General overview to understand the adsorption mechanism of textile dyes and heavy metals on the surface of different clay materials

Abstract

The adsorption process is one of the most cost-effective methods for eliminating various types of pollutants from water. Clay minerals can be converted into biosorbents for environmental remediation. This literature review summarizes the different types of natural clays, their crystal structures, classifications, physical and chemical properties, and industrial applications. Also the main results of recent studies on the process and mechanism of adsorption on natural clay materials to eliminate heavy metals and highly emerging toxic dyes. The Langmuir and Freundlich models are the most commonly used isotherms in most previous studies. In addition, the adsorption kinetics of the majority of dyes and heavy metals using natural clays are based on the pseudo-second-order model. High adsorption capacities of 909.09 mg g−1 for synthetic dyes and 179 mg g−1 for heavy metals were observed. This review article suggests that clays can be modified by various methods to improve their adsorption efficiencies by increasing their specific surface areas. The clays' low cost and ability to regenerate show that these materials are environmentally friendly and beneficial for industrial ecology.

Keywords

• Adsorption mechanism
• Clays
• Dyes
• Heavy metals
• Regeneration
• Specific surface area