Development of Gold and Silver Extraction Technology from Ores and Intermediate Products Containing Mercury

For a long time the ores of placer deposits were processed using amalgamation method, and this resulted in contamination of mine sites and products of treatment with mercury. Adverse effects of mercury manifested themselves at different stages of the precious metals extraction process using cyanide technology.

With the aim of improving the process the physico-chemical behaviour of mercury during cyanidation, sorption and desorption using activated carbons and ion exchange resins, electrowinning and cementation was studied. The studies came up with a set of conditions of the cyanidation process which prevented mercury from passing into a solution or brought its solubilization up to 80%.

Studies on the selective removal of mercury from cyanide solutions using different chemical methods were carried out. A settling reagent for cyanide solutions causing almost complete precipitation of mercury was found.

Tests on gold and silver extraction from mercury-free cyanide solutions by sorption, electrowinning and cementation onto carbon were conducted. No problems were encountered during these tests. A process flowsheet including two stages of cyanidation in a cone-type device, removal of mercury from solutions, precipitation of gold and silver by electrowinning was devised. The flowsheet provides complete recycling of barren solutions and purification of cyanidation cakes. The suggested flowsheet was tested in plant conditions and is recommended for use.     

透辉石/AlTiB增韧补强氧化铝基陶瓷材料烧结动力学和烧结机制

研究了透辉石/AlTiB增韧补强Al2O3基陶瓷材料的无压烧结致密化过程,通过绘制lg(ΔL/L0)-lgt图,用最小二乘法计算了透辉石/AlTiB增韧补强Al2O3基陶瓷材料的表观激活能.计算结果表明:纯Al2O3致密化机制为扩散机制控制;透辉石/AlTiB增韧补强Al2O3基陶瓷材料在烧结初期的致密化机制为液相流动和颗粒重排,在中、后期致密化机制转为扩散机制控制.根据烧结温度和保温时间对复合材料线收缩率的影响,建立了透辉石/AlTiB增韧补强Al2O3基陶瓷材料的烧结动力学方程;纯Al2O3陶瓷材料的烧结特征指数n约为2.5,其烧结过程中的物质迁移机制由体扩散控制;透辉石/AlTiB增韧补强Al2O3基陶瓷材料的烧结特征指数n值介于2.5与3.0之间,其在烧结中、后期的物质迁移机制既有体扩散,也有晶界扩散.     

Formation and evolution of macro inclusions in IF steels during continuous casting

The evolution of macro inclusions during continuous casting was investigated by large-area inclusion characterization using ASPEX and analysis of nozzle blockage deposits. Six kinds of inclusions over 5?μm were observed in samples taken from the tundish and the slabs: single alumina particles, alumina dendrites, refractory-related alumina, alumina associated with bubbles, alumina clusters and Al–Ti complex oxides. By examining the morphology of the nozzle blockage deposit, it was concluded that the refractory-related alumina in the slabs came from the decarburization layer washed away by the steel stream. Some of the alumina clusters that came from the nozzle blockage deposit dislodged by the steel flow, were formed by the agglomeration and sintering of 5–20?μm inclusions that were carried over from the tundish. Two kinds of Al–Ti oxides were found in the tundish, and their evolution mechanisms during the casting process were proposed.     

Processing of Mica for Extraction of Alumina and Potash Values

Mica sample containing 34% alumina and 9% potash has been investigated as a potential dual source of alumina and potash. It was found that planetary milling had a strong effect on structure breakdown as well as on the release of alumina and potash values. Both alumina and potash were extracted from mica using mechanical milling followed by hydrochloric acid leaching and precipitation process. The optimal conditions derived from statistical design yielded 72% alumina and 75% potash values in the form of γ-alumina and sylvinite. The analysis of the final precipitate was carried out by different characterization techniques such as XRD, SEM–EDS, XRF, BET surface area analysis.

     

高铝粉煤灰高效增值利用新技术

针对当前高铝粉煤灰综合利用技术难题,提出了高铝粉煤灰预脱硅烧结法提取氧化铝新工艺。新工艺取消了铝酸钠溶液碳酸化分解工序,改为全种子分解工艺。通过合成技术优化,采用高苛性比合成技术,种分母液与预脱硅后的硅酸钠溶液可制备出合格的洗涤用4A沸石。生产过程中,通过补充少量水玻璃用于调节氢氧化铝和4A沸石两种产品的产出比例,可以较好地保障生产系统物料平衡。新工艺取消了石灰炉、氧化铝焙烧炉、铝酸钠溶液碳酸化分解和深度脱硅工序,工艺能耗降低,废渣排放量减少,碳排放量降低。此技术生产流程相对简单、技术可行、经济性好、竞争力较强。     

