One-Step Hydrothermal Synthesis of Zeolite X Powder from Natural Low-Grade Diatomite

Zeolite-based nanoparticles drug delivery systems in modern pharmaceutical research and environmental remediation

This review explores the potential of zeolite-based nanoparticles in modern pharmaceutical research, focusing on their role in advanced drug delivery systems. Zeolites, integrated into polymeric materials, offer precise drug delivery capabilities due to their unique structural features, biocompatibility, and controllable properties. Additionally, zeolites demonstrate environmental remediation potential through ion exchange processes. Synthetic zeolites, with modified release mechanisms, possess distinctive optical and electronic properties, expanding their applications in various fields. The study details zeolites' significance across industrial and scientific domains, outlining synthesis methods and size control techniques. The review emphasizes successful encapsulation and functionalization strategies for drug delivery, highlighting their role in enhancing drug stability and enabling targeted delivery. Advanced characterization techniques contribute to a comprehensive understanding of zeolite-based drug delivery systems. Addressing potential carcinogenicity, the review discusses environmental impact and risk assessment, stressing the importance of safety considerations in nanoparticle research. In biomedical applications, zeolites play vital roles in antidiarrheal, antitumor, antibacterial, and MRI contrast agents. Clinical trials featuring zeolite-based interventions underscore zeolite's potential in addressing diverse medical challenges. In conclusion, zeolite-based nanoparticles emerge as promising tools for targeted drug delivery, showcasing diverse applications and therapeutic potentials. Despite challenges, their unique advantages position zeolites at the forefront of innovative drug delivery systems.

Synthesized Zeolite Based on Egyptian Boiler Ash Residue and Kaolin for the Effective Removal of Heavy Metal Ions from Industrial Wastewater

The increase of global environmental restrictions concerning solid and liquid industrial waste, in addition to the problem of climate change, which leads to a shortage of clean water resources, has raised interest in developing alternative and eco-friendly technologies for recycling and reducing the amount of these wastes. This study aims to utilize Sulfuric acid solid residue (SASR), which is produced as a useless waste in the multi-processing of Egyptian boiler ash. A modified mixture of SASR and kaolin was used as the basic component for synthesizing cost-effective zeolite using the alkaline fusion-hydrothermal method for the removal of heavy metal ions from industrial wastewater. The factors affecting the synthesis of zeolite, including the fusion temperature and SASR: kaolin mixing ratios, were investigated. The synthesized zeolite was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), particle size analysis (PSD) and N₂ adsorption-desorption. The SASR: kaolin weight ratio of 1:1.5 yields faujasite and sodalite zeolite with 85.21% crystallinity, which then shows the best composition and characteristics of the synthesized zeolite. The factors affecting the adsorption of Zn²⁺, Pb²⁺, Cu²⁺, and Cd²⁺ ions from wastewater on synthesized zeolite surfaces, including the effect of pH, adsorbent dosage, contact time, initial concentration, and temperature, have been investigated. The obtained results indicate that a pseudo-second-order kinetic model and Langmuir isotherm model describe the adsorption process. The maximum adsorption capacities of Zn²⁺, Pb²⁺, Cu²⁺, and Cd²⁺ ions onto zeolite at 20 °C were 12.025, 15.96, 12.247, and 16.17 mg·g^-1, respectively. The main mechanisms controlling the removal of these metal ions from aqueous solution by synthesized zeolite were proposed to be either surface adsorption, precipitation, or ion exchange. The quality of the wastewater sample obtained from the Egyptian General Petroleum Corporation (Eastern Desert, Egypt) was highly improved using the synthesized zeolite and the content of heavy metal ions was significantly reduced, which enhances the utilization of the treated water in agriculture.

Conversion of polypropylene-derived crude pyrolytic oils using hydrothermal autoclave reactor and ni/aceh natural zeolite as catalysts

The accumulation of plastic waste has urged researchers to develop methods of waste conversion into valuable products, which is fuel. This study aimed to synthesize Ni embedded onto Aceh natural zeolite (Ni/Aceh-zeolite) as a cheap catalyst which could be used in the reforming process to improve the quality of oil produced from polypropylene (PP) pyrolysis. Ni/Aceh-zeolite was synthesized from Ni(NO₃)₂·6H₂O and acid-activated natural zeolite through impregnation and calcination. The catalyst was found to have particle sizes ranging from 100 to 200 nm of 20 wt% Ni content. The reforming process using Ni/Aceh natural zeolite with Ni loading of 15 wt% yielded the highest amounts of liquid product (yield = 65%) and gasoline fractions (C₅-C₁₂, 96.71%). However, the highest high heating value of 45.467 MJ/kg was found in the liquid product obtained with 20% Ni/Aceh-zeolite. In conclusion, Ni/Aceh-zeolite could be used in the reforming process of PP pyrolysis-derived oil, which could reach a quality similar to that of commercial gasoline.

