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Noble metal modification is one of efficient ways to improve the catalytic activity of perovskite-type catalysts towards VOC oxidation. However, precisely how the occurrence of noble metals in perovskite, i.e., substitution and deposition constrain the catalytic activity remains controversial. In this study, Ag substituted LaCoO3 perovskite (La1-xAgxCoO3) and LaCoO3 supported Ag (Ag/LCO) catalysts were synthesized by the one-pot method and impregnation, respectively, followed by the characterization of XRD, XPS, HRTEM, O2-TPD, H2-TPR, and periodic steady-state catalytic oxidation of toluene. In the La1-xAgxCoO3 series, Ag+ was incorporated in structure at the low substitution level, but at high substitution level, partial Ag+ diffused to the surface and was reduced as Ag0. Among Ag/LCO catalysts, different microstructures of Ag, i.e., surface Ag2O, surface Ag0, and both surface Ag0 and substituted Ag+ were obtained under calcinations at 250, 450 and 700 °C, respectively. The catalytic activity of above catalysts was compared in terms of the temperatures for toluene conversions of 50% (T50), 90% (T90), and specific reaction rate (Rs). The catalytic activity of La1-xAgxCoO3 was enhanced with Ag content, but was lower than the Ag/LCO catalysts with identical Ag content. The activity of Ag/LCO increased in the following sequence: LaCoO3

Highly ordered and hexagonal mesoporous silica materials containing aluminum were successfully synthesized from natural rectorite mineral via a novel strategy. Silicon and aluminum sources were obtained from rectorite mineral by a pretreatment method involving acid leaching, alkali leaching and strongly acidic cation exchange resins (SACERs) treating, followed by a hydrothermal reaction with hexadecyl trimethyl ammonium bromide (CTAB) as template and subsequent calcination to prepare Al-MCM-41. More importantly, Wide angle X-ray diffraction (WAXRD), fourier transform infrared spectroscopy (FT-IR) and solid-state magic-angle-spinning nuclear magnetic resonance (MAS NMR) results indicated that acid treatment did not destroy the structure of natural rectorite. Unlike other silicate minerals, natural rectorite failed to provide suitable silicon sources because of residual hydroxide from alkali leaching process. In this paper, SACERs instead of inorganic acids were adopted to neutralize residual hydroxide, which avoided excessive inorganic anions to hinder the synthesis of Al-MCM-41 by a hydrothermal reaction. The final Al-MCM-41 products were amorphous SiO2, with a surface area of 1032 m2/g, pore volume of 0.97 cm3/g and an average pore diameter of 2.6 nm. A proposed mechanism for synthesizing mesoporous silica from natural rectorite was suggested.

A functional palygorskite-supported Fe/Ni (Pal-Fe/Ni) nanocomposite material is synthesised to remove 2,4-dichlorophenol (2,4-DCP) in an aqueous solution. The hypothesis is that Pal-Fe/Ni has superior efficacy than other Fe materials, such as Pal-Fe and Fe/Ni with regard to 2,4-DCP removal even though it requires less loading amount of metallic influencing the reaction. The surface morphology and surface chemical environments of Pal-Fe/Ni are studied using SEM, TEM, XRD and XPS characterisation methods. As revealed from batch experiments, initial pH, sample amount and reaction time are the key parameters influencing the 2,4-DCP removal efficiency. A further experiment reveals that iron leaching plays a main role for 2,4-DCP removal. Kinetic study reveals that removal of 2,4-DCP can be described by pseudo first-order model. A synergistic adsorption and catalytic reduction mechanism for the removal of 2,4-DCP by Pal-Fe/Ni is studied using UV–Vis, total organic carbon and HPLC-MS analyses. The results reveal complete dechlorination and 2,4-DCP degradation together with high total organic carbon removal. This study on immobilising Fe/Ni bimetallic nanoparticles onto palygorskite creates a new prospect for the practical application of Pal-Fe/Ni nanocomposite in remediation of contaminated aqueous solutions.

The current research focuses on the development of novel mycotoxins adsorbents using zwitterionic surfactants modified montmorillonites (ZMts) for simultaneous removal of highly health-hazardous polar aflatoxin B1 (AFB1) and low polar zearalenone (ZER). Two types of ZMts including dodecyl dimethyl betaine (BS-12) and lauramidopropyl betaine (LAB-35) modified montmorillonites (BS-12/Mts and LAB-35/Mts) were fabricated, and the structural, interfacial and textural features of which were explored by different techniques. It is indicated that ZMts have different structural configurations based on the surfactant type and loadings, convert from hydrophilic to hydrophobic property, with a mesoporous network inherited from Mt. The resultant adsorbents show significant improvements on the detoxification efficiency of both AFB1 and ZER. pH has little effect on the adsorption of ZMts, suggesting no desorption happens. The adsorption mechanisms of raw Mt, BS-12/Mts and LAB-35/Mts to AFB1 and ZER were proposed based on the characterizations and adsorption isotherms. This study demonstrates that ZMts possess simultaneous detoxification functions to mycotoxins with different polarities, and provides new insights into development of versatile mycotoxins adsorbents.

Aluminum nitrides (AlNs) have many unique properties for broad applications. However, their mechanical behaviour has not been well understood. In this work, the notch effects on the deformation of wurtzite AlN (w-AlN) and amorphous AlN (a-AlN) under tension were investigated using molecular dynamics simulations. As compared to w-AlN, lower strength sensitivity to the notch and the improved fracture toughness are observed in a-AlN, which are attributed to the short-range ordered atomic arrangement, rupture, reconstruction and rotation of bonds during deformation. The introduction of notch leads to obviously reduced strength and ductility in the w-AlN and a-AlN, respectively. The deformation in intact a-AlN is dominated by the formation of shear bands, followed by void coalescence. On the other hand, the deformation in notched a-AlN starts from the development of shear transformation zone near to the notches, followed by void coalescence. These results are useful in design of AlN based systems and devices.

The emission of volatile organic compounds (VOCs) from industrial and commercial processes is detrimental to human health and the environment. Though numerous catalysts have been reported to eliminate the pollution of VOCs, their deactivation and regeneration are still largely unknown. In this study, the prepared palygorskite-supported Cu-Mn oxides displays slight decrease of catalytic activity in the initial stage of formaldehyde oxidation. After the thermal treatment of spent catalyst at 400 °C, the catalytic activity is partially recovered. A deactivation and regeneration mechanism is proposed, based on the stability test and the comprehensive characterizations of fresh and spent catalysts. The accumulation of formate species and the depletion of oxygen on the surface of Cu-Mn oxides are responsible for the decline of activity. Thermal treatment of deactivated catalyst at 400 °C recovers the catalytic activity because it gasifies the carbonaceous intermediates and replenishes surface oxygen. The obtained results will be of great significance for the application of transition metal oxide-based catalysts in the abatement of VOCs.