Simulating the Effect of Sulfate Addition on Methylmercury Output from a Wetland

The watershed analysis risk management framework (WARMF) model was applied to Wetland S6 of the Marcell Experimental Forest, using the data from a field experiment, conducted to investigate the effect of sulfate additions on mercury methylation in the wetland. The wetland was modeled as interconnected land catchments. Actual meteorology data and mercury and sulfate concentrations of precipitation were input to the model. To simulate the sulfate sprinkling, the experimental section of the bog was irrigated with sulfate water on the actual dates of sulfate additions. The model simulated wetland outflows that matched the measured outflows with an R-square of 0.856. WARMF also simulated other phenomena observed in the experiment: higher sulfate and MeHg levels at the wetland outlet after every sulfate addition, and higher sulfate and MeHg levels in the pore water of the bog after only the May addition, not the July and September additions. According to WARMF, the low groundwater table in May allowed the sprinkled sulfate to percolate to the soil stratum 10–30 cm below the ground level of the bog, where the pore water was sampled. In July and September, the sulfate could not reach that zone because the percolation was blocked by high groundwater tables. The sampled soil stratum was not the site of methylation that contributed MeHg to the wetland outlet. The saturated zone of the top 10 cm of bog was the site that produced MeHg, which was flushed to the outlet after all sulfate additions. WARMF predicted that quadrupling the sulfate deposition would increase the MeHg output by 216%, which might become lower with more data and better model calibration.     

Titanium preconditioning of Al2O3 for liquid-state processing of Al-Al2O3 composite materials

Chemical vapor deposition (CVD) of titanium onto the surface of alumina substrates was used to improve the wetting by molten aluminum prior to infiltration. The CVD titanium coatings on alumina substrates were characterized by X-ray diffraction and energy-dispersive X-ray spectroscopy (EDS) as dual-phase, elemental titanium and titanium aluminide, Ti₃Al. The kinetics of the coating process were quantified and analyzed using established reaction kinetics models. An overall activation energy of 219 kJ/mole was calculated for the formation of the titanium coatings on planar alumina substrates, for the temperature range of 610 °C to 870 °C. The CVD-coated planar and porous alumina substrates were immersed in molten aluminum, and wetting of planar substrates and infiltration of porous bodies were documented. Formation of both aluminum-rich and titanium-rich reaction products was observed through EDS cross-sectional analysis.     

国产氧化铝在铝电解生产中的应用实践

通过使用国产氧化铝在铝电解生产中的变化，从国产氧化铝和进口氧化铝特性的比较分析，找到对生产影响的原因，进而通过一系列工艺调整达到国产氧化铝替代进口氧化铝后的生产正常平稳运行，获得良好的经济技术指标。     

复合溶胶凝胶法制备TiB2可湿性阴极涂层

针对铝工业阴极和阳极碳电极以及侧壁耐蚀导电二硼化钛陶瓷涂层技术,研究用非有机溶剂湿化学陶瓷清洁制造技术,替代沥青粘结工艺。通过氧化铝胶体中的纳米粒子,分散清洁二硼化钛,形成均匀陶瓷悬浮涂料,经刷涂或喷涂形成TiB2涂层。对二硼化钛与工业铝电解体系熔体、气相的化学侵蚀性进行了理论计算,分析了炭基TiB2涂层的耐蚀性、捕获钠的机理。用SEM分析了二硼化钛涂层断面,二硼化钛在氧化铝胶粒的分散下,迁移、渗入多孔的碳基底,在热处理条件下,与基底间形成很强的化学键合,可形成微米至数毫米厚、无龟裂的涂层。涂层的电性能检测结果表明,浆料中氧化铝胶体含量为 10%Wt时电阻率较低,电阻率随烧结温度升高而降低。     

氧化铝工业碳排放核算方法

氧化铝工业作为重要的原材料产业,其生产工艺主要为拜耳法、烧结法及拜耳—烧结联合法,工艺流程复杂,产业规模巨大,造成大量二氧化碳排放。分析了氧化铝工业碳排放核算现状,根据工艺生产过程中的具体物料衡算,以物料平衡核算法为主、排放因子核算法为辅,分别对拜耳法氧化铝生产工艺、烧结法氧化铝生产工艺,以及并联、串联、混联三种联合法氧化铝生产工艺进行了碳排放核算,明确了相关核算公式,并选取相关数据进行了实际核算。     

浅析影响管道化溶出器汽耗的因素及降低汽耗的措施

分析了低温拜耳法氧化铝生产工艺中的管道化溶出器汽耗的影响因素,通过计算得出理论汽耗,找出了实际汽耗与理论汽耗之间的差距。结合拜耳法氧化铝生产物料特性,针对影响汽耗的因素,利用自蒸发器孔板闪蒸新技术,进行多方位改造和余热回收利用,降低了溶出器的汽耗,有效降低了氧化铝生产成本。     

氧化铝种分过程的粒度分析

用粒数衡算的方法对氧化铝生产种分过程氢氧化铝粒度分布进行了分析,通过计算得到各种分槽产品氢氧化铝的晶体生长速率和净粒子生成数,由此推测了氧化铝实际生产过程中成核、生长、附聚过程发生的位置及生产条件。并分析了晶体生长速率与种分进行时间之间的关系。     

Design and Operation of Point-of-Use Treatment System for Arsenic Removal

A point-of-use (POU) system was designed and constructed using commercially available activated alumina to remove arsenic from drinking water. Testing with City of Albuquerque chlorinated tap water containing an average of 23 ug/L arsenic found that 1 L of adsorbent would provide water for direct consumption by a family of four for 435 days. It was estimated that the POU system constructed for this study could be sold for $162, and the arsenic adsorption columns were estimated to cost $4. A monthly cost to the customer of $10/month was estimated to purchase, install, and operate this POU system, assuming annual replacement of adsorption media cartridges. The implications of relying upon POU systems to comply with a new drinking water standard for arsenic are discussed.     

