Use of digital image analysis combined with fractal theory to determine particle morphology and surface texture of quartz sands

The particle morphology and surface texture play a major role in influencing mechanical and hydraulic behaviors of sandy soils. This paper presents the use of digital image analysis combined with fractal theory as a tool to quantify the particle morphology and surface texture of two types of quartz sands widely used in the region of Vitória, Espírito Santo, southeast of Brazil. The two investigated sands are sampled from different locations. The purpose of this paper is to present a simple, straightforward,reliable and reproducible methodology that can identify representative sandy soil texture parameters.The test results of the soil samples of the two sands separated by sieving into six size fractions are presented and discussed. The main advantages of the adopted methodology are its simplicity, reliability of the results, and relatively low cost. The results show that sands from the coastal spit(BS) have a greater degree of roundness and a smoother surface texture than river sands(RS). The values obtained in the test are statistically analyzed, and again it is confirmed that the BS sand has a slightly greater degree of sphericity than that of the RS sand. Moreover, the RS sand with rough surface texture has larger specific surface area values than the similar BS sand, which agree with the obtained roughness fractal dimensions. The consistent experimental results demonstrate that image analysis combined with fractal theory is an accurate and efficient method to quantify the differences in particle morphology and surface texture of quartz sands.

A Study of the Adsorption of Molecular Deposition Filming Flooding Agent MD-1 on Quartz Sand

Molecular deposition filming flooding (MDFF) is a novel oil recovery technique based on the thermopositive monolayer electrostatic adsorption of the MDFF agent on different interfaces within reservoir systems. In this paper, the adsorption property of the MDFF agent, MD-1, on quartz sand has been studied through adsorption experiments at different pH and temperatures. Experimental data are also analyzed kinetically and thermodynamically. The results show that the adsorption of MD-1 on quartz sand takes place mainly because of electrostatic interactions, which corresponds to adsorption that increases with pH. Kinetic analyses show that at a higher pH the activation energy for adsorption gets lower and, therefore, the adsorption becomes quicker for MD-1 on quartz sand. Thermodynamic analyses show that pH plays an important role in the adsorption of MD-1 on quartz sand. At a higher pH, more negative surface charges result in the increase of electrostatic interactions between MD-1 and quartz sand. Therefore, the saturated adsorption amount increases and more adsorption heat will be released.

S. E. M. analysis of quartz sand grains from selected Hong Kong and Chinese littoral environments

This pilot study attempts to demonstrate some underlying scanning electron microscopy themes of quartz grain surface textures. A variety of textural patterns and individual features are described for grains selected from various littoral environments. An attempt was made to differentiate samples on surface textures alone, but limitations of using this technique in sedimentological isolation were apparent. Statistical analysis of checklist data and photographic evidence revealed some of the more important feature combinations used in environmental diagnosis. The use of discriminant analysis provided quantitative sample separation.

Adsorption and Transport of Ciprofloxacin in Quartz Sand at Different pH and Ionic Strength

Effects of pH and ionic strength on ciprofloxacin adsorption in quartz sand were studied through a batch equilibrium adsorption experiment in this paper. The experimental data were fitted by empirical formulas from Langmuir and Freundlich adsorption isothermal curves, and the transport experiments in quartz sand at different pH and ionic strength were conducted to investigate the transport characteristics of ciprofloxacin. It was found that with the increase of pH value or ionic strength, adsorption capacity of ciprofloxacin decreased, so that it could move easier. The results indicated that low pH or ionic strength was conductive to the adsorption of ciprofloxacin in quartz sand. Meanwhile, a higher initial concentration or stronger ionic strength could result in a smaller linear distribution coefficient of ciprofloxacin, which meant a low adsorption capacity. According to the fitting results, the adsorption of ciprofloxacin in quartz sand could be described well by both Langmuir and Freundlich equations, of which Freundlich equation had a better efficacy.