Vermiculite is a hydrous clay mineral that occasionally occurs in raw materials for brickmaking. The presence of vermiculite affects the drying and firing processes of brick production; thus, the functions of this clay mineral should be clarified. In this study, vermiculite from 0 wt% to 30 wt% have been added to clay mixtures for brick button firing. Through effective integration of in-situ XRD, thermogravimetric and dilatometric analyses, the real-time thermal behaviours have been interpreted, and the microstructure, physical and compressive characteristics of brick buttons have been investigated. The incorporation of vermiculite has changed the temperatures of kaolinite dehydroxylation and rutile formation. Enstatite, cordierite and amorphous contents increased in fired brick buttons, while mullite, quartz and cristobalite decreased. Vermiculite retained a partial sheet-like morphology at 1150 °C firing. From 25 to 1150 °C, five weight loss steps have been defined with six shrinkage/expansion processes observed. Cracks appeared on brick button surfaces when 30 wt% of vermiculite was added. The colour of fired brick buttons changed from “light camel” to “black olive”. Drying shrinkage, firing shrinkage and bulk density increased with an increased proportion of vermiculite. The maximum compressive strength reached 150.94 MPa (a rise of 21.6% towards the control sample) when 5 wt% of vermiculite was added.

As the heterogeneous Fenton reactions are always restricted by the unsatisfied reduction efficiency of Fe(III) and ineffective consumption of H2O2, many strategies have been developed. In this work, we prepared hydrothermal carbons (HTC) with different graphitization degrees using glucose under different hydrothermal times, and then they were combined with ferrihydrite (Fh). Interestingly, although 30%HTC/Fh has much better BPA degradation efficiency than Fh (26 times larger of calculated degradation rate constants), the decomposition rate of H2O2 in the former system is lower. The generated Fe(II) of HTC/Fh is much higher than that of Fh during the heterogeneous Fenton reactions, and the degradation of BPA is almost unaffected by p-benzoquinone (scavenger of superoxide radicals (O2•-)) while greatly inhibited by isopropanol (scavenger of hydroxyl radicals (HO•)). These results indicate that HTC act as electron donors due to the abundant carbon-centered persistent free radicals (PFRs) to directly reduce Fe(III) to Fe(II) and therefore decrease the H2O2 consumption by Fe(III), which subsequently inhibits the generation of less active O2•- and promote the utilization efficiency of H2O2. HTC with a low graphitization degree contain more PFRs for Fe(III) reducing, significantly enhancing the Fenton catalytic activity of Fh.

Herein, we have reported an effective strategy to solve the rate-limiting step in a heterogeneous Fenton reaction, i.e., the generation of Fe(II) from Fe(III), which also inevitably consumes a large amount of H2O2. For the first time, a novel heterogeneous photo-Fenton catalyst - Ag/AgBr/ferrihydrite (Ag/AgBr/Fh) was successfully developed by combing AgBr with ferrihydrite (Fh) and then in-situ generating Ag nanoparticles on the surface of AgBr/Fh. This strategy can introduce photo-generated electrons from semiconductor-based plasmonic photocatalysts to heterogeneous Fenton catalysts and significantly increase the efficiency to degrade contaminants. The presence of both AgBr and Ag nanoparticles was proved by a combination of structural characterization studies (i.e., XRD, SEM, TEM, and XPS). Under visible light irradiation, the generated Fe(II) on the samples and the degradation rate constants of bisphenol A (BPA) followed the same order: Ag/AgBr/Fh > AgBr/Fh > Fh, which could be attributed to the accelerated reduction of Fe(III) to Fe(II) by the photo-generated electrons from AgBr and Ag nanoparticles, and also profit from the strong electron trapping ability of Ag nanoparticles in separating the electron-hole pairs of AgBr. The Ag/AgBr/Fh system could produce more hydroxyl radicals (•OH), and its catalytic performance was less affected by decreasing H2O2 concentration, which suggested a more efficient utilization of H2O2. The Ag/AgBr/Fh system exhibits relatively high photo-Fenton reactivity even at neutral pH. In addition, a much lower Fe3+ dissolution indicates that a large portion of the contribution is from the direct heterogeneous Fenton reaction in this system.

In this study, palygorskite (Pal), a natural nanorod-like clay mineral, is applied as the support of mixed Cu Mn oxides for formaldehyde (HCHO) oxidation, with focus on their dispersion, microstructure, and relative role during the catalytic oxidation. The composite material loaded with Cu Mn oxides retains the nanorod-like morphology of Pal, while the oxide particles in the size of 10–40 nm are well dispersed in the slit pores stacked by rods of Pal. Most of the Cu Mn oxides on Pal are with spinel structure, where Cu2+ ions occupy the tetrahedral sites and Mn3+ ions occupy the octahedral sites. The Pal-supported Cu Mn oxides achieves 90% CO2 generation at 207-258 °C, and displays better catalytic performance than solely supported catalyst. The presence of Cu obviously improves the reducibility of composite and the adsorption of HCHO, resulting in the acceleration of HCHO oxidation. The water resistance of composite catalyst also enhances with the increase of Cu content. Based on all these benefits, the catalytic performance of Cu Mn oxides on Pal can be optimized with an increase of Cu level.

The conventional heterogeneous Fenton reaction is often confined by the lower regeneration of Fe2+, which then inhibits the decomposition of H2O2 and the generation of OH. Here we propose a novel idea to significantly accelerate the redox cycling of Fe2+/Fe3+ in heterogeneous Fenton reaction by introducing photo-generated electrons from plasmonic particles. Towards this aim, novel plasmonic Ag/AgCl nanoparticles coated ferrihydrite (Ag/AgCl/Fh) have been synthesized. Compared with pure Fh, a remarkable enhancement in the photo-Fenton degradation towards bisphenol (BPA) can be observed for all Ag/AgCl/Fh samples under visible light. Noticeably, the rate constant of 6%Ag/AgCl/Fh is 0.0506 min−1, which is about 5.1 times as high as that of pure Fh (0.0099 min−1). Moreover, the catalytic activity of 6%Ag/AgCl/Fh on the degradation of BPA remains quite efficient with a low Fe leaching after 4 recycles. The results of the effect of initial pH indicates that Ag/AgCl/Fh samples exhibit relatively high photo-Fenton catalytic activity even at pH 6. The electron spin resonance (ESR) analysis reveals that OH plays a significant role in the photo-Fenton reaction. The concentration of OH can even reach 267.6 μmol/L after 60 min, which is much higher than that of pure Fh (69.2 μmol/L). The measurement of Fe2+ concentration and the XPS Fe2p spectra of Ag/AgCl/Fh before and after the degradation of BPA indicate the loading of Ag/AgCl can accelerate the conversion of Fe3+/Fe2+ by the photo generated electrons from Ag nanoparticles due to the surface plasmon resonance (SPR) effect under the visible light irradiation.

