Biosustainable Hybrid Nanoplatforms as Photoacoustic Agents.

The development of biosafe theranostic nanoplatforms has attracted great attention due to their multifunctional behavior, reduced potential toxicity, and improved long-term safety. When considering photoacoustic contrast agents and photothermal conversion tools, melanin and constructs like melanin are highly appealing due to their ability to absorb optical energy and convert it into heat. Following a sustainable approach, in this study, silver-melanin like-silica nanoplatforms are synthesized exploiting different bio-available and inexpensive phenolic acids as potential melanogenic precursors and exploring their role in tuning the final systems architecture. The UV-Vis combined with X-Ray Diffraction investigation proves metallic silver formation, while Transmission Electron Microscopy analysis reveals that different morphologies can be obtained by properly selecting the phenolic precursors. By looking at the characterization results, a tentative formation mechanism is proposed to explain how phenolic precursors' redox behavior may affect the nanoplatforms' structure. The antibacterial activity experiments showed that all synthesized systems have a strong inhibitory effect on Escherichia coli, even at low concentrations. Furthermore, very sensitive Photoacoustic Imaging capabilities and significant photothermal behavior under laser irradiation are exhibited. Finally, a marked influence of phenol nature on the final system architecture is revealed resulting in a significant effect on both biological and photoacoustic features of the obtained systems. These melanin-based hybrid systems exhibit excellent potential as triggerable nanoplatforms for various biomedical applications.

Use of Zeolites in the Capture and Storage of Thermal Energy by Water Desorption-Adsorption Cycles.

In this work, four zeolite-bearing materials (three naturally occurring and one of synthetic origin) were considered for thermal energy capture and storage. Such materials can store thermal energy as heat of desorption of the water present therein, heat that is given back when water vapor is allowed to be re-adsorbed by zeolites. This study was carried out by determining the loss of water after different activation thermal treatments, the water adsorption kinetics and isotherm after an activation step of the zeolites, the intergranular and intragranular porosity, and the thermal conductivity of the zeolite-bearing materials. Moreover, the thermal stability of the framework of the zeolites of the four materials tested was investigated over a large number of thermal cycles. The results indicate that zeolite 13X was the most suitable material for thermal energy storage and suggest its use in the capture and storage of thermal energy that derives from thermal energy waste.

Application of Surfactant Modified Natural Zeolites for the Removal of Salicylic Acid-A Contaminant of Emerging Concern.

This work aimed to test composites (surfactant modified zeolites prepared by treatment of natural zeolites-clinoptilolite (IZ CLI) and/or phillipsite (PHIL75)-rich tuffs with two different amounts of cationic surfactants: cetylpyridinium chloride (CPyCl) and Arquad® 2HT-75 (ARQ)) for the adsorption of salicylic acid (SA)-a common contaminant of emerging concern. Adsorption of SA was studied at different initial drug concentrations (in the range of 2-100 mg/L) in water solution. The Langmuir isotherm model showed the highest adsorption was achieved by bilayer composite of IZ CLI and CPyCl-around 11 mg/g. Kinetic runs were performed by using the initial drug concentration of 20 mg/L in the time interval from 0 to 75 min and pseudo-second order had good correlation with experimental data. The influence of the four different temperatures on the SA adsorption was also investigated and thermodynamic parameters suggested that the adsorption drug onto composites is an exothermic and nonspontaneous process, followed by the decrease of randomness at the solid/liquid interface during the adsorption. Zeta potential and Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) had been performed for the characterization of composites after adsorption of SA confirming the presence of the drug at composite surfaces.

Thermodilatometric Study of the Decay of Zeolite-Bearing Building Materials.

