱状重晶石

Barite is the major resource for every barium compounds and calcined at 1000-1200ﾟC in the presence of coke or pitch to convert black ash containing barium sulfide. However, this process needs the treatment of sulfide as a by-product. So, a development of new treatment process of Barite is expected, and this process is required energy conservation and low impact for environment. A new process consisting of leaching barite with an EDTA solution at moderate temperature and precipitating barium sufate under hydrothermal conditions is studied in this work. Barium salt can be prepared directly from the leaching Solutions containing Ba (edta)^<2-> complex as controlled morphology and size distribution without producing troublesome hydrogen sulfide in the process. The process operating between 80-250ﾟC can use low temperature waste heat and EDTA liberated in the precipitation can be recycled.[Leaching of barite with EDTA solutions]Kinetic study was carried out for processing barite. The leaching rate increased remarkably with temperature and the stirring speed from 450-1100rpm affected little the rate at 60-90ﾟC.The rate increased twice when the particle size became half. The mechanism could not be analyzed by the shrinking core model even within one hour due to the formation of many and deep cracks on the barite particles with processing the leaching. Consequently a modified model was with proceeding the apparent activation energy was 16kcal/mol. Thus, the rate process is controlled by any chemical reaction.[Precipitation of barite]Ba (edta)^<2-> solutions containing 0.024M [Ba^<2+>]_T and 0.08M [edta]_T were prepared by leaching barite with [edta]/[barite] molar ratio of 1 at 90ﾟC for 10h. Ten ml of 0.2 or 0.4 M sodium sulfate solution was added to equal volume of the Ba (edta)^<2-> solution and the resulting solution in a glass tube (Duran) was heated in air bath at 180-200ﾟC for 0-10h. Barium ion precipitated as pillar-like barite