本文關(guān)鍵詞： 磷石膏 α-半水硫酸鈣 常壓鹽溶液法 轉(zhuǎn)晶速率 溶解動(dòng)力學(xué)　出處：《華東理工大學(xué)》2017年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：為實(shí)現(xiàn)磷石膏有效資源化利用,本研究選取鹽溶液為介質(zhì)在常壓下對(duì)磷石膏進(jìn)行轉(zhuǎn)晶制備αα-半水硫酸鈣。通過(guò)對(duì)磷石膏進(jìn)行浸取除雜,對(duì)比了不同條件下水洗、硫酸浸取工藝對(duì)磷石膏中P_2O_5、F-的去除率;以磷石膏為原料在Ca-Mg-K復(fù)合鹽溶液中進(jìn)行轉(zhuǎn)晶反應(yīng)制備αα-半水硫酸鈣,采用FESEM、XRD、TG-DTA等分析方法對(duì)不同Ca~(2+)濃度及pH值條件下反應(yīng)體系中的產(chǎn)物進(jìn)行了表征;對(duì)各反應(yīng)體系在不同反應(yīng)時(shí)間內(nèi)固、液兩相組成及含量的變化進(jìn)行測(cè)定,計(jì)算得到了相應(yīng)Ca~(2+)濃度以及pH條件下的轉(zhuǎn)晶速率;建立了磷石膏溶解動(dòng)力學(xué)模型,對(duì)溶質(zhì)飽和度C*以及磷石膏溶解速率R_s進(jìn)行擬合,得到了不同反應(yīng)條件下的反應(yīng)動(dòng)力學(xué)方程。主要研究?jī)?nèi)容和結(jié)論如下:(1)研究了磷石膏除雜工藝,結(jié)果表明,單一水洗除雜能夠有效去除磷石膏中水溶性P_2O_5、F-,在水洗60min,溫度65℃的條件下,磷石膏中可溶性P_2O_5含量下降了66.54%,F-含量下降了 64.33%;硫酸浸取除雜過(guò)程中,隨著浸取液H_2SO_4質(zhì)量分?jǐn)?shù)的增大、反應(yīng)溫度的升高,浸取液的除雜效率相應(yīng)提高,在55℃下,質(zhì)量分?jǐn)?shù)為35%的硫酸溶液中浸取2h后,磷石膏樣本中P205含量降低了 75.6%,F-含量降低了 78.4%。(2)考察了不同pH以及Ca~(2+)濃度的反應(yīng)條件下產(chǎn)物晶體微觀結(jié)構(gòu)及晶體形貌的影響。通過(guò)FESEM對(duì)不同初始反應(yīng)體系中的產(chǎn)物晶體形貌進(jìn)行表征后發(fā)現(xiàn),當(dāng)體系中Ca~(2+)濃度較高時(shí),其產(chǎn)物晶體尺寸較大,長(zhǎng)徑比低,此時(shí)產(chǎn)物結(jié)構(gòu)較為理想,當(dāng)Ca~(2+)濃度大于4.2M時(shí)將嚴(yán)重延緩磷石膏的轉(zhuǎn)晶速率;pH對(duì)產(chǎn)物長(zhǎng)徑比有顯著影響,在pH=7.0～8.0的中性-弱堿性條件下,產(chǎn)物長(zhǎng)徑比低,產(chǎn)物晶體呈短柱狀或棒狀;而當(dāng)體系中pH值降低,產(chǎn)物晶體長(zhǎng)徑比增加,向細(xì)針狀晶型生長(zhǎng)。(3)pH值以及Ca~(2+)濃度對(duì)產(chǎn)物含水率以及轉(zhuǎn)晶速率有重要影響。產(chǎn)物含水率反映了產(chǎn)物中半水相所占比例,在Ca~(2+)濃度高的體系當(dāng)中,二水硫酸鈣的溶解速率較慢,因而其轉(zhuǎn)晶速率也變慢;而當(dāng)體系中pH值下降,磷石膏溶解速率變快,溶液中的游離態(tài)SO42-離子濃度增加,反應(yīng)速率加快。(4)建立了磷石膏溶解動(dòng)力學(xué)模型,研究了不同Ca~(2+)濃度下磷石膏的溶解動(dòng)力學(xué)特征。通過(guò)測(cè)定溶解階段液相硫酸根離子濃度隨時(shí)間的變化,對(duì)溶質(zhì)飽和度C*及瞬時(shí)溶解速率Rs進(jìn)行擬合,得到了反應(yīng)動(dòng)力學(xué)參數(shù)。結(jié)果表明,磷石膏的溶解過(guò)程屬于表面反應(yīng)控制,在Ca~(2+)濃度2.5M-3.5M的范圍內(nèi)的中性環(huán)境中,溶解反應(yīng)的表觀反應(yīng)級(jí)數(shù)相差不大,平均值為1.533。
[Abstract]:In order to realize the effective utilization of phosphogypsum, a 偽 偽 -hemihydrate calcium sulfate was prepared by transprystallization of phosphogypsum in salt solution under atmospheric pressure, and the impurity removal was carried out by leaching phosphogypsum. The removal rate of P _ S _ 2O _ 5 F- in phosphogypsum by water washing and sulfuric acid leaching under different conditions was compared. Calcium 偽 -hemihydrate was prepared by transprystallization of phosphogypsum in Ca-Mg-K complex salt solution. The products in the reaction system were characterized by TG-DTA and other analytical methods under different Ca~(2 concentration and pH value. The changes of the composition and content of solid and liquid in different reaction time were determined. The corresponding Ca~(2) concentration and the transgranular rate at pH were calculated. The dissolution kinetics model of phosphogypsum was established, and the solute saturation C * and the dissolution rate of phosphogypsum R _ s were fitted. The reaction kinetics equations under different reaction conditions were obtained. The main contents and conclusions are as follows: 1) the impurity removal process of phosphogypsum is studied, and the results show that. The water soluble P _ 2O _ 5F in phosphogypsum can be effectively removed by single washing and removing impurity under the condition of water washing for 60 min and temperature 65 鈩，

本文編號(hào)：1449249