The Effect of Sustainable Applications of Chitin and Chitosan to Remove Dyed Pollutants Using Adsorption: A Review

Sustainable wastewater treatment methods are very important and necessary because they help to protect the environment and the health of humans, animals and other living organisms. With the increase in industries and population, toxic dyes produced in various industries have created a serious issue for public health and the main concern of environmental protection. This method affects the quality of purified water and causes various diseases, and as a result, it ends in death. Water purification is very important and plays an important role in the environment. Pollutant removal has different methods that include physicochemical and biological treatment. Each of these methods shows different pollutant removal capabilities that are studied here, depending on the experimental limitations. Among the different methods of wastewater treatment, the methods that have a high cost are not used today, and the results have shown that researchers consider more in the fields that have a low cost of material and testing. Surface adsorption is considered the most efficient method due to its high removal efficiency, easy operation, cost-effectiveness and recyclability of adsorbents. In this paper, the sustainable applications of wastewater treatment for the removal of colored pollutants have been investigated. Here, chitin and chitosan are more commonly used nowadays due to the naturalness of the polymer material, and it is not toxic and has many uses in various fields that can be used by adsorption. In this context, this work aims to provide a comprehensive summary of the adsorption of dyes from wastewater by nano-biopolymers, especially chitin and chitosan, as adsorbents. First, a summary of biopolymers, the properties of chitin and chitosan and synthesis techniques are presented. After the classification of dyes, the techniques for removing them from the wastewater are described. In addition, the adsorption process and isotherms used for adsorption are described with different models. Among various adsorbents, such as carbon materials, metals/metal oxides and zeolites, nano-biopolymers, especially chitin and chitosan, are the most promising ones for environmental sustainability. The results show that the use of biocompatible biopolymers to remove dye pollutants in different dyeing and textile industries plays an important role in determining the sustainable methods of wastewater treatment and can reduce the environmental effects of industries. Surface adsorption can be compatible with the environment and remove various colored pollutants well so that we have clean and pollution-free water and can use water.