In this work, at different temperatures, thermal characteristics, structure transformation process and calcination products of Mt, Al13-PILM and Al30-PILM have been investigated and compared in detail. The thermal stability of Mt after intercalating and pillaring by Keggin-Al13 and Keggin-Al30 cations could be enhanced significantly. For Al13-PILM and Al30-PILM, layers of Mt don't collapse until 800 °C, which is due to the protection of aluminum oxides pillars formed in the interlayer space. Results of thermogravimetric (TG) analysis, high temperature X-ray diffraction (HTXRD) characteristics and N2 adsorption-desorption investagation have proved that Al30-PILM is more stable than Al13-PILM. Abundance of micropores and mesopores were still retained in Al30-PILM even under 800 °C. When heated to high temperature at 1100 °C, layered structures of Mt are destroyed and new phases could form. This work is a continuation of our previous innovative work on Keggin-Al30 pillared montmorillonite (Al30-PILM) and the fundamental finding will offer exciting opportunities to the preparation of excellent porous materials with superior thermal stability properties.

In this paper, acid-activated palygorskite (APal x ) samples were prepared by a facile acid treatment method with different concentrations of HCl (0.5, 1, 3, 5 and 7 mol/L). The dynamic toluene adsorption performances of APal x were evaluated and the relevant adsorption mechanism was discussed. The prepared adsorbents were characterized using X-ray diffraction (XRD), elemental analysis, transmission electron microcopy (TEM), nitrogen adsorption-desorption isotherms and Fourier-transform infrared spectroscopy (FTIR). The results show that the palygorskite has a good resistant ability to acid attack, the structure still remains when the acid concentration is as high as 7 mol/L. Acid activation could significantly enhance the surface area (228, 250, 271, 273, 329 and 308 for Pal, APal0.5, APal1, APal3, APal5 and APal7, respectively) and porosity of palygorskite. APal5 has the best toluene adsorption capacity (90.4 mg/g) due to its highest S BET (329 m 2 /g) and V micro (0.055 cm 3 /g). The adsorption performance in terms of dynamic toluene adsorption capacities follows the order of Pal (44.6 mg/g) x to become a promising candidate for the adsorption of volatile organic compounds in practical applications.

This research presented six natural clay minerals (NCM) evaluated for the effectiveness of NH4+ adsorption from aqueous solution. For the first time, the NH4+ adsorption capacities of kaolinite, halloysite, montmorillonite, vermiculite, palygorskite, and sepiolite were examined and compared in the same study. All the NCM were fully characterized by XRD, SEM/EDS, XRF,FTIR, CEC, zeta potential and nitrogen adsorption-desorption isotherms to better understand the adsorption mechanism-property relationship. Adsorption kinetics showed that the adsorption behavior followed the pseudo-second-order kinetic model. The adsorption isotherms fitted by the Langmuir model illustrated that among all the NCM studied, vermiculite (50.06 mg/g) and montmorillonite (40.84 mg/g) showed the highest ammonium adsorption capacities. Our results revealed that the cation exchange is the main mechanism for the NH4+ adsorption. Additionally, negatively charged surface, water absorption process and surface morphology of NCM might also contribute to the high adsorption capacity for the NH4+. The maximum adsorption capacities for all NCM were rapidly obtained within 30 min with a dosage of 0.3 g/25 mL at pH of 7. The results illustrated that the NCM have significant potential as economic, safe and effective adsorbent materials for the NH4+ adsorption from the aqueous solution.

This work aims at exploring the potential of nonionic surfactant octylphenol polyoxyethylene ether (OP-10) modified montmorillonites (NMts) as mycotoxins adsorbent. The resulting NMts has different structural configurations, organic carbon contents, surface hydrophobicity and textural properties at different surfactant loadings. The prepared NMts were used for adsorption of polar aflatoxin B1 (AFB1) and weak polar zearalenone (ZER) in both single and binary-contaminate systems by simulating conditions of gastrointestinal tract. The adsorption capacities of NMts to AFB1 and ZER increased up to 2.78 and 8.54 mg/g respectively from 0.51 and 0.00 mg/g of raw montmorillonite (Mt). High adsorption capacities of NMts to AFB1 and ZER could be reached at low surfactant loadings. There was little decrease from pH of 3.5 to 6.5 but became negligible with increasing the surfactant loadings. In binary-contaminate adsorption system, the adsorption of ZER was obviously affected by the existence of AFB1, while ZER had little effect on the adsorption process of AFB1 due to different adsorption mechanism. This study demonstrates that NMts could be a promising adsorbent for simultaneous detoxification of polar and non-polar mycotoxins.

Highlights Nowadays, two-dimensional (2D) nanosheets, such as layered double hydroxides (LDH), have received considerable attention for their potential to meeting clean energy demand and solving environmental problems. In this work, novel and efficient photocatalysts of plasmonic Ag nanoparticles coated Zn/Ti-LDH nanosheets have been synthesized through low-temperature reduction method. The structural characteristics of the as-prepared products were investigated by a series of characteristic methods The scanning electron microscopy (SEM) and transmission electron microscope (TEM) images showed that Ag nanoparticles were distributed on the surface of Zn/Ti-LDH uniformly. The UV–vis diffuse reflectance spectra (DRS) showed that the absorbance of Ag/LDH in visible-light region enhanced markedly and presented a broad band at 500–600 nm, which was resulted from the surface plasmon resonance (SPR) effect of Ag nanoparticles. The photocatalytic activities of Ag/LDH were evaluated by degradation of Rhodamine-B (RhB) and NO. The photocatalytic experiments showed that Ag/LDH had higher photocatalytic activity than that of pure LDH, and 2%Ag/LDH exhibited the highest photocatalytic activity. In addition, the 2%Ag/LDH exhibited high photochemical stability after multiple reaction runs. The obtained results from photoluminescence (PL) spectroscopic measurement and transient photocurrent (I–V) analysis both revealed the existence of Schottky barriers between LDH and Ag nanoparticles. The electron spin resonance (ESR) showed that radical dotOH were the dominant active species in the photo-degradation process. The enhanced photocatalytic performance of the composite should be ascribed to both the SPR effect of Ag nanoparticles in visible light and the Schottky barriers between LDH and Ag nanoparticles.

The environmental behaviors and pollution control of engineered nanomaterials are drawing increasing interests nowadays. This work showed that the calcined layered double hydroxides (LDH), i.e., layered double oxides (LDO), could effectively adsorb polyhydroxy fullerenes (PHF) from aqueous solution. The maximum adsorption capacity of LDO reached ~ 476 mg/g, much higher than that on LDH (~ 47 mg/g) and activated carbon (~ 28 mg/g). All of the three equilibrium adsorption isotherms could be well fitted with the Langmuir equation. The high adsorption capacity of PHF on LDO can be attributed to the enhanced accessibility to the adsorption sites for PHF during structural reconstruction of LDO. In addition, the rehydrated LDH, with a net positive surface charge, has high affinity for negatively charged PHF through an electrostatic interaction. Cl−, CO32 −, and SO42 − could slightly enhance the adsorption of the PHF on LDO, while HPO42 − showed an evident inhibiting effect in the whole concentration range of PHF. The adsorbents before and after the adsorption of PHF were characterized by XRD, FT-IR, and TG. The obtained results indicated that the adsorbed PHF could not intercalate into the interlayer spaces of the reconstructed LDH, but could effectively compete with CO32– during the adsorption process.

