K2SO4/KCl添加剂对脱硫石膏晶须结晶的影响

以提纯后的脱硫石膏为原料,分别以K2 SO4和KCl为添加剂,采用水热法制备了脱硫石膏晶须,研究了添加剂用量对晶须显微结构、长径比和溶液组成的影响,并探讨了其作用机理.研究结果表明:添加剂用量对晶须形貌影响较大,但并不影响其物相组成;当K2SO4、KCl用量分别为3;和5;时,制备的晶须结晶良好,长径比分别达80和50.加入K2SO4后,脱硫石膏在反应溶液中的溶解度减小,而加入KCl,其溶解度增大.强电解质离子K+的加入,促使晶须延c轴生长,从而使其长径比增大.     

制备方法与Ce3+对二水硫酸钙晶须形貌的影响

本文以稀土石膏为原材料研究了制备方法对硫酸钙晶须(CSW)形貌和结构的影响，并以二水硫酸钙(分析纯)为原材料，CeCl₃·7H₂O为铈源，探究稀土铈的加入对CSW的结构和形貌的影响。利用SEM、XRD、XPS和FL等表征手段对CSW的结构、形貌和组成及其荧光性能等进行表征和分析。研究结果表明：采用微波法可以制备高长径比的CSW,其平均长度为263μm,平均长径比为39.50。Ce³⁺以原子置换的形式进入CSW,对晶须的晶体结构不产生影响，但改善了CSW的形貌。添加2%(质量分数)的Ce³⁺能够促进晶须向一维生长，使得CSW的长径比显著增加，而过量的Ce³⁺会促使晶须横向生长。研究证明稀土石膏中含有微量的稀土元素Ce,同时发现由稀土石膏制备的CSW具有发射蓝光的特性，这对开发利用稀土石膏具有重要的理论指导意义。     

混合助晶剂促进大长径比硫酸钙晶须的调控研究

以预处理后的磷石膏为原料,氯化镁、丙三醇、丙三醇/无水乙醇、丙三醇/硬脂酸为助晶剂,采用水热法制备了硫酸钙晶须,利用XRF、SEM、XRD和FT-IR分别对硫酸钙晶须的成分含量、表面形貌、物相特征等进行了表征.结果表明,混合助晶剂能够明显增大硫酸钙晶须的长径比,提高晶须合成率,改善晶须形貌.在丙三醇/无水乙醇体系中,当V(无水乙醇)/V(丙三醇)=0.8时,硫酸钙晶须的合成率为96;,长径比可达90.在丙三醇/硬脂酸体系中,当m(硬脂酸)/m(磷石膏)=2;时,硫酸钙晶须的合成率为94;,长径比可达75.     

H2SO4-H2O中硝酸铜对脱硫石膏晶须生长的影响

以处理后的脱硫石膏为原料,在H₂SO₄-H₂O体系中以Cu(NO₃)₂为晶形控制剂采用水热法制备脱硫石膏晶须,探讨了Cu(NO₃)₂对脱硫石膏晶须生长的影响机理。结果表明:Cu(NO₃)₂对脱硫石膏有明显促溶作用,其中Cu²⁺可减小溶液中各离子的活度系数,使溶液中的Ca²⁺浓度增大。NO^-₃通过静电作用在Ca²⁺周围聚集并对SO^2-₄产生屏蔽作用,导致脱硫石膏继续溶解并使Ca²⁺和SO^2-₄的浓度处于相对稳定状态,有利于半水脱硫石膏晶体的形核与生长。此外,Cu²⁺还可在晶须的生长过程中选择性吸附在晶须表面,生成CuSO₄,促进了脱硫石膏的结晶生长,最终在Cu(NO₃)₂用量为2.0%(质量分数)时制备的脱硫石膏晶须长径比约为73。     

