【作者】 刘永红；

【导师】 胡红青；

【作者基本信息】 华中农业大学 ， 土壤学， 2012， 博士

【摘要】 本研究选取产自湖北的3利中低品位磷矿,采用几种低分子量有机酸(Low molecular weight organic acids,简称LMWOAs)和无机酸(盐酸、硫酸)进行磷矿活化试验,比较了不同酸的活化效果,探讨了有机酸的浓度、活化时间、活化温度、溶液pH、酸根、液固比、磷矿粉粒径大小等因素对磷释放的影响,以及磷矿粉释磷过程中Ca2+、Mg2+释放特点,并利用傅立叶转换红外光谱(FTIR)、拉曼光谱(Raman)、X-射线衍射(XRD)、扫描电子显微镜/能谱分析(SEM/EDS)和X-射线光电子能谱(XPS)等研究草酸与磷矿粉的作用机理。在此基础上,还研究了磷矿粉及草酸活化磷矿粉对水溶液中Cu2+的去除效果和影响因素,并应用Raman、XRD、XPS等手段研究Cu2+与磷矿粉、活化磷矿粉作用机理。主要研究结果有：(1)供试酸均能活化磷矿粉释放磷,不同酸活化释磷效果不同。本试验浓度范围内(0.10-0.50mol/L),酸活化磷矿释磷效果顺序为：硫酸>草酸>盐酸>柠檬酸>酒石酸>甲酸>苹果酸>琥珀酸>乙酸。有机酸活化磷矿粉释磷与酸的强弱有关,酸性越强,释磷量越高；供试有机酸对磷矿粉的活化效果为：三元酸>二元酸>一元酸；混合有机酸活化效果并不比单一酸的效果好。(2)磷矿粉释磷量与诸多因素有关。草酸和柠檬酸浓度越高,磷矿粉活化效果越好；磷矿粉中磷的释放量与溶液pH呈负相关；有机酸溶液和磷矿粉的液固比越高、磷矿粉粒径越小、全磷量越高,磷的释放量越大。(3)磷的释放也受有机酸浓度和活化时间影响,各阶段可用不同动力学方程描述。当草酸和柠檬酸浓度为0.50mol/L时,磷矿粉释磷量随时间的延长而增加,一级动力学方程可合理拟合全过程。24小时内,磷的释放可用Elovich方程拟合。之后,磷释放速率减缓,一级动力学方程较合理。而当草酸和柠檬酸浓度为20mol/L时,磷矿粉中磷的释放速率一直呈减小的趋势,线性方程可拟合保康和南漳磷矿粉释磷趋势,钟祥磷矿粉可用Elovich方程拟合。(4)磷矿粉释磷过程也伴随着Ca2+、Mg2+的释放,但不同浓度酸对钙、镁的释放有差异。0.10-0.50mol/L草酸和柠檬酸与磷矿粉作用后,3种磷矿粉中Ca2+的释放量差异显著,而释放的Mg2+无差异。0.01-0.05mol/L草酸和柠檬酸与磷矿粉作用后,3种磷矿粉中Ca2+的释放量无差异,Mg2+的差异显著。(5)有机酸根对磷矿粉释磷的影响各有不同。当草酸根浓度(1-20mol/L)增加时,不同浓度酸根间的释磷量差异显著(p<0.01)；而不同浓度柠檬酸根间的磷释放量差异不大。当控制溶液pH,改变有机酸根的浓度时,磷的释放量随着酸根浓度的增加而增加,不同酸根浓度间的磷释放量差异显著(p<0.01)。(6) FTIR、Raman、XRD、SEM/EDS和XPS研究均表明：草酸与磷矿作用后,磷矿粉中的磷灰石和磷酸钙因溶解而减少,同时产生了磷酸二氢钙和大量草酸钙晶体,而柠檬酸与磷矿作用只生成磷酸氢钙。(7)磷矿粉和活化磷矿粉可以除去水溶液中的重金属Cu2+,去除效果与溶液pH有关,在pH3-5范围内,磷矿粉对Cu2+的吸附量随pH升高而逐渐升高。等温吸附方程显示,Freundlich方程能较好的拟合吸附曲线,高温利于Cu2+的固定。反应介质的离子强度和其他共存重金属Cd2+对磷矿粉去除Cu2+有影响,且随着离子强度的增加而减小,随共存离子Cd2+浓度的升高而降低,Cu2+和Cd2+在磷矿粉中存在竞争。活化磷矿粉去除Cu2+的效果大于磷矿粉。(8)Cu2+在磷矿粉和活化磷矿粉表面发生了吸附作用,FTIR、XRD、Raman和XPS的结果表明,Cu2+没有与磷矿粉和活化磷矿粉发生表面吸附而被固定,它们之间以物理吸附为主,兼有化学吸附。更多还原