Adsorption of Heavy Metals in Contaminated Water Using Zeolite Derived from Agro-Wastes and Clays: A Review

Due to climate change and anthropogenic activities such as agriculture, mining, and urbanization, water contamination has become a very real modern problem. Modern solutions such as activated carbon, reverse osmosis, and ultrafiltration, among others, have been employed in the decontamination of water. These methods are, however, expensive to set up and maintain and therefore have proved a challenge to implement in developing countries. Zeolite materials exhibit excellent structural properties, such as high ion exchange capacity, porosity, and relative surface area, which make them attractive to water decontamination processes. However, conventional zeolites are expensive, and recent research has focused on utilizing low-cost materials such as agro-wastes and clays as raw materials for the synthesis of zeolites. This review aims to discuss the role of low-cost zeolites in their removal of heavy metals and the feasibility of agro-wastes and natural clays in the synthesis of zeolites. Recent research studies based on the synthesis of zeolites from clays and agro-wastes and their application in heavy metal removal have been reviewed and discussed. Agro-wastes such as rice husk ash and sugarcane bagasse ash and layered silicate clays such as kaolinite and smectites are particularly of interest to zeolite synthesis due to their high silica to alumina ratio. Zeolites synthesized through various methods such as hydrothermal, molten salt, and microwave irradiation synthesis have been discussed with their effect on the adsorption of various heavy metals.

Two-step hydrothermal synthesis and conversion mechanism of zeolite X from stellerite zeolite

We investigated the conversion mechanism of stellerite zeolite to zeolite X under two-step hydrothermal conditions. To elucidate the conversion mechanism, solid products were separated from the mixtures at different crystallization times and characterized by XRD, FESEM, FT-IR, Raman, solid-state NMR, XRF, and TEM. The results indicate that in this reaction process, the Si, Al, and Na in the gel solid phases were continuously dissolved and transformed into the gel-liquid-phase. When the concentration of each component reached supersaturation in the gel-liquid-phase, Si, Al, and Na were transferred to the surface of the gel-solid-phase, and nucleation and crystallization occurred on the surface. Abundant nuclei were formed during the second hour of the crystallization. As the crystallization time increased, the nuclei rapidly grew into zeolite X crystals, and the relative crystallinity of zeolite X reached a maximum when the crystallization time reached 4 h. These phenomena indicate that the formation mechanism of zeolite X is a liquid-phase conversion mechanism.

Removal of Lead by Merlinoite Prepared from Sugarcane Bagasse Ash and Kaolin: Synthesis, Isotherm, Kinetic, and Thermodynamic Studies

This study introduces a merlinoite synthesized from sugarcane bagasse ash (SBA) and kaolin and evaluates its application as an adsorbent to remove lead from wastewater. The synthesis was performed via the hydrothermal method, and optimal conditions were determined. The adsorption of Pb by merlinoite was also optimized. Determination of the Pb2+ remaining in the aqueous solution was determined by atomic absorption spectroscopy (AAS). Adsorption isotherms were mainly studied using the Langmuir and Freundlich models. The Langmuir model showed the highest consistency for Pb adsorption on merlinoite, yielding a high correlation coefficient (R2) of 0.9997 and a maximum adsorption capacity (qmax) of 322.58 mg/g. The kinetics of the adsorption process were best described by a pseudo-second-order model. Thermodynamic studies carried out at different temperatures established that the adsorption reaction was spontaneous and endothermic. The results of this study show that merlinoite synthesized from kaolinite and SBA is an excellent candidate for utilization as a high-performance adsorbent for lead removal from wastewater.

High Removal Efficiency of Diatomite-Based X Zeolite for Cu2+ and Zn2

Diatomite-based X zeolite was obtained and its crystallinity, morphology, and interface properties were investigated by XRD, BET, SEM, EDS, and XRF. The obtained X zeolite possessed a unique meso-microporous structure and showed good ion exchange properties for Cu²⁺ and Zn²⁺. The pseudo-second-order model and Langmuir isotherm model can best describe the adsorption kinetics and isotherms of Cu²⁺ and Zn²⁺, respectively. The maximal adsorption capacities of X zeolite for Cu²⁺ and Zn²⁺ were 146 and 195 mg/g at 323 K, respectively. Meanwhile, the adsorption process for Cu²⁺ and Zn²⁺ were chemical adsorption and ion exchange, respectively. Furthermore, the adsorption data turned out to be an endothermic and spontaneous process. Compared with other reported materials, the adsorption capacity of X zeolite synthesized from diatomite was among the highest. Therefore, it could be a promising adsorbent for the disposal of wastewater that contains metal ions.

