提纯硅藻土对废水中磷的吸附研究

通过提纯后的硅藻土对模拟废水中磷素的吸附研究,考察了硅藻土的用量、吸附时间、溶液pH值、吸附温度对吸附过程的影响。研究结果表明:硅藻土的最佳用量为3.5g硅藻土/0.1mg磷左右;最佳震荡吸附时间为20min左右;溶液的最佳pH值为3.0左右,且随着pH值的增大吸附率减小,特别在溶液呈碱性的时候吸附效果明显变差;最佳吸附温度约为25℃;硅藻土对废水中磷素的吸附过程符合Freundlich等温吸附方程。     

硅藻土制备硅酸钙板的研究

我国硅藻土资源丰富,由于其具有多孔性、密度小、强度高的特点,用来制备轻质保温建筑材料具有较好的发展前景。本文以硅藻土、水泥、木纤维为原料,流浆成型后经180℃(1MPa)蒸压养护8h获得了硅酸钙板,并探讨了硅藻土、木纤维的添加量对所制备硅酸钙板性能的影响。结果表明,通过改变硅藻土的加入量可以制备出性能指标达到D0.8~1.3-II、D0.8~1.3-Ⅲ类别的硅酸钙板,其导热系数均小于0.16W/(m·K)、吸水率与硅藻土加入量呈线性关系;但通过改变木纤维的加入量来制备不同类别硅酸钙板的尝试不具可行性。     

硅藻土附载丁香酚缓释对草莓的保鲜作用

采用不同质量附载丁香酚的硅藻土对草莓进行保鲜处理,在4℃条件下贮藏,研究贮藏期间草莓品质的变化。结果表明:在4℃贮藏条件下,1 g～7 g质量的丁香酚/硅藻土均能达到保鲜效果,但其中3 g质量的丁香酚/硅藻土效果最好,能显著抑制草莓的腐烂和质量损失,降低草莓可溶性固形物、可滴定酸和Vc含量的下降速率,还能延缓果实表层及果肉硬度的下降,抑制抗氧化酶活性的下降以及MDA积累,使其维持较好的感官品质,且无不良气味产生;在贮藏9 d时,空白腐烂率达到50%,而经质量3 g的丁香酚/硅藻土缓释处理的草莓在贮藏15 d时,腐烂率仅42.51%,能延长5 d的贮藏期,此时草莓的失重率1.25%,可溶性固形物含量为4.45%,可滴定酸和Vc含量分别为0.91%和34.56 mg/100 g,MDA含量为29.21 nmol/g,SOD和POD活性分别为334.15 U/mL和0.67 U/mg,草莓表层硬度和果肉硬度分别为69.20%和67.17 g。由此可见,硅藻土附载丁香酚缓释处理对草莓具有一定的保鲜作用,其中,3 g丁香酚/硅藻土效果最佳。     

H3PW12O40/酸改性硅藻土催化剂的制备、表征及催化合成乙酸正丁酯

以硫酸改性后的硅藻土为载体，Keggin结构磷钨酸为活性组分，通过浸渍法制备出负载型催化剂H₃PW₁₂O₄₀/改性硅藻土，并对催化剂进行傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）、扫描电镜（SEM）、X射线能谱（EDS）和N₂-程序升温脱附（N₂-TPD）表征。结果表明：酸改性后硅藻土的微孔增大增多，比表面积增大。H₃PW₁₂O₄₀均匀分布在改性硅藻土载体上，负载后磷钨酸仍保持Keggin结构。以H₃PW₁₂O₄₀/改性硅藻土为催化剂催化乙酸和正丁醇液相合成乙酸正丁酯，通过正交试验探索优化工艺条件。在较优工艺条件下，即w(40%H₃PW₁₂O₄₀/改性硅藻土)=1.1%（基于反应物质量），n(酸)∶n(醇)=1∶3，125℃反应2.0h，酯化率高达98.1%。催化剂重复催化使用5次，酯化率仍可达86.1%。H₃PW₁₂O₄₀/改性硅藻土可作为催化合成乙酸正丁酯的高效催化剂，具有活性高、用量少、价格低廉、制备简单、后处理简便、无废液排放等优点。     

一维普鲁士蓝/硅藻土复合材料对Cs+的吸附

含137Cs的放射性废水处理在核能及核技术应用中具有重要意义。以表面活性剂十六烷基三甲基溴化钾和十二烷基磺酸钠为模版，合成了一维结构的普鲁士蓝并将其附着在硅藻土表面，制备成一维普鲁士蓝/硅藻土复合材料；在不同的温度、吸附时间、pH值下，分别探究了一维普鲁士蓝/硅藻土复合材料对Cs⁺的吸附性能，并研究了溶液中其他阳离子对吸附的影响。结果表明：一维普鲁士蓝/硅藻土对Cs⁺的吸附能力随温度（293～318 K）的升高而增加（从42.4 mg/L到61.6 mg/L），其吸附行为符合Langmuir等温线和准二级动力学方程。     

