Adsorption of diquat, paraquat and methyl green on sepiolite: experimental results and model calculations

Adsorption of the divalent organic cations paraquat (PQ), diquat (DQ) and methyl green (MG) on sepiolite was determined experimentally and investigated with an adsorption model. The largest amounts of DQ, PQ and MG adsorbed were between 100% and 140% of the cation exchange capacity (CEC) of sepiolite. In previous experiments with monovalent organic cations (dyes), the largest amounts of dyes adsorbed were about 400% of the CEC of sepiolite. Consequently, it was proposed that most of this adsorption was to neutral sites of the clay. The large differences between the adsorption of these divalent organic cations and the monovalent dyes may indicate that there is almost no interaction between DQ, PQ and MG and the neutral sites of sepiolite. This assumption was confirmed by infrared (IR) spectroscopy measurements, that did not show changes in the peaks arising from the vibrations of external Si---OH groups of the clay when the divalent organic cations were added. Adsorption results were compared with calculations of an adsorption model that combines the Gouy–Chapman solution and specific binding in a closed system. The model considers cation adsorption on neutral sites of the clay, in addition to adsorption to mono- or divalent negatively charged sites, forming neutral or charged complexes. The model could adequately simulate the adsorption of the divalent organic cations DQ and PQ when added alone, and could yield good fit for the competitive adsorption experiment between the monovalent dye methylene blue and DQ. In competitive adsorption experiments, when total cationic charges exceeded the CEC, monovalent organic cations were preferentially adsorbed on the clay at the expense of the divalent cations.     

不同粘土矿物与聚羧酸减水剂相互作用机理研究

通过X射线衍射(XRD)、红外光谱(IR)、有机碳吸附(TOC)、饱和吸水率以及净浆流动性等试验方法,研究了不同粘土矿物与聚羧酸减水剂的相互作用机理.结果表明:聚羧酸减水剂的侧链可进入粘土矿物蒙脱石的层间,发生插层反应,即层间吸附,而其侧链结构不进入伊利石、高岭土、海泡石等粘土矿物的层间,仅发生表面吸附,且吸附量大小为蒙脱石>高岭土>海泡石>伊利石;饱和吸水率试验显示,粘土矿物的饱和吸水率大小为蒙脱石>高岭土>海泡石>伊利石;流动度试验表明,粘土矿物对水泥-减水剂体系净浆流动度均有不同程度的影响,且蒙脱石影响程度最大.由此可知,粘土矿物对自由水和聚羧酸减水剂的吸附是造成流动度损失的主要原因.     

铁改性杭锦土对磷的吸附及对沉积物磷释放的控制

以天然粘土矿物杭锦土(HJ)为原料,采用浸渍法制备表面负载铁氧化物的铁改性杭锦土(FHJ)吸附剂.采用BET、SEM、XRD等技术对其进行表征,并考察了铁负载比例、pH、共存离子对FHJ除磷的影响.结果表明,浸渍法成功将铁氧化物负载在杭锦土表面;溶液pH越低越有利于FHJ对磷酸盐的吸附;除磷性能受CO32-、SiO32...     

Synthesis of kappa-carrageenan-g-poly(acrylamide)/sepiolite nanocomposite hydrogels and adsorption of cationic dye

In this study, nanocomposite hydrogels from grafting of acrylamide onto kappa-carrageenan biopolymer were prepared in the presence of sepiolite clay. Methylenebisacrylamide and ammonium persulfate were used as cross-linker and initiator, respectively. The sepiolite nanoclay was introduced into hydrogel matrix without any chemical treatment. The structure of nanocomposites was investigated by FTIR, SEM, TEM, and TGA techniques. The TEM image showed that sepiolite exists as individual needle’s shape. The swelling of hydrogels were studied in distilled water, salt solutions, and various pHs. The obtained nanocomposites were evaluated to remove of cationic crystal violet (CV) dye from water. The kinetic and isotherm of adsorption of dye onto nanocomposites were studied and analyzed according to kinetic and isotherm models. The results showed that the pseudo-second-order adsorption kinetic was predominated for the adsorption of CV onto nanocomposites. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The results corroborated that the experimental data fit the Langmuir isotherm the best. By varying the pH of initial dye solution, while the clay-free hydrogel showed relatively pH-independent adsorption behavior, the nanocomposites depicted pH-dependent adsorption.     

