Laser-Induced Calcite—Aragonite Transition

High-pressure phases of CaCO₃, namely aragonite, calcite II, and possibly calcite III, were synthesized in air by exposing 10- to 20-μm-size particles of CaCO₃ (calcite I phase) to a CO₂ laser radiation at short pulse lengths (≤0.1 ms). The process, therefore, has the same effect as exposing the particles to at least several hundred megapascals pressure. Processing at higher pulse lengths resulted in the decomposition of CaCO₃ to CaO and CO₂. The extent of decomposition increased with increasing pulse length.     

淀粉类多糖在方解石和萤石表面吸附特性及作用机理

通过吸附试验，Ｘ－射线光电子能谱（ＸＰＳ）和俄歇电子能谱（ＡＥＳ）、浮选试验、系统地研究了糊精在萤石和方解石表面作用行为，结果发现，方解石经糊精作用前后ＣａＬＭＭ俄歇参数变化值为０．８０ｅＶ，变化显著，这说明糊精与方解石表面作用为化学键合；而萤石经糊精处理前后ＣａＬＭＭ俄歇参数变化值为－０．２０ｅＶ，变化不明显，说明糊精与萤石表面化学作用很弱，更接近物理作用－氢键作用；浮选试验结果证实了测试结果可     

Microhardness of rhombohedral crystals: Calcite and sodium nitrate

The variation of hardness of rhombohedral single crystals of calcite and sodium nitrate with quenching temperature is studied. Vickers and Knoop hardness numbers are determined from the indentations produced on freshly-cleaved crystal surfaces for various loads. The variation of hardness number with quenching temperature can be represented byHT _q ^k =constant where the exponentk is less than unity and its sign determines the nature of material.     

诱导结晶法回收磷的试验研究

以天然方解石为晶种通过诱导结晶法处理模拟含磷废水,考察了水力停留时间(HRT)、钙磷比(Ca/P)和PO43-浓度对诱导结晶除磷的影响.结果表明:HRT对诱导结晶除磷的影响最大,Ca/P值次之,PO43-浓度最小;对PO43-的平均去除率随HRT、Ca/P值和PO43-浓度的增大均有所提高;诱导结晶除磷的最佳HRT为10 min,HRT越长则出水PO43-浓度越低,但试验后期对磷的去除率增幅越来越小;最佳Ca/P值为3,适当增大Ca/P值有利于除磷,但投加的钙盐越多则越易形成均相沉淀,对磷的回收难度就越大;PO43-浓度越高则除磷越易实现,此时宜适当减小Ca/P值(投药量),反之则应适当增大Ca/P值(投药量).     

SHALLOW-MARINE MICROPOROUS CARBONATE RESERVOIR ROCKS IN THE MIDDLE EAST: RELATIONSHIP WITH SEAWATER Mg/Ca RATIO AND EUSTATIC SEA LEVEL

The formation of shallow-marine microporous carbonate reservoir rocks remains poorly understood in spite of their economic importance, particularly in the Middle East. In this paper, we investigate relationships between the stratigraphic occurrence of these carbonates in the Middle East and (i) the evolution of the Mg/Ca ratio in seawater; and (ii) cyclic variations in relative sea-level.
An inventory of carbonate formations in the Middle East was compiled for three geological time intervals characterised by different seawater chemistries: the Late Carboniferous to Triassic (aragonite seas); the Cretaceous (calcite seas); and the Cenozoic (transitional from calcite to aragonite seas). For each time interval, carbonate formations described as microporous have been listed.
During the Cretaceous calcite sea, eleven microporous carbonate formations were deposited in the Middle East. However, no microporous carbonates were formed during the Late Carboniferous to Triassic, a time of aragonite seas. During the Cenozoic, four of the five microporous carbonate formations recorded were deposited before the transition from calcite to aragonite seas. Thus, these shallow-marine microporous carbonates appear to have developed from precursor muds which were mainly composed of low-Mg calcite crystals. Moreover, during the Cretaceous and the Cenozoic, microporous carbonate formations in the Middle East were generally associated with major transgressions and highstands of relative sea level.
The relatively high stability of low-Mg calcite muds may explain why shallow-marine microporous carbonates formed during time intervals with calcite seas. In contrast to muds composed of aragonite or high-Mg calcite crystals, the original microfabric (including intercrystalline microporosity) of low-Mg calcite muds can partly survive moderate diagenesis.     