Double Acid-Base Extraction of Silicic Acid from Quartz Sand

Silica is becoming more attractive as plant nutrient for non-graminae crops particularly in relation with drought-stress tolerant. Many efforts have been conducted to obtain an efficient technique to produce silica fertilizer worldwide, but the results are varying considerably due to various factors including raw material and extraction technique. This study was carried out to develop an efficient extraction technique for ortho-silicic acid (OSA-H4SiO4) from a Bangka-Belitung quartz sand by employing acid-base dissolution method. A 325-mesh size quartz sand was boiled in HCl solution at various concentrations. The optimum concentration was then used in the following experiment at several different volumes of solution. The sand obtained from optimum concentration and volume of HCl solution was then reacted with different amounts of NaOH (s), and heated until a wet mixture was obtained. As a reference the best extraction conditions were applied to a natural zeolite sample. All OSA analyses were done in triplicates with spectrophotometric method. Supporting evidences were collected from x-ray diffraction and scanning-electron-microscopy analyses of the treated samples. The yield of quartz sand-originated OSA was 183 g·kg-1 and significantly increased linearly with increasing weight of NaOH (R2 = 0.99**), whereas that from zeolite was only 104.2 g·kg-1 at 80 g NaOH. XRD and SEM data confirmed the evidences that the acid-base extraction disrupted the quartz mineral structure and as a consequence releasing more water soluble OSA.

Removal from Water and Adsorption onto Natural Quartz Sand of Hydroquinone

Hydroquinone (HQ) is the most important hydroxy aromatic compound which is produced on a large scale. Understanding its fate in the environment is therefore of primary importance to prevent its migration in the soil and/or the contamination of the aquatic ecosystems. Here we present a column based method to investigate the physicochemical processes controlling the removal from the aqueous phase and the adsorption onto natural quartz sand (NQS), of organic pollutant such as HQ molecules. We will focus on the interactions that occur between the organic pollutant and the NQS substrate. Thus, column reactors filled with NQS were used to investigate the influence of physicochemical parameters such as the ionic strength, the pH, the flow rate, and the nature of the electrolyte cation, on the HQ adsorption from water onto NQS substrate. The data indicate that, when divalent instead of monovalent cations, are present in the effluent water injection phase, and/or when the ionic strength of the effluent increases, the adsorbed HQ amount decreases. Similar decrease of the adsorbed HQ amount was also observed, at constant ionic strength, by increasing either, the pH from 3 to 9, the flow rate Q from 1 to 3 ml·mn-1, or by decreasing the HQ initial concentration, C0 from 30 to 6 mg·L-1. Further, large amount of the organic pollutant (up to 93 wt% of HQ molecules) was removed from the effluent water phase by using NQS column. The overall data seem to indicate that the adsorption of HQ molecules on the NQS surface is mainly controlled by electrostatic interaction forces occurring between the organic molecule polar groups and the inorganic matrix silanol groups.

Comparison of quartz sand, anthracite, shale and biological ceramsite for adsorptive removal of phosphorus from aqueous solution

The choice of substrates with high phosphorus adsorption capacity is vital for sustainable phosphorus removal from waste water in constructed wetlands. In this study, four substrates were used： quartz sand, anthracite, shale and biological ceramsite. These substrate samples were characterized by X- ray diffractometry and scanning electron microscopy studies for their mineral components （chemical components） and surface characteristics. The dynamic experimental results revealed the following ranking order for total phosphorus （TP） removal efficiency： anthracite 〉 biological ceramsite 〉 shale 〉 quartz sand. The adsorptive removal capacities for TP using anthracite, biological ceramsite, shale and quartz sand were 85.87, 81.44, 59.65, and 55.98 mg/kg, respectively. Phosphorus desorption was also studied to analyze the substrates＇ adsorption efficiency in wastewater treatment as well as the substrates＇ ability to be reused for treatment. It was noted that the removal performance for the different forms of phosphorus was dependent on the nature of the substrate and the adsorption mechanism. A comparative analysis showed that the removal of particulate phosphorus was much easier using shale. Whereas anthracite had the highest soluble reactive phosphorus （SRP） adsorptive capacity, biological ceramsite had the highest dissolved organic phosphorus （DOP） removal capacity. Phosphorus removal by shale and biological ceramsite was mainly through chemical adsorption, precipitation or biological adsorption. On the other hand, phosphorus removal through physical adsorption （electrostatic attraction or ion exchange） was dominant in anthracite and quartz sand.

