Geopolymer is an emerging material that is known to have excellent properties. Numerous applications of geopolymer have been reported in various studies, for example, in the construction and building sector, nuclear waste management, and wastewater treatment industry. It gains popularity in the wastewater treatment sector as it can effectively adsorb pollutants (e.g., heavy metals). However, the performance of this material varies depending on different factors such as the type of precursors, mix formulation, process conditions, etc. Moreover, optimal selection should also consider the potential environmental impact and safety to the general public before field application. The utilization of coal fly ash and other potential material was investigated to develop a pervious geopolymer. In this study, selection of optimized geopolymer mix for heavy metal removal using TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) and AHP (Analytic Hierarchy Process) with a spherical fuzzy approach was employed. An illustrative case study is presented for the proposed decision modeling technique in optimally selecting pervious geopolymer mix.