Latest advances and progress in the microbubble flotation of fine minerals:Microbubble preparation,equipment,and applications

In the past few decades,microbubble flotation has been widely studied in the separation and beneficiation of fine minerals.Compared with conventional flotation,microbubble flotation has obvious advantages,such as high grade and recovery and low consumption of flotation reagents.This work systematically reviews the latest advances and research progress in the flotation of fine mineral particles by microbubbles.In general,microbubbles have small bubble size,large specific surface area,high surface energy,and good selectivity and can also easily be attached to the surface of hydrophobic particles or large bubbles,greatly reducing the detaching probability of particles from bubbles.Microbubbles can be prepared by pressurized aeration and dissolved air,electrolysis,ultrasonic cavitation,photocatalysis,solvent exchange,temperature difference method(TDM),and Venturi tube and membrane method.Correspondingly,equipment for fine-particle flotation is categorized as microbubble release flotation machine,centrifugal flotation column,packed flotation column,and magnetic flotation machine.In practice,microbubble flotation has been widely studied in the beneficiation of ultrafine coals,metallic minerals,and nonmetallic minerals and exhibited superiority over conventional flotation machines.Mechanisms underpinning the promotion of fine-particle flotation by nanobubbles include the agglomeration of fine particles,high stability of nanobubbles in aqueous solutions,and enhancement of particle hydrophobicity and flotation dynamics.

Theoretical analysis of JMC effect on stress wave transmission and reflection

Taking the joint matching coefficient(JMC) which represents the contact area ratio of the joint in rock masses as the key parameter, a one-dimensional contacted interface model(CIM-JMC) was established in this study to describe the wave propagation across a single joint. According to this model, the reflected and transmitted waves at the joint were obtained, and the energy coefficients of reflection and transmission were calculated. Compared with the modified Split Hopkinson pressure bar(SHPB) experiment, it was validated by taking the incident wave of the SHPB test as the input condition in the CIM-JMC, and the reflected and transmitted waves across the joint were calculated by the model. The effects of four sets of JMCs(0.81, 0.64, 0.49, and 0.36) on the transmission and reflection of the stress wave propagation across the joint were analyzed and compared with the experimental results. It demonstrated that the values of CIM-JMC could represent both the transmission and reflection of the stress wave accurately when JMC > 0.5, but could relatively accurately represent the reflection rather than the transmission when JMC < 0.5. By contrasting energy coefficients of joints with different JMCs, it was revealed that energy dissipated sharply along the decrease of JMC when JMC > 0.5.

Deciphering fluid origins in the Paleozoic Laoshankou Fe-Cu-Au deposit, East Junggar: Constraints from noble gases and halogens

To constrain the ore-fluid source(s)of the Laoshankou Fe-Cu-Au deposit(Junggar orogen,NW China),we analyzed the fluid inclusion(FI)noble gas(Ar,Kr and Xe)and halogen(Cl,Br and I)compositions in the hydrothermal epidote and quartz.Four hypogene alteration/mineralization stages,including(I)pre-ore Ca-silicate,(II)early-ore amphibole-epidote-magnetite,(III)late-ore pyrite-chalcopyrite,and(IV)post-ore hydrothermal veining,have been identified at Laoshankou.Stage II FIs have salinity of 15.7 wt.%(NaCl eq.),I/Cl molar ratios of 75×10^(−6)-135×10^(−6),and Br/Cl molar ratios of 1.4×10^(−3)-2.1×10^(−3).The moderately-high seawatercorrected Br*/I ratios(0.5-1.5)and low 40ArE/Cl slope(-10−5)indicate the presence of sedimentary marine pore fluid,which was modified by seawater reacting with the Beitashan Fm.volcanic rocks.Stage III fluid is more saline than their stage II and IV counterparts,reaching up to 23.3 wt.%(NaCl+CaCl2 eq.)close to halite saturation(-26 wt.%).The fluid has I/Cl ratios of 75×10^(−6)-90×10^(−6) and Br/Cl ratios of 1.5×10^(−3)-1.8×10^(−3).Considering the increasing 40ArE/Cl trend toward bittern brine and the higher 36Ar content than air-saturated water(ASW),a bittern fluid source is inferred from seawater evaporation,which was modified by interaction with organic-rich marine sedimentary rocks.Stage IV FIs have lower temperature(110-228°C)and Br/Cl(0.90×10^(−3)-1.2×10^(−3)),but higher 36Ar content than ASW,indicative of dissolved evaporite or halite input.Considering also the lowδDfluid(−114‰to−144‰)andδ18Ofluid(2.1‰-3.5‰)values,meteoric water(with minor dissolved evaporites)likely dominated the stage IV fluid.The evaporites may have formed through continuous evaporation of the stage III surface-derived bittern.Involvement of non-magmatic fluids and different ore-fluid origins in stages II and III suggest that the ore-forming process was different from a typical magmatichydrothermal fluid-dominated skarn mineralization,which was previously proposed for Laoshankou.Our noble gas and halogen study at Laoshankou provide new insights on the fluid sources for the Paleozoic Fe−Cu(−Au)deposits in the Central Asian Orogenic Belt(CAOB),and our non-magmatic fluid source interpretation is consistent with the basin inversion setting for the mineralization.

