Role of tannin pretreatment in flotation separation of magnesite and dolomite

Flotation separation of magnesite and its calcium-containing carbonate minerals is a difficult problem.Recently,new regulat-ors have been proposed for magnesite flotation decalcification,although traditional regulators such as tannin,water glass,sodium carbon-ate,and sodium hexametaphosphate are more widely used in industry.However,they are rarely used as the main regulators in research because they perform poorly in magnesite and dolomite single-mineral flotation tests.Inspired by the limonite presedimentation method and the addition of a regulator to magnesite slurry mixing,we used a tannin pretreatment method for separating magnesite and dolomite.Microflotation experiments confirmed that the tannin pretreatment method selectively and largely reduces the flotation recovery rate of dolomite without affecting the flotation recovery rate of magnesite.Moreover,the contact angles of the tannin-pretreated magnesite and dolomite increased and decreased,respectively,in the presence of NaOl.Zeta potential and Fourier transform infrared analyses showed that the tannin pretreatment method efficiently hinders NaOl adsorption on the dolomite surface but does not affect NaOl adsorption on the magnesite surface.X-ray photoelectron spectroscopy and density functional theory calculations confirmed that tannin interacts more strongly with dolomite than with magnesite.

Literature overview of basic characteristics and flotation laws of flocs

Flocculation flotation is the most efficient method for recovering fine-grained minerals,and its essence lies in flotation and recovery of flocs.Fundamental physical characteristics of flocs are mainly determined by their apparent particle size and structure(density and morphology).Substantial researches have been conducted regarding the effect of floc characteristics on particle settling and water treatment.However,the influence of floc characteristics on flotation has not been widely studied.Based on the floc formation and flocculation flotation,this study reviews the fundamental physical characteristics of flocs from the perspectives of floc particle size and structure,summarizing the interaction between floc particle size and structure.Moreover,it thoroughly discusses the effect of floc particle size and structure on floc floatability,further revealing the influence of floc characteristics on bubble collision and adhesion and elucidating the mechanisms of interaction between flocs and bubbles.Thus,it is observed that floc particle size is not the only factor influencing flocculation flotation.Within the appropriate apparent particle size range,flocs with a compact structure exhibit higher efficiency in bubble collision and adhesion during flotation,thereby resulting in enhanced flotation performance.This study aims to provide a reference for flocculation flotation,targeting the development of more efficient and refined flocculation flotation processes in the future.

Insights into the influence of temperature on the adsorption behavior of sodium oleate and its response to flotation of quartz

Temperature affects the flotation of quartz in the calcium/sodium oleate(Na OL)system,while there is a lack of understanding of its potential mechanism.Therefore,in this work,the flotation response of quartz to temperature was investigated via micro-flotation experiments,interface property analyses,and theoretical calculations.Flotation results demonstrated that increasing temperature contributed to higher flotation recovery of quartz,which enhanced the removal of quartz from hematite.Surface tension results revealed that higher temperatures lowered the critical micelle concentration(CMC)and surface tension of the Na OL solution,and thus enhanced its surface activity.Solution chemistry calculations and X-ray photoelectron spectroscopy(XPS)measurements confirmed that the increased content of Ca(OH)+achieved by increasing temperatures enhanced the adsorption amounts of calcium species(acting as activation sites)on the quartz surface.Dynamic light scattering(DLS)measurements verified that the association degree of RCOOàto form(RCOO)22àwas strengthened.Furthermore,adsorption density measurements and molecular dynamics(MD)simulations confirmed that increasing the temperature facilitated Na OL adsorption toward the surface of the quartz,which was attributed to the stronger interaction between Na OL and the calcium-activated quartz surface at higher temperatures.As a result,quartz flotation was improved by increasing temperatures.Accordingly,a possible adsorption model was proposed.

某含砷硫金精矿酸性氧化预处理机理及其反应动力学

针对国内某金精矿中金嵌布粒度细且大部分被黄铁矿、毒砂包裹,难以浸出的现状,采用HCl-H2O2体系对其进行酸性氧化预处理,分析了氧化预处理的机理和动力学.结果表明,在盐酸浓度0.7 mol/L、矿浆浓度40 g/L、金精矿粒度小于48μm占90%以上、搅拌速度400 r/min、温度60℃和H2O2浓度0.5 mol/L的条件下,金精矿中Fe和As的溶解率分别达45.9%和99.6%,利于包裹金释放和浸出.酸性条件下,金精矿中的黄铁矿和毒砂可被H2O2氧化分解,符合产物层扩散为速率控制的固相反应收缩核模型.

Role of surface roughness in the magnesite flotation and its mechanism

Surface roughness has a significant influence on mineral flotation.The assisting effect of surface roughness on minerals flotation is extensively investigated from its physical properties(e.g.,the existing form of asperity and its size),however,the associated effect on mineral flotation based on the differences in surface chemical property caused by surface roughness has been rarely touched.With such a question in mind,in this study,we investigated the flotation recoveries of two batches of magnesite particles with varying degree of surface roughness produced by two different mills,and associated the flotation performances to their surface chemical properties(amount of adsorption sites for the collector)via a series of detections,including Scanning Electron Microscope-Energy Dispersive Spectrometry(SEM-EDS)observations,X-ray photoelectron spectroscopy(XPS)analysis,adsorption capacity tests,and contact angle measurements.Finally,we concluded that rougher magnesite particles could provide more active sites(Mg^(2+))for a larger capacity of sodium oleate(NaOL),thereby improving the hydrophobicity and floatability.

Investigation of the flotation behavior and interaction characteristics of micro-fine quartz and magnesite in a dodecylamine system under ultrasonic treatment

Ultrasonic treatment,as an important surface modification method,profoundly affects the flotation behavior of minerals.This study examined the impact of ultrasonic treatment on the surface properties and flotation performance of magnesite and quartz in a dodecylamine(DDA)flotation system.Atomic force microscope detection results revealed that the surface roughness and roughness size of both magnesite and quartz increased after ultrasonic treatment.Flotation tests indicated that the recovery rates of magnesite and quartz were lower after ultrasonic treatment.At pH of 10 and DDA of 75 mg/L,ultrasonic treatment led to a 0.66%,3.46%,and 0.33%decrease in the flotation recovery rates for three different magnesite particle sizes.Following ultrasonic processing,the flotation recovery rates for three different quartz particle sizes decreased by 8.48%,30.76%,and 43.69%,in that order.X-ray photoelectron spectroscopy detection results showed an increased presence of characteristic Mg and Si sites on the surfaces of magnesite and quartz following ultrasonic treatment.DDA acted on the surfaces of the two minerals through electrostatic adsorption and hydrogen bonding adsorption and repelled the flotation of minerals owing to the same charge as characteristic sites,thereby reducing flotation recovery.Adsorption capacity tests and contact angle measurements demonstrated a decrease in DDA adsorption and contact angle on the surfaces of magnesite and quartz after ultrasonic treatment,explaining the reduced floatability.Extended Derjaguin–Landau–Verwey–Overbeek theoretical calculations indicated that before ultrasonic treatment,there was a repulsive energy between magnesite and fine-grained quartz particles.After ultrasonic treatment,the interaction energy between magnesite and fine quartz particles is mutual attraction.