Functionalized sepiolite for heavy metal ions adsorption

Surface modification of clays has become increasingly important due to the practical applications of clays such as fillers and adsorbents. The surface modification of sepiolite with [3-(2-aminoethylamino)propyl]trimethoxysilane has been employed. The modified sepiolite surface was investigated by FTIR, XRD and DTA/TG analysis. It was found that the chemical bonding takes place between the hydroxyl groups and/or oxygen atoms within the structure of sepiolite and methoxy groups of [3-(2-aminoethylamino)propyl]trimethoxysilane. The changes on electrokinetic properties of modified sepiolite particles were studied by measuring the zeta potential of particle as a function of metal concentration and equilibrium pH of solution. It was found that the zeta potential of the clay particles was always negative independent of the metal concentration in solution. This study also provides some evidence for the adsorption of metal ions on modified sepiolite. The adsorption of metal ions onto modified sepiolite has varied with the type of metal cations. The available basic nitrogen centers covalently bonded to the sepiolite skeleton were studied for Co(II), Cu(II), Mn(II), Zn(II), Fe(III) and Cd(II) adsorption from aqueous solutions. It was found that the amount of metal ion adsorbed onto modified sepiolite increases with increase in solution equilibrium pH and temperature, whereas it generally decreases with the ionic strength. The experimental data were correlated reasonably well by the Langmuir adsorption isotherm and the isotherm parameters (q_m and K) were calculated. The ability to adsorb the cations gave a capacity order of Zn(II) > Cu(II) ~ Co(II) > Fe(III) > Mn(II) > Cd(II) with affinities of 2.167×10⁻⁴, 1.870×10⁻⁴, 1.865×10⁻⁴, 1.193×10⁻⁴, 0.979×10⁻⁴ and 0.445×10⁻⁴ mol g⁻¹, respectively.     

The Adsorption of Arsenic Ions Using Beidellite,Zeolite, and Sepiolite Clays: A Study of Kinetic,Equilibrium and Thermodynamics

Arsenic contamination in drinking water resources is a global problem; therefore, its removal from drinking water has become an important sustainable matter. The adsorption process can be more cost-effective and applicable, especially, if the absorbents used in the process are low-cost natural geo-materials. Beidellite, zeolite, and sepiolite are inexpensive and natural minerals available locally, modified, and used as adsorbents for the removal of arsenic ions from aqueous solutions in batch experiments. The kinetics of the adsorption process was separately tested for the pseudo-first order and pseudo-second order reactions and intra-particle diffusion models. The rate constants of adsorption for all these kinetic models were calculated. The comparison among the models showed that the pseudo second-order model best described the adsorption kinetics. Applied to the experimental equilibrium, at different temperatures were the Langmuir and Freundlich isotherm models. The Langmuir isotherm was used to calculate the adsorption capacities (Q°) of minerals for arsenic ions. The adsorption capacities of these three modified minerals, at different temperatures, ranged from 476 to 841 µg/g. Thermodynamic studies showed that the arsenic uptake reactions by minerals were endothermic and spontaneous in nature. Bottled spring water containing arsenic, sold in markets, was used to conduct the arsenic adsorption study beidellite, zeolite, and sepiolite, minerals which efficiently removed the arsenate ions from the bottled drinking water. The use of modified beidellite, zeolite, and sepiolite as adsorbents in the arsenic ion removal processes is possible, based on the optimum parameters found.     

Sepiolite-supported urease

The properties of the fibrous clay sepiolite as a support for enzyme immobilization have been studied using urease. Simple adsorption does not result in enzyme inactivation and appears to be a valuable method of immobilizing the enzyme at high ionic strength. This behaviour has been related to the existence of protein-clay hydrophobic interactions. The sepiolite-supported urease has been characterized in terms of pH and ionic strength dependencies, thermal and storage stability, reusability, and kinetic parameters. These studies indicate that sepiolite is a valuable support for simple adsorption of enzymes.     

粘土矿物对水中Pb~(2+)的处理技术研究进展

天然或改性粘土矿物对水中重金属离子具有良好的吸附作用,将其用于水中Pb2+的去除是目前水处理研究的热点.本文在介绍凹凸棒土、膨润土、硅藻土、海泡石这四种粘土矿物的结构和性质的基础上,对其在水中Pb2+处理方面的技术研究进展进行了综述,并对其应用前景进行展望.     

