Preparation of Multifunctional β-hemihydrate Gypsum using Oyster Shell Powder as the Partial Replacement of Ag/TiO2 Particle

This work aimed to use oyster shell powder (OSP) as the partial replacement of Ag/TiO2 particle to obtain multifunctional β-hemihydrate gypsum.Thus,the β-hemihydrate gypsum was mixed with different contents of OSP and Ag/TiO2 particle.Antibacterial and MB removal experiments were conducted to assess the antibacterial characteristic and photocatalytic activity of β-hemihydrate gypsum with Ag/TiO2 particle and OSP.Besides,the formaldehyde degradation test was carried out to evaluate its formaldehyde removal ratio.Moreover,their setting times,compressive and flexural strengths at 1,3,and 28 days were comparatively analyzed.The experimental results prove that the composite use of OSP and Ag/TiO2 particle provide feasible multifunction for the β-hemihydrate gypsum.They can further improve the bactericidal rates and exhibit extra MB removal ratios compared with the gypsum plasters with single Ag/TiO2 particle.Besides,they can increase the formaldehyde degradation ratios,and this promotion is related to the introduction of Ag/TiO2 particle.However,OSP delays the initial setting time but promotes the final setting time of β-hemihydrate gypsum,and Ag/TiO2 particle hardly affects the setting times.Furthermore,OSP reduces the strengths of plasters at 1,3,and 28 days.But in general,the composite addition of OSP and Ag/TiO2 particle increase the compressive and flexural strengths of gypsum plasters at 1,3,and 28 days.These results provide theoretical guidance for the recycling of OSP and the preparation of gypsum-based products with antibacterial and formaldehyde degradation capabilities.

Deep decalcification of factory-provided freezing acidolysis solution to achieveα-high-strength gypsum

The freezing acidolysis solution of the nitric acid-phosphate fertilizer process has a high calcium content,which makes it difficult to produce fine phosphate and high water-soluble phosphate fertilizer products.Here,based on the potential crystallization principle of calcium sulfate in NH_(4)NO_(3)-H_(3)PO_(4)-H_(2)O,the deep decalcification(i.e.calcium removal)technology to achieveα-high-strength gypsum originated from freezing acidolysis-solutions has been firstly proposed and investigated.Typically,calcium can be removed from the factory-provided freezing acidolysis-solution by neutralizing it with ammonia,followed by the addition of ammonium sulfate solution.As a result,the formation of calcium sulfate in the reaction system undergoes the nucleation and growth of CaSO_(4)·2H_(2)O(DH),as well as its dissolution and crystallization into short columnarα-CaSO_(4)·0.5H_(2)O(α-HH).Remarkably,with the molar ratio of SO_(4)^(2-)/Ca^(2+)at 1.8,the degree of neutralization(NH_(3)/HNO_(3) molar ratio)at 1.7,the reaction temperature of 94℃,and the reaction time of 300 min,the decalcification rate can reach 86.89%,of which the high-strengthα-CaSO_(4)·0.5H_(2)O(α-HH)will be obtained.Noteworthy,the deep decalcification product meets the standards for the production of fine phosphates and highly water-soluble phosphate fertilizers.Consequently,the 2 h flexural strength ofα-HH is 5.3 MPa and the dry compressive strength is 36.8 MPa,which is up to the standard of commercialα-HH.

盐溶液水热法制备α-半水脱硫石膏工艺条件研究

利用脱硫石膏呈湿态粉体、品位较高的特点，采用常压盐溶液介质水热法制备α-半水石膏。研究了盐溶液浓度、反应温度、反应时间、料浆浓度、pH值等因素对脱水反应动力学过程及α-半水脱硫石膏产物形态的影响，确定了脱硫石膏制备α-半水石膏的最佳工艺条件：盐溶液浓度为15％，反应温度不低于95℃，反应时间2h，pH值=5～7，料浆浓度为20％。

脱硫石膏在淮北矿业相山水泥有限公司中的应用

简要介绍了脱硫石膏的特性以及与天然石膏的性能区别;重点就淮北矿业相山水泥有限责任公司用脱硫石膏替代天然石膏作缓凝剂生产水泥的实验方案、试验效果及其在实际商业生产中的应用情况和经济效益分析作了介绍。结果表明:脱硫石膏可100%替代天然石膏生产,且节约生产成本效益显著。

脱硫石膏代替天然石膏作缓凝剂的生产实践

哈尔滨水泥有限公司进行了用热电厂脱硫石膏全部或部分代替天然石膏生产水泥的生产实验并获成功应用。文章介绍了热电厂脱硫石膏的形成过程;分析了脱硫石膏与天然石膏的物理化学性能;总结了化验实小磨实验和工业试生产情况。实验和应用结果表明,用脱硫石膏全部或部分替代天然石膏生产普通硅酸盐水泥和复合水泥是完全可行的,且经济、社会效益显著。

脱硫石膏在水泥生产中的应用实践

研究了脱硫石膏和天然石膏对水泥性能影响的差异,探讨了脱硫石膏完全代替天然石膏生产水泥的途径,并在实际生产中成功应用脱硫石膏作水泥缓凝剂生产出符合国标要求的水泥。

浅谈脱硫石膏替代天然二水石膏应用的几点体会

实验用脱硫石膏代替天然石膏作水泥缓凝剂，结果表明，脱硫石膏能正常调节水泥凝结时间，脱硫石膏掺量为2．5％～5％时，各品种的水泥凝结时间均能满足国家标准的要求，而且脱硫石膏作缓凝剂的水泥强度与用天然石膏的水泥相当，部分水泥品种的强度还有一定幅度的提高。最后简单介绍了脱硫石膏实际应用经验和取得的社会经济效益。

FDN在α半水脱硫石膏表面的吸附特性与分散作用

采用紫外吸收光谱分析仪、微电泳仪、X光电子能谱分析技术研究了FDN在α半水脱硫石膏表面的吸附特性、表面电化学性质及其对流动性的影响。结果表明:α半水脱硫石膏对FDN吸附为化学吸附,吸附等温线基本符合Langmuir方程,吸附热为5.76kJ/mol,吸附层厚度为9nm;FDN为平躺吸附,吸附层空间位阻小,其分散作用主要依赖ξ电位的静电斥力,而ξ电位取决于FDN首层吸附量;α半水脱硫石膏水化很快,其水化产物覆盖对静电斥力有屏蔽效应,静电斥力分散作用的稳定性差,流动度经时损失较大。