Six zeolite-bearing rocks, often used as building materials, were analyzed by thermodilatometry, together with a rock not bearing zeolites and a plaster covering a containing wall made of zeolite-bearing dimension stones, up to 250 °C. The main results obtained were the following: (i) the zeolite-bearing rocks exhibited very small, if any, positive variation of ΔL/Lo (%) up to about 100 °C, whereas they more or less shrank in the temperature range 100-250 °C (final values ranging from -0.21 to -0.92%); (ii) the rock not bearing zeolites regularly expanded through the whole temperature range, attaining a final value of 0.19%; (iii) the plaster showed a thermodilatometric behavior strongly affected by its water content. Obtained results were interpreted based on plain thermal expansion, shrinkage by dehydration, cation migration and thermal collapse of the zeolitic structure. The decay of the zeolite-bearing building materials was essentially related to: (i) the large differences recorded in the thermodilatometric behavior of the various rocks and the plaster; (ii) the different minerogenetic processes that resulted in the deposition of the various zeolite-bearing rocks.

Removal of non-steroidal anti-inflammatory drugs from water by zeolite-rich composites: The interference of inorganic anions on the ibuprofen and naproxen adsorption.

Composites of two natural zeolites - clinoptilolite and phillipsite, and cationic surfactants (cetylpyridinium chloride and Arquad® 2HT-75) were tested for the removal of two emerging contaminants - ibuprofen and naproxen. For each zeolite-rich rock, two different modifications of the zeolitic surfaces were prepared (monolayer and bilayer surfactant coverage). The influence of the initial drug concentrations and contact time on adsorption of these drugs was followed in buffer solution. The Langmuir model showed the highest adsorption capacity for the composite characterized by a bilayered surfactant at the clinoptilolite surface: 19.7 mg/g and 16.1 mg/g for ibuprofen and naproxen, respectively. Also, to simulate real systems, drug adsorption isotherms were conducted in natural water (Grindstone creek water - Columbia, Missouri, USA) by using the best performing adsorbent; in this case, a slight decrease of drug adsorption was recorded. Kinetic runs were performed in distilled water as well as in the presence of ions such as sulfates and bicarbonates; also, in this case, the interfering agents defined an adsorption decrease for bilayer composites.

Surface modified natural zeolites (SMNZs) as nanocomposite versatile materials for health and environment.

The present research deals with the evaluation of a clinoptilolite-rich rock, occurring in the Nizný Hrabovec deposit (Slovakia), for high-value technological applications based on sorption and in vitro release of nonsteroidal anti-inflammatory drugs (i.e., ibuprofen sodium salt). This georesource was surface modified (SMNZ) using four cationic surfactants. Results demonstrate that ibuprofen sorption is very fast and SMZNs can sorb up to ˜26 mg/g of drug as a function of the type of counterion and morphology of surfactant, as well as the hydrophobicity and molecular structure of the drug. Maximum sorption capacities observed for all SMNZs are fully comparable to other adsorbent carriers usually used for removal of contaminants in wastewaters. Sorption of ibuprofen is controlled by a dual mechanism: external anionic exchange and partition into the hydrophobic portion of the patchy bilayer. A prompt drug release in simulated intestinal fluid (SIF) was also observed, making this natural material also suitable to provide rapid soothing effects in potential pharmacological applications. Comparing the results of this study with other recent investigations, a good technological performance of clinoptilolite-rich rock can be inferred despite the relatively low zeolite content (˜56 wt.%).

On the Use of Nonsteroidal Anti-Inflammatory Drugs as Rheology Modifiers for Surfactant Solutions.

Surfactant molecules can give rise to different morphological structures, depending on numerous parameters such as temperature, surfactant concentration, and salinity. Specifically, the salt content can be easily tuned in a way to induce morphological transitions and modulate the rheological response. It is shown that nonsteroidal anti-inflammatory drugs can be used in the same way as classical binding salts in changing the rheological properties of the resulting gel-like system. On the one hand, the experimental results show that by tuning small details in the molecular conformation of the drug and its concentration in the micellar solution, it is possible to obtain the desired mechanical response. On the other hand, the results prove that rheology can be considered as a powerful tool to detect the drug release content, with obvious consequences on possible applications.

