Anticorrosion Behavior of Zeolite Coatings Obtained by In Situ Crystallization: A Critical Review

The Effectiveness of Pahae Natural Zeolite-Cocoa Shell Activated Charcoal Nanofilter as a Water Adsorber in Bioethanol Purification

Pahae natural zeolite potentially can be used as a filtration material because of its high adsorption capacity. However, it is known that other supportive materials such as activated charcoal are needed to optimize the utilization of natural zeolite as an adsorber. This study aims to investigate the potential use of activated charcoal which was synthesized from cocoa shells waste and natural zeolite in nanosize as the adsorber in order to increase the concentration of bioethanol. The mixing process of nanozeolite and activated charcoal of cocoa shells was carried out through mechanical mixing, while the nanofilter was made using a press-printing technique followed by sintering at several temperature variations. The results showed that the activated zeolite produced in this study has a particle size of 118.4 nm with water absorption capacity of 52.08%. In line with that, the bioethanol concentration was increased up to 78.92% during the adsorption with a 45 min contact time with water vapor. Thus, based on the results, it can be concluded that nanosized zeolite-based adsorbents and activated charcoal produced from cocoa shells can be utilized as adsorbers to significantly increase the concentration of bioethanol generated.

An Industrial Approach for the Optimization of a New Performing Coated Adsorber for Adsorption Heat Pumps

In the present work, the optimization of a new coating formulation was investigated, taking attention to an industrially focused research approach used for the engineering design of the adsorber. The adsorbent was a composite zeolite or silica-gel based coating applied by using new flexible polymer matrices. The FC-80 formulation represents a good compromise between mechanical stability and absorption capacity. Using the developed coating process, a new compact HEX design was developed to reach the AHP target performance with easy and fast manufacturing. The specific cooling power of the coated heat exchanger was estimated to be about 500 W/kg of adsorbent. The new coated HEX was integrated in a new adsorption chiller and has been tested by a laboratory test-rig under realistic operating conditions. Results of preliminary testing demonstrated that the prototype provides a cooling capacity of around 10 kW with a COP of 0.54.

Effect of Lime Stabilization and Partial Clinoptilolite Zeolite Replacement on the Behavior of a Silt-Sized Low-Plasticity Soil Subjected to Freezing–Thawing Cycles

Soil stabilization, through either physical or chemical techniques of coating-cementation development, is a commonly adopted practice in geotechnical and transportation engineering projects used to strengthen soils and mitigate negative geo-environmental impacts. This can be particularly important in enhancing the mechanical properties of soils which are prone to degradation of their response because of freezing and thawing actions. It was attempted in this research study to examine the effect of lime–zeolite stabilization on the behavior of a silt-sized natural soil of low plasticity, by performing standard compaction tests as well as unconfined compressive experiments evaluating the strength of the composite samples. The natural soil mixed with various contents of lime and zeolite partial replacement was subjected to consecutive freezing and thawing cycles. The results from the study showed significant improvement of the mechanical performance of the treated soil when mixed with lime partially replaced with zeolite in terms of strength and durability and, based on scanning electron microscopic images, additional insights were attempted to be obtained on the microstructure of the specimens subjected to temperature changes.

On the Anti-Corrosion Property of Dry-Gel-Conversion-Grown MFI Zeolite Coating on Aluminum Alloy

MFI zeolite film coated on AA6061 alloy was prepared from fumed silica modified with/without n-octyldecyltrimethoxysilane (ODS) by means of dry gel conversion (DGC) method. The DGC-grown MFI zeolite film could form a strong barrier to protect AA6061 surface against the corrosion from NaCl solution. By using fumed silica as a starting material, the hydrophilicity and anti-corrosion capability of the MFI zeolite film declined with increasing humidity in the DGC synthesis. By silanization with ODS, the surface hydrophobicity of the MFI zeolite film increased, leading to substantial enhancement in anti-corrosion capability. On the other hand, MFI film grown from ODS-modified fumed silica exhibited low hydrophilicity and a much improved anti-corrosion protection property by four orders of magnitude, even stronger than the ODS post-treated MFI film. The strong anti-corrosion capability is attributed to the "thick layer" surface hydrophobicity of zeolite crystal.

Recent Developments in Coating Technologies for Adsorption Heat Pumps: A Review

The use of adsorbent heat pumps as heating and cooling systems is particularly relevant thanks to their ability to exploit low-grade heat (e.g., below 90 °C) from renewable energy sources and waste energy streams with prospective applications in several fields, e.g., industrial and residential. Their development began in the 20th century and is still in full evolution. The great interest in their improvement and optimization was determined by some key factors inherent to their sustainability compared to traditional refrigeration systems (e.g., low electricity consumption and the low environmental impact of the employed refrigerants). Recently, strong efforts have been dedicated to increasing the achievable heating/cooling power density of this technology through the development of innovative adsorbent coating technologies. Indeed, the deposition of thin coatings on the surface of the heat exchanger could reduce the heat transfer resistance existing on the adsorbent material side, thus increasing the overall adsorption dynamics. Three main approaches have been assessed, namely a thick consolidated bed, binder-based composite coatings and in situ directly crystallization coatings. This paper provides a brief overview of some of the main achievements related to adsorbent coating technology developments for adsorption heat pump applications.

A Brief Overview on the Anticorrosion Performances of Sol-Gel Zeolite Coatings

Research activity concerning nanoporous zeolites has grown considerably in recent decades. The structural porosity of zeolites provides versatile functional properties such as molecular selectivity, ion and molecule storage capacity, high surface area, and pore volume which combined with excellent thermal and chemical stability can extend its application fields in several industrial sectors. In such a context, anti-corrosion zeolite coatings are an emerging technology able to offer a reliable high performing and environmental friendly alternative to conventional chromate-based protective coatings. In this article, a focused overview on anti-corrosion performances of sol-gel composite zeolite coatings is provided. The topic of this review is addressed to assess the barrier and self-healing properties of composite zeolite coating. Based on results available in the literature, a property–structure relationship of this class of composites is proposed summarizing, furthermore, the competing anti-corrosion active and passive protective mechanisms involved during coating degradation. Eventually, a brief summary and a future trend evaluation is also reported.