Effect of slurry conditioning on flocculant-aided filtration of coal tailings studied by low-field nuclear magnetic resonance and X-ray micro-tomography

The present work aimed to study the effect of slurry conditioning on flocculant-aided filtration of coal tailings by the analysis of filtration kinetics and filter cake structure.Laboratory filtration tests of the coal tailings showed that both the shear rate and agitation time have significant effects on filtration rate and cake moisture.Moderate agitation at the shear rate of 92 s^-1 was favorable for fast filtration,but high cake moisture was encountered.The low-field 1H nuclear magnetic resonance(NMR)measurements of the filter cake showed that the slurry conditioning has a significant effect on the residual water in large pores and a negligible effect on the residual water in small pores.The X-ray micro-tomography(XRM)measurements indicated that the filter cake formed at the shear rate of 92 s^-1 has more macro-pores and higher porosity than that formed at the shear rate of 53 s1,hence more residual water was entrapped in filter cake.The slurry conditioning in the presence of flocculant will change the structure of filter cake and affect the filtration performance.There was a paradox between fast filtration rate and low filter cake moisture.The findings enable better understanding of the effect of slurry conditioning on flocculant-aided filtration of coal tailings.

Performance investigation of Fe_3O_4 blended poly(vinylidene fluoride) membrane on filtration and benzyl alcohol oxidation:Evaluation of sufficiency for catalytic reactors

Fe_3O_4-PVDF membranes were prepared by blending of magnetic Fe_3O_4 powders with polyvinylidene fluoride to investigate whether those were usable or not in catalytic membrane reactors. Filtration performances and catalytic activity of membranes in microwave conditions were measured in separate processes. Composite Fe_3O_4-PVDF membranes were characterized by TG-DTA, FTIR, XRD, SEM and contact angle techniques.Disappearing of α-phases at PVDF was observed with increasing amount of additives from XRD diffraction patterns. Decomposition of polymer fastened due to catalytic effect of Fe_3O_4. Finger-like structures and large number of small pores were observed at the SEM images. Those provided effective transportation of substrate among the active sites of catalyst. At the experiments conducted in batch reactor, 51%, 77%, 66% and 63% benzyl alcohol conversion were recorded for 2%, 4%, 6% and 8% Fe_3O_4-PVDF composite pieces respectively. Catalyst were separated magnetically and reused several times. On the other hand Fe_3O_4 blended PVDF membranes provided improved flux and BSA rejection compared with performance of bare PVDF membrane; 41.6% BSA rejection was obtained with 4% Fe_3O_4-PVDF whereas it was only 6.7% for PVDF. Fe_3O_4-PVDF composites performed high activity for the benzyl alcohol oxidation in batch reactor and also better filtration at filtration cell. These results promise to obtain practical and low cost membrane material for catalytic reactors usable in microwave support to get fast results.

Study on Optimizing High-Gradient Magnetic Separation—Part 2: Experimental Evaluation of the Performance of a New Designed Magnetic Filter

The introduction of functionalized magnetizable particles and high-gradient magnetic separation represents a time and money saving alternative to conventional purification and separation unit operations in the biotechnical sector. This technique has some advantages especially for the recycling of immobilized enzymes. A new magnetic filter with sight glasses was constructed and produced to study the performance of high-gradient magnetic separation at varied parameters. By optical analysis the buildup of a clogging was identified as the major parameter which affected the separation performance. For the cleaning procedure, a two-phase flow of water with highly dispersed air bubbles was tested which led to a nearly complete cleaning of the filter chamber.

Study on Optimizing High-Gradient Magnetic Separation—Part 1: Improvement of Magnetic Particle Retention Based on CFD Simulations

The introduction of functionalized magnetizable particles for the purification of enzymes or for the multi-use of pre-immobilized biocatalysts offers a great potential for time and cost savings in biotechnological process design. The selective separation of the magnetizable particles is performed for example by a high-gradient magnetic separator. In this study FEM and CFD simulations of the magnetic field and the fluid flow field within a filter chamber of a magnetic separator were carried out, to find an optimal separator design. The motion of virtual magnetizable particles was calculated with a one-way coupled Lagrangian approach in order to test many geometric and parametric variations in reduced time. It was found that a flow homogenisator smoothed the fluid flow, so that the linear velocity became nearly equal over the cross section in the direction of flow. Furthermore the retention of magnetizable particles increases with a high total edge length within the filter matrix.