The mineralogical transformation of clay material is critical to the firing process for brick manufacturing. In this study, a series of in-situ integrated techniques are used to study the properties of two clay mixtures routinely for production of bricks at a local factory in Queensland, Australia. In-situ XRD, thermal expansion/contraction, thermal weight loss, and microstructural evolution of brick bodies at high temperature have been investigated. Illite/mica persists until 950 °C during the firing process, while K-feldspar transforms into plagioclase with the addition of Ca cations from starting materials. A slower ramp rate decreases the onset temperature of many reactions, including the decomposition of calcite and nucleation/crystallisation of mullite. An increase of firing temperature from 950 to 1150 °C has significantly enhanced the compressive strength of the prepared brick buttons. In addition, six length changing steps have been identified across the temperature range from 30 °C to 950 °C. The contraction of kaolinite between about 420 °C to 850 °C might compensate for the thermal expansion of typical bricks, and may minimise the potential for failure during the α- to β-quartz inversion. However, the rapid shrinkage of metakaolin above 850 °C increases the risk of cracking in manufactured bricks.

This work aims to prepare and characterize novel organo-montmorillonites (OMts) using a nonionic surfactant - octylphenol polyoxyethylene ether (OP-10), and apply the materials for the removal of cationic organic dyes. The nonionic surfactant OP-10 can be successfully intercalated into the interlayer of montmorillonite and the obtained OMts still keep cation exchange capacity. The structural configuration of surfactant molecules between clay mineral layers varies from the surfactant loadings. Moreover, OMts with higher surfactant loadings have higher organic carbon content but lower specific surface area. The prepared OMts showed enhanced adsorption capacities towards cationic organic dye methylene blue (MB), and the adsorption amount increases with an increase of surfactant loading. The high adsorption capacity can be attributed to the fact that the novel OMts still keep cationic exchange capacity and OP-10 has plentiful polyoxyethylene ether chains in its molecule structure, which can capture MB molecules through hydrogen bonding. A probable mechanism for the removal of MB was proposed to be a synergistic effect of ion exchange, partition adsorption, hydrogen bonding and electrostatic interactions. Kinetic and isotherm data could be fitted with pseudo-second order model and Langmuir isotherm. The adsorption thermodynamics study has proved the spontaneous and endothermic nature of the adsorption process. The nonionic surfactant modified OMts could be promising candidate adsorbents for the removal of cationic organic dyes.

In this present work, a novel intercalation mechanism of zwitterionic surfactant modified montmorillonites (ZSMMt) has been introduced. Using 3-(N,N-dimethylpalmityl-ammonio) propane sulfonate (SB16) and montmorillonite (Mt), a series of zwitterionic surfactant modified Mt were synthesized. The resulting organoclays were investigated by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), and thermogravimetric (TG) analysis, corroborated by the useful information provided by the element analysis. As revealed by XRD results, the basal spacing of ZSMMt increases from 1.47 nm to 4.13 nm with the increase of zwitterionic surfactant loading from 0.2 to 4.0 times of the cation exchange capacity (CEC). According to chemical composition analysis results, the number of Ca2 + ions released during the process of ZSMMt preparation is very limited and the ratios of Ca/Si and Ca/Al of ZSMMt are comparable with those of raw Mt. These results suggest that Ca2 + still remain in the interlayer spaces of Mt. There is no noticeable exchange reaction that takes place between the zwitterionic surfactant and the interlayer Ca2 +. After the zwitterionic surfactant intercalation, the IR vibration shifts from 1194 to 1191 cm− 1, which implies a new bonding between the Ca2 + and sulfonate group of SB16. The decomposition temperature of the ZSMMt, almost 60–80 °C higher than that of bulk surfactants, clearly reflects the strong interaction force after intercalation. The present study thus concludes that the intercalation mechanism of ZSMMt is not an exchange process but an ion-dipole interaction between Mt and zwitterionic surfactant, thereby, a novel cross-coupling intercalation mechanism of preparing organoclays has been proposed.

Highlights - Keggin-Al30 pillared montmorillonites were successfully prepared for the first time. - Both liquid and solid-state 27Al NMR were employed to give proofs on Al30 cations. - Al30-PILM has larger specific surface area and total pore volume than Al13-PILM. Abstract Pillared interlayered clays (PILCs) draw intensive attention in the fields of chemistry and material sciences, owing to their strong surface acidity and large microporosity. These materials are superior selective heterogeneous catalysts and adsorbents. However, conventional hydroxy-aluminum pillared clays are based on Al13, which cannot provide desirable properties due to its inherent limitation of size. Herein, a convenient method has been developed to prepare Al30 PILCs from montmorillonite (Mt) and a base-hydrolyzed solution of Al (III) chloride. To the best of our knowledge, this is the first time that porous pillared interlayered Mt with large Al30 pillars (2 × 1x1 nm) has been successfully prepared. This fundamental work may open up entirely new avenues for developing novel PILCs as heterogeneous catalysts and porous adsorbents.

This work investigated the mechanism and limit of cation adsorption by reconstruction of calcined layered double hydroxide (CHT) for the first time. Mg x Al-CHT was used to adsorb Zn 2+ and Ni 2+ from aqueous solution. As a result, adsorption amount of cation was approximately equal to dissolved amount of Mg 2+ from CHT. In other words, the molar ratio was close to 1:1 between exchanged cation (Zn 2+ or Ni 2+ ) and released Mg 2+ . Besides, Zn 2+ adsorption and Mg 2+ dissolution took place synchronously until equilibrium. XRD and SEM indicated that CHT rebuilt layered double hydroxide (LDH) after adsorbing Zn 2+ and Ni 2+ . Furthermore, molar ratios of Mg 2+ /Zn 2+ and Mg 2+ /Ni 2+ were 1:1 in reconstructed CHT regardless of the original Mg 2+ /Al 3+ ratio. Based on these results, it was proposed that half of octahedral Al 3+ in LDH transformed into tetrahedral ones after calcination, resulting in half of Mg 2+ bond being distorted in CHT and ready for a potential exchange. When CHT was used to adsorb bivalent cation (Me 2+ ), the maximum amount of adsorption was the half amount of Mg 2+ , and MgMeAl-LDH was formed by dissociation-deposition.