Assembly of gelatin biopolymer to fibrous sepiolite clay for efficient dye removal from wastewater

This work aimed to fabricate nanocomposites using low-cost and natural materials for fast and efficient dye adsorption from wastewater. To achieve this, fibrous sepiolite clay was incorporated into the gelatin (GE) biopolymer. The obtained nanocomposites were characterized by Fourier transform infrared spectroscopy and scanning electron microscope techniques. The effects of sepiolite/GE ratio, adsorbent dosage, solution pH, contact time, and initial dye concentration on the adsorption capacity of nanocomposites were well studied and optimized through batch adsorption study. Kinetics, isotherms, and thermodynamics analysis were also performed for methylene blue adsorption. The adsorption data were better fitted with the pseudo-second-order and Langmuir isotherm models. The prepared nanocomposites demonstrated a fast and efficient adsorption performance toward the MB dye with the maximum adsorption capacity as high as 684.8 mg g⁻¹ within only an equilibrium time of 30 min, which revealed their promising potential in wastewater treatment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48266.     

Effect of sepiolite on the flocculation of suspensions of fibre-reinforced cement

Sepiolite is used to increase thixotropy of cement slurries for easier processing, to prevent sagging and to provide a better final quality in the manufacture of fibre-reinforced cement products. However, the effect of sepiolite on flocculation and its interactions with the components of fibre cement are yet unknown. The aim of this research is to study the effects of sepiolite on the flocculation of different fibre-reinforced cement slurries induced by anionic polyacrylamides (A-PAMs). Flocculation and floc properties were studied by monitoring the chord size distribution in real time employing a focused beam reflectance measurement (FBRM) probe. The results show that sepiolite increases floc size and floc stability in fibre-cement suspensions. Sepiolite competes with fibres and clay for A-PAMs adsorption and its interaction with A-PAM improves flocculation of mineral particles.     

Surface modification of sepiolite particles with polyurethane and polyvinyl alcohol

Sepiolite is a clay mineral that has many industrial applications due to its advantageous properties such as white color, low specific gravity, high absorption capacity, chemical composition and low thermal conductivity. In this study, the effect of the addition of polymers, polyvinyl-alcohol and polyurethane, on the rheological properties of the sepiolite dispersions have been investigated. The rheological parameters of clay suspensions can be used to examine particle–particle interactions. The polymers that have been added to the clay suspensions interact with clay particles, depending on their ionic or non-ionic character. Firstly, the sepiolite dispersions were characterized by the rheological properties, mineral structure and content. Then the effect of the polymers on the flow, structural, and surface properties of sepiolite dispersions was investigated by rheological, electrokinetical, and scanning electron microscopy (SEM) measurements. The measurements showed that polymer molecules bind on the surface of sepiolite particles and changed the flow properties of the dispersions as stable dispersions at some certain concentrations. It is also determined that PU polymer covered the surface of the sepiolite faster than PVA, but the coverage of the PVA was much more smoothly. The thermal properties of the sepiolite improved with PVA more than PU, as a result of the homogenous surface coverage.     

黏土结构对聚氯乙烯/黏土复合材料性能的影响

用两种不同结构的黏土伊利石和海泡石作为填料填充到聚氯乙烯(PVC)树脂中,研究黏土结构对PVC性能的影响。结果表明:黏土的结构不同,对PVC的性能影响也存在明显差异。伊利石对提高PVC的拉伸强度优于海泡石;而海泡石对提高PVC的冲击强度优于伊利石。伊利石提高了PVC的弯曲强度,对弯曲模量的影响不大;而海泡石降低了PVC的弯曲强度,但明显加大了PVC的弯曲模量。海泡石对提高PVC的热变形温度优于伊利石。     

改性海泡石除亚硝酸盐的影响因素实验

用盐酸、氯化铁和焙烧对海泡石进行综合改性,得到高吸附性的改性海泡石;研究了其用于处理亚硝酸盐废水的各种影响因素。结果表明:改性后的海泡石对亚硝酸盐的去除效果明显优于未经改性的海泡石。在室温25℃,pH为9左右,固液比1∶500,吸附时间35 min条件下,亚硝酸根离子的去除率可达到92%,处理后的水质达到国家排放的标准。对数据的方程进行拟合可知,改性海泡石对亚硝酸根离子的吸附较符合Freundlich方程。     

