With the beginning of industrialization and globalization, the world has experienced drastic growth and connectivity which has largely escalated the energy demand. Coal has been the most cost effective and dominant source of energy since long time. It has been crucial in the economic development and technological advancement. However, this has come at a significant environmental cost, creating massive quantities of coal fly ash (CFA) as an industrial byproduct of coal fired thermal power plants. Traditionally it was considered as a waste material resulting in improper disposal and landfilling resulting in significant environmental damage including water contamination, air pollution, and land pollution. This poses a great obstacle for the sustainable development goal. CFA is rich in silica (SiO₂) and alumina (Al₂O₃) along with crystalline phases like quartz and mullite. Silica and Alumina are the primary building blocks for zeolites. Zeolites are hydrated aluminosilicate crystalline minerals composed of a three-dimensional lattice of [SiO₄] and [AlO₄] tetrahedral. Synthesis of zeolites from CFA provides a sustainable route for CFA management, reducing environmental impact and converts a low-value, problematic industrial waste into a high-value adsorbent material. Various techniques like fusion method, hydrothermal method etc. are employed for this synthesis. This reduces the cost of zeolite synthesis to about one-fifth of its traditional costs. This review covers the application of CFA-derived zeolites to remove Heavy metal ions (Ni, Hg, Mn, Cu, Zn, Cd, Pb, Cr, Co) both from synthetic solutions replicating industrial wastewater and actual wastewater streams. Industrial wastewater may consist of different pollutant types, but of specific interest to this work are heavy metals, which are among the most dangerous pollutants due to their toxicity and carcinogenicity.
