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铬盐是我国重要的无机化工原料，广泛应用于冶金、电镀、鞣革、染料、木材防腐等领域。在铬盐生产过程中，铬铁矿中的铬、铝、钒分别生成相应的水溶性钠盐，形成Na2CrO4-NaAlO2-NaVO3-H2O多元复杂碱性浸出液。普遍采用中和除铝、加钙沉钒的分步脱除方法进行铝、钒等杂质的脱除，但在中和除铝过程中会产生以Al(OH)3胶体为主的含铬铝泥，加钙沉钒过程中会产生含铬沉钒钙渣。这些废渣不仅含水量大、难于处理，而且含有铬、钒等国家重点防控的重金属污染物，对生态环境危害巨大，同时造成铝和钒资源浪费，严重制约了铬化工行业的可持续发展，目前已被列为危险固废。因此，亟需研发铬盐多元复杂溶液体系中铝、钒脱除与资源化利用新方法、新技术。本论文基于铬盐多元复杂溶液体系硫酸中和过程原位生成的γ-AlOOH选择性吸附钒的原创发现，开展了大比表面介孔γ-AlOOH定向合成、高铬低钒溶液中V(V)选择性吸附及原位合成-协同吸附等研究，提出了铝钒同步分离及资源化应用技术，从源头避免了含铬钒酸钙渣的产生，并建立了铝泥综合利用的新方法。本论文主要取得如下创新性成果：（1）构建了NaAlO2和硫酸中和制备大比表面介孔γ-AlOOH的新方法，并查明了在高铬低钒溶液中选择性吸附V(V)的规律。在单一V(V)溶液中，其最大吸附容量可达3.61 mmol/g。而在高铬低钒溶液中，V(V)与Cr(VI)吸附分离比达到了500以上，并揭示了选择性吸附机理为Cr(VI)的吸附由化学吸附转变成物理吸附，而V(V)吸附依然为化学吸附。（2）针对铬盐多元复杂溶液体系，提出了原位中和—协同吸附新思路，建立了在高铬低钒溶液中同步分离铝钒的新方法。该过程可瞬间完成吸附平衡，同时钒铬吸附分离比达到2000以上，并揭示了瞬态pH和纳观尺度传质的影响机理。（3）完成了铬盐生产过程中铝钒同步分离技术中试验证。以铬盐浸出液为原料，在间歇化生产过程中，能够稳定的合成出大比表面介孔γ-AlOOH，可实现中和液中V<0.08 g/L，脱Al、Si和Fe均可达到0.001 g/L。在连续化生产过程中，钒铬吸附分离比达到50000以上，可稳定的实现V(V)从700 mg/L降低到2 mg/L，Al(III)含量稳定在2 mg/L以下（以Al2O3计）。（4）针对羟基铝泥，提出表面调控制备高效除Cr(VI)吸附剂的思路，建立了废水处理-羟基铝泥综合利用的新方法。将壳聚糖与羟基铝泥进行交联反应，制备高效吸附剂，可实现对Cr(VI)最大吸附容量为120.2 mg/g。而对吸附后产物经硫酸溶解可分离出壳聚糖，实现循环利用，并制备成铝-铬鞣剂。;Chrome salt, as an important inorganic chemical material, is widely used in metallurgy, electroplating, tanning, dye, wood corrosion and other fields. In the chromate production process, the Cr(VI), Al(III) and V(V) from chromite are separated in the form of water soluble sodium salt to form Na2CrO4-NaAlO2-NaVO3-H2O multiple complex solutions. In order to obtained Na2CrO4 solutions to prepare sodium dichromate products, the acid and calcium compounds are added to separate Al(III) and V(V), respectively, taking advantage of the low solubilities of Al(OH)3 and Ca(VO3)2. The separation method produces Cr(VI) containing Al(OH)3 residue and CaCrO4 containing Ca(VO3)2 residue. It is difficult to dispose due to the high moisture and the low content of vanadium and chromium distributed in slag. It not only does harm to the ecological environment, but also causes the waste of aluminum and vanadium resources, which seriously restricts the sustainable development of chrome salt industry. At present, they have been classified as hazardous solid waste. Therefore, there is an urgent demand for developing a novel method to eliminate the aluminum and vanadium residues and realize the utilization of resources in the multiple complex solutions. The thesis mainly focused on the synthesis of mesoporous γ-AlOOH with high BET surface area, and the selectively separation of V(V) from highly concentrated Cr(VI) multiplex complex solutions and in situ synthesis-synchronous adsorption. The idea of synchronous separation and the resource utilization of aluminum and vanadium were proposed, avoiding the chromium containing calcium vanadate slag from the source. The new method for comprehensive utilization of aluminum mud was established. The main innovative achievements were summarized as follows: (1) The new synthesis method of mesoporous γ-AlOOH was established by reacting NaAlO2 with H2SO4. The selective adsorption of V(V) from highly concentrated Cr(VI) multiplex complex solutions. was investigated. The maximum adsorption capacity of V(V) on the mesoporous γ-AlOOH could achieve at 3.61 mmol/g in single vanadium solution. While the adsorption ratio of V(V) to Cr(VI) reached more than 500 in the solution with highly concentrated Cr(VI) and low concentrated V(V). The adsorption mechanism was expressed that the adsorption of Cr(VI) changed from chemical adsorption to physical adsorption, while the adsorption of V(V) remained chemical adsorption.(2) The method of in situ synthesis-synchronous adsorption was proposed in term of chromium salt multiple complex solution system, achieving the synchronous separation of aluminum and vanadium from highly concentrated Cr(VI) multiplex complex solutions. The equilibrium adsorption time of V(V) and Cr(VI) was achieved instantaneously. The in situ synthesis and synchronous adsorption ratio of V(V) to Cr(VI) reached more than 2000. The mechanism of transient pH and nano scale mass transfer was also revealed.(3) The pilot plant test of the synchronous separation of aluminum and vanadium in chromium salt production was completed. In the process of batch operation, the mesoporous γ-AlOOH with large specific surface area was obtained The residual contents of V(V) and Al(III), Si(IV), Fe(III) after adsorption decreased to 0.08 g/L, 0.001 g/L, 0.001 g/L and 0.001 g/L, respectively. In the process of the continuous operation, the adsorption ratio of V(V) to Cr(VI) reached more than 50000. The results showed that the content of V(V) decreased from approximately 700 mg/L-2 mg/L. Additionally, the residual concentration of A(III) in solutions are less than 2 mg/L.(4) The idea for the preparation of Cr(VI) removal adsorbent by surface regulation of γ-AlOOH was proposed in term of aluminum mud. The new method of comprehensive utilization of γ-AlOOH hazardous wastes and textile wastewaters was established. By crosslinking between γ-AlOOH and chitosan to prepare adsorbents, Cr(VI) could be adsorbed from the Cr(VI)-containing solutions by the adsorbents with the maximum adsorption capacity of 120.2 mg/g. After adsorption, the adsorbents were dissolved H2SO4 solution. The insoluble chitosan was recycled in a closed loop, and the chromium-aluminum tanning agent was prepared as product.
|张海林. 铬盐清洁生产过程中铝钒同步分离及资源化应用基础研究[D]. 中国科学院大学,2020.|
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