粘土/聚丙烯酸（钾）复合材料的制备及性能研究

以部分中和的丙烯酸单体为原料,分别添加海泡石、蒙脱石、凹凸棒石,采用溶液聚合法制备粘土/聚丙烯酸（钾）复合材料,并制备粘土/聚丙烯酸（钾）包膜复合肥。探讨粘土种类、添加量对复合膜材料吸水倍率的影响。采用红外光谱对复合膜材料的结构进行表征。结果显示：海泡石、凹凸棒石和蒙脱石的添加量分别在2%、5%和10%时,复合材料的吸水倍率达到最大值;包膜肥料中N、P和K均具有较好的缓释效果。     

Clay mineral-supported gold nanoparticles

Supported gold nanoparticles were prepared on clay minerals from the smectite and sepiolite–palygorskite groups (particularly montmorillonite and sepiolite) by cation adsorption from the cationic gold precursor Au(en)₂Cl₃ (en = ethylenediamine). Thermal gravimetric analysis, X-ray diffraction, transmission electron microscopy (TEM), high resolution TEM (HRTEM) and energy dispersive X-ray spectroscopy (EDS) were used to characterize these potential gold catalysts. The results show that the mean diameters of gold particles supported both on sepiolite and on montmorillonite are below 5 nm after calcination at 350–450 °C when the gold loading is lower than 2 wt.%. An increase of the amount of the gold precursor results in agglomeration of gold nanoparticles. An organosilane functionalized sepiolite was also used as support to obtain highly dispersed gold nanoparticles on the modified mineral surfaces, with narrow size distribution and an average size of 2.7 nm.     

海泡石对废水中有机物和重金属的吸附

简述了海泡石的结构特点,及其改性方法,总结了海泡石对废水中有机物和重金属的吸附效果,分析了改性方法、pH、温度、污染物性质与浓度、海泡石用量和吸附时间等因素对吸附效果的影响．探讨了海泡石的吸附机理与等温式,展望了海泡石在废水处理中的应用前景。     

海泡石对蓖麻油脱色工艺的研究

通过酸活化海泡石对蓖麻油进行脱色,研究了干燥温度、干燥时间、脱色温度、脱色时间及脱色剂用量等因素对海泡石吸附脱色性能的影响,确定了最佳活化条件及吸附工艺。该研究表明酸活化海泡石对蓖麻油的脱色效果优于其他传统脱色剂,该研究结论为蓖麻油及其他植物油的脱色剂选择提供一种参考。     

Saudi Arabian clays for lead removal in wastewater

Three types of local clays–Tabuk, Baha, and Khaiber–were tested for their abilities to adsorb lead ions from wastewater. The effect of pH on the adsorption of lead ions was also investigated. The clays were treated with hydrochloric acid to activate adsorption sites within clay particles. Untreated Tabuk clay had the largest adsorption capacity, about 30 mg lead/g clay, in comparison with those of Baha and Khaiber clays. The smallest adsorption was observed with Khaiber clay, about 10 mg lead/g clay; this may be attributed to the prior existence of lead within the clay. The adsorption of the acid-activated clays was not enhanced compared to those of untreated clays. The Langmuir model described the experimental data for all untreated clays, while the Freundlich model described the experimental data of untreated Khaiber clay and treated Baha clay. The local clays tested in this study, especially Tabuk clay, may be utilized as cost-effective and efficient adsorbent materials for removing heavy metals from wastewater in Saudi Arabia.     

Short Review on Sepiolite-Filled Polymer Nanocomposites

Latest developments in mineral clay nanocomposites area are reviewed in this report, with a specific focus on sepiolite clay mineral. Rigorous research has been conducted on the sepiolite clay mineral by both academicians and industrial researchers. The properties of the nanocomposites are significantly dependent on the polymer matrices, their nature, modification, and preparation technique. Thus, preparation, structure, and characteristics of polymer sepiolite nanocomposites are thoroughly discussed, in addition to the scientific literature to support and find any gaps for future research.     

蒙脱石和高岭石吸附水溶液中重金属离子的实验研究

综述了近几年研究人员以蒙脱石、高岭石和膨润土作为吸附材料,去除水溶液中的砷、镉、铬、铜、铅几种重金属离子。通过酸性活化改性,有机分子嫁接改性,纳米氧化物涂层和柱撑等手段,提高了粘土矿物的吸附性能,达到更好的吸附效果。结果表明有机改性更有利于蒙脱石等粘土矿物对于重金属离子的吸附,同时指出pH是影响吸附效果的关键因素。