Adsorption of the mycotoxin zearalenone by clinoptilolite and phillipsite zeolites treated with cetylpyridinium surfactant.

In this study, organozeolites were prepared by treatment of the natural zeolites (clinoptilolite and phillipsite) with cetylpyridinium chloride (CP) equivalent to 50 and 100% of their external cation exchange capacities (ECEC). Organoclinoptilolites (ZCPs) and organophillipsites (PCPs) were characterized by FTIR spectroscopy, thermal analysis, determination of the point of zero charge and zeta potential. Adsorption of zearalenone (ZEN) by ZCPs and PCPs at pH 3 and 7 was investigated. Results showed that adsorption of ZEN increases with increasing amounts of CP at the zeolitic surfaces for both ZCPs and PCPs but the adsorption mechanism was different. Adsorption of ZEN by ZCPs followed a linear type of isotherm at pH 3 and 7 while ZEN adsorption by PCPs showed non linear (Langmuir and Freundlich) type of isotherm at both pH values. Different interactions between the ZEN molecule (or ion) and ZCPs and PCPs occurred: partition (linear isotherms) and adsorption in addition to partition (non linear isotherms), respectively. For the highest level of organic phase at the zeolitic surfaces, the maximum adsorbed amount of ZEN was 5.73mg/g for organoclinoptilolite and 6.86mg/g for organophillipsite at pH 3. Slightly higher adsorption: 6.98mg/g for organoclinoptilolite and 7.54mg/g for organophillipsite was achieved at pH 7. The results confirmed that CP ions at both zeolitic surfaces are responsible for ZEN adsorption and that organophillipsites are as effective in ZEN adsorption as organoclinoptilolites.

Surface modified zeolite-based granulates for the sustained release of diclofenac sodium.

In this study, a granulate for the oral controlled delivery of diclofenac sodium (DS), an anionic sparingly soluble nonsteroidal anti-inflammatory drug, has been realized by wet granulation, using a surface modified natural zeolite (SMNZ) as an excipient. The surface modification of the zeolite has been achieved by means of a cationic surfactant, so as to allow the loading of DS through ionic interaction and bestow a control over the drug release mechanism. The granules possessed a satisfactory dosage uniformity, a flowability suitable for an oral dosage form manufacturing, along with a sustained drug release up to 9h, driven by both ion exchange and transport kinetics. Furthermore, the obtained granulate did not elicit a significant cytotoxicity and could also induce a prolonged anti-inflammatory effect on RAW264.7 cells. Taking also into account that natural zeolites are generally abundant and economic, SMNZ can be considered as an attracting alternative excipient for the production of granules with sustained release features.

Surface modified natural zeolite as a carrier for sustained diclofenac release: A preliminary feasibility study.

In view of zeolite potentiality as a carrier for sustained drug release, a clinoptilolite-rich rock from California (CLI_CA) was superficially modified with cetylpyridinium chloride and loaded with diclofenac sodium (DS). The obtained surface modified natural zeolites (SMNZ) were characterized by confocal scanning laser microscopy (CLSM), powder X-ray diffraction (XRPD) and laser light scattering (LS). Their flowability properties, drug adsorption and in vitro release kinetics in simulated intestinal fluid (SIF) were also investigated. CLI_CA is a Na- and K-rich clinoptilolite with a cationic exchange ability that fits well with its zeolite content (clinoptilolite=80 wt%); the external cationic exchange capacity is independent of the cationic surfactant used. LS and CLSM analyses have shown a wide distribution of volume diameters of SMNZ particles that, along with their irregular shape, make them cohesive with scarce flow properties. CLSM observation has revealed the localization of different molecules in/on SMNZ by virtue of their chemical nature. In particular, cationic and polar probes prevalently localize in SMNZ bulk, whereas anionic probes preferentially arrange themselves on SMNZ surface and the loading of a nonpolar molecule in/on SMNZ is discouraged. The adsorption rate of DS onto SMNZ was shown by different kinetic models highlighting the fact that DS adsorption is a pseudo-second order reaction and that the diffusion through the boundary layer is the rate-controlling step of the process. DS release in an ionic medium, such as SIF, can be sustained for about 5h through a mechanism prevalently governed by anionic exchange with a rapid final phase.

