Cotton fiber is soft in texture, has excellent hygroscopicity, alkali resistance and heat resistance, and has high tolerance to bleaching agents, organic solvents, etc. It is the fiber that consumes the most after polyester. In addition, cotton products have excellent comfort performance, making pure cotton and its blended products mainstream products in the market and favored by consumers [1]. However, with the continuous improvement of people's living standards and medical and health standards, the upgrading of cotton textiles has become more frequent, and cotton products are easy to wrinkle under the action of water washing and the outside world. The colored products will also appear obvious fading after repeated washing. This leads to a short lifetime of cotton textiles. Coupled with the extensive use of disposable cotton products in the medical and service industries, waste cotton textiles have become the most important source of waste textiles. Although cotton fiber can degrade naturally as a natural material, cotton will occupy and consume a large amount of land and water from planting to processing and then to production, resulting in resource shortage. The pollution of pesticides to soil and water during planting cannot be ignored. Some studies have shown that the consumption of pesticides in cotton cultivation is estimated to account for 11 % of the global pesticide use [2]. It is also worth noting that when the blended article containing cotton is discarded, the part of the artificial chemical fiber will not be degraded naturally, but will cause a large amount of microplastic fiber pollution [[3], [4], [5]]. Microplastic fiber pollution not only has irreversible effects on organisms in soil, ocean and rivers, but also has unpredictable hazards to human body, such as causing different degrees of damage to the digestive tract of organisms, affecting the reproduction rate and enzyme activity of some organisms, and changing the microbial structure in human lungs and gastrointestinal tract [[6], [7], [8]]. If cotton fiber can be effectively separated and recycled, it can not only prevent pollutant diffusion, reduce environmental pressure, but also save resources.

The most common waste textile recycling strategy is to transfer them to the new owner through donation, exchange and resale; when the textile is no longer suitable for use, its fabric can be recycled into new products, such as interior decoration, low-grade blankets, industrial rags and insulating materials; it can also be disassembled for the production of non-woven fabrics, sound insulation equipment, toys [9] (Fig. 1). However, as the fiber is shortened and degraded in each round of recycling process, the added value of the product continues to decrease, and the textile will eventually be landfilled or incinerated, thus polluting the natural environment, and causing waste of resources. Cotton fiber contains a large amount of cellulose, which has attracted much attention due to its renewable, widespread availability, low cost, biocompatibility and biodegradability. It is regarded as the most likely raw material to replace petroleum-based polymers. It is of great value for commercial and industrial applications. The vast amount of waste cotton textiles generated globally contains an abundance of cellulose. If this cellulose can be fully recycled and utilized as an alternative to current sources, it would reduce the need for deforestation and the occupation of arable land, thereby protecting the environment while conserving land resources [[10], [11], [12]]. With the shortage of resources and the improvement of human awareness of environmental protection, more and more scholars have paid attention to the recycling and high-value recycling of waste textiles, and a series of new physical, chemical, and biological recycling technologies and methods have been developed one after another [13,14]. Among them, the solvent method is regarded as the most potential recovery method, because an efficient solvent system can not only dissolve cellulose in cotton fibers, but also effectively separate cotton fibers and synthetic chemical fibers when processing blended products. Regarding cellulose textile waste, the sole industrialized upcycling option so far has been dissolving it into a cellulose solution and spinning it into “new” fibers [15,16]. However, numerous studies currently showcase the feasibility of creating a variety of high-value porous materials, such as cellulose aerogels.

Cellulose aerogels have the characteristics of low density, porosity, low thermal conductivity, and good toughness. They have been successfully applied in the fields of housing structure [[17], [18], [19]], aerospace [20,21], safety protection [22,23], environmental management [[24], [25], [26]], and drug delivery [27,28]. The preparation of regenerated cellulose aerogel presents an idea approach for recycling waste cotton and cellulose textile waste (Fig. 2). Consequently, this article will concentrate on the high-value regenerated cellulose aerogel produced from waste cotton or cotton fibers via solvent methods in recent years. It will detail the structure, preparation strategies, and functional applications of the aerogel, with the goal of advancing the waste textile recycling industry.