【作者】 陈平；

【导师】 金奇庭；

【作者基本信息】 西安建筑科技大学 ， 环境工程， 2004， 博士

【摘要】 载体诱导沉淀结晶技术的特点是在沉淀反应体系中人为地加入大量合适的诱晶载体粒子，使沉淀反应加速，并使沉淀物随诱晶载体粒子一起沉降，从而使化学沉淀工艺时间大大缩短。文献表明，该技术在国内研究报道很少，国外研究主要关心去除对象的脱除情况，而缺少理论研究。为此，本文较系统地研究了石英砂诱导CaCO₃沉淀反应动力学、热力学及其诱导机理，石英砂诱导沉淀结晶软化水，石英砂诱导CaF₂沉淀结晶脱氟及其诱导机理。 在搅拌反应器中研究了沉淀剂Na₂CO₃加入量、石英砂粒子加入量、搅拌强度、温度对石英砂诱导CaCO₃沉淀反应的影响。通过测定反应过程中的Ca²⁺浓度、pH值，并根据相关平衡关系计算相应的CO₃^2-浓度。首次得到石英砂诱导CaCO₃沉淀反应动力学方程：r=k′ S[Ca²⁺][CO₃²]+b；石英砂粒子浓度约250g／L时、无石英砂粒子时，CaCO₃沉淀反应活化能分别为14.07KJ／mol、31.74KJ／mol。说明石英砂在反应动力学上诱导CaCO₃沉淀反应。 在搅拌反应器中研究了有无石英砂粒子时CaCO₃沉淀反应的诱导时间、启动过饱和度和剩余过饱和度。通过测定沉淀剂Na2CO₃加入后体系中Ca²⁺浓度的变化确定诱导时间。根据诱导时间与沉淀剂加入量的线性拟合方程得到诱导时间为零时的沉淀剂加入量即反应启动需要的沉淀剂加入量。沉淀体系中Ca²⁺浓度稳定时认为沉淀反应结束。分别测定上述两种情况下体系中的相关参数，计算得到CaCO₃沉淀反应的启动过饱和度和剩余过饱和度。在25℃时，与无石英砂粒子时相比，浓度约100g／L的石英砂粒子使CaCO₃沉淀反应的诱导时间缩短5-6min；浓度约100g／L的石英砂粒子使启动过饱和指数从1.6降到1.44；浓度约74g／L、250g／L的石英砂粒子分别使剩余过饱和指数从0.421降到0.398、0.371。说明石英砂在反应热力学上诱导CaCO₃沉淀反应；石英砂粒子浓度越大，反应结束时体系越稳定。 通过电泳、红外光谱测定和化学分析研究了诱导沉淀反应中石英砂粒子的表面荷电特性、表面特征基团及对Ca²⁺、F^-的吸附情况。发现石英砂粒子的表面特征基团为羟基；石英砂粒子对Ca²⁺、F^-有吸附作用，且随体系pH值增大，对Ca²⁺的吸附能力增强；在石英砂诱导CaCO₃沉淀反应中，石英砂粒子表面荷负电；在石英砂诱导CaF₂沉淀反应中，石英砂粒子表面荷正电。结合表面络合吸附模式及沉淀体系的酸碱性，得出在石英砂诱导CaCO₃、CaF₂沉淀反应中，石西安建筑科技大学博士学位论文英砂粒子的主要表面荷电形式分别为:二XO一、二XOCa+，进而提出石英砂粒子表面的双电层结构分别为:{2m〔二xo一〕·（m一x）C尹}2x-xG尹、{m〔三x0Ca+〕·（m一x）F一}x+xF一。由上述双电层结构可见，表面双电层中至少含有一种沉淀物的构成离子时固体粒子才能诱导沉淀反应。 通过对比搅拌悬浮态和流化态石英砂体系中软化、脱氟稳定需要的水力停留时间和出水浊度，分析了石英砂粒子悬浮方式对软化速度、脱氟速度和软化沉淀物、脱氟沉淀物在石英砂上粘附的影响。搅拌悬浮态石英砂粒子浓度为8%（V/V）;流化态石英砂粒子浓度为52.7%（vN）。在搅拌悬浮态石英砂体系中软化水时，软化稳定需要的水力停留时间为10rllixl，且反应结束时体系浊度增加很大;在流化态石英砂体系中软化水时，软化稳定需要的水力停留时间为:簇0.47 Ilnin，且进出水蚀度不变;在搅拌悬浮态石英砂体系中脱氟时，脱氟稳定需要的水力停留时间为4min，且反应结束时体系浊度增加很大;在流化态石英砂体系中脱氟时，脱氟稳定需要的水力停留时间为:簇0.377n血，且进出水浊度不变。说明在流化态石英砂体系中的软化速度、脱氟速度较大，且软化沉淀物、脱氟沉淀物均粘附在流化态石英砂粒子上;流化床反应器比搅拌反应器更适于石英砂诱导沉淀结晶软化水及脱氟。 在流化态石英砂诱导沉淀结晶软化水连续试验中，连续试验时间为40h，进水参数为:Ca2+1.货刘mo比、总硬度2.36nuno比、碱度248mmo比、s时一1 .29nnno比、PH7.sl、浊度3井度。在连续试验过程中，出水浊度、软化稳定需要的水力停留时间分别为2一5度、(0.471 mill;在出水中caZ+浓度刚稳定时，出水中caZ十浓度和总硬度分别为:0.43 nunoVL、0.86^OFL:在连续试验5h后，出水中c之浓度和总硬度分别为0. lllYUno比、0.55n加幻比;显微图像显示，沉淀物容易粘附在石英砂粒子表面粗糙之处;%.46%（侧w）的沉淀物为C翻C伪.说明流化态石英砂诱导沉淀结晶能够连续稳定地软化水:搜盖CaC伍的石英砂粒子对C副C伪沉淀反应的诱导能力大于石英砂粒子本身的诱导自幼;在软化水中使用表面粗糙的石英砂粒子利于沉淀物的粘附。 在流化态石英砂诱导沉淀结晶脱氟中，对Fee79.sm泌、蚀度为1度的酉己水，脱氟稳定需要的水力停留时间为:簇0.377min;出水浊度为l度;出水中F一浓度可达4.33m叭，该浓度达到了污水综合排放标准（。B名卯8-88）10In叭的要求.说明石英砂诱导沉淀结晶可用于工业废水脱氟。更多还原

