2. Experimental and modeling approach2.1. Synthesis of nanoporous geopolymer material (basemedia)In the first step of the synthesis, a potassium silicate solutionwas prepared by dissolving an appropriate amount of KOHpellets (Sigma Aldrich) in deionized water in a polypropylenecup placed in a water bath. A suitable amount of fumed silica(Cabot, CA-BO-SIL® EH-5) was then added into the KOHsolution and the mixture was stirred with a Stir-Pak laboratorymixer for 30 minutes at 800 rpm to give a clear solution. Thegeopolymer resins were then prepared by mechanically mixingmetakaolinite into the potassium silicate solution to form ahomogenous fluidic liquid. The metakaolinite was produced inadvance by calcining kaolinite (Al2Si2O7·H2O, Alfa Aesar) at750 °C for 10 h. Eight different samples were prepared byvarying the amounts of water, K/Al ratio and Si/Al ratio(Table 1). The pH of the resins was about 14 for all the compositions.Canola oil (The J.M. Smucker Company, Crisco®),paraffin oil (Alfa Aesar) or a mixture of both oils (Table 1) wasthen added to the resin at a 1:1 oil-to-water volume ratio andmixed for an additional 15 minutes to give a homogeneous butviscous emulsion. The emulsion was transferred to a polypropylenecup and cured in a laboratory oven at 60 °C for 24 h. Thecured monolithic product was then broken into small pieces(approximately 1 × 1 × 1 cm3) and subjected to Soxhlet extractionwith n-butanol as a solvent. The resulting nanoporousgeopolymer (base media) pieces free of organics were driedovernight in the lab oven maintained at 120 °C. Completeremoval of organics was confirmed by CHN analysis and infraredspectroscopy (data not shown).2.2. In-situ synthesis of iron (hydr)oxide