Highlights - A review of contaminants removed by clay-nZVI composite materials from aqueous solutions is made. - Reaction mechanisms of the materials with contaminants are discussed. - Excellent removal efficiencies of contaminants by composite materials are reported. - The review suggests research needs for future work. Abstract Recent industrialization and urbanization have increased the aqueous concentrations of a wide range of contaminants, which are toxic to human health and the environment. Therefore, remediation of aqueous solutions has turned into an important environmental issue. Over the last decade, growing attention has been paid to clay-supported nanoscale zero-valent iron (nZVI) composite materials as efficient and promising remediation materials in wastewater treatment and groundwater remediation technologies. This paper gives an overview of the clay minerals, zero-valent iron materials, clay-supported nZVI composites, and progress obtained during the remediation of contaminated aqueous solutions utilizing the clay-supported nZVI composites for the removal of heavy metals, nitrate, selenate, dyes, phenolic compounds, chlorinated organic compounds, nitroaromatic compounds and polybrominated diphenyl ethers. Reaction mechanisms and removal efficiencies were studied and evaluated. It was reported that the clay-supported nZVI composites have appreciable removal efficiency for different types of contaminants. This paper also reviews the use of ZVI-clay technology for the remediation of contaminated sites. Concerning clay-supported nZVI composites for future research, some recommendations are proposed and conclusions are drawn.

A novel and efficient photocatalyst was synthesized by surface hybridizing Zn/Ti-LDH (LDH) with C60 molecules. The structural characteristics of the resulting products (C60/LDH) were studied using a variety of characterization methods, and the photocatalytic activities of C60/LDH were tested using Orange II (OII) as a model contaminant under simulated solar irradiation. The FT-IR spectra showed that the characteristic mode of C60 at 1182 cm-1 split into two peaks at approximately 1240 and 1156 cm-1; in addition, the Raman spectra showed the band at 1422 cm-1 for C60 was upshifted to 1431 cm-1 with the increased doping amount of C60. In addition, the XPS spectra revealed that the peaks of O1s, Zn 2p, and Ti 2p were downshifted slightly. These results demonstrated that chemical interaction existed between C60 and LDH on C60/LDH. The UV-vis diffuse reflectance spectra confirmed that the absorbance of C60/LDH in visible-light region enhanced markedly, as compared with that of pristine LDH. The photoluminescence (PL) spectroscopic measurement revealed that the C60/LDH composites exhibited much weaker PL intensity than that of LDH sample, and the transient photocurrent (I-V) analysis showed that C60/LDH had higher photocurrent density than pristine LDH. The results of PL spectra and I-V analysis suggested that C60 molecule could effectively transfer the photoelectrons from the conduction band of LDH, leading to a lower recombination rate of the photo-induced electrons and holes. The photocatalytic experiments showed that C60/LDH had much higher photocatalytic activity in the decolorization of OII than that of pristine LDH, and 2%C60/LDH composite exhibited the highest photocatalytic activity. Furthermore, the stability test indicated that the decolorization efficiency of OII by 2%C60/LDH was still quite efficient after being used for 5 cycles.

Clay mineral-water interactions are ubiquitous, and crucial to a variety of natural processes including all aspects of geology, sedimentology, edaphology, geomorphology, seismology, geophysics, astrobiology, geotechnical engineering, petroleum engineering, materials science, environmental science, water science, and atmospheric science. For example, the geological ultrafiltration of clay minerals results in the enrichment or depletion of solutes and isotope fractionation in mudstones, shales, and marine sediments. The hydration/dehydration of clay minerals influences partitions of water between clay and the environment. In Earth science, this partition is significant for the water cycle in the Earth's interior. In recent decades, clay mineral-water interactions have been extensively investigated. This article provides a comprehensive overview of clay mineral-water interactions from the perspective of the technical evolution of characterization methods. A comprehensive survey of numerous literature demonstrates that our insights into the clay mineral-water interactions accumulate and deepen with the development of characterization methods, from ex situ to in situ methods (e.g., X-ray diffraction (XRD)), theory (e.g., small-angle X-ray scattering (SAXS), infrared spectroscopy (IR), nuclear magnetic resonance (NMR), and neutron scattering (NS)) to visualization (e.g., cryogenic-scanning/transmission electron microscopy (cryo-SEM/TEM,) atomic force microscopy (AFM), and transmission X-ray tomography (TXM)), and macroscopic scale (e.g., swelling/collapse) to mesoscopic scale (e.g., assembly of platelets and particles) and then to microscopic/atomic scale (e.g., atomic and platelet interactions). The information of various techniques (XRD, SAXS, AFM, TXM, spectroscopies, NS, computation, and simulation) that can obtain on clay mineral-water interactions are summarized. The advantages and disadvantages of various techniques are compared. This review may help readers gain insight into clay mineral-water interactions, and select suitable characterization methods to obtain target information.

Fullerol (polyhydroxyfullerene, PHF) has shown favorable electron accepting properties in semiconductor photocatalytic systems, but little is known about the possibility of electron transfer mediation of PHF in heterogeneous photo-Fenton processes. This work intends to investigate the effect of PHF on the heterogeneous photo-Fenton activity of ferrihydrite (Fh). PHF/ferrihydrite (PHF/Fh) composites were prepared and their photo-Fenton activities in the degradation of acid red 18 under simulated sunlight irradiation were examined. The structural characteristics of the as-synthesized samples were studied using XRD, SEM-EDS, SPM, DRS, and N2 adsorption-desorption. The results showed that PHF/Fh had much higher catalytic activities than Fh, and appropriate contents of PHF on PHF/Fh could enhance the stability of Fh. In addition, the presence of PHF on PHF/Fh could enhance the production of 1O2 and OH as compared with pure Fh. We propose that the excited state PHF could efficiently sensitize the ground state O2 to generate 1O2, and at the same time could transfer electrons to the Fe3+ on Fh, leading to an accelerated reduction of Fe3+ to Fe2+. As a result, the decomposition of H2O2 (by Fe2+) into OH could be promoted as well. On the other hand, based on the results of GAMESS calculation and GC–MS analysis, the degradation pathway of AR18 was further proposed.

In this study, TiO2-pillared montmorillonite (Ti-PILC) supported Fe catalysts were synthesized and used for the catalytic oxidation of toluene. The prepared catalysts were characterized by a combination of XRD, N2 adsorption-desorption isotherms, XPS, H2-TPR and NH3-TPD. The Fe introduction preserves the mesoporous structure and porosity of Ti-PILC. In the steady-state catalytic test and kinetic analysis, the toluene oxidation over studied catalysts follows the Mars-Van Krevelen mechanism. By the generation of strong acid sites and abundant surface oxygen species, Fe introduction obviously improves the catalytic activity of Ti-PILC for toluene oxidation. But with the increase of Fe content, the activity initially enhances, and then decreases. The effect of Fe species on the promoted toluene oxidation over Ti-PILC was discussed in view of reaction mechanism and above-mentioned variations of physicochemical properties. Furthermore, the Ti-PILC supported Fe catalysts display high stability and superior activity in the presence of water vapor, which present an applied interest.

