BACKGROUND: This work employs low-grade kaolin as raw material in the economical production of nano-porous silica with extended surface area via the hydrothermal acidification of intermediate zeolite composite to remove methylene blue from wastewater. Hydrosodalite fabricated through the modification of meta-kaolin (MK) with sodium aluminate (NaAlO2) was used as a precursor in the hydrothermal acidification step. RESULTS: The direct conversion of MK to zeolite composite generating a low crystalline phase, containing quartz which was eliminated in the acidification step, exhibited a strong affinity towards dye adsorption. It was indicated that the NaAlO2/MK ratio could influence the hydrosodalite crystallization as well as adsorption efficiency of the nano-porous silica obtained from acidification of zeolite composite. The nano-porous silica formation involved the ion extraction from hydrosodalite cabbage-like particles, depending on crystallinity of intermediate zeolite composite. CONCLUSION: The mesoporous silica represented the appropriate adsorptive behavior when produced from precursor modified with lower NaAlO2 content, NaAlO2/MK = 0.24, attributed to superior specific surface area, 420 m(2) g(-1), with average pore diameter about 3.3 nm. The equilibrium data was better correlated by Redlich-Peterson isotherm. Compared to the surface area of silica powders fabricated from high grade kaolins, Al2O3/SiO2, > 0.83, by the acid-etched strategy, the mesoporous silica produced from the low-grade kaolin by the template free method indicates higher value. (c) 2020 Society of Chemical Industry