Anion exchange selectivity of surfactant modified clinoptilolite-rich tuff for environmental remediation.

Lately, the functionalization of industrial minerals with high technological properties, such as natural zeolites, is shaping as a promising approach in environmental sphere. In fact, under the specific conditions, the surface functionalization via adsorption of cationic surfactants reverses the surface charge of the mineral, enabling zeolites to simultaneously interact either with organic contaminants or inorganic anions. This aspect allows zeolites to be used in the remediation of contaminated fluids. The present research shed new light on some still not fully understood aspects concerning exchange kinetics such as anion-exchange mechanisms and selectivity of surface modified minerals. For this purpose the mineralogical characterization and the surface properties evaluation (X Ray Powder Diffraction, chemical analysis, thermal analysis, ECEC and AEC) of a clinoptilolite-rich tuff were performed, and the anion exchange isotherms of the sample, modified with hexadecyltrimethylammonium chloride or bromide (HDTMA-Cl/-Br), were determined. Ion-exchange equilibrium data of uni-uni valent reaction were obtained by solutions containing Br(-), Cl(-), NO3(-) or ClO4(-). Liquid phase was analysed via high performance liquid chromatography. Thermodynamic quantities (Ka and ΔG(0)) were determined and compared with the Hofmeister series. The value of the ECEC, calculated in batch conditions, was about 137 mmol/kg, in good agreement with that evaluated in dynamic conditions, while the AEC data were different for the SMNZ-Br and -Cl samples, amounting to 137 and 106 mmol/kg, respectively, thus indicating a different compactness of the bilayer formed in the two cases. Moreover, the anion isotherm results and the mathematical evaluation of the thermodynamic parameters, demonstrated the good affinity of SMNZ-Br towards chloride, nitrate and perchlorate, and of SMNZ-Cl for nitrate and perchlorate, also endorsing the possibility of using the same thermodynamic approach developed to describe cation exchange selectivity in zeolites. Finally, it was also verified that the zeolite modified with HDTMA-Cl is able to better exploit its anion exchange capacity compared to the same zeolite modified with HDTMA-Br.

Solidification of Cd-bearing zeolitic tuff by reaction with lime.

This article aims to find a reliable procedure by which to remove Cd(2+) from water and store it safely. The proposed procedure includes Cd(2+) uptake by a zeolitic tuff, a natural cation exchanger, followed by stabilization of the contaminated solid in a hardened lime matrix. Several tuff-lime pastes were examined and their safety tested by cation leaching and mechanical strength measurement. It was demonstrated that a very cheap mixture, containing only 10% lime, is able to safely retain the harmful cation and may be disposed of in a segregated landfill.

An unconventional method for the recovery of caustic soda from spent Al-rich pickling solutions.

This work presents an unconventional procedure for the recovery of spent Al-rich caustic soda solutions from the pickling of dies for the production of aluminium extrusions. Caustic soda was regenerated at roughly 70%, by precipitating aluminate, after addition of a silica source, in the form of zeolite A, a microporous material that is widely used in many technological sectors. It was shown that the process is reliable and can be repeated for several cycles, provided the concentration of the caustic soda solution is suitably restored. The by-product obtained, zeolite A, proved to be a high-grade material with performance as a cation exchanger and physical sorbent that is certainly comparable to that reported in literature (e.g., cation exchange capacity equal to 5.14 meq g(-1) vs. 5.48 meq g(-1) and water vapour adsorption capacity of 26.5% vs. 27.6% at 16 torr and 298 K). The economics of the process, although not examined yet, would appear generally favourable, considering that zeolite A is a valuable by-product which widely covers the costs for the recovery of the spent solutions. There are, therefore, significant prospects for the use of zeolite A, particularly as a builder in detergent formulation.