Novel heterogeneous Fenton composite materials were developed by grafting acid precursors and nano zero-valent iron particles on an acid leached diatomite, which can sequentially generate acid and ferrous ions in situ. The results show that the composite materials can potentially solve two of the biggest obstacles, which prevent the conventional Fenton reaction from being widely and practically adopted, namely: the continuous feed of ferrous ions and the maintenance of the optimum acidic pH condition during the reaction. In this study, samples were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Thermogravimetric analysis and micro organic analysis. The novel materials’ degradation capacities for bisphenol A (BPA) were evaluated and optimized. This material can be easily applied to treat wastewater via Fenton-like reaction without changing pH or adding ferrous ions. The relationships between BPA removal efficiency, the amount of grafted organosilane acid precursor and doped nZVI particles on the composite materials were investigated. It is evident from the results that the novel composite materials afford highly effective removal of BPA from water at 250 mg/g. The work thus demonstrates that the novel materials could potentially be utilized for efficient remediation of recalcitrant organic compounds from the environment.

A novel iron oxide-based porous ceramsite (IPC) was synthesized and applied as a microbial biofilm carrier in a biological aerated filter (BAF) to treat domestic wastewater and compared to commercially available ceramsite (CAC). The results indicate that IPC has a higher porosity in comparison to CAC. The uniformity and interconnectivity of pores, as well as the rough surface of the IPC are suitable for microbial biofilm growth. Biofilm growth occurs in the internal pores of the media and promotes nitrogen and phosphorus removal. The effect of air-water ratio (A/W) on the removal of total organic carbon, ammonia nitrogen, total nitrogen, and phosphorus were investigated. The results show that the performance of IPC BAF is much better than CAC BAF. For instance, at an A/W ratio of 3:1, the total nitrogen removal was 46.26% with IPC and 15.64% with CAC, and the PO 4 3− removal was 72.25% with IPC compared with only 33.97% with CAC. An analysis of the microbial community in the IPC BAFs by polymerase chain reaction denaturing gradient gel electrophoresis identified Dechloromonas sp., Sphaerotilus sp., and Nitrospira sp. microbes. The diversity on microbial population, along with the attached growth benefit from the morphological properties of IPC, allows enhancement in the simultaneous nitrification and denitrification performance in IPC BAF. Hence, IPC can be considered a very effective novel media material in BAF for the simultaneous removal of nitrogen and phosphorus.

Inorganic-organic montmorillonites (IOMts) obtained by modifying polyhydroxy-aluminum (Al 13 )-pillared montmorillonite (AlPMt) with the cationic surfactant (C16) and zwtterionic surfactant (Z16) were investigated with the aim to remove phenol, phosphate and Cd(II) simultaneously. The structures of IOMts prepared using different surfactant doses (0.4 and 1.0CEC) strongly depended on the types and doses of the surfactants. The Al 13 contents of C16 modified AlPMts (C-AlPMts) decreased with increasing C16 loading while that of Z16 modified AlPMt (Z-AlPMts) did not. In the single adsorption system, all IOMts could efficiently remove phenol and phosphate, but not Cd(II). IOMts, however, could efficiently remove all three contaminants simultaneously in the multi-contaminant adsorption system. The adsorptions of phenol on IOMts were not affected by the other two inorganic components and vice versa. Whereas the adsorptions of phosphate and Cd(II) were significantly enhanced in the multi-contaminant system, and the adsorption of one increased with increasing initial concentration of the other one, especially the adsorption of Cd(II). The enhancements of adsorption of phosphate and Cd(II) on the IOMts with higher Al 13 content were much larger than that on IOMts with lower Al 13 content. The adsorption mechanism for phosphate and Cd(II) uptake in the multi-contaminant system possible involve the formation of phosphate-bridged ternary complexes.

Clay minerals and their modified derivatives have composed a large family of adsorbents which can be used for the adsorption of most of the chemical contaminants from aqueous solution. Among this family of adsorbents, those based on montmorillonite (Mt), a typical 2:1 type clay mineral, have been most extensively studied. This article intends to give a general overview of the microstructure, adsorptive characteristics, and environmental applications of the Mt based adsorbents. A comprehensive survey of the numerous literatures shows that Mt based adsorbents have rather complicated structural and adsorptive characteristics. They may have porous or nonporous structure and contain various functional groups; their interlayer structure may be evidently affected by the incorporation of water molecules in aqueous medium. With the complicated structural characteristics, these adsorbents can be used for a wide variety of contaminants, including hydrophobic organic contaminants, cationic/anionic dyes, heavy metal cations, oxyanions, radioactive nuclides, etc. Accordingly, a wide variety of mechanisms are involved for the uptake of these contaminants, such as surface adsorption, partition, ion exchange, surface precipitation, and structural incorporation. Finally, the approaches for proper disposal/reutilization of the spent adsorbents after contaminant adsorption will be briefly discussed. This review on one hand can help the readers in choosing proper and developing novel clay mineral based adsorbents for target contaminants, and on the other hand can give a proper example to systematically show the various mechanisms for the uptake of contaminants on adsorbents.

A novel method has been presented to characterize electron transfer in layered double hydroxides (LDHs) utilizing an investigation combing FTIR and infrared emission spectroscopy. At room temperature, electron could transfer to interlayer Fe(3+) through monodentate ligand cyanide, and resulted in a reduction of 40% Fe(3+) to Fe(2+). When the environmental temperature increased from 25 to 300°C, reduction of Fe(3+) and Ni(2+) increased to 94% and 42%. Furthermore, electron also transferred to interlayer cation through multidentate ligand EDTA. As a result, LDHs has been proven to be an effective electron donor, and FTIR was a feasible tool in characterizing this property by monitoring the valence state of cations. It was also concluded that octahedral units with OH(-) groups in LDH layer functioned as electron donor centers. Driving force for electron transfer is attributed to the charge density difference between cation layer and probe anion. These results could help to explain the mechanism of various applications of LDHs in catalysis and photocatalysis.

Ferrihydrite (Fh) is of great importance in affecting the migration and transformation of heavy-metal cations and oxyanions. To advance the understanding of co-adsorption reactions on Fh surface, the co-adsorption of phosphate and Zn(II) from aqueous solution to a synthesized Fh was determined. The batch experiments demonstrated a synergistic adsorption of phosphate and Zn(II) on Fh. In the pH range of 3.5-6, the adsorption of the two contaminants showed strong pH dependence in the single solute adsorption systems, but the dependence alleviated in the simultaneous adsorption system. X-ray photoelectron spectroscopy (XPS) revealed that the chemical shifts of Zn 2p1/2 and Zn 2p3/2 binding energies were more significant than that of P 2p in the single and simultaneous adsorption systems. On the other side, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) observed increased formation of outer- and inner-sphere complexes of phosphate in the simultaneous system. Thus, the synergistic adsorption of the two contaminants could be attributed to the formation of ternary complexes as well as electrostatic interactions, while surface precipitation could not be completely ruled out. On the basis of the results from both the batch adsorption experiments and structural characterization, these two contaminants were likely to form phosphate-bridged ternary complexes (≡Fe-P-Zn) in the simultaneous adsorption system.