The Micro-Scale Mechanism of Metal Mine Tailings Thickening Concentration Improved by Shearing in Gravity Thickener

Higher concentration is beneficial for the Paste and Thickened Tailings(PTT)operation in metal mine.Partial paste thickeners are produced lower density underflow.Flocculated tailings are intended to form a water entrapped network structure in thickener,which is detrimental to underflow concentration.In this study,the continuous thickening experiment was carried out for ultra-fine tungsten tailings to study the influence of rake shearing on underflow.The micro pores structure and seepage flow in tailings bed before and after shearing are studied by CT and simulation approach to reveal the shearing enhancement mechanism of thickening process.The results shown that,the underflow concentration is increased from 61.4 wt%to 69.6 wt%by rake shearing in a pilot scale thickener,the porosity decreased from 46.48%to 37.46%.The entrapped water discharged from sticks structure more than sphere spaces.In items of seepage,after shearing,the seepage flow channel of tailings underflow is becoming longer,which caused the decreasing average flow rate decreases and absolute permeability.The absolute permeability is negatively correlated with tortuosity.The rake shearing can destroy the flocs structure;change the effective stress to increase the concentration.Higher underflow concentration improves the waste recycling and water recovery rate,especially for arid areas.

Extractant(2,3-dimethylbutyl)(2,4,40-trimethylpentyl) phosphinic acid(INET-3) impregnated onto XAD-16 and its extraction and separation performance for heavy rare earths from chloride media

(2,3-Dimethylbutyl)(2,4,40-trimethylpentyl)phosphinic acid(INET-3) was impregnated onto dry macroporous resins XAD-16 and pretreated XAD-16 with ethyl alcohol and HCl(Pre-XAD-16) to prepare the solvent impregnated resins SIRs-INET-3/XAD-16 and SIRs-INET-3/Pre-XAD-16. The molecular weight distribution of the low molecular weight(LMW) polymers washed off by ethyl alcohol during XAD-16 pretreatment was determined by gel permeation chromatography(GPC). The macroporous resins(XAD-16 & Pre-XAD-16), the corresponding solvent impregnated resins(SIRs-INET-3/XAD-16 &SIRs-INET-3/Pre-XAD-16) and the PVA coated SIRs-INET-3/Pre-XAD-16 with boric acid as cross-linking agent were characterized by FT-IR, SEM-EDS and TGA. The effects of XAD-16 pretreatment and PVA coating technology on RE(III) adsorption equilibrium time, INET-3 losses during extraction and adsorption capacity were investigated. The adsorption kinetics, selectivity and stripping behaviors of SIRs-INET-3/XAD-16 were further studied. The washed off LMW polymers had the Mn of 36,656, Mw of 40,310 and polydispersity coefficient of 1.10. The SIRs-INET-3/XAD-16 had shorter equilibrium time,less INET-3 loss and more Tm(III) adsorption capacity than the SIRs-INET-3/Pre-XAD-16. The PVA coated SIRs-INET-3/Pre-XAD-16 had less INET-3 loss and more Tm(III) adsorption capacity but longer equilibrium time than the uncoated SIRs-INET-3/Pre-XAD-16. The adsorption of RE(III) on the SIRsINET-3/XAD-16 followed the pseudo-second-order kinetic model. The Tm(III) accumulative adsorption amounts onto SIRs-INET-3/XAD-16 after eight extraction stages was 23.6 mg/g. The separation factors of adjacent heavy RE(III) β_(Er/Ho), β_(Tm/Er), β_(Yb/Tm) and β_(Lu/Yb) values were 1.76, 2.59, 2.56 and 1.19,respectively. The adsorbed Lu(III) onto the SIRs-INET-3/XAD-16 can be stripped completely by 1.0 mol/L H_2SO_4.

China’s intra-and inter-national carbon emission transfers by province:A nested network perspective

Since China carries an increasingly significant responsibility in carbon emission reduction,a systematic assessment from the multi-scale and multi-regional perspective is essential to examine the region-specific carbon emissions and different kinds of carbon transfer patterns.By identifying carbon emission flows among 31 domestic provincial administrative regions and 184 foreign countries/economies,this work examines the domestic and foreign carbon emission flows of Chinese provinces/municipalities based on the intra-and inter-national relations.Overall,the provinces and municipalities in China are divided into 4 patterns according to carbon emission flows,among which inland provinces mainly engage in domestic carbon emission transfers,western regions generally receive carbon emissions with main carbon outflows in northeastern and central provinces,and coastal regions play an essential role in balancing carbon emission surpluses and deficits between domestic and foreign regions.For different sub-regions in China,recognizing carbon emission transfer relations contributes to the synergetic and sustainable regional development from a tele-connected perspective.With the nested network analysis,the multi-scale and multiregional assessments focusing upon China’s provinces and municipalities extend the existing research to both national and global scales,providing a solid foundation for sustainable regional development in China.

