Insight into the performance of novel kaolinite-cellulose/cobalt oxide nanocomposite as green adsorbent for liquid phase abatement of heavy metal ions: Modelling and mechanism

A cost-efficient kaolinite-cellulose/cobalt oxide green nanocomposite (Kao-Cel/Co₃O₄ NC) was successfully synthesized, and utilized as a promising material for removing Pb²⁺ and Cd²⁺ from aqueous solution. The fabricated nanocomposite has been characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy-energy dispersive X-ray, high-resolution transmission electron microscopy, and Brunauer-Emmett-Teller analysis. The batch methodology was exploited for optimization of process parameters and the optimized conditions were found to be adsorbent dosage (2.0 g/L), extraction time (50 min), initial concentration (60 mg/L), and initial solution pH (6). Kao-Cel/Co₃O₄ NC displayed excellent adsorption properties and achieved maximum saturation capacity (Q_m) of 293.68 mg Pb²⁺/g and 267.85 mg Cd²⁺/g, with an equilibration time of 50 min at 323 K. The Langmuir model best expressed the isotherm data recommending the adsorption onto energetically homogeneous NC surface, while the compatibility of kinetics data with pseudo-second-order model revealed the dependency of adsorption rate on adsorption capacity, and probable involvement of chemisorption in the rate-controlling step. Electrostatic interaction and ion exchange mechanism were responsible for the uptake of Pb²⁺ and Cd²⁺ by Kao-Cel/Co₃O₄ NC as demonstrated by Fourier transform infrared spectroscopy and pH studies. Thermodynamic parameters confirmed the physical, spontaneous, and endothermic sequestration processes. Real water investigation specified that the present adsorbent could be effectively used for liquid phase decontamination of Pb²⁺ and Cd²⁺. The nanocomposite exhibited high reusability, which could be utilized efficiently for five runs with sustainable results. In summary, this study portrayed the present nanocomposite as an emerging material for the adsorption of heavy metal ions particularly Pb²⁺ and Cd²⁺.     

微波加热在高岭石表面制备ZnO纳米微晶及其机理分析

报道了一种新的制备纳米氧化锌的方法, 即在微波辐射条件下, 将熔融态聚乙二醇(PEG)直接插入到高岭石层间, 继续延长辐射时间使高岭石发生剥片. 以剥片的高岭石片晶为模板, 经微波加热水解, 在其表面合成了簇状纳米氧化锌晶须.     

由27Al的核磁共振谱看高岭土与针铁矿的胶结本质

通过对高岭土与针铁矿的人工胶结样的²⁷ Al核磁田共振谱的分析,认为氢键生成是胶结本质。     

Flocculation and rheology of kaolinite/quartz suspensions

Rheological properties of suspensions of Na-kaolinite and colloidal quartz (Min-U-Sil) at constant overall volume concentration of 2% are determined with a Weissenberg Rheogoniometer using a combined Couette and cone-and-plate geometry. The results are interpreted in terms of the flocculation behaviour of the constituent particles in the presence of high salt concentrations (0.1–0.75m NaCl) at pH 6, 7 and 8. In these chemical environments these suspensions are pseudoplastic for much of the range of mixture compositions becoming Newtonian for suspensions containing only quartz. These properties reflect the dominant influence of interactions between kaolinite particles on the flocculation behaviour of the mixture.Nomenclature a ₁, a₂ radii of spheres - A Hamaker constant - b radius of cylinder - C volumetric solids concentration - e ₀ electronic charge - H ₀ shortest distance between surfaces - I ionic strength - J collision frequency per unit volume - k Boltzmann constant - l length of cylinder - m number in eq. (2) - N particle number concentration - S (H ₀ + b)/b in eq. (4) - T absolute temperature - U electrophoretic mobility - V _A van der Waals attractive energy - V _R coulombic energy - V _T total energy of interaction - X H ₀/2a₁ in eq. (5) - Y a ₂/a₁ in eq. (5) - thickness of plate - shear rate - permittivity - zeta potential - k Debye-Hückel parameter - µ dynamic viscosity - µ _pl plastic viscosity - v valency of counter ion - shear stress - _B Bingham stress - ₁, ₂ dimensionless potentials - ₁, ₂ surface potentials     

