【作者】 兰叶；

【导师】 王毓华；

【作者基本信息】 中南大学 ， 再生材料工程， 2007， 硕士

【摘要】 铝土矿浮选脱硅产生的铝硅酸盐尾矿是铝土矿选矿—拜耳法生产氧化铝新工艺的主要废弃物之一。目前，铝土矿浮选尾矿以自然堆积法储存于尾矿坝，不仅占用了大量土地，而且会对地下水源造成污染，因此，开展铝土矿浮选尾矿再利用研究具有重要的意义。本文在总结和分析大量国内外相关文献的基础上，围绕铝土矿浮选尾矿改性及处理废水的课题进行了较系统的试验研究。通过改性试验和吸附试验，研究了铝土矿正浮选尾矿对不同离子吸附性能的影响规律。借助光电子能谱分析、电位测试、红外光谱分析、溶液化学计算、热力学和动力学计算，对尾矿改性及吸附离子组分的作用机理进行了探讨。改性试验结果表明：浸出法优于焙烧法；盐酸和氯化铁改性效果优于其他改性剂。对FeCl₃改性剂，在30℃下以170r／min的转速振荡，用0.1mol／L FeCl₃改性12h，矿浆浓度为250g／L的条件下，得到的改性尾矿投加量20g／L情况下可使30mg／L含Cr（Ⅵ）离子溶液中的Cr（Ⅵ）离子去除率达到68.81％。吸附试验结果表明：FeCl₃改性尾矿有利于吸附阴离子，原尾矿有利于吸附阳离子，FeCl₃改性尾矿和原尾矿对染料有机物（亚甲基蓝）都有很好的去除效果。FeCl₃改性尾矿用于吸附阴离子溶液，对30mg／LCr（Ⅵ）离子溶液最大去除率达到97％；1mg／L As（Ⅴ）离子去除率接近于100％；40mg／L F（Ⅰ）去除率可以达到90％以上。原尾矿用于吸附阳离子溶液，40mg／L的Pb（Ⅱ）离子去除率接近100％，40mg／L的Cd（Ⅱ）离子去除率接近100％。以上离子溶液吸附后均能符合第二类污染物最多排放标准。通过条件实验证明，对亚甲基蓝的吸附主要影响因素是吸附剂用量，与吸附剂种类和pH值无关，当尾矿投加量为20g／L时，去除率都接近于100％，所以认为该吸附过程应该是一种物理吸附过程。晶体结构分析表明：铝土矿尾矿中主要矿物在浮选后，表面暴露有大量的Al-0键和Si-0键，易与阳离子发生静电及吸附作用。电位分析测试表明：与FeCl₃改性作用后，尾矿zeta电位的正值增大，等电点由3.63偏移至5.08，表明氯化铁在尾矿表面吸附较多。由于氯化铁改性后，尾矿表面zeta电位正值增大，有利于吸附阴离子物质Cr（Ⅵ）离子，吸附后的等电点由5.08偏移至3.26。原尾矿吸附Pb（Ⅱ）离子后，其表面zeta电位正值增大，等电点从3.63升至5.86，增加了2.23。溶液化学计算分析表明：尾矿改性后，其表面可能吸附了Fe（OH）²⁺、Fe（OH）₂⁺及Fe（OH）₃等羟基铁物质。铬离子的最佳吸附pH值为3.52，对应主要组分为HCrO₄，铅离子的最佳吸附pH值为6.2，对应主要组分为pb²⁺、PbOH⁺。红外光谱分析表明，尾矿经氯化铁改性后，3453cm^-1自由的OH伸缩振动吸收峰增强，—C—CH₃特征峰消失，Si-O和Al-O峰的吸收减弱，证明了铁离子以羟基铁的形式在尾矿表面存在。Cr（Ⅵ）离子溶液与改性尾矿作用后在672cm^-1处还出现了一个新峰，新峰对应为Cr₂O₇²离子的特征峰，表明Cr（Ⅵ）离子溶液与改性尾矿表面发生化学吸附并生成了新的物质。通过等温吸附模型计算，改性尾矿对Cr（Ⅵ）离子的吸附能很好地符合Freundlich模型，而原尾矿对Pb（Ⅱ）的吸附则符合Langmuir描述。动力学模型计算得出，二级动力学方程比一级动力学方程更适合于改性尾矿对Cr（Ⅵ）离子和原尾矿对Pb（Ⅱ）离子的吸附数据。更多还原