Study on pilot-scale centrifugal separator for low-grade diatomite purification using response surface methodology

This study investigated the performance and optimal operating conditions of a pilot-scale centrifugal separator for low-grade diatomite purification using response surface methodology (RSM). The individual and interactive effects of the feeding concentration (mass concentration of solids in the feeding slurry), centrifugal speed, feeding rate, and feeding time on the mass concentrations of centrifugal overflow and the SiO₂ contents of centrifugal concentrate was investigated by RSM. Two second-order polynomial equations between the response and independent variables were proposed to describe the influence of different variables on the mass concentrations of the centrifugal overflow and SiO₂ contents of centrifugal concentrate. It is indicated that the feeding concentration has the greatest influence on the tailing concentration. The operating conditions of the centrifugal separator were further optimized and the SiO₂ content of purified diatomite was increased from 80.17% to 86.89% under the optimal conditions. Compared with raw minerals, the purity and porosity of diatomite were significantly improved after purification from chemical, x-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. It is concluded that this type of pilot-scale centrifugal separator is a potentially reliable instrument for low-grade diatomite purification at low cost in the industry.     

Mechanical and microstructural properties of calcined diatomite powder modified high strength mortars at ambient and high temperatures

In this experimental work, mechanical and microstructural properties of calcined diatomite powder (CDP) modified high strength mortars (HSMs) at ambient and high temperatures were researched. In the HSM mixtures, Portland cement was replaced with CDP at ratios of 0%, 5%, 10%, 15% and 20%. Several experiments regarding the hardened properties were carried out at 14, 28, 56 and 90 days at the ambient temperature of 25 °C. HSMs were heated up to high temperatures of 400 °C to 1000 °C at the age of 56 days, separately. Then, high temperature resistances of HSMs were quantified in terms of the residual hardened properties and the changes in the microstructural properties after heating. The residual performance was found to be higher in the HSMs modified with CDP than in the reference HSM (R-HSM) which was made 0% CDP. Based on the test results, it was seen that the HSM modified with 15% CDP (15CDP-HSM) exhibited the highest mechanical properties at ambient and high temperatures.     

浙江嵊县硅藻土及其在钒催化剂中的应用

介绍浙江嵊县硅藻土的资源及质量，以及用该硅藻土作钒催化剂载体的研究开发。认为浙江嵊县硅藻土具有较好的物化结构，采用适当的精制工艺可大大提高其质量。用该硅藻土生产的硫酸钒催化剂具有强度高、活性好、寿命长的特点。     

硅藻土对沥青组分吸收作用的研究

选用4种沥青与四种硅藻土,将硅藻土加入沥青中,制成沥青胶浆,通过化学4组分的分析,证明硅藻土对沥青中的轻组分有较强地吸收作用,硅藻土通过吸收沥青中的饱和芬与芳香芬而改善沥青的道路使用性能,并对机理进行分析。     

Loading of Fe/Al compounds and adsorption of vanadium (V) on diatomite from Changbai Mountain

Abstract

In this study, the loaded diatomite was prepared with Changbai Mountain diatomite as the carrier according to different Fe/Al molar ratios. The structure and adsorption of the above materials were characterized by XRD, SEM, and ICP-OES. The effects of Fe/Al molar ratio, adsorption time, initial concentration of V(V), and the initial pH value of the solution on the adsorption performance of loaded diatomite were explored. The diatomite loaded with Fe/Al compounds could significantly improve the removal efficiency of V(V), and the removal efficiency of loaded diatomite prepared according to a Fe/Al molar ratio of 1:3 was better. Reaction equilibrium time is 24?h and the pseudo second-order kinetic equation can better describe the adsorption kinetic behavior of V(V) on loaded diatomite. When the initial concentration of V(V) increased from 15.85?mg/L to 122.5?mg/L, the unit adsorption capacity and removal rate of V(V) by loaded diatomite increased continuously. The adsorption behavior of V(V) on loaded diatomaceous earth belongs to the chemical adsorption via the multi-molecular layer, which is consistent with the Freundlich isotherm adsorption model. A weak acid environment is beneficial to the adsorption behavior of V(V) on loaded diatomaceous earth and the strong alkaline environment should be avoided.