Experimental investigation in the permeability of methane hydratebearing fine quartz sands

The permeability is one of the intrinsic parameters that determines the fluid flow in the porous media.The permeability in hydrate-bearing sediments affects the gas recovery and production of hydrate reservoirs significantly.The irregular permeability characteristics are challenging for fine-grained hydratebearing sediments.In this study,a series of experiments was conducted using an one-dimensional pressure vessel to investigate the hydrate formation characteristics and the permeability in hydratebearing fine quartz sands(volume weighted mean diameter was 36.695 mm).Hydrate saturations(0 e26%in volume)were controlled and calculated precisely based on the amount of injected water and gas,the system pressure and temperature.The results indicated that the hydrate nucleation induction period was completed during gas injection,and the average time of hydrate formation was within 500 min.The permeability of methane hydrate-bearing fine quartz sands was investigated by steady gas volume flow.For hydrate saturation lower than 13.94%,the hydrate mostly formed in grain-coating,the permeability reduction exponent calculated by Parallel Capillary,Kozeny Grain Coats and Simple Cubic Filling models were 2.00,2.10 and 1.74 respectively,and Simple Cubic Filling model was in accordance with the experimental data best.However,for hydrate saturation ranged from 13.94%to 25.91%,the permeability increased due to the flocculation structure formation of fine quartz sands and hydrate,which caused the increase of effective porosity.A new relationship among hydrate saturations,effective porosity,the ratio of permeability in the presence and the absence of hydrate was developed.This study developed the mathematical models for predicting the permeability with hydrate saturation in fine quartz sands,which could be valuable for understanding the characteristics of hydrate-bearing finegrained sediments.

Sliding friction of shale rock on dry quartz sand particles

The sliding friction of rock, involving all kinds of particles at the contact surface, is relevant to many problems, ranging from those in artificial engineering to earthquake dynamics. In this work, the frictional performance of the shale rock–dry quartz sand contact was investigated using a self-developed testing device. The study showed that the coefficient of friction of the contact increases with nominal stress and that the corresponding friction force increases approximately linearly with nominal stress, which is directly related to the contact stress between each single sand particle and rock shale. An overall dynamic coefficient, γ, reflecting the response of friction force to nominal stress, first decreases and then increases with area ratio, which is determined by not only the contact stress but also the interparticle friction force. These have important repercussions for a preliminary understanding of the frictional properties of the shale rock–dry quartz sand contact in hydraulic fracturing and related industrial applications.

β-FeOOH/SiO_(2)复合非均相Fenton催化剂制备及对甲基橙溶液的降解

采用简单、环保的方法合成β-FeOOH/SiO_(2)复合非均相Fenton催化剂,采用红外光谱仪(FT-IR)、X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)、透射电子显微镜(TEM)对催化剂进行表征分析,考察质量比、合成温度和合成时间对催化剂催化活性的影响,通过分析催化剂类型、用量及双氧水用量,探究β-FeOOH/SiO_(2)复合催化剂处理染料废水的最佳工艺条件。结果表明:β-FeOOH/SiO_(2)复合催化剂制备工艺简单,操作条件温和,易于工业化生产;β-FeOOH/SiO_(2)复合催化剂在满足m(β-FeOOH)/m(SiO_(2))=1∶1,反应温度为90℃,反应时间为8 h时,具有最佳的催化活性;在30℃条件下,β-FeOOH/SiO_(2)的加入量为5 g/L,过氧化氢的加入量为0.1 L/L时,200 mg/L甲基橙染料废水的去除率最大,达到98.85%,对亚甲基蓝和罗丹明B的去除率分别达到90.44%和99.25%;β-FeOOH/SiO_(2)复合催化剂对染料废水具有良好的降解效果。

西山煤田煤层气井水力压裂效果剖析及启示

水力压裂是改善煤层渗透率的常用方法,其改造效果直接影响煤层气井的产能。详细观测了西山煤田屯兰区块5口煤层气井的井下揭露煤层及裂隙展布情况,并联合体视镜、扫描电镜和显微CT等研究煤体结构、微裂隙、石英砂和煤粉的分布特征,结合区域地应力和水力压裂施工参数,剖析煤层气井的压裂效果。研究结果表明:水力压裂产生的宏观裂隙形态复杂多样,包含水平型、垂直型、X型和T型。距离煤层气井筒越近,煤体越破碎,以碎裂煤和碎粒煤为主,水力压裂裂隙发育,远离煤层气井筒的煤体主要是原生结构煤,以原生裂隙为主。石英砂主要铺置在水平裂隙内,仅有少量分布在T型裂隙内。石英砂与煤的裂隙面强烈摩擦、碰撞和嵌入,与压裂液破裂煤体叠加形成大量煤粉,造成煤粉裹挟石英砂堵塞裂隙。宏观裂隙内的煤粉主要受水力压裂时煤体破裂、压裂液冲刷煤体及石英砂与裂隙面摩擦而产生,微观裂隙内的煤粉在煤体破断时产生。煤粉与石英砂混合堆积在裂隙内,对携砂液产生巨大阻力,造成石英砂无法向煤层气井的远端运移。地应力的大小和方向、煤层及顶底板的强度是影响水力压裂裂隙张开与延展方向的重要因素,携砂液黏度低无法悬浮石英砂,容易造成石英砂与煤粉聚集堵塞裂隙。