白钨矿与含钙脉石的浮选分离研究

对萤石、方解石和白钨矿进行了单矿物和实际矿石浮选试验,并通过红外光谱和Zeta电位研究了矿物与捕收剂TAB-3和调整剂水玻璃的作用机理。结果表明:用Na2CO3调介质pH为8~11时,有利于白钨矿与方解石的浮选分离;用NaOH调介质pH≥11时,有利于白钨矿与萤石的浮选分离。捕收剂TAB-3在白钨矿、萤石和方解石表面均发生化学吸附,但加入水玻璃后,捕收剂TAB-3在萤石和方解石表面的吸附减弱。因此,添加水玻璃有利于白钨矿与萤石的浮选分离,更有利于白钨矿与方解石的浮选分离。     

球形碳酸钙的控制合成研究

以硼酸为控制剂,氯化钙和碳酸钠为原料,采用共沉淀法制备了方解石型碳酸钙球形晶体。研究了控制剂浓度、反应温度、反应时间、反应物浓度等因素对碳酸钙粒径和形貌的影响。结果表明：在硼酸浓度为0.4 mol/L、氯化钙浓度为0.1 mol/L、20 ℃饱和碳酸钠溶液滴速为4.9 mL/min、反应时间为60 min、陈化时间为60 min、反应温度为50 ℃、氯化钙与碳酸钠物质的量比为1∶1条件下,制备的球形碳酸钙颗粒大小均匀,平均粒径为1.57 μm。     

Effect of calcite/activated carbon-based post-combustion CO2 capture system in a biodiesel-fueled CI engine—An experimental study

The present study aims to reduce carbon dioxide (CO₂) emission from a CI engine using calcite/activated carbon-based post-combustion CO₂ capture system fueled with Calophyllum inophyllum biodiesel (B100). The tests were conducted in a two-cylinder CI engine used in tractors at different load conditions. The performance and emission parameters of diesel and B100 with and without calcite and activated carbon-based CO₂ capture system were studied. The results show that compared to diesel, CO₂ emission increased by 19% for B100 due to high fuel-bound oxygen and carbon. Higher NO emission with a slightly reduced smoke opacity is observed with B100 combustion. CO₂ emission is reduced with the CO₂ capture system for both diesel and B100. CO₂ emission is reduced by 11.5% and 7.3% for diesel with calcite and activated carbon, respectively, and reduced by 15.8% and 10.5% for B100 with calcite and activated carbon. Due to the adsorption capacity of both calcite and activated carbon, NO and smoke opacity are reduced considerably. The results display that calcite is better in reducing CO₂ compared to activated carbon-based CO₂ capture system. It is perceived that the combination of biofuel and calcite-based CO₂ capture system can both reduce engine-out emissions and cause a net negative CO₂ emission as it is renewable aiding in mitigation of global warming effects.     

东营凹陷页岩油储层中方解石的成因及证据

为明确东营凹陷页岩中方解石矿物成因和储层成岩特征,利用薄片、X衍射、碳氧同位素等分析技术,首次发现了牛页1井页岩中方解石脉具有示顶底构造和机械双晶特征,是地质构造运动产生地应力作用于页岩方解石脉上留痕的直接岩石学证据,为页岩地层地应力的研究提供了载体矿物。通过对研究区页岩中泥晶方解石和亮晶方解石的碳氧同位素对比分析发现:页岩中泥晶方解石的形成主要隶属于与甲烷细菌活动生成生物气有关的碳酸盐,亮晶方解石脉极可能为泥晶方解石溶蚀后再沉淀重结晶的产物。生烃增压等作用形成微裂缝是方解石脉形成的先决条件,有机酸对泥晶方解石的溶蚀和再沉淀是必要条件。根据发现的4个岩石学特征和碳氧同位素证据,阐述了从生烃增压、微裂缝形成、有机质热演化排出有机酸、泥晶方解石被溶蚀、方解石重结晶,直至方解石脉形成的整个同生演化过程,并探讨了页岩与相邻砂岩的碳库来源和砂泥岩协同成岩演化过程。     

砂土内微生物诱导碳酸钙结晶的检测方法研究

为了寻找砂土中微生物诱导碳酸钙结晶(MICP)过程的无损检测方法,采用3种粒径的砂子和两种浓度的胶结溶液进行了砂土的胶结试验,检测了砂土流出液的流量、p H值、尿素浓度和Ca2+浓度等化学指标变化情况,并对碳酸钙晶体的生成数量和分布进行了分析。试验结果显示:砂土流出液的流量和Ca2+浓度能够预测MICP过程中碳酸钙晶体的生成数量,p H值和尿素浓度能够预测MICP过程中尿素的水解程度;砂土中碳酸钙晶体的生成数量与注入的Ca2+总量呈现线性增长的关系,其线性系数可以通过砂土的粒径和胶结溶液的浓度表示,胶结后砂柱的碳酸钙分布并不均匀,小粒径的砂柱上部碳酸钙含量较高,而大粒径的砂柱下部碳酸钙含量较高。