添加CaSO4·2H2O为晶种制备磷石膏半水硫酸钙晶须

以固体废弃物磷石膏为原料,在传统常压醇水热法的基础上添加CaSO₄·2H₂O为晶种制备半水硫酸钙晶须。采用单因素试验法探究了晶种含量、丙三醇含量和磷石膏质量分数对晶须结构和形貌的影响,确定晶须的最佳制备工艺条件。采用SEM和XRD对样品进行表征分析,实验结果表明:添加CaSO₄·2H₂O晶种制备晶须的长径比(49.29)比只添加丙三醇的样品的长径比(30.99)提高了近60%;当丙三醇与水的体积比(V)为1、晶种含量为1%、磷石膏质量分数为5%时制备的晶须的平均直径为0.65 μm,长径比达到了62.15,晶须的尺寸均匀。这说明添加1%CaSO₄·2H₂O晶种、V为1的丙三醇和质量分数为5%的磷石膏在常压下能制备出高长径比和尺寸均匀的半水硫酸钙晶须。     

白云石精制液中不同离子对碳酸钙晶须的影响

以白云石精制液和二氧化碳为实验原料,采用气液接触法制备碳酸钙晶须。研究了杂质离子Mg²⁺、NH⁺₄和NO^-₃对碳酸钙晶须长径比和形貌的影响。采用扫描电镜(SEM)和X射线衍射仪(XRD)对样品的形貌和晶体结构进行表征。结果表明:NH⁺₄浓度在0.3 mol/L,Mg²⁺浓度在0.05 mol/L,NO^-₃浓度在0.2 mol/L的情况下碳酸钙晶须的形貌和长径比最佳,其中长径比最高可以达到25以上;最后再结合晶体生长理论,阐明了碳酸钙晶须的结晶过程和生长机理。     

机械力活化对脱硫石膏制备硫酸钙晶须的影响

对脱硫石膏原料进行机械力活化,然后采用降温重结晶法制备出硫酸钙晶须.借助扫描电镜、图像粒度分析仪和相关软件进行表征,并初步讨论了机械力活化对晶须成核和生长过程的影响.结果表明:经过机械力活化的脱硫石膏可以制备有较大长径比的硫酸钙晶须.在水浴反应温度为75℃,硫酸浓度为2.5 mol/L,机械力活化时间为3.5 h,浆料浓度为2;的条件下,制备的硫酸钙晶须平均长径比为150,平均直径为2.1μm.     

高长径比三水碳酸镁晶须的合成研究

本文以MgCl2·6H2O和NH4HCO3作为反应物料,采用低温液相合成法制备出三水碳酸镁晶须.考查了Mg2+初始浓度、NH4HCO3溶液的滴加速度、搅拌速度及表面活性剂种类等因素对三水碳酸镁晶须的长度及长径比的影响.研究结果表明:在Mg2+初始浓度为0.5 mol/L、NH4HCO3的滴加速度5 mL/min、搅拌速度为120 r/min、选用KH2PO4作表面活性剂的试验条件下,可以合成出长度325 μm、直径8.25 μm,长径比高达32的三水碳酸镁晶须产品.     

磷石膏蒸压制备半水硫酸钙晶须

以磷石膏为原料,利用蒸压法制备半水硫酸钙晶须.采用均匀设计实验的基础上,进一步考察了料浆固液比、反应时间、蒸压压力对产品长径比的影响,并借助透射偏光显微镜、X射线衍射仪(XRD)等仪器对产品进行表征.结果表明,最佳反应条件:料浆固液比0.15 g· mL-1、反应时间0.5h、蒸压的压力0.3 MPa,在此条件下制备出了长径比99.07、晶须直径约1μm、纯度高、结晶良好的晶须产品.并从微观形貌、晶体结构、物相分析三个方面阐明了半水硫酸钙晶须生长规律.本研究对磷石膏的高值化利用具有指导意义.     

脱硫石膏重结晶法制备硫酸钙晶须及其除砷性能初探

以电厂脱硫石膏为原料,利用重结晶原理制备二水硫酸钙晶须.考察了溶液过饱和度、硫酸浓度、陈化温度/时间以及降温速率对晶须生长特性的影响,并初步研究了硫酸钙晶须对含砷水溶液的除砷性能.结果表明:所研究的操作条件对晶须形貌、尺寸均有一定影响.在H2SO4溶液重结晶体系中,控制硫酸钙过饱和度为0.5、陈化温度为20℃、陈化时间为3h并采用自然降温时,制备的二水硫酸钙晶须结晶度较好、形貌尺寸均匀,长径比为50～200.该二水硫酸钙晶须在pH为12时,能将初始浓度低于1 mg/L的含砷水溶液净化至满足地表水标准(0.05mg/L),展示了其在砷污染水体净化方面的应用潜力,可配合石灰-硫酸亚铁两段法除砷,降低废水处理成本.     