Effect of La2O3 on Microstructure and Transmittance of Transparent Alumina Ceramics

Optically transparent alumina ceramics were fabricated by conventional process and sintered without pressure in H2 atmosphere. The results indicate that relative densities of alumina specimens increase to theoretical densities （T. D. ） with increasing content of La2O3. With increasing holding time during sintering, much less pores and larger grains were found in the sintered alumina samples. Higher transmittance was achieved in alumina codoped with MgO and La2O3 as compared with that doped with MgO only. The total-transmittance of alumina sample is up to 86% at twavelength range of 300 - 800 nm.     

中水替代新水用于氧化铝生产的实践

氧化铝生产用水量大、对水质要求各不相同。生活污水经处理成为中水,具有水源可靠、成本低、距离用户近等优点。本文介绍了中水其替代新水用于氧化铝生产的具体做法和取得的效果。     

Modeling the Sorption of Fluoride onto Alumina

Fluoride is a potentially toxic ion that occurs in aquifers both naturally and as a result of anthropogenic activity. Sometimes remediation of the aquifer is required. One potential aquifer decontamination strategy is an “interception-sorption trench”—one of a number of “reactive wall” technologies. This remediation strategy relies upon natural hydraulic gradients to transport the fluoride through the aquifer to the interception-sorption trench where it partitions onto a strong sorbent—alumina. In this paper, the focus is on the development and calibration of an equilibrium-based geochemical model that will be employed in the development of a quantitative reactive transport model, which in turn will be used for the design of an interception-sorption trench. The geochemical model described here takes into account a variety of ions likely to be present in a sandy aquifer, chemical activities, and the surface charge on the alumina. The model is calibrated over a wide pH range and for high initial fluoride concentrations using experimental results obtained from batch tests. It is found that pH dependent equilibrium constants are needed to capture the behavior of the experimentally observed fluoride sorption. The presence of sodium sulfate in solution is investigated, and it is found that sodium significantly interferes with the sorption of fluoride onto alumina under alkaline conditions. The geochemical model indicates that under acidic conditions, the alumina may release potentially large and unacceptable concentrations of aluminum into the aquifer. As a way of managing this potential problem, it is proposed that aluminum concentrations in the pore fluid may be mitigated by the inclusion of tree bark within the interception-sorption trench.     

从赤泥中联合提取铁和氧化铝试验

 赤泥是从铝土矿中浸出氧化铝后产生的固态废渣,含有一定量的铁、氧化铝以及其他有价金属元素。为了综合回收赤泥中铁和氧化铝,开发了赤泥配碳制备成含碳球团,含碳球团直接还原-熔分生产金属铁,熔渣自粉化浸出氧化铝的方法。试验研究了不同工艺参数对赤泥中铁和氧化铝提取结果的影响,得到的最佳工艺条件为：碳氧比为1.8,还原温度为1 250 ℃,还原时间为60 min,熔分温度为1 500 ℃,熔分时间为20 min,熔渣冷却速度小于20 ℃/min,钙铝比为1.6。在最佳工艺参数下,得到的生铁磷、硫质量分数分别为0.047%和0.017%,熔渣中[w(FeO)]为1.26%,熔渣自粉化完全,自粉化渣中Al2O3浸出率可以达到86.65%。     

氰化堆淋法提金过程中汞的污染与治理的研究

本文研究了汞，金地球化学的相关性，考查了氰化堆淋法提金时尔的富集过程和机理，提出了综合综合治理汞毒污染的工艺及措施。     

拜尔液中草酸钠浓度调控的研究进展

在拜耳法生产氧化铝过程中,草酸钠对工业生产造成了极大影响。文章简单介绍了草酸钠的来源以及危害,主要概述了拜尔法生产氧化铝过程中草酸钠浓度调控的研究进展,包括在晶种分解过程中抑制草酸钠的析出以及在后续生产操作中促进草酸钠的析出,以期为工业生产提供一种低成本的解决方案。     

基于(火用)分析的氧化铝双流法溶出工序的节能

阐述了热分析和(火用)分析在氧化铝溶出工序节能降耗中的作用,建立了该工序的热分析和(火用)分析模型,并以此对某厂该工序进行热效率和朋效率的计算,分析了工艺参数对该工序(火用)效率的影响,指出了其节能降耗途径.