Studies on a New System of Lithium Fast Ion Conductors Based on Kaolinite and LiZr_2(PO_4)_3

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Temperature and pressure effects on zeta potential values of reservoir minerals

An experimental study of the effect of temperature and pressure on zeta potential of typical reservoir minerals, including quartz, kaolinite, and calcite, is presented. Experiments included the design and construction of an electrophoretic cell for zeta potential measurements at variable pressure and temperature. Electrolyte concentration was varied in the range from 0.0001 to 0.1 M in the pH range from 2 to 9. For all the minerals it is found that the zeta potential decreases with temperature at a rate characteristic of each mineral; values are around -2.3 mV/degrees C for quartz, -0.96 mV/degrees C for kaolinite, and -2.1 mV/degrees C for calcite for pressure values less than 45 psi. The effect of pressure is found to depend on the mineral nature and pH of the electrolytic solution. In the case of quartz, a systematic increase in the value of the zeta potential with pressure is observed, whereas a decreasing trend is measured for the kaolinite. In the case of calcite, a decreasing trend is observed for pressures up to 45 psi, whereas the experimental data suggest an increasing trend for higher pressure values.     

江西“高洲石”的矿物学和谱学特征研究

印章石是我国特有的具有民族历史文化特色的艺术品, 江西“高洲石”是近年来新发现并在市场上流通的印章石品种。采用X射线粉晶衍射(XRD)、X射线荧光光谱分析(XRF)、红外光谱分析(FTIR)、扫描电镜(SEM)及差热分析(DTA)对“高洲石”的矿物学特征和谱学特征进行了系统的研究。粉晶衍射结果表明, “高洲石”的主要矿物成分为高岭石族矿物和叶蜡石, 其次含有少量的绢云母和伊利石等。其中高岭石和地开石多型可通过18°～40°(2θ)范围内一系列地开石特有的衍射峰鉴别。“高洲石”中高岭石族矿物同时出现高岭石和地开石的特征衍射峰, 主要为高岭石-地开石过渡矿物。“高洲石”主要化学成分为SiO2和Al2O3, 次要成分为Fe2O3和K2O和Na2O等, 这与高岭石族矿物的化学成分相一致。红外光谱的结果显示“高洲石”中高岭石-地开石过渡矿物在高频区一般出现3 689, 3 645和3 615 cm-1三个谱带, 其中归属于面外羟基振动的3 689 cm-1谱带和面内羟基振动的3 615 cm-1谱带强度近似相等, 部分略有变化, 其变化因含高岭石层或地开石层较多造成。扫描电镜下观察到“高洲石”中高岭石矿物的形态主要呈直径为0.5～4 μm的不规则片状或假六方板状, 与我国其他产地印石的扫描电镜特征较为相似。差热分析结果表明高岭石族矿物的脱羟吸热谷温度与其矿物种属有一定对应关系, 同时此温度还受矿物颗粒大小的影响。综合研究表明, “高洲石”的矿物类型与我国四大印石(寿山石、昌化石、青田石、巴林石)相似, 作为四大印石的替代品, “高洲石”具有广阔的市场前景。     

由29Si NMR谱看高岭土与针铁矿的胶结本质

通过对高岭土与针铁矿的人工胶结样的²⁹Si NMR谱的分析,认为氢键生成是胶结本质.     

Ice formation on kaolinite: Lattice match or amphoterism?

The long-standing belief that kaolinite is one of the most efficient natural ice nucleating agents because it provides a close lattice match to the basal plane of ice is called into question. Instead we show through an extensive series of first principles calculations that amphoterism is key to many of the interesting properties of kaolinite with regard to water adsorption and ice nucleation.     

高岭土与针铁矿胶结样中27Al、29Si NMR谱与其原子电荷关系

由NMR谱实验得高岭土与针铁矿胶结样中²⁷Al、²⁹Si的化学位移较单一高岭土分别正移了2.7ppm和2.33ppm.由CNDO/2方法计算得到胶结样中Al、Si原子电行比高岭土分别减少了0.0787和0.0286.胶结样中Al、Si原子电荷的减少与²⁷Al、²⁹Si NMR谱化学位移相吻合,可以认为在高岭土与外铁矿的界面上形成了氢键而呈现胶结态.