Geothermal industry waste-derived catalyst for enhanced biohydrogen production

The main aim of this work was to develop sustainable catalyst from geothermal waste by hydrothermal process for enhanced biohydrogen production. The effects of Si/Al ratio and pH neutralization on the catalyst were also investigated to provide further insight into the hydrogen production capability. Results have shown with increasing Si/Al ratio, a lower amount of catalyst was synthesized and smaller particle size was obtained. pH neutralization treatment resulted in higher conversion compared to non-neutralized ones. Meanwhile, the highest conversion of biohydrogen from ethanol through steam reforming process (95.19%) was obtained from catalyst with pH neutralization treatment and Si/Al ratio of 10. The catalyst developed in this study was concluded to be suitable for framework/supporting catalyst due to relatively low selectivity.

Obsidian as a Raw Material for Eco-Friendly Synthesis of Magnetic Zeolites

A sample of rhyolitic obsidian (OS) was used as raw material for zeolite synthesis by long (4 days) and fast (2 h)-aging hydrothermal processes. Zeolite synthesis was also performed by a fast (2 h) sonication method. The products were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) both immediately after and 3 years after their formation in order to determine the stability of synthetic materials according to the method used. The results confirm zeolitization of obsidian both by long-aging conventional hydrothermal heating and fast hydrothermal process. However, the data highlight the efficiency of direct ultrasound energy in achieving more stable zeolite crystals over time. These results carried out using a natural source, follow those already obtained using wastes and pure sources as raw materials thus providing a definitive validation of the different mechanisms controlling zeolite formation according to the process used. Moreover, the results confirm the effectiveness of ultrasonic energy in the formation of zeolites that are more stable over time. Due to the chemical composition of the obsidian precursor, all synthetic zeolites show good magnetic properties (i.e., saturation magnetization), in view to potential magnetic separation.

Aluminosilicate Nanocomposites from Incinerated Chinese Holy Joss Fly Ash: A Potential Nanocarrier for Drug Cargos

An incredible amount of joss fly ash is produced from the burning of Chinese holy joss paper; thus, an excellent method of recycling joss fly ash waste to extract aluminosilicate nanocomposites is explored. The present research aims to introduce a novel method to recycle joss fly ash through a simple and straightforward experimental procedure involving acidic and alkaline treatments. The synthesized aluminosilicate nanocomposite was characterized to justify its structural and physiochemical characteristics. A morphological analysis was performed with field-emission transmission electron microscopy, and scanning electron microscopy revealed the size of the aluminosilicate nanocomposite to be ~25 nm, while also confirming a uniformly spherical-shaped nanostructure. The elemental composition was measured by energy dispersive spectroscopy and revealed the Si to Al ratio to be 13.24 to 7.96, showing the high purity of the extracted nanocomposite. The roughness and particle distribution were analyzed using atomic force microscopy and a zeta analysis. X-ray diffraction patterns showed a synthesis of faceted and cubic aluminosilicate crystals in the nanocomposites. The presence of silica and aluminum was further proven by X-ray photoelectron spectroscopy, and the functional groups were recognized through Fourier transform infrared spectroscopy. The thermal capacity of the nanocomposite was examined by a thermogravimetric analysis. In addition, the research suggested the promising application of aluminosilicate nanocomposites as drug carriers. The above was justified by an enzyme-linked apta-sorbent assay, which claimed that the limit of the aptasensing aluminosilicate-conjugated ampicillin was two-fold higher than that in the absence of the nanocomposite. The drug delivery property was further justified through an antibacterial analysis against Escherichia coli (gram-negative) and Bacillus subtilis (gram-positive).

Nitrate reduction on surface of Pd/Sn catalysts supported by coal fly ash-derived zeolites

In this study, we synthesized four zeolites (i.e., Zeolite-X&A9, -X&A&HS12, -X&HS15, -X&HS18) from coal fly ash (CFA), and evaluated their potential for use as support materials to fabricate novel Pd-Sn bimetallic catalysts for reactive and selective reduction of NO₃^- to N₂. The successive transformation of zeolite (Na-A and Na-X to hydroxy sodalite (HS)) was observed with increasing crystallization time from 9 to 18 h, which resulted in different degrees of crystallinity, morphology, BET surface area, and pore volume. Compared to other monometallic and bimetallic catalysts, Pd-Sn/Zeolite-X&HS15 (crystallization time = 15 h) showed remarkable nitrate removal (100%) with the highest kinetic rate constant (k = 0.055 min^-1, K' = 0.219 min^-1 g_cat^-1, K'' = 2.922 L min^-1 g_Pd^-1) and N₂ selectivity (88.1%). These results can be attributed to high surface area and stability of each of the zeolite phases (i.e., Na-X and HS). The reaction mechanism was elucidated by Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses, demonstrating the presence of Pd°, Sn°, and Sn²⁺ and the uniform distribution of proximate Pd-Sn ensembles on the surface. These results suggest new promising strategies for applying industrial solid waste-derived zeolites to the synthesis of novel bimetallic catalysts to ensure efficient and economical denitrification of wastewater.