石膏晶须的制备方法与应用

石膏晶须是一种性价比高、力学性能良好以及对环境友好的材料,可应用于复合材料、造纸、催化、可生物降解材料等领域.石膏晶须的制备大多停留在工艺参数研究上,对石膏晶须特征和应用研究不足.本文讨论了石膏晶须的结构,从产物形成过程上对石膏晶须的制备方法进行了分类和评述;对不同制备方法和不同应用领域的石膏晶须的产物特征进行了总结,讨论了制备和应用之间的相关性;并讨论了石膏晶须未来的发展方向.     

Preparation,characterization and in vitro assessment of ibuprofen loaded calcium phosphate/gypsum bone cements

In the present study, pure and mixed calcium phosphate/gypsum cements were prepared and characterized. Chara‐cterizations were performed using X‐ray diffraction FTIR spectroscopy, thermogravimetric analysis, and Scanning Electron Microscopy. Furthermore, the mechanical proper‐ties of the materials were studied and it was found that they depend with the gypsum content. Bioactivity tests after incubation in 2xSBF solution revealed dense apatite structure on the samples containing α‐tricalcium phosphate while the pure gypsum specimens showed sparse distributed tiny apatite crystals. Finally, 1% and 2% wt of the anti‐inflammatory drug ibuprofen incorporated into the cement paste and the release behaviour of the drug was stu‐died for 18 days in PBS solution. The results showed marked differences in the release profiles of ibuprofen for the different formulations. Complete release of the drug was noticed in the case of pure calcium phosphate cements within 18 days whereas ca. 35–40% of the drug was released from its congeners containing gypsum at the same timescale.     

Growth morphology of gypsum in the presence of copolymers

Gypsum is the most abundant natural sulphate, and in industrial application it plays an important role in gypsum based binders. Furthermore, it plays a critical role in the hydration of Portland cement, and then gypsum is one of the most important cement additive. In this paper we investigated the role of two commercial polymeric additives in modifying the crystal habits and size of gypsum, growth in aqueous solution. These two additives belong to the categories of acrylic polymers and they are known only by their commercial names of SP1 and SP3. We found that these substances can act as shape modifiers mainly at concentration over 0.04% by weight, with a shortening in the elongation of gypsum crystal and some change in the characters of {001} form, from stepped to flat, due to a change in the growth mechanism. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

磷酸盐和不同价态的阳离子氯化物对石膏硬化体结构与性能的影响

以不同种类的磷酸盐(Na3PO4、Na5P3O10和(NaPO3)6)和不同价态的阳离子氯化物(NaCl、MgCl2、AlCl3)为添加剂,借助SEM等其他测试手段分析石膏硬化体的显微结构,研究半水石膏浆成型和石膏硬化体性能的变化.结果表明,氯化物无机盐中阳离子价态的升高对半水石膏浆的凝结时间无明显影响,但会引起石膏硬化体的吸水率显著提高,硬化体强度略有下降;加入磷酸盐后石膏浆的缓凝时间显著增长,石膏硬化体的吸水率下降,强度提高,其中以(NaPO3)6影响最为显著.当磷酸盐添加量达到0.12;时,硬化体性能趋于稳定,添加了(NaPO3)6和Na5P3O10的石膏硬化体结构中存在着较多柱状晶体.     