【Abstract】 The features of carrier induction crystallization are that a large amount of the grains of suitable carrier are added in precipitation reaction system, the grains speed reaction up, precipitates sedimentate with the grains and the time of precipitation process is shorten.Its researches have been absent in China, mainly focused on application fields and its theory researches have been absent overseas. This paper has studied the reaction kinetics and thermodynamics of silica induction CaCO3 precipitation reaction and its induction mechanism, water softening with silica induction crystallization, fluoride removal with silica induction CaF2 crystallization and its induction mechanism.The effects of Na2C03 quantity, the quantity of silica grains, stirred speed, temperature on silica induction CaCO3 precipitation reaction have been studied in stirred reactor. The concentrations of Ca2+ and pH were measured during reaction and the corresponding CO32- concentrations were calculated. The kinetics equation of silica induction CaCO3 precipitation reaction could be described as r=-k’ S[Ca2+][CO32-]+b; its activation energies were 14.07KJ/mol and 31.74KJ/mol respectively when the concentration of silica grains was about 250g/L and there were no silica grains. The results demonstrate that silica induces CaCO3 precipitation reaction in the reaction kinetics.The induction times, start-up supersaturations and residual supersaturations of CaCO3 precipitation reaction have been studied in stirred reactor when there were and there were no silica grains. The induction times were determined by the transformation of the concentrations of Ca2+after precipitation agent Na2CO3 were added in reaction system. The precipitation agent quantities when induction timeswere zero, which were the precipitation agent quantities when precipitation reactions started wereobtained by the linear fitting equations of induction times and precipitation agent quantities. When the concentrations of Ca2+ were stable precipitation reactions had ended. The relevant parameters of the two situations above were measured and the start-up supersaturations and residual supersaturations were calculated. At 25℃, comparing with no silica grains, silica that the concentration of its grains was about 100g/L shortened induction times 5-6min; when the concentration of silica grains was about100g/L the start-up supersaturations was decreased from 1.6 to 1.44, when the concentrations of silica grains were about 74g/L and 250g/L the residual supersaturations were decreased from 0.421 to 0.398 and 0.371 respectively. The results demonstrate that silica induces CaCO3 precipitation reaction in the reaction thermodynamics; higher the concentration of silica grains, more stable the system when reaction has ended.The peculiarities of the surface charge of silica grains, the characteristic function group on the surface of silica grains, the absorption of Ca2+ F- on the surfaces of silica grains have been studied by electrophoresis, IR and chemical analysis. The characteristic function group on the surfaces of silica grains was hydroxyl; silica grains absorbed Ca2+ F~, and increasing pH, the quantities of Ca2+ which were absorbed on silica grains increased; in silica induction CaCO3 precipitation reaction, the silica grains had negative surface charges; in silica induction CaF2 precipitation reaction, the silica grains had positive surface charges. According to the surface complexation models, the alkalinities of precipitation systems and the tests results, the main surface charge forms of silica grains were =Xo- and = XOCa+ respectively in silica induction CaCO3and CaF2 precipitation reaction, and the forms of surface electric double layer of silica grains were (2m (=XO-) (m-x) Ca2+} 2x- xCa2+ and {m ( = XOCa+) (m-x) F-)x+x F-respectively. According to the the forms of the surface electric double layer above, when there is one ion at least in their surface electric double layer which is one of the ions of precipitates, carrier grains induce precipitation reac更多还原