砂颗粒矿物成分对MICP过程的影响及机理

微生物诱导碳酸钙沉淀(MICP)是一种绿色环保的新型土体加固技术,具有广泛的应用前景。为了研究砂颗粒矿物成分对MICP过程的影响,分别选用石英砂和钙质砂为代表性研究对象,利用环氧树脂胶结固化后打磨制成样片,再在配置好的菌液和胶结液中对样片表面进行MICP处理,结合X射线衍射(XRD)、扫描电镜(SEM)以及超声震荡试验定量分析了碳酸钙产量、矿物晶型、晶貌及界面胶结特性。结果表明:(1)钙质砂颗粒比石英砂颗粒更利于微生物诱导生成碳酸钙,平均单位面积碳酸钙生成量前者约为后者的5倍;(2)两种砂颗粒表面生成的碳酸钙主要为球霰石和方解石,钙质砂界面能更低,诱导生成更多的方解石;(3)石英砂表面生成的碳酸钙主要为较大的球形颗粒,而钙质砂表面的碳酸钙形貌主要为板片状;(4)微生物在钙质砂颗粒上诱导生成的碳酸钙呈现更高的界面胶结强度,经超声波震荡后,石英砂颗粒上碳酸钙的质量损失率约为钙质砂的10倍。在此基础上,运用微生物学、晶体化学、结晶矿物学等其他相关学科的理论,系统分析了石英砂和钙质砂对MICP过程及效果的影响机理,取得了新的认识,对优化MICP技术在岩土工程中的应用有重要意义。

一步水热改性石英砂支撑剂及性能研究

为提高石英砂在压裂液中的分散稳定性,采用十六烷基三甲基氯化铵(CTAC)对传统石英砂表面进行改性。结果表明,CTAC质量分数为0.6%,在80℃中性条件下与石英砂反应120 min,可以使石英砂的沉降速度降低44.85%。改性前后石英砂与水的接触角由28.233°增至87.853°,表明石英砂表面的疏水性有大幅度改善,石英砂颗粒与水分子之间的排斥力增大。表面自由能由83.342 mJ/m^(2)降至22.379 mJ/m^(2),表面自由能降低使系统更加稳定,从能量的角度解释了改性后石英砂沉降速度降低的原因。改性后石英砂的zeta电位是改性前的2倍,石英砂颗粒之间的静电斥力明显增大,从而使颗粒之间不容易聚沉,体系更加稳定。

低品位脉石英热压浸出工艺动力学研究

为解决低品位脉石英中杂质元素含量高的问题,采用湖北蕲春灵虬山脉石英为原料,研究了液固比、反应时间和反应温度对杂质去除效果的影响。结果表明,经过热压浸出工艺提纯后,石英砂SiO_(2)含量(质量分数,下同)由97.766%增至99.974%,主要金属元素杂质的去除率显著提高。阿弗拉米动力模型表明,杂质去除过程受内扩散和化学反应共同控制。研究结果为优化脉石英的提纯工艺提供了理论依据和实践指导。

页岩气井用石英砂的耐老化机理研究

石英砂是非常规气体开采中非常实用的一种基础材料,在地层水模拟石英砂服役过程中,发现其破碎率下降。选用两种规格的石英砂在地层水中恒温浸泡不同时间,通过对浸泡前后的石英砂进行XRF、XRD、SEM、EDS、XPS、FT-IR等表征,探索石英砂的耐老化机理。XRF结果表明石英砂浸泡后ClO_(2)含量增加,XRD结果出现了SiCl_(4)和钙长石新峰,XPS结果出现了Cl2p和Ca 2p峰。这些结果揭示出地层水中的Cl-离子进入石英砂间隙中,与SiO_(2)反应生成SiCl_(4),从而生成硅酸凝胶,包覆在石英砂表面,阻断了石英砂与水的接触,加上石英砂表面附着有生成的钙长石,增加了石英砂的强度,从而提高了石英砂的抗破碎能力。