【Abstract】 Aluminosilicate-tailings are the main waste generated during aluminum production from bauxite by a combined Bayer Process and bauxite flotation method. It is reported that 0.2 tons of aluminosilicate-tailings will be generated when 1 tons of bauxite ore is treated by flotation. The enormous quantity of tailings generated every year posses a very serious and alarming environmental problem, such as dust pollution caused by fine particles, land occupation and so on. The main compositions of bauxite tailings are diaspore, kaolinlite, illite and pyrophyllite. So, on the basis of summary and analyse of many interrelated documents both at home and abroad, systematical experiments had been carried out in order to find out effective and low-cost sorbent and realize the renewable use of bauxite tailings.Various ions had been used for the study of removal behaviors of bauxite tailings under the different conditions by modifying and adsorption test. Various measurement techniques had been carried out, such as photoelectron spectroscopy analysis, Zeta potential measurement, infrared spectroscopy, micrography, account of solution chemistry, thermodynamics and kinetics to determine the reaction mechanisms between sorbents and minerals.The results of modifying tests indicate that leaching is more effective than calcinations. Hydrochloric acid and FeCl₃ modified bauxite tailings are more effective than other acide, alkali, organic and other salt in the removal of Cr（Ⅵ） ion. But the dosage of HC1 is large, so FeC1₃ was chosen as the best modified reagent for bauxite tailings. In optimization tests, a removal rate of Cr（Ⅵ） ion （30mg/L） 68.81% was also obtained under the conditions that bauxite tailings samples （20g/L） were treated with 0.1M FeC1₃ shaking for 12h in speed of 170±3 stroks min^-1 at 30±1℃.The results of adsorption indicate that tailings modified by FeC1₃ are conducive to anion adsorption, and unmodified tailings are easy for cation adsorption. Modified tailings by FeC1₃ and unmodified tailings both show good adsorption on methylene blue. The maximum removal rate of Cr（Ⅵ） and As（Ⅴ） are 97% and almost 100% by modified bauxite tailing, respectively. The maximum removal rate of Pb（Ⅱ） and Cd（Ⅱ） are almost 100% by unmodified bauxite tailing. After adsorption, all solutions with the second class contamination emission level can be obtained. The condition tests show that the most influence factor on adsorption of methylene blue is adsorbent dosages, and it doesn’t relate with the species of sorbent and pH. The maximum removal rate of methylene blue is almost 100%, so it can be considered the process is a physical adsorption process.The broken bonds on the surface of minerals in tailings are ionic/covalent A1-O bonds and Si-O bonds, that cause absorption and electrostatic action with anion reagents. The zeta potential measurements show that the potential of tailings are increased after modified, and its isoelectric point shifts from 3.63 to 5.08, which indicates that there is much absorption of FeC1₃ on the surface of tailings. So the modified tailings are conducive to Cr（Ⅵ） ion adsorption, and its isoelectric point shifts from 5.08 to 3.26. After the adsorption of Pb（Ⅱ）, the isoelectric point shifts from 3.63 to 5.86.The account of solution chemistry shows that after modifying tests, the surface of bauxite tailings can adsorb hydrated iron oxide as form of Fe（OH）²⁺, Fe（OH）₂⁺ and Fe（OH）₃. The optimal pH condition of adsorption Cr（Ⅵ） ion is 3.52 in which the main form of Cr（Ⅵ） ion is HCrO₄. The optimal pH condition of adsorption Pb（Ⅱ） ion is 6.2 in which the main form of Pb（Ⅱ） ion is Pb²⁺, PbOH⁺.The results of infrared spectroscopy show that the modified tailings samples have a strong band of O—H—O at 3431 cm^-1, and the band of—C—CH₃ (1427 cm^-1) is disappeared while the adsorption bands of Si—O and A1—O is weaken. This indicates that the modification of tailings may have taken place on these positions on the surface of theunmodified tailings and produce hydrated iron oxide. There is a new band at 672 cm^-1 which is due to Cr₂O₇^2-. It suggests that Cr（Ⅵ） adsorbed on the modified tailings surface in the form of chemistry adsorption.Freundlich model fits better than Langmuir model to the adsorption of Cr（Ⅵ） by modified tailings. However, Langmuir model represents the adsorption process better than Freundlich model for the adsorption of Pb（Ⅱ） on unmodified tailings. The results of this study show that Pb（Ⅱ） can be adsorbed successfully in significant amounts of unmodified tailings.A batch of adsorption kinetic experiments reveal that the adsorption of Cr（Ⅵ） and Pb（Ⅱ） on unmodified and modified tailings is well represented by the pseudo-second-order kinetic model.更多还原