2型糖尿病患者肾功能损伤及氧合水平的BOLD MRI分析

目的 探讨采用血氧水平依赖磁共振成像(BOLD MRI)技术分析2型糖尿病(diabetes mellitus type2,T2DM)患者的估算肾小球滤过率(estimated glomerular filtration rate,eGFR)不同水平的肾缺氧改变。方法 选取T2DM患者以及同期健康正常者共78例,其中64例T2DM患者作为T2DM组,14例同期健康正常者作为对照组,均进行BOLD MRI检查。根据eGFR将64例T2DM患者又分为eGFR正常组(A组)、轻度功能损害组(B组)、中重度肾功能损害组(C组),测定肾脏髓质、皮质R2*(MR2*、CR2*)。采用单因素方差分析数据MR2*、CR2*的组间差异及其与eGFR的相关性,并采用受试者工作特征曲线(receiver operating characteristic cure, ROC)分析MR2*、CR2*值的诊断效能。结果 与对照组相比,A、B、C组MR2*、CR2*值均显著升高,差异有统计学意义(P均<0.05),均与eGFR呈正相关(P均<0.05),均可鉴别T2DM组与对照组,但MR2*值的鉴别敏感度稍高。结论 BOLD MRI可无创评估T2DM患者早期肾脏功能性缺氧改变,监测eGFR不同阶段的肾脏氧合水平,对临床治疗具有指导意义。

非对比增强磁共振血管成像联合肾动态显像对动脉粥样硬化性肾动脉狭窄的诊断价值

目的:探讨非对比增强磁共振血管成像(NCE-MRA)联合肾动态显像对动脉粥样硬化性肾动脉狭窄(ARAS)的诊断价值。方法:选择2019年1月至2023年1月于河南省人民医院行肾动脉数字减影血管造影(DSA)的172例患者,按肾动脉DSA结果分为ARAS组(n=107)和非ARAS组(n=65)。比较两组患者的临床特征,分析NCE-MRA对ARAS的诊断价值,以肾动态显像测得的两侧GFR差值及比值单独或联合NCE-MRA诊断结果绘制受试者工作特征(ROC)曲线,评估对ARAS的诊断价值。结果:NCE-MRA与肾动脉DSA诊断ARAS的一致性较好(Kappa=0.828,P<0.001),NCE-MRA诊断ARAS的敏感度、特异度、准确性、阳性预测值(PPV)和阴性预测值(NPV)分别为92.52%,90.77%、91.86%、94.29%、88.06%;双肾GFR比值及差值用于诊断ARAS的AUC为0.771和0.708,最佳诊断界值为1.371和13.900 mL/(min·1.73 m^(2)),敏感度为52.3%和45.8%,特异度为90.8%和89.2%;GFR比值及差值联合NCE-MRA诊断ARAS的AUC分别为0.948和0.942,敏感度为95.3%和94.4%,特异度均为89.2%。结论:NCE-MRA对ARAS具有较高的诊断效能,联合肾动态显像可提高对ARAS的诊断价值。

应用功能磁共振成像判断急性肾损伤患者肾脏慢性病变及预测肾功能转归

目的:探索功能磁共振(fMRI)在评估急性肾损伤(AKI)患者是否存在慢性基础肾脏病变及肾功能预后转归中的价值。方法:回顾性分析国家肾脏疾病临床医学研究中心诊断为AKI并同时行fMRI检查及肾活检的13例患者资料。收集患者常规病理数据(包括免疫荧光、光镜、电镜)以及病理诊断,统计患者fMRI中体素内不相干运动成像的标准表观弥散系数参数值(IVIM Standard-ADC)和磁共振弹性成像(MRE)的弹性参数值,估算的肾小球滤过率(eGFR)在基线和12月内的随访数据,分析IVIM Standard-ADC和弹性参数值与随访期间eGFR变化斜率之间的关系。结果:13例AKI患者中男性8例、女性5例,中位年龄33(21~44)岁。平均基线eGFR为31(16.5~43.5)mL/(min·1.73 m^(2)),随访中平均年eGFR变化斜率为12.29(4.42~25.66)。经肾活检病理证实,7例存在基础慢性病变,6例为单纯AKI。12月随访中eGFR变化斜率与IVIM Standard-ADC及45 Hz条件下的弹性值均无明显相关关系,但与60 Hz条件下的弹性值呈显著正相关(rs=0.709,P=0.022),进一步将两者作回归分析可得出60 Hz条件下的弹性值可作为随访12月eGFR变化斜率的预测因素(r^(2)=0.456,P=0.032)。45 Hz条件下的弹性值也得到同样类似的结果,可作为随访12月eGFR变化斜率的预测因素(r^(2)=0.440,P=0.036)。即MRE可相对区分肾脏损伤程度及不同的eGFR恢复斜率。结论:MRE可作为一种新的方法预测AKI患者肾功能预后情况。相比于单纯AKI患者,AKI合并CKD患者的肾功能难以完全恢复正常,二者基线弹性值有显著差别。

Magnetic filtration with magnetized granular beds:Basic principles and filter performance