钢纤维-海泡石纤维优化铁尾矿砂-石英砂混合砂浆性能试验研究

为了在保证经济性的同时改善铁尾矿砂-石英砂混合砂浆的性能,选用钢纤维、海泡石纤维优化混合砂浆,研究了钢纤维、海泡石纤维单掺和以不同比例混掺对混合砂浆工作性能、力学性能和自然干燥收缩率的影响。结果表明,在单掺情况下,海泡石纤维对流动性的负面影响高于钢纤维,两种纤维分别以合适掺量掺入混合砂浆中,钢纤维对抗折强度和28 d自然干燥收缩率的改善效果优于海泡石纤维,而海泡石纤维对抗压强度的改善效果更佳;钢纤维-海泡石纤维以0.50%-1.0%和0.75%-1.0%组合混掺对矿浆力学性能和干燥收缩改善效果最佳。从性能改善效果和经济性角度综合考虑,确定了最优纤维掺量组合,即钢纤维、海泡石纤维掺量分别为0.50%、1.0%。在此掺量组合下,混合砂浆3 d、7 d和28 d抗折强度分别提升了15.8%、13.0%和12.5%,混合砂浆3 d、7 d和28 d抗压强度分别提升了16.2%、14.7%和13.9%,28 d自然干燥收缩率降低了32.8%,且经济性良好,每吨混合砂浆仅增加28.8元左右的成本。

湖北省恩施某光伏玻璃用石英砂提纯制备实验

这是一篇关于矿物加工工程领域的文章。光伏玻璃用石英砂是支撑新能源行业发展必不可少的原料之一,其供应安全保障事关我国双碳政策的成功实施。本文以湖北省恩施州某大型石英砂矿为研究对象,开展了工艺矿物学与除杂提纯实验研究,发现该石英砂矿的主要杂质为斜长石、云母、褐铁矿和金红石,采用了“分级-重选-磁选-酸浸”选矿工艺流程,最终获得符合粒度要求(0.106~0.500 mm)的石英砂精矿产率为67.61%,其SiO_(2)含量由97.36%提高至99.79%,有害元素Fe_(2)O_(3)、TiO_(2)与Al_(2)O_(3)含量则分别降低至75、80、630 g/t,石英精矿产品各项指标达到了光伏玻璃用硅质原料的生产要求,实现了该石英砂矿的有效利用。

典型光伏坩埚用高纯石英砂工艺属性对比研究

以美国矽比科公司、挪威TQC公司和中国江苏太平洋石英股份有限公司生产的3种坩埚用高纯石英砂为研究对象,通过激光粒度分析、光学显微镜、扫描电镜、X射线衍射等分析测试手段,对3种坩埚用高纯石英砂的粒度分布、微观形貌、化学成分、晶胞参数等特征进行分析。结果表明,美国矽比科公司和挪威TQC公司生产的坩埚用高纯石英砂粒度集中在200μm左右,形状和尺寸均匀程度均优于中国江苏太平洋石英股份有限公司生产的石英砂;3个样品均存在包裹体和个别元素含量略高情况,但不影响石英坩埚生产;石英砂化学元素含量会影响晶胞参数的变化,3个样品a值均偏小,中国江苏太平洋石英股份有限公司石英砂样品c值偏大;结合不同浸出介质石英砂微观形貌对比分析,3个石英样品均经过高温煅烧处理及氢氟酸酸浸处理,挪威TQC公司生产的坩埚用高纯石英砂中还存在硝酸酸浸的痕迹。

复合改性砂滤料制备及生物砂滤池对受污染原水的净化效果

为改善普通石英砂(QS)表面特性,提高生物砂滤池生物附着量及对水中污染物的去除效果,对QS进行氨基、铝离子及铝钙双氢氧化物改性,制得氨基改性砂(AMS)、铝离子改性砂(ALS)和铝钙双氢氧化物改性砂(CAS),以四种滤料填充滤池考察对受污染原水的净化效果。结果表明,与QS相比,ALS与CAS表面覆盖了金属离子,AMS、ALS、CAS表面形态及比表面积均得到改善,成膜后表面生物附着量分别增加3.6、5.5、6.9 mg/g;滤速为5 m/h时,CAS滤池对浊度和COD平均去除率分别为90.1%、51.8%。与AMS、ALS滤池相比,CAS滤池表面生物量最大,对水中污染物去除效果良好。