This study aims to synthesize mullite powders using the sol-gel method and explore their potential for water purification and removing copper ion contaminants. The effects of synthesis temperature, pH value, and solvent type on the samples’ specific surface area and microstructural properties were thoroughly examined. The impact of different solvents, including aqueous and aqueous-polymeric solvents, was also investigated. Subsequently, the adsorption properties of the PVA membranes containing synthesized materials as adsorbents in a solution containing copper ions were investigated. According to XRD results, samples treated under acidic conditions in the presence of polyethylene glycol as solvent demonstrated crystallization of 100% of the mullite phase at lower temperatures (1350 °C) which is higher than that of samples synthesized at basic conditions or in aquas media. BET results and SEM images of the thermally treated samples at 1350 and 1550 °C revealed that the acid-treated samples, PW0 and W0, exhibited more porous and uneven surfaces than the basic-treated samples, PW13 and W13. According to BET and PSA results, synthesized samples at acidic conditions in a polymeric substrate demonstrated a higher specific surface area (11 m3/g) and smaller particle size (0.4 μm) in comparison to samples synthesized in the basic and/or aqueous substrate conditions. These characteristics enhance the adsorption capacity of the synthesized materials in this series. Moreover, ICP results indicated that the PW0-1550–1 h sample exhibited the highest adsorption capacity. Under the conditions using 0.06 g of this adsorbent, the adsorption rate was 58%, and increasing the adsorbent amount to 0.12 g resulted in a 70% adsorption rate.

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