This study is devoted to the explanation of different characteristics of magnetic filtration and the way these characteristics affect the important filtration parameters. Magnetic fields in pores and the force effect of these fields on magnetic particles and the magnetization properties of packed beds composed of ferromagnetic spheres and metal chips are evaluated. The profile of accumulation and capture regions of the particles, the variation of the fluid velocity in these regions and analytic expressions of particle capture radius are presented. The effects of filtration regime parameters on magnetic filter performance were investigated. An analytical expression has been obtained for the dependence of the logarithmic efficiency coefficient on filtration velocity, the geometry of filter elements, the particle size and other parameters of filtration. The stationary and non-stationary equations of the magnetic filtration processes are given. An expression of magnetic filter performance is shown with dimensionless parameters obtained from the filtration system. These relations are useful for calculations in engineering practice, including the design of magnetic filters, provision of suggestions on construction, and optimization and control of filter operation.

Magnetic filtration of an iron oxide aerosol by means of magnetizable grates

The cleaning of gases with low concentrations of small ferromagnetic or paramagnetic particles is a difficult task for conventional filtration. A new alternative procedure, magnetic filtration, is used in this work. Iron oxide aerosol was generated by elutriation of iron oxide particles from a fluidized bed consisting of a mixture of Geldart-C iron oxide powder and large spherical Geldart-B sand particles. The aerosol was filtered by means of a magnetic filter which consisted of one, two or three iron grates staggered to each other. The experimental installation contained also an isokinetic sampling system and a Microtrac SRA 150 Particle Analyser. A theoretical expression for filtration efficiency was deduced from a previous model taking into account the different forces acting on the iron oxide particles. Experimental filtration efficiency matches quite well calculated theoretical efficiency. It was found that an increase in particle size, in thee number of grates or in the applied magnetic field produced higher filtration efficiencies up to 100% in some cases. In all filtration experiments pressure drop through the magnetic filter was very small.

聚乳酸/磁性金属有机框架材料复合熔喷布的制备及其空气过滤性能

为制备一种磁性生物可降解空气过滤用熔喷布,将用水热法合成的磁性金属有机框架材料(MMOF)与聚乳酸(PLA)熔融共混后,再通过熔喷加工工艺制成不同质量比的PLA/MMOF复合熔喷布,对其形貌、结构和性能进行研究。结果表明:随着MMOF质量占比的增加,复合熔喷布中纤维的表面粗糙程度增加,平均直径和孔径也不断增大;当MMOF的含量较高时,复合熔喷布的玻璃化转变温度有所增加,其结晶温度和熔融温度随着MMOF质量占比的增加而升高,加入适量的MMOF对PLA的结晶有异相成核作用,且赋予了PLA/MMOF复合熔喷布磁性;与纯PLA熔喷布相比,PLA/MMOF复合熔喷布的透气率提高,过滤阻力降低,当PLA与MMOF的质量比为1∶0.03时,复合熔喷布的空气过滤效率和断裂强度均达到最大,分别为65.03%和0.21 MPa。

水源性致病微生物检测中水样前处理方法研究进展

水中的微生物水平(细菌、病毒、原虫等)是衡量水质安全的重要指标,水源性致病微生物通过饮水和直接接触等途径感染人体,存在传播各类疾病的风险,关乎人群生命健康。由于致病微生物在环境水体中通常以较低浓度存在,在检测过程中均需先对水样进行前处理将其浓缩成较小的体积。文中介绍了可用于水体中致病微生物富集浓缩的富集培养、离心、过滤和磁性分离等前处理方法的研究进展,讨论了不同前处理方法的优缺点和适用范围,以实现水体中致病微生物的准确检测,真实反映致病微生物在水体中的赋存状况,为水体中致病微生物分析检测和风险控制提供技术支撑。如离心和过滤适用范围广泛,适用于水源性致病微生物的非特异性富集,富集培养和磁性分离特异性较强,更适用于水源性致病微生物的特异性富集。

磁场驱动用螺旋碳纳米线截断筛选及磁性修饰

为实现螺旋碳纳米线新型微纳米机器人磁场驱动运动,开展了螺旋碳纳米线截断、磁性修饰及磁场驱动运动研究。提出硝酸氧化-超声振动-滤纸过滤的长度截断筛选方法,实现了螺旋碳纳米线分散且可控截取长度2~8μm。实验对比研究了磁控溅射镍、化学镀镍、水热法生长Fe_(3)O_(4)纳米颗粒的磁性修饰方法。通过扫描电子显微镜、能量色散X射线谱分析等方法对修饰效果进行了评价,获得了具有较强磁性的螺旋碳纳米线。微流道液体中磁场驱动特性实验表明:磁控溅射修饰的螺旋碳纳米线可实现较为快速(3.35μm/s)的微纳米机器人运动特性,轨迹运动精度可控小于5μm。