【Abstract】 Three medium-grade PRs were selected from Hubei province, experiments with several common low molecular weight organic acids (Low molecular weight organic acids, LMWOAs) and inorganic acid (hydrochloric acid, sulfuric acid) were carrie out. And comparison of the activation effectiveness between the acids was analyzised. The different effects of phosphorus(P) release, such as the concentration of organic acids, activation time, activation temperature, pH, acid ion, liquid-solid ratio, particle size of PR, on PRs were investigated. At the same time, the calcium (Ca) and magnesium (Mg) release were determined. The morden techniques, such as infrared spectroscopy (IR), Raman spectroscopy (Raman), X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and X-ray photoelectron spectroscopy (XPS) were used to investigate the mechanism between oxalic acid and PR. In this paper, the Cu2+removal from aqueous solution with PR and activated phosphate rock (APR) and its influencing factors were also investigated. The techniques of Raman, XRD and XPS were applied to analysis the reaction between Cu2+and PR (as well as APRs). The main results are as follows:(1) The results of PRs dissolution in the presence of acids showed that:inorganic acids and organic acids can activate the PRs, but the effects of P release from PRs vary different acids. In laboratory experiment, as the acids concentrations are ranged from0.10to0.50mol/L, the P release from PRs is as follows:sulfuric acid> oxalic acid> hydrochloric acid> citric acid> tartaric acid> formic acid> malic acid> succinic acid> acetic acid. In terms of the same type of organic acid, the effectiveness of the acids on the P release is as this order: oxalic acid> tartaric acid> malic acid> succinic acid, and formic acid> acetic acid. The results indicate that acids would activate the PRs, and the more th amount of P release are, the more the stronger the acids are. If the acidity of the LMWOAs are the similar, their activation effect on PRs are as follows:ternary-acid> dicarboxylic-acid> mono-acid. The effectiveness of mixed acids is not stronger than that of single acid(2) The amount of P release is related to various factors. In terms of oxalic acid and citric acid, the results that the results of effects on PRs activation show that:the higher the concentration of acids were, the better the activation effectiveness were; there was a better negative correlation between the pH and the amount of phosphorus release from PRs. The higher the ratios of liquid-solid (volume of acid solution to amss of PR) were, the smaller the particle size of PR was, the more the phosphorus content of PR was, the more the P release from PR was.(3) The amount of P release from PRs is related to the acids concentration and reaction time. The processes of PRs dissolution were described with different kinetic equations. When the concentrations of oxalic acid and citric acid were0.50mol/L, the amount of P release from PRs increased with time. Within24hours, the rate of P release was rapid, and the firrst-order equation would be described the tendency. After6days, the P release rate further slowed down, and the Elovich equation would be stated the next process. When the concentration of oxalic acid and citric acid was20mmol/L, the P release from PRs was shown a decreasing trend. The P release processes of BKPR and NZPR would be described with linear equation, and ZXPR with Elovich equation.(4) The Ca2+and Mg2+release from PRs was also accompanied with the process of P release, but there were differences in Ca2+and Mg2+release from PRs. While the concentration of oxalic acid and citric acid was0.10-0.50mol/L, the amount of Ca2+release were significantly different in concentrations; while the Mg2+release was no difference. While the concentrations of oxalic acid and citric acid were0.010-0.050mol/L, the results were on the contrary.(5) The effects of organic acids ion P release from PRs varied. When the concentration of oxalate increased, the difference of P release between various concentrations of acid ion were significant difference (p<0.01), but the difference of citrate was not significant (p>0.1). When the pH of solution was controlled, the P release increased with the acid ion concentration increasing, there were significantly different in P release between different concentrations.(6) The spectra of FTIR, XRD, Raman, SEM/EDS and XPS of the tested samples indicated that there were obviously significant differences between PRs and activated PRs. And the results stated that when the PRs reacted with oxalic acid and citric acid, some new substances calcium oxalate monohydrate and calcium hydrogen phosphate dihyrate in oxalic aicd, and only new material, calcium dihydrogen phosphate monohyrate, was in presence of citric acid.(7) The PR and APR could be a new passivating agent to remove the heavy metals Cu2+ in aqueous solution. The effectiveness of Cu2+removal with PR and APR was related with the pH of the solution. When pH ws ranged from3-5, the amount of Cu2+fixed in minerals gradually increased with pH increasing. Adsorption isotherm equation showed that the Freundlich equation could be better described the adsorption reaction, and the temperature was conducive to Cu2+removal. The ionic strength of the medium and other co-existed heavy metal Cd2+could influence Cu2+removal with PRs and APRs. With the increase in ionic strength decrease and the concentration of Cd2+ions increase, the amount of Cu2+removal decreased. There was competition and collaboration between the Cd2+and Cu2+. The amount of Cu2+adsorbed in APR was more than that of PR.(8) When the PR and APR were added into the Cu2+solution, the Cu2+adsorption occurred in the surface of PR and APR. The results of FTIR, Raman, XRD and XPS showed that the new copper salts were not found in the surface of PR and APR; there was mainly physical adsorption between the Cu2+and PR (APR), maybe was chemical adsorption.更多还原