The Effects of Temperature on the Hydrothermal Synthesis of Hydroxyapatite-Zeolite Using Blast Furnace Slag

Blast furnace slag, an industrial by-product, is emerging as a potential raw material to synthesize hydroxyapatite and zeolite. In this study, the effects of temperature on the hydrothermal synthesis of hydroxyapatite-zeolite from blast furnace slag were investigated. Specimens were synthesized at different temperatures (room temperature, 50, 90, 120, or 150 °C). The synthesized specimens were analyzed qualitatively and quantitatively via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), BET/BJH, and scanning electron microscopy/energy dispersive using X-ray analysis (SEM/EDX). It was found that the hydroxyapatite phase was synthesized at all the reaction temperatures, while faujasite type zeolite appeared in the specimens synthesized at 90 and 120 °C. Moreover, faujasite was replaced by hydroxysodalite in the specimens synthesized at 150 °C. Additionally, the crystals of the hydroxyapatite tended to become larger and total crystallinity increased as the reaction temperature increased.

Overview of Current and Future Perspectives of Saudi Arabian Natural Clinoptilolite Zeolite: A Case Review

After a thorough review of existing studies of clinoptilolite zeolites, three areas for potential investigation of the Saudi Arabian zeolites were found. They are the characterizations, the catalytic activity, active sites, and uses of natural clinoptilolite zeolites. First, no analysis is available worldwide to compare the percentage weight of local zeolites with those sourced from other countries, nor does one exist for the establishment on the zeolite conversion of MBOH with water on acidic catalysts at lower temperatures. Secondly, a review of current literature on the topic revealed that basic and active sites of Saudi Arabian zeolites have yet to be examined. Future investigation of zeolite catalytic activity can be achieved by methyl butynol test reaction (MBOH) and absorption-desorption of ammonia. In the characterization of a range of international materials, the methyl butynol test reaction was utilized, including on natural zeolites, natural clays, and synthesized hydrotalcites. However, the catalytic performance of natural Saudi Arabian clinoptilolite zeolites by test reaction of MBOH conversion has not been yet investigated. Therefore, this article also includes an outline of the general testing conditions and parameters required to execute the accurate characterization of local Saudi clinoptilolite under optimal test conditions. Likewise, knowledge of the important active acidic centers of local materials is prescribed. This can be ascertained by determining the conditions together with the test parameters for the application of the “temperature-programmed desorption of ammonia” method in order to obtain an accurate determination of local Saudi clinoptilolite acidic centers. Additionally, an outline of the catalytic activity of worldwide clinoptilolite is given in this article together with kinetic investigations of other sources for the clinoptilolite zeolite in order to form the basis for the testing of local Saudi clinoptilolite. The percentage average of chemical composition (Wt.%) of natural clinoptilolite from various countries is also included. Finally, a future research plan is proposed here. This will form the basis for a complete study or survey to be compiled detailing the modifications needed to increase the surface areas for Saudi natural clinoptilolite zeolites using different methods of modifications. This could enhance its application as acid catalysts for use in the retardation of coke formation and for membrane separation on cationic exchange.

Antimicrobial activity of X zeolite exchanged with Cu2+ and Zn2+ on Escherichia coli and Staphylococcus aureus

The biocidal cations of Cu²⁺ and Zn²⁺ were hosted on the surfaces and in the cavities of X zeolite via ion exchange. The microstructure and interface properties of the exchanged zeolite X samples were analyzed by XRD, SEM, XPS, and XRF. The as-prepared samples showed excellent antimicrobial activity towards gram-negative bacteria of Escherichia coli and gram-positive bacteria of Staphylococcus aureus. Furthermore, the batch antimicrobial experiments showed that the bacterial disinfection process fitted well with the first order model. The Cu²⁺-zeolite showed excellent and better antibacterial performance on S. aureus than on E. coli, and the mortalities of E. coli and S. aureus were almost 100% after 1 h with the initial Cu²⁺-zeolite concentrations of 1000 ppm and 100 ppm, respectively. However, the Zn²⁺-zeolites were found to be less effective on S. aureus than on E. coli, and the mortalities of E. coli and S. aureus were almost 100% after 1 h with the initial Zn²⁺-zeolite concentrations of 500 ppm and 1000 ppm, respectively. In addition, the relationships between the apparent rate constant (k) and reagent concentration (C) were also systematically investigated. The present results suggest that the as-prepared samples could be promising antibacterial materials for the efficient disinfection of contaminated water with bacteria.