Quantitative evaluation of organic richness from correlation of well logs and geochemical data: a case study of the Lower Permian Taiyuan shales in the southern North China Basin

Marine-continental transitional shale is a potential energy component in China and is expected to be a realistic field in terms of increasing reserves and enhancing the natural gas production.However,the complex lithology,constantly changing depositional environment and lithofacies make the quantitative determination of the total organic carbon(TOC)suitable for marine shales not necessarily applicable to transitional shales.Thus,the identification of marine-continental transitional organic-rich shales and the mechanism of organic matter enrichment need to be further studied.As a typical representative of transitional shale,samples from Well MY-1 in the Taiyuan Formation in the southern North China Basin,were selected for TOC prediction using a combination of experimental organic geochemical data and well logging data including natural gamma-ray(GR),density(DEN),acoustic(AC),neutron(CNL)and U spectral gamma-ray(U),and TH spectral gamma-ray(TH).The correlation coefficient,coefficient of determination,standard deviation,mean squared error(MSE)and root mean squared error(RMSE)were selected to conduct the error analysis of the evaluation of different well log-based prediction methods,involving U spectral gamma logging,ΔlogR,and multivariate fitting methods to obtain the optimal TOC prediction method for the Taiyuan transitional shale.The plots of TOC versus the remaining volatile hydrocarbon content and the generation potential from Rock Eval show good to excellent potentials for hydrocarbon generation.The integrated results obtained from the various log-based TOC estimation methods indicate that,the multivariate fitting method of GR-U-DEN-CNL combination is preferable,with the correlation coefficients of 0.78 and 0.97 for the entire and objective interval of the Taiyuan Formation respectively,and with the minimum MSE and RMSE values.Specifically,the U spectral gamma logging method based on single logging parameter is also a better choice for TOC prediction of the high-quality intervals.This study provides a reference for the exploration and development of unconventional shale gas such as transitional shale gas.

Breaking pore size limit of metal–organic frameworks:Bio-etched ZIF-8 for lactase immobilization and delivery in vivo

Expanding pore size range of metal–organic frameworks(MOFs)promotes their versatility and feasibility for various biomedical applications.However,natural pore size greatly restricts large guest molecule accommodation.Customizing and tailoring pore apertures ranging from micropores to mesopores controllably is desired but still critically challenging.Herein,we developed a facile method with super mildness based on pH-sensitive zeolitic imidazolate framework(ZIF)-8 to increase porosity,providing pore size with maximum 20 nm,which is 8 times larger than average.Glucose oxidase(GOx)was introduced in ZIF-8 for bioetching,benefitted from the resultant acidic microe-nvironment during biocatalytic process.Different synthesis methods were assessed for obtaining different morphologies and size distributions.Reaction time,GOx encapsulation efficiency,and Zn2+concentration was optimized to precisely control the mesopore size distribution of MOFs.It was found that bio-etching strategy was capable of producing stable mesopores which were large enough for loading lactase with good enzymatic activity retained,verified both in vitro and in vivo.This strategy breaks natural pore size limitation of MOFs and thereby facilitates biomolecule delivery,catalysis,and other biomedical applications with enhanced stability and performance.

Flow characteristics of silicon oil in nanochannels

The nonlinear flow of liquids through nanoscale channels play an important role in the separation and purification properties of porous membranes,the manufacture of biofilm ionic channels and microfluidic chips,the production of micro electro-mechanical systems.Silicon oil flow experiments were conducted through anodic alumina films with pore sizes of 26,67,89,and 124 nm,in which flow mechanism and characteristics of the oil through the nanoscale channels were analyzed.Four nanoflow features are revealed:(1)The experimental flow rate is less than the theoretical flow rate through nanochannels,as solid-liquid interaction increasing flow resistance.(2)At small shear rate,the boundary layer is one,indicating existence of a threshold pressure of oil flow through nanochannels.(3)The boundary layer decreases with the increasing of shear rate,and it rapidly decreases as shear rate increases when the value of shear rate is small.(4)The drag coefficient decreases nonlinearly with increasing shear rate,decreasing more slowly when value of shear rate is big,and trending towards 1 in the case of large shear rate.It is shown that the non-linearity of flow is induced by great solid-liquid interaction in nano and microscale,and increasing the driving force can raise the efficiency at the nanometer scale.