钽铌矿冶炼废渣的资源化利用

广东某钽铌矿冶炼企业主要生产氟钽酸钾及氧化铌,年处理钽精矿130 t、铌钽铁合金220 t,年产生中和渣量约672 t,但由于原有工艺没有对酸溶渣、中和渣和废液进行分离,造成最终废物量大、放射性活度高和难处理等问题,厂区历史遗留中和渣约1万t。现该企业对生产工艺进行了改进,包括车间排放口处理废水、增加压滤机、总排放口优化、建设中和渣堆场和中和渣资源化利用等措施。经技术改进后,实现了渣液分离,产生的废水放射性物质达标排放,对历史遗留的中和渣进行资源化利用,减少中和渣填埋处置费用约3 000万元,获得了较好的经济效益、环境效益和社会效益。     

The perils of foreign intervention: the Nile perch disaster for Lake Victoria

The present study involved the use of a pilot scale water treatment plant to treat turbid surface water from a stream using processed Moringa oleifera seed and alum as primary coagulants. At low initial turbidity of 21.5 to 49.3 NTU, residual turbidities of 2.7, 1.8 and 1.4 NTU were achieved after treatment using Moringa oleifera, alum, and alum with Moringa oleifera as coagulant‐aid, respectively. For medium turbidities varying from 51.8 to 114 NTU, lowest residual turbidities of 2.9, 1.2 and 1.4 were achieved after treatment using Moringa oleifera, alum, and alum with Moringa oleifera as coagulant‐aid, respectively. For high turbidity varying from 163 to 494 NTU, minimum residuals of 1.4, 1.9 and 0.9 NTU were achieved after treatment using Moringa oleifera, alum, and alum with Moringa oleifera as coagulant‐aid, respectively. The proposed mechanism for turbidity removal by Moringa oleifera seed in this study is a combination of partial‐charge neutralization and micro‐bridging or an electrostatic patch mechanism based on the results of zeta potential measurements.     

Simulation and thermodynamic analysis of chemical looping reforming and CO2 enhanced chemical looping reforming

The production of hydrogen from methane via two chemical looping reforming (CLR) processes was simulated and thermodynamically analysed, one process being the conventional CLR process, the other being a CO₂ sorption enhanced process. The aim of the work was to identify suitable operating conditions for obtaining an optimum hydrogen gas purity and yield, whilst operating auto-thermally, at atmospheric pressure and with no carbon formation. In both simulations, the reactors were simulated using the Gibbs minimisation technique. NiO was used as the oxygen storing species, whilst CaO was used as the CO₂ adsorbent.     

用湿法磷酸生产工业级磷酸二氢钾工艺技术的研究

研究用湿法磷酸中和法制备工业级磷酸二氢钾的工艺过程,主要研究了反应终点p H对净化效果及磷收率的影响,以及磷酸浓度对磷收率的影响。研究结果表明:当反应终点溶液p H达到3.96时,铁、铝和氟脱除较完全,钙脱除率其次,镁脱除率较低;磷酸浓度升高,磷收率降低,反应终点p H升高,磷收率也有所降低;在实验条件下,磷酸二氢钾溶液经浓缩、冷却结晶后得到的磷酸二氢钾产品w(KH2PO4)可达99%以上。     

精对苯二甲酸生产废水处理与CO2协同利用技术的实践与展望

在全球变暖的严峻形势和我国“双碳”目标的大背景下,本文提出了“化工废水处理与CO₂协同利用”概念,选择精对苯二甲酸（PTA）生产废水处理与CO₂协同利用生产微藻生物质,开展了实验室研究和为期124天的中试试验。实验结果表明,实现了PTA生产废水COD去除率达到92%以上,对CO₂（体积分数10%）捕集率达到93%以上,CO₂捕集强度为9~11kg/t废水。产生的剩余生物质通过热裂解处理,生物质热裂解率>95%。通过闭环的碳转化,利用体系处理,利用废水、气体和固体中的碳,实现了从“无用碳”到“可用碳”的转化,为化工企业的碳中和目标提供了新的思路。     

Extraction of valuable metals from low nickel matte by calcified roasting−acid leaching process

A calcified roasting−acid leaching process was developed as a highly effective method for the extraction of valuable metals from low nickel matte in the presence of CaO additive. The influences of process parameters on the metal extraction were studied, including the roasting temperature, roasting time, addition of CaO, H₂SO₄ concentration and liquid−solid ratio. Under the optimum condition, 94.2% of Ni, 98.1% of Cu, 92.2% of Co and 89.3% of Fe were recovered. Additionally, 99.6% of Fe was removed from the leachate as goethite by a subsequent goethite iron precipitation process. The behavior and mechanism of CaO additive in the roasting process was clarified. The role of CaO is to prevent the formation of nonferrous metal ferrite phases by a preferential reaction with Fe₂O₃ during the roasting process. The metal oxides (CuO and Ni_xCu_1−xO) remained stable during high-temperature roasting and were subsequently efficiently leached using a sulfuric acid solution.     

Comparative studies of grain refinement of commercial purity Mg by CaO and Ca addition

ABSTRACT

The comparative studies of grain refinement of commercial purity Mg by CaO/Ca addition have been investigated by using TP-1 tests, optical microscope, XRD characterisation and TEM (STEM) observation along with EDX analysis. Experimental results showed that Ca/CaO addition significantly refines the grain structure of commercial purity Mg. Compared with Ca addition, CaO exhibits finer grain size and the average grain size remains invariable with further CaO addition. CaO addition is readily reduced to Ca by Mg melt and forms Mg₂Ca on the surface of MgO particles. First-principle calculations were used to understand the nucleation of Mg₂Ca layer by a coherent interface model calculating the work of adhesion and the interface energy between Mg₂Ca and α-Mg. The combination of experiments and calculations showed that the formation of Mg₂Ca layer on MgO facilitates the nucleation of α-Mg and then refines the grain structure by Ca or CaO addition.     

Transesterification of Canola Oil to Biodiesel Using CaO/Talc Nanopowder as a Mixed Oxide Catalyst

A series of heterogeneous catalysts including different molar ratios of CaO/talc was synthesized to study the transesterification reaction of canola oil and methanol under different reaction conditions. Characterization and kinetic results revealed that the activity of this catalyst was enhanced due to the increase of CaO/talc molar ratio value leading to an improvement in the biodiesel production. Moreover, the effect of various parameters on the activity of the undertaken catalysts was studied in order to determine the optimum process conditions. Leaching measurements and the durability of the CaO/talc catalyst under several reaction cycles were evaluated and proved it to be a stable catalyst.     

固体CaO在3CaO·P2O5-2CaO·SiO2饱和熔渣中的溶解及反应机理

摘要：为了深入了解非均相脱磷剂中固体CaO在3CaO·P2O5-2CaO·SiO2（C2S-C3P）饱和熔渣中的溶解及反应机理，采用静态浸入法和旋转圆柱法研究固体CaO在C2S-C3P饱和CaO-SiO2-FetO-P2O5（10%）渣中的溶解行为，运用FESEM/BSED EDS对固体CaO和熔渣界面进行了观察，分析了固体CaO与C2S-C3P饱和熔渣间的反应机理。结果表明，加强对熔池的搅拌，能够加快固体CaO在熔渣中的侵蚀速度和溶解速度；发现了固体CaO在饱和熔渣中的溶解数量受熔渣中FeO通过边界层向固体内部渗透深度的影响，FeO渗透深度越深，溶解越多；固体CaO先与熔渣中的硅和磷反应生成磷含量低的C2S-C3P固溶体，待一段时间后，最终生成磷含量高的Ca5(PO4)2SiO4。