Fe–montmorillonite (Fe–Mt) was prepared and tested for its potential application in the simultaneous removal of hexavalent chromium (Cr(VI)) and rhodamine B (RhB) from aqueous solution. The adsorption kinetics and capacities of Fe–Mt toward Cr(VI) and RhB were determined in relation to the initial contaminant concentration, pH of the solution and concentration of coexist contaminant. The adsorption kinetics of Cr(VI) or/and RhB in both single and simultaneous systems were investigated, which showed that an equilibrium time of a few hours was needed for the adsorption of Cr(VI) and RhB on Fe–Mt. The pseudo-second order model offers a better fit than pseudo-first order model for the Cr(VI) and RhB adsorption. Compared with the single adsorption systems, adsorption rates and quantities of Cr(VI) and RhB adsorbed on Fe–Mt were slightly enhanced in the simultaneous adsorption system. The most effective pH range for the removal of Cr(VI) and RhB was found to be 3.0–4.0. Cr(VI) adsorption isotherms were best represented by the two-site Langmuir model while RhB isotherms followed the Freundlich model. For both contaminants, the adsorption of one contaminant increases with increase in the initial concentration of the other one. Therefore, Fe–Mt could simultaneously remove Cr(VI) and RhB from water. The properties of Fe–Mt were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TG). The findings of this study provide novel information for the development of clay-based adsorbents toward dyes and heavy metals.

The generation of Fe(II) from Fe(III) is the rate-limiting step in the heterogeneous Fenton reaction, and accelerating this step is critical for enhancing the reaction efficiency and also the subject of extensive studies. In this work, the oxidized multi-walled carbon nanotubes (CNTs) were coupled with ferrihydrite (Fh) to synthesize novel and highly efficient heterogeneous Fenton catalysts (CNTs/Fh). Interestingly, the calculated apparent rate constants by 3%CNTs/Fh could reach ∼7.1 times as high as that by Fh, well in agreement with the accelerated decomposition rate of H2O2, as well as the enhanced generation rate of Fe(II) and hydroxyl radicals in the CNTs/Fh system. The density functional theory calculations and the cyclic voltammograms curves both well indicated that the Fe(III)/Fe(II) redox cycling on CNTs/Fh could be significantly enhanced during the Fenton reaction, from both dynamic (accelerating the electron transfer from H2O2 to Fh) and thermodynamic (lowering Fe(III)/Fe(II) redox potential) aspects.

Adsorption has been considered as an efficient method for the treatment of dye effluents, but proper disposal of the spent adsorbents is still a challenge. This work attempts to provide a facile method to reutilize the spent Mg/Al layered double hydroxide (Mg/Al-LDH) after the adsorption of orange II (OII). Herein, the spent hybrid was carbonized under the protection of nitrogen, and then washed with acid to obtain porous carbon materials. Thermogravimetric analysis results suggested that the carbonization could be well achieved above 600°C, as mass loss of the spent hybrid gradually stabilized. Therefore, the carbonization process was carried out at 600, 800, and 1000°C, respectively. Scanning electron microscope showed that the obtained carbon materials possessed a crooked flaky morphology. Nitrogen adsorption-desorption results showed that the carbon materials had large BET surface area and pore volume, e.g., 1426 m(2)/g and 1.67 cm(3)/g for the sample carbonized at 800°C. Moreover, the pore structure and surface chemistry compositions were tunable, as they were sensitive to the temperature. Toluene adsorption results demonstrated that the carbon materials had high efficiency in toluene removal. This work provided a facile approach for synthesizing porous carbon materials using spent Mg/Al-LDH.

The exact location of surfactant molecules on clay minerals is critical for the synthesis of clay polymer nanocomposites and their applications in environmental remediation. The location and thermal characteristics of zwitterionic surfactant (Z16) composites with montmorillonite (Mt), Al 13 -pillared montmorillonite (AlPMt), calcined AlPMt (AlPMt/500), and talc (Tlc) were investigated by using X-ray diffraction (XRD) and thermogravimetric analysis (TG). The basal spacing of Mt was markedly increased after modification with Z16, while that of Tlc, AlPMt, and AlPMt/500 was essentially unchanged. The decomposition temperature of Z16/Tlc composite (~ 294 °C) was similar to that of the pure surfactant. Sulfobetaine apparently failed to penetrate into the interlayer space of talc; instead it was confined to external surfaces. On the other hand, the DTG pattern of Z16-modified Mt showed two main peaks (404 and 336 °C), indicating two different intercalation mechanisms of Z16 on Mt. Sulfobetaine, loaded to AlPMt and AlPMt/500, was found to decompose at 355 and 370 °C, respectively, suggesting that Z16 occupied the interpillar space in these samples. Much more Z16 was taken up by AlPMt than by AlPMt/500, although the specific surface areas of both materials were practically identical, suggesting that the surfactant molecules in the interlayer space of AlPMt were largely adsorbed by electrostatic attraction between the negatively charged groups of Z16 and the positively charged Al 13 cations.

The surfaces of natural beidellite were modified with cationic surfactant octadecyl trimethylammonium bromide at different concentrations. The organo-beidellite adsorbent materials were then used for the removal of atrazine with the goal of investigating the mechanism for the adsorption of organic triazine herbicide from contaminated water. Changes on the surfaces and structure of beidellite were characterised by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and BET surface analysis. Kinetics of the adsorption studies were also carried out which show that the adsorption capacity of the organoclays increases with increasing surfactant concentration up until 1.0 CEC surfactant loading, after which the adsorption capacity greatly decreases. TG analysis reveals that although the 2.0 CEC sample has the greatest percentage of surfactant by mass, most of it is present on external sites. The 0.5 CEC sample has the highest proportion of surfactant exchanged into the internal active sites and the 1.0 CEC sample accounts for the highest adsorption capacity. The goodness of fit of the pseudo-second order kinetic confirms that chemical adsorption, rather than physical adsorption, controls the adsorption rate of atrazine.

The molecular structure of the copper-lead silicate mineral luddenite has been analysed using vibrational spectroscopy. The mineral is only one of many silicate minerals containing copper. The intense Raman band at 978 cm(-1) is assigned to the ν1 (A1g) symmetric stretching vibration of Si5O14 units. Raman bands at 1122, 1148 and 1160 cm(-1) are attributed to the ν3 SiO4 antisymmetric stretching vibrations. The bands in the 678-799 cm(-1) are assigned to OSiO bending modes of the (SiO3)n chains. Raman bands at 3317 and 3329 cm(-1) are attributed to water stretching bands. Bands at 3595 and 3629 cm(-1) are associated with the stretching vibrations of hydroxyl units suggesting that hydroxyl units exist in the structure of luddenite.