表面改性磁种-磁滤技术处理含油废水的研究

将表面改性后的磁粉、磁性颗粒分别作为磁种和磁滤材料,以出水含油量、除油率为试验指标,采用磁种-磁滤技术处理江苏油田废水。试验结果表明,经改性后的Fe3O4磁种粒度小、比表面积大,与油滴的吸附亲和力增强,且包覆在Fe3O4表面的偶联剂能阻止Fe3O4微粒聚结,减缓沉降速度,从而提高除油效果。当进水含油量为140.3mg/L,磁种投加量300mg/L、搅拌强度250r/min、搅拌时间20min、磁滤速度25m/h、磁感应强度0.0839T时,出水含油量降为19.8mg/L,除油率达85.9%。

准噶尔盆地基底构造分区的重磁异常分析

利用准噶尔盆地及周边地区1∶200000重磁异常,采取多种处理与分析方法,在准噶尔盆地内共确定主要断裂48条,其中一级断裂7条、二级断裂6条、三级断裂35条。尤其是通过详细的资料处理,并结合盆地盖层沉积特点确定了基底南北、东西向断裂F6、F1的存在。研究认为,准噶尔盆地可划分为Ⅰ(南部)、Ⅱ(中部)、Ⅲ(北部)3个一级构造区,其中Ⅱ(中部)构造区可进一步划分为4个亚区并构成盆地内部的4个象限,而其中的每个象限又可划分出若干个次一级的构造单元。这4个象限的结构、密度分布、磁化强度各不相同,形成空间与时间上的差异特征。

超滤对磁化水的影响及截留微粒成分分析

研究了超滤对磁化的碳酸氢钙水溶液的电导率及产生沉淀的温度的影响,利用扫描电镜分析了超滤膜截留的微粒成分。实验结果表明:饱和的碳酸氢钙水溶液经磁化-超滤处理后,电导率开始就有差异,透过液的电导率最低。在加热出现肉眼可见沉淀的温度由高到低的顺序为:透过液>浓缩液>原水;超滤膜截留的微粒成分复杂,主要由硅、铝、钙、硫、铁等元素组成,不是单一的碳酸钙晶体。

磁稳流化床空气过滤器特性研究

对用磁稳流化床过滤含尘气体进行了研究。建立了磁稳流化床过滤器的过滤模型 ,实验研究了磁场强度、气体表观流速、床层厚度、颗粒平均粒径、粉尘在床层中的积累等因素对磁稳流化床过滤效率的影响 ,结果表明 ,在磁稳状态 。

磁种-磁滤法在洗车废水回用处理的研究

采用磁种磁滤法对洗车废水进行处理,以便能达到废水回用的目的。考察了磁种投加量、混凝剂用量、磁场强度和磁滤速度对出水浊度的影响,并在最佳条件下对实际废水进行了处理。结果表明,在磁种投加量为80mg/L,聚合氯化铝用量为45mg/L,磁场强度为2000Gs,磁滤速度为80m/h的条件下,出水达到了生活杂用水水质标准的要求(CJ25.189)。

肾脏ADC值与滤过功能相关性的初步研究

目的 研究扩散加权成像(DWI)测量的肾脏ADC值与99Tcm DTPA肾动态显像测定的肾小球滤过率(GFR)之间的关系。方法 55例患者同时行DWI和99 Tcm DTPA肾动态显像,DWI检查采用的b值为0,500 s/mm2 并测量全肾ADC值,根据GFR把110个肾脏分为正常组、肾功能轻度受损组、肾功能中度受损组和肾功能重度受损组。比较四组间肾脏ADC值的差异并分析肾脏ADC值与滤过功能的相关性。结果 4组肾脏ADC值间的差异有显著性意义,肾脏ADC值与GFR之间存在较好的正相关性r=0.709。结论 滤过功能受损的肾脏ADC值低于正常肾脏者。肾脏DWI可以用来评价肾脏滤过功能。

用磁稳流化床过滤含尘气体的实验研究

研究磁场强度、气体表观流速比、铁磁性颗粒平均粒径、床层厚度、粉尘在滤料中的积累等因素对除尘效率的影响．结果表明，在磁稳状态，磁稳流化床的过滤效率大于９９％，且随床层厚度的增加和铁磁颗粒粒径的减小而增大．另一方面，随着床内粉尘的积累，磁稳流化床将退出磁稳状态，使过滤效率下降．退出磁稳状态的临界饱和点粉尘量与磁场强度有关，当磁场强度为４３００Ａ／ｍ，临界饱和点粉尘与铁磁颗粒的质量百分比约为６．７％．

高梯度磁过滤技术及展望

介绍一种新型分离技术——高梯度磁过滤技术 (简称 HGMF)及展望 ,并预测超导磁过滤技术是未来高梯度磁过滤技术的发展方向。