Physico-chemical modification of natural mordenite-clinoptilolite zeolites and their enhanced CO₂ adsorption capacity

Natural zeolites are an attractive material to be used as adsorbents for the removal of carbon dioxide (CO₂) due to their low cost and abundant availability in many regions around the world. However, the performance of these materials is quite limited because of their small pore size and restricted specific surface area. In this work, we report on the physicochemical modification (calcination and dealumination) of natural Indonesian calcite-rich mordenite-clinoptilolite zeolites by acid and high temperature calcination treatment to enhance their CO₂ adsorption capacity. We demonstrated that the specific surface area of the original material can be finely tuned via simple adjustment of the concentration of HCl. Amongst different preparations, the zeolites treated with the 12 M HCl and calcination at 400 °C registered the highest specific surface area of 179.44 m²/g. This modification resulted in the highest CO₂ adsorption capacity of 5.2 mmol/g at 0 °C and 30 bar, corresponding to specific surface area normalized CO₂ adsorption capacity of 2.91 × 10⁻² mmol/m². This promising result revealed that careful modification of low-cost natural zeolite via a simple phisicochemical treatment not only enhanced the specific surface area and the pore size but also led to excellent CO₂ adsorption affinity when compared with the more costly synthetic materials. This finding demonstrates the potential of low cost natural product to be developed and utilized as a cost-effective adsorbent for CO₂.