Polyelectrolytes inhibition effect on crystallization of gypsum

The spontaneous precipitation of calcium sulfate dihydrate (gypsum) at 30 °C was investigated in the presence of polyelectrolytes. The degree of inhibition is measured as the reduction in initial crystallization rate, determined by conductivity of the crystallizing solution. The inhibition increases with acid content of the copolymer. Changing the butyl ester to a hydrophilic ethylene oxide resulted in higher inhibition efficiency. The inhibition efficiency is believed to arise from the closer chain packing on the crystal surface. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of CuCl2 on hydrothermal crystallization of calcium sulfate whiskers prepared from FGD gypsum

Using purified flue‐gas desulfurization (FGD) gypsum as raw material, effects of CuCl₂ on crystal morphology, phase structure, aspect ratio and crystallization of hydrothermal products prepared via hydrothermal crystallization in H₂SO₄‐H₂O solutions were investigated. The results show that dosage of CuCl₂ has a significant effect on the morphology, aspect ratio and crystallization of calcium sulfate whiskers (CSWs), but no effect on their phase transformation . At a dosage of 15 g CuCl₂/kg FGD gypsum, the produced calcium sulfate whiskers had diameters ranging from 1 to 3 μm with average aspect ratio greater than 200 . Transmission electron diffraction patterns and highly magnified surface morphology of CSWs were found different from those of self‐assembly crystals. Compared to self‐assembly crystals, the produced CSWs showed a single crystal structure and their surface was very smooth.     

Influence of citric acid on calcium sulfate dihydrate crystallization in aqueous media

The crystallization of Calcium sulfate dihydrate produced by the reaction between pure Ca(OH)₂ suspension and H₂SO₄ solution was investigated at different pH values, temperatures and citric acid concentrations. Crystal size distributions, filtration rates and zeta potentials of gypsum were determined as a function of citric acid concentrations at pH 3.5 and 65°C. The influence of citric acid on the morphology of gypsum was also investigated and discussed. The average particle size of gypsum was reached to maximum in the presence of approximately 2500 ppm citric acid concentration, where the minimum cake resistance and maximum filtration rate were obtained. In the presence of citric acid, various crystal morphologies such as tabular, plate‐like, double‐taper leaf‐like and flower‐like, etc., were obtained. The change of morphology is related to the preferential adsorption of citric acid on different crystallographic faces. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of citric acid and 1,2‐dihydroxybenzene 3,5‐disulfonic acid on crystallization of calcium sulfate dihydrate under simulated conditions of phosphoric acid production

The effect of citric acid and 1,2‐dihydroxybenzene 3,5‐disulfonic acid (DHBDSA), as additives, on the crystallization of gypsum was studied under simulated conditions of the of phosphoric acid production. Calcium hydrogen phosphate and sulfuric acid were mixed with dilute phosphoric acid at 80 °C, and the turbidity of the reaction mixture was measured at different time periods to calculate the induction time of gypsum crystals formation. Addition of citric acid increased the induction time and decreased the growth efficiency while addition of DHBDSA decreased the induction time and increased the growth efficiency compared with in absence of additives. The crystals mean and median diameters were found to decrease in the presence of citric acid and increased in the presence of DHBDSA. The surface energy decreased with citric acid and increased with DHBDSA compared to the baseline (without additives). Interestingly, the majority of the formed crystals are tabular with DHBDSA and needle‐like type with citric acid and baseline     

Effect of trace metals on reactive crystallization of gypsum

The effect of Fe²⁺, Fe³⁺, and Cr³⁺ ions on crystallization of calcium sulfate dihydrate (gypsum) produced by the reaction between calcium hydroxide suspension and sulphuric acid solution was investigated at 3.5 pH and 65°C in the absence and presence of 2500 ppm citric acid concentration. Crystal size distributions, filtration rates, and morphology of gypsum were determined and discussed as a function of ion concentration. Average particle size of gypsum was not affected significantly by the presence of Fe²⁺, Fe³⁺, and Cr³⁺ ions individually. Variation of gypsum morphology depending on ion concentration affected the filtration characteristics. The presence of Fe³⁺ or Cr³⁺ ions besides 2500 ppm citric acid influenced both average particle size and filtration characteristics. The effect of citric acid on gypsum morphology was suppressed at high Fe³⁺ and Cr³⁺ ion concentrations. The change of morphology is related to the complex formation between Fe³⁺ or Cr³⁺ ions and citric acid at high ion concentrations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)