| Because of the special physical and chemical properties,boron and boride account for an important position in whole national economy.The boron resources are abundant in China,whose known economic reserve is about 32 million tons(in B2O3)and most of them are paigeite ore.Influenced by the complex dissemination characteristics,fine particles size of and high content of gangue minerals,a big technical problem and economic issue has to be faced during the utilization of paigeite ore.Along with the intensification of industrialization in our country,boron is becoming more popular and the demands of boron continue to increase.However,after decade years' utilization of boron resources,the high grade boron ore is extremely exhausted.The shortage of raw materials limits the sustainable development of boron industry in China.Considering these factors,it is very important to strengthen the research on efficient utilization of paigeite ore for ensuring the sustainable development of boron industry.Faced with many challenges in exploitation and utilization of paigeite ore,strengthen fundamental research on the separation of paigeite ore has significant theoretical and practical meaning for guiding the separation of paigeite ore and promoting the technological advance of paigeite ore processing.In this research,Zeta potential analysis,X-ray photoelectron spectroscopy(XPS),fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(S EM),X-ray diffraction(XRD)and atomic force microscopy(AFM)are used to study the three main minerals in paigeite(ascharite,serpentine and magnetite).A systematical study was carried out by theoretical analysis and experimental researches,and some achievements,having obviously scientific and technological significance,were obtained.The research on surface property of mineral showed that the points of zero charge of serpentine,ascharite and magnetite were at pH of 9.2,7.8 and 5,6,respectively.Serpentine and ascharite could dissolve easily in water solution leading to an increase of Mg and B concentration in water and a remarkable increase of pH value of the pulp.Besides,the point of zero charge was also changed after dissolution Lager amount of hydroxyl existed on the surface of serpentine and ascharite,the transfer of hydroxyl from mineral surface to solution was the main reason that led to the increase of pH value.The addition of HCl into the pulp can accelerate the dissolution of serpentine and ascharite,which generated to a remarkable increase of Mg,B concentration in solution.Meanwhile,more hydroxyl dissolved into water,so the pulp showed a strong buffer capacity to acid.The study on the surface charge development mechanism showed that the incongruent dissolution of surface ions was the basic reason resulting in the surface to be charged.After dissolved in solution,the elements relative content of Mg and B reduce obviously,indicating that a large number of ions transfer from surface to solution.Because of more cationic ions dissolved than anionic ions,the surfaces were more negatively charged and the point of zero charge became lower.The floatability of signal minerals was investigated by signal mineral flotation experiments.The results showed that the floatability of ascharite and magnetite were very well when dodecylamine and sodium oleate were used as collector.Serpentine can be collected by dodecylamine and optimum recovery is 42%,but it can be hardly collected by sodium oleate.All inhibitors used in this research,sodium hexametaphosphate(SHMP),sodium carboxymethylcellulose(CMC),calcium lignosulphonate and sodium silicate could inhibit the floatability of ascharite,serpentine and magnetite.The separation performance of mixed minerals among ascharite,serpentine and magnetite were investigated through flotation experiments.The results indicated that serpentine and ascharite were prone to be floated into concentrate if dodecylamine was used as collector,which lowered the B2O3 grade in concentrate.When sodium oleate was used as collector,ascharite can be separated from serpentine and magnetite easily at pH of 9.3.By comparison with dodecylamine,sodium oleate was a better choice to be used as collector.The flotation results also showed that the particles size and content of serpentine were the major causes leading to a lower flotation recovery of ascharite.With the increase of serpentine particles size and content,and the former one was the main reason When dodecylamine was used as collector,SHMP was used as inhibitor to limit the adverse effect of serpentine on ascharite flotatioa The results revealed that-38?m serpentine can be obviously inhibited by SHMP,but it had little effect on+38?m serpentine particles.When sodium oleate was used as collector,the inhibitory effect of fine quartz particles on serpentine was studied through heterocoagulation It indicated that a proper addition of quartz into the pulp was good to improve ascharite flotation.Because the detrimental effect of serpentine on ascharite was weakened by quartz,then ascharite flotation was improved.However,excessive usage of quartz was bed to improve ascharite flotation recovery.Seen form the calculation results of DLVO theory,the total particles interaction enrgy between serpentine and ascharite is negative,indicating that serpentine was prone to adhere to the ascharite surface at pH of 9.0.As the pH value were switched to 11.0,the total energy changed positive.It showed that serpentine particles were dispersed with ascharite particles.At pH of 9.0,the total interaction energy between serpentine and quartz is negative,so adhesion occurred easily between serpentine and quartz.In this condition,the total interaction energy between quartz and ascharite is positive,indicating that quartz dispersed well with ascharite particles.The difference on the surface charge.was the basic reason that resulted in particles interaction The change of surface charge could easily lead to a transform of sign of total interaction energy,and then the particles interaction behavior was changed.The AFM results showed that the force between serpentine and ascharite,quartz were attractive force,and the force between ascharite and quartz was repulsive force at pH of 9.0.However,the attractive force between serpentine and ascharite was weakened apparently at pH of 11.0.The AFM results were in accordance with the results of DLVO theory.Besides,the adhesion states between particles were detected by SEM and the results were in agreement with calculation results.The mechanism of agents on minerals surface showed that dodecylamine work with serpentine and ascharite surface through physical adsorption,and sodium oleate work with ascharite through chemical adsorption.Both chemical adsorption and hydrogen bond affected the adsorption of sodium oleate on serpentine.A hydrophilic complex compound was generated after the adsorption of SHMP on the Mg2+on serpentine surface,and then the serpentine was inhibited.The adsorption of CMC on serpentine occurred through chemical reaction and it reacted with the Mg2+ on serpentine surface to limit the floatability of serpentine.Calcium lignosulphonate and sodium silicate could inhibit the serpentine through chemical adsorption.The research results of this paper have enriched the fundational theory on flotation separation of paigeite ore,which not only guides the separation of paigeite and provides a theoretical support for efficient utilization of paigeite ore,but also provides reference for other related theoretical research work. |
PDF Full Text Request