Study On Bridging Flocculation Characteristics And Magnetic Capture Mechanism Of Fine Specularite

China has abundant reserves of fine iron ore among the complex and refractory iron ore resources.Conventional technology is generally difficult to effectively recover fine minerals with a particle size of less than 10μm,resulting in a part of useful minerals lost to tailings.In this paper,a basic research on bridging flocculation and sorting behavior of fine specularite was investigated.Through flocculation-magnetic separation and flocculation-sedimentation test,the influences of flocculant types and dosage,dispersant dosage,pulp pH value,and stirring intensity on the flocculation performance of specularite were explored.Then,the suitable parameters were determined.The particle size characteristic of the specularite flocs was analyzed using a laser particle size analyzer,and the microstructure of the flocs was observed using an optical microscope.Zeta potential and infrared spectroscopy tests were also carried out to analyze the mechanism of action of flocculants and specularite surfaces.Based on the research of specularite bridging flocculation,the mixed minerals of specularite and quartz were separated by selective flocculation-high gradient magnetic separation process.The effects of flocculation pretreatment conditions and high gradient magnetic separation conditions on mineral separation indexes were investigated.Then,the flocculation-magnetic separation process was compared with the magnetic separation process to explore the degree of enhanced recovery of specularite.Based on the matrix capture model,the magnetic capture kinetics and capture efficiency of different flocs were also studied.Combined with the characteristic parameters of flocs and magnetic separation parameters,the recovery effect of flocculation-magnetic separation technology on fine specularite was theoretically obtained.The bridging flocculation study of specularite showed that under the optimal conditions,adding cross-linked corn starch,carboxymethyl tapioca starch and sodium alginate to pretreat the pulp,the magnetic separation recovery rates were 81.29%,75.15%,86.58%respectively.Compared with no flocculant,the recovery rate increased by 13.00%,6.86%,18.29%respectively.The settlement rates of specularite flocs were 98.43%,75.15%,98.90%,and the settlement rates of quartz were 59.74%,57.80%,71.49%.Sodium alginate can flocculate specularite and quartz,indicating that this flocculant had poor selectivity.Carboxymethyl tapioca starch had good selectivity,but its flocculation ability was poor.Cross-linked corn starch can selectively flocculate fine specularite.The laser particle size analysis of specularite showed that the addition of flocculant to the slurry can increase the size of specularite flocs,and the content of fine mineral with a particle size of less than 20μm was significantly reduced.Compared with the pulp without flocculant,the content of fine mineral(less than 20μm)decreased by 19.79%,15.61%,and 38.17%respectively after adding cross-linked corn starch,carboxymethyl tapioca starch,and sodium alginate.The order of the effects of the three flocculants was:sodium alginate>cross-linked corn starch>carboxymethyl tapioca starch.The microscopic appearance of the flocs presented that the specularite without flocculant was in a dispersed state,and there were a quantity of extremely fine particles.After adding flocculant,a large number of bridging flocs were produced.The results of image analysis software showed that the size of flocs increased with the increase of flocculant.Cross-linked corn starch and sodium alginate had the same flocculation effect on specularite,and they were significantly better than carboxymethyl tapioca starch.Zeta potential and infrared spectroscopy tests showed that cross-linked corn starch and carboxymethyl tapioca starch hardly had physical or chemical adsorption on the quartz surface,while sodium alginate had hydrogen bond adsorption.These three flocculants had hydrogen bond adsorption on the surface of specularite.Mixed minerals(specularite and quartz)selective flocculation-high gradient magnetic separation test showed that the minerals were flocculated under the optimal conditions of cross-linked corn starch 6mg/L,sodium silicate 10mg/L,pulp pH 10,and agitation intensity 500r/min.The flocs were sorted under the conditions of magnetic field intensity 0.8T,round matrix with a horizontal and vertical distance of 2mm,water flow rate 100mL/s,pulsating impulse 170 times/min,and stroke 11.40mm.The iron grade of the concentrate was 62.92%,the iron recovery rate was 76.98%,and the beneficiation efficiency was 68.27%.Compared with the direct magnetic separation process,the iron grade of the concentrate decreased by 2.15%,but the recovery rate increased by 6.66%,the beneficiation efficiency increased by 1.97%.The study on the capture mechanism of matrix showed that in the case of fixed magnetic separation parameters,the capture radius of the matrix increased with the increase of particle size.When the amount of cross-linked starch was 0mg/L,6mg/L and 8mg/L,the capture efficiency of the matrix was 66.27%,74.89%,77.50%,respectively.Bridging flocculation of specularite with starch enhanced recovery of fine specularite.When the specularite characteristic parameters were fixed,the capture radius and efficiency of matrix both increased with the increase of background magnetic field intensity;The capture radius of matrix increased as the round rod increase,but the efficiency increased first and then decreased;The capture radius and efficiency of matrix both decreased with the increase of the initial velocity of the fluid.Therefore,the suitable magnetic separation parameters can also enhance the capture effect.The research results of this paper enriched the theory of bridging flocculation of specularite,and had certain guidance for the efficient utilization of fine-grained weakly magnetic iron minerals.