Recent progress in micro and nano-encapsulation techniques for environmental applications: A review

In recent years, micro- and nano-encapsulation methods have received considerable interest in the field of environmental research. These simple coating approaches retain the active material of interest inside a semi-permeable membrane or carrier matrix, which allows the transfer of materials between the matrix and the reaction medium. This enables the development of particles with a controlled or triggered-release mechanism. The use of pH, temperature and pressure-responsive agents is commonly employed to regulate the release of core material from encapsulated particles. Diverse applications, from water treatment to energy storage and agricultural practices, have seen the use of encapsulated materials especially in the micro and nano size range. Within the water treatment sector, studies with encapsulated materials have shown improved stability and reusability of various adsorbents for pollutant removal. However, challenges remain in separating encapsulated metal and nonmetal-based matrix-type composites from the aqueous phase. Major applications of encapsulated materials in the energy sector involve their use in different energy storage systems such as phase change materials (PCMs). Encapsulation of PCMs in a suitable shell material provides a large surface area and excellent thermal properties and helps overcome leakage problems associated with conventional PCMs. Within the agriculture domain, encapsulated particles provide controlled and extended delivery of agrochemicals at target site and protect the core materials from harsh environmental conditions. Hydrogel-based products improve sustainability in agriculture by conserving water needs. Overall, this review aims to provide a comprehensive overview of encapsulation synthesis techniques, their merits and challenges, as well as highlight the applications and future prospects of encapsulated materials within the environmental domain.