摘要
采用微量热法研究了白钨矿在NaOH溶液中的溶解及其与油酸钠作用的热动力学,并通过扫描电子显微镜(SEM)、总有机碳(TOC)及傅里叶变换红外光谱(FTIR)对白钨矿在NaOH溶液体系中的溶解特性及其与油酸钠的作用方式进行表征,同时进行了单矿物浮选试验研究。结果表明:白钨矿在NaOH溶液中溶解为吸热反应,反应级数n=3,pH=10时溶解反应热最大,溶解反应热与Ca^(2+)浓度成正相关。白钨矿表面Ca^(2+)在NaOH溶液中吸附油酸根离子为放热反应,反应级数n=1,相对白钨矿溶解发生了热量转变,不同pH条件下的吸附反应热大小与白钨矿溶解反应热趋势一致,在pH=12时反应速率均较快。不同pH条件下油酸根离子的吸附量与其反应热大小成正比,这与单矿物浮选结果一致。
Microcalorimetry was an on-line and non-destructive method for the determination of thermal effects. The change of enthalpy and specific heat caused by the reaction of material was measured and analyzed by microcalorimeter,and the corresponding thermodynamic and kinetic parameters were obtained to study the reaction process. At present,there were few reports on the dissolution and adsorption of scheelite under alkaline conditions by microthermal method. Therefore,the study of the thermodynamic and kinetic parameters of the dissolution and surface adsorption of scheelite under alkaline conditions by microthermal method had important theoretical guiding significance. The scheelite used in this study were a synthetic one,and the Na2WO4 and Ca(NO3)2 used in the synthesis of scheelite were both analytically pure. The pH regulators were NaOH and its purity was analyzed. The collector was sodium oleate,analytically pure. The experimental water was ultrapure water. The trace thermal kinetics of scheelite dissolution and scheelite adsorption sodium oleate were tested by Microcalorimeter. The absorption quantity of sodium oleate on scheelite surface was tested by adsorption experiment. The structure transformation of scheelite surface was tested by Fourier infrared spectrum analysis and verified by flotation experiment. The results mainly included the following five parts:(1)It could be seen that the dissolution of scheelite in NaOH solution was endothermic reaction. At pH=10,the integral area of the heat rate curve(heat of reaction)was at its maximum Q=-24.38 mJ,and at pH=12,the minimum heat of reaction Q=^(-1)8.99 mJ. The order of the reaction heat dissolved in NaOH solution of scheelite was pH=10>pH=11>pH=9>pH=8>pH=12. In short,the reaction rate constant(k)tended to decrease first and then increase. When pH=12,the reaction rate constant reached its maximum. The reaction order(n)was approximately equal to 3,indicating that scheelite wasdissolved in NaOH at different pH values as a third-order reaction.(2)D50 changed with pH after dissolution of scheelite in NaOH solu-tion,and the result was pH=10>pH=11>pH=9>pH=8>pH=12,which was consistent with the law of Ca^(2+)dissolution. The reaction heat of dissolution was positively correlated with the concentration of Ca^(2+).(3)The reaction of scheelite with sodium oleate in NaOH was exothermic. The order of reaction heat of scheelite surface acting with sodium oleate was pH=10>pH=11>pH=9>pH=8>pH=12. There was a faster reaction rate in low base and high base. The reaction order(n)was approximately equal to 1,indicating that scheelite reacts with sodium oleate in NaOH with different pH values as a first-order reaction.(4)According to the Fourier infrared spectrum,1546 cm^(-1) was the asymmetric stretching vibration absorption peak of-COO-,the carboxylic acid negative ion(-COO-)in the calcium oleate molecule produced anti-symmetric stretching vibration,and was the characteristic spectral band of calcium oleate. It could be seen that the oleate ion was adsorbed on the scheelite surface to produce calcium oleate,which was chemical adsorption. The peak strength of anti-symmetric stretching vibration generated from carboxylic acid radical anion(-COO-)to small was pH=10>pH=11>pH=9>pH=8>pH=12. This was consistent with the pH sequence of sodium oleate adsorption.(5)According to the flotation experiment,when the natural pH was 7.3,the concentration of sodium oleate had a great impact on the flotation recovery of scheelite. With the increase of the concentration of sodium oleate,the flotation recovery of scheelite first increased and then decreased,and reached a maximum of 81.72% when the concentration of sodium oleate was 40 mg·L^(-1). The optimal concentration of sodium oleate was selected to be 40 mg·L^(-1). With the increase of pH,the flotation recovery of scheelite first increased. When pH=10,recovery had maximum,and the pH continued to increase,the flotation recovery of scheelite began to decline. The order of the recovery rate of scheelite flotation was pH=10>pH=11>pH=9>pH=8>pH=12. It was clear that the Ca^(2+)on the surface of tungsten ore would be adsorbed with oleic acid ions by chemically,and the formation of calcium oleate would lead to the enhancement of its hydrophobicity,so as to achieve the purpose of flotation scheelite. Scheelite dissolved in NaOH solution as endothermic reaction,reaction order n=3. When pH=10,the maximum heat of dissolution Q was-24.38 mJ;when pH=12,the minimum heat of dissolution Q was^(-1)8.99 mJ;the order of dissolution heat was pH=10>pH=11>pH=9>pH=8>pH=12;the dissolution heat was positively correlated with the concentration of Ca^(2+),and the dissolution rate was the fastest when pH=12. Adsorption of scheelite in NaOH solution to sodium oleate was an exothermic reaction,with reaction order n=1.Relative to scheelite dissolution,there was a heat change,which was a spontaneous reaction. The order of reaction heat of adsorption sodium oleate by scheelite was consistent with that of dissolution reaction heat of scheelite. When pH=10,the maximum heat of adsorption reaction Q was 18.77 mJ;when pH=12,the minimum heat of adsorption reaction Q was 16.60 mJ;when pH=12,the adsorption reaction rate was the highest. Under different pH conditions,the adsorption quantity of oleic acid ions was in direct proportion to its reaction heat.The infrared spectrum test results showed that oleic acid ions were adsorbed on the scheelite surface and Ca^(2+)generate calcium oleate,resulting in its enhanced hydrophobicity. Moreover,the absorption peak strength and adsorption quantity were in the same order,which was consistent with the flotation results.
作者
匡敬忠
马强
刘鹏飞
黄哲誉
Kuang Jingzhong;Ma Qiang;Liu Pengfei;Huang Zheyu(Faculy of Resource and Enironmental Engineering,Jiangxi University of Science and Technology,Ganzhou 341000,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2021年第3期322-332,共11页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(51664019)资助。
关键词
微量热法
热动力学
白钨矿
油酸钠
溶解
吸附
microcalorimetry
thermokinetics
scheelite
sodium oleate
dissolution
adsorption