Raman spectra of two well-defined ferrimolybdite samples, Fe2(3+)(Mo6+O4)3·7-8H2O, from the Krupka deposit (northern Bohemia, Czech Republic) and Hůrky near Rakovník occurrence (central Bohemia, Czech Republic) were studied and tentatively interpreted. Observed bands were assigned to the stretching and bending vibrations of molybdate anions, Fe-O units and water molecules. Number of Raman and infrared bands assigned to (MoO4)(2-) units and water molecules proved that symmetrically (structurally) nonequivalent (MoO4)(2-) and H2O are present in the crystal structure of ferrimolybdite. Approximate O-H⋯O hydrogen bond lengths (2.80-2.73 Å) were inferred from the published infrared spectra.

Novel nano zero-valent iron/palygorskite composite materials prepared by evaporative and centrifuge methods are tested for the degradation of bisphenol A in an aqueous medium. A systematic study is presented which showed that nano zero-valent iron material has little effect on bisphenol A degradation. When hydrogen peroxide was added to initiate the reaction, some percentage of bisphenol A removal (∼20%) was achieved; however, with the aid of air bubbles, the percentage removal can be significantly increased to ∼99%. Compared with pristine nano zero-valent iron and commercial iron powder, nano zero-valent iron/palygorskite composite materials have much higher reactivity towards bisphenol A and these materials are superior as they have little impact on the solution pH. However, for pristine nano zero-valent iron, it is difficult to maintain the reaction system at a favourable low pH which is a key factor in maintaining high bisphenol A removal. All materials were characterized by X-ray diffraction, scanning electron microscopy, elemental analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. The optimum conditions were obtained based on a series of batch experiments. This study has extended the application of nano zero-valent iron/palygorskite composites as effective materials for the removal of phenolic compounds from the environment.

The mineral beraunite from Boca Rica pegmatite in Minas Gerais with theoretical formula Fe(2+)Fe5(3+)(PO4)4(OH)5⋅4H2O has been studied using a combination of electron microscopy with EDX and vibrational spectroscopic techniques. Raman spectroscopy identifies an intense band at 990 cm(-1) and 1011 cm(-1). These bands are attributed to the PO4(3)(-) ν1 symmetric stretching mode. The ν3 antisymmetric stretching modes are observed by a large number of Raman bands. The Raman bands at 1034, 1051, 1058, 1069 and 1084 together with the Raman bands at 1098, 1116, 1133, 1155 and 1174 cm(-1) are assigned to the ν3 antisymmetric stretching vibrations of PO4(3-) and the HOPO3(2-) units. The observation of these multiple Raman bands in the symmetric and antisymmetric stretching region gives credence to the concept that both phosphate and hydrogen phosphate units exist in the structure of beraunite. The series of Raman bands at 567, 582, 601, 644, 661, 673, and 687 cm(-1) are assigned to the PO4(3-) ν2 bending modes. The series of Raman bands at 437, 468, 478, 491, 503 cm(-1) are attributed to the PO4(3-) and HOPO3(2-) ν4 bending modes. No Raman bands of beraunite which could be attributed to the hydroxyl stretching unit were observed. Infrared bands at 3511 and 3359 cm(-1) are ascribed to the OH stretching vibration of the OH units. Very broad bands at 3022 and 3299 cm(-1) are attributed to the OH stretching vibrations of water. Vibrational spectroscopy offers insights into the molecular structure of the phosphate mineral beraunite.

Raman spectroscopy complimented with infrared spectroscopy has been used to study the molecular structure of the mineral of plumbophyllite. The Raman spectrum is dominated by a very intense sharp peak at 1027 cm(-1), assigned to the SiO stretching vibrations of (SiO3)n units. A very intense Raman band at 643 cm(-1) is assigned to the bending mode of (SiO3)n units. Raman bands observed at 3215, 3443, 3470, 3494 and 3567 cm(-1) are assigned to water stretching vibrations. Multiple water stretching and bending modes are observed showing that there is much variation in hydrogen bonding between water and the silicate surfaces. Because of the close similarity in the structure of plumbophyllite and apophyllite, a comparison of the spectra with that of apophyllites is made. By using vibrational spectroscopy an assessment of the molecular structure of plumbophyllite has been made.

We have studied the hydrated hydroxyl silicate mineral inesite of formula Ca2(Mn,Fe)7Si10O28(OH)⋅5H2O using a combination of scanning electron microscopy with EDX and Raman and infrared spectroscopy. SEM analysis shows the mineral to be a pure monomineral with no impurities. Semiquantitative analysis shows a homogeneous phase, composed by Ca, Mn(2+), Si and P, with minor amounts of Mg and Fe. Raman spectrum shows well resolved component bands at 997, 1031, 1051, and 1067 cm(-1) attributed to a range of SiO symmetric stretching vibrations of [Si10O28] units. Infrared bands found at 896, 928, 959 and 985 cm(-1) are attributed to the OSiO antisymmetric stretching vibrations. An intense broad band at 653 cm(-1) with shoulder bands at 608, 631 and 684 cm(-1) are associated with the bending modes of the OSiO units of the 6- and 8-membered rings of the [Si10O28] units. The sharp band at 3642 cm(-1) with shoulder bands at 3612 and 3662 cm(-1) are assigned to the OH stretching vibrations of the hydroxyl units. The broad Raman band at 3420 cm(-1) with shoulder bands at 3362 and 3496 cm(-1) are assigned to the water stretching vibrations. The application of vibrational spectroscopy has enabled an assessment of the molecular structure of inesite to be undertaken.

Phosphohedyphane Ca2Pb3(PO4)3Cl is rare Ca and Pb phosphate mineral that belongs to the apatite supergroup. We have analysed phosphohedyphane using SEM with EDX, and Raman and infrared spectroscopy. The chemical analysis shows the presence of Pb, Ca, P and Cl and the chemical formula is expressed as Ca2Pb3(PO4)3Cl. The very sharp Raman band at 975 cm−1 is assigned to the PO 4 3 - ν1 symmetric stretching mode. Raman bands noted at 1073, 1188 and 1226 cm−1 are to the attributed to the PO 4 3 - ν3 antisymmetric stretching modes. The two Raman bands at 835 and 812 cm−1 assigned to the AsO 4 3 - ν1 symmetric stretching vibration and AsO 4 3 - ν3 antisymmetric stretching modes prove the substitution of As for P in the structure of phosphohedyphane. A series of bands at 557, 577 and 595 cm−1 are attributed to the ν4 out of plane bending modes of the PO4 units. The multiplicity of bands in the ν2, ν3 and ν4 spectral regions provides evidence for the loss of symmetry of the phosphate anion in the phosphohedyphane structure. Observed bands were assigned to the stretching and bending vibrations of phosphate tetrahedra. Some Raman bands attributable to OH stretching bands were observed, indicating the presence of water and/or OH units in the structure.