Micro-mesopore analysis of Cu2+ and Ag+ containing Al-pillared bentonite

Copper impregnated Cu@Al-PILCs, silver impregnated Ag@Al-PILCs and copper aluminum mixed Cu/Al-PILCs were prepared using a bentonite sample from the Hançılı region, Turkey. Incorporation of the Cu2+ or Ag+ ions forming CuO and Ag2O after calcination at 573 K decreased the basal spacing of 1.85 nm for Al-PILC by approximately 0.35 nm. The specific BET surface area and mesopore + micropore volumes measured by 77 K nitrogen adsorption after calcination at 573 K decreased from 236 m2 g− 1 and 0.174 cm3 g− 1 to 174 m2 g− 1 and 0.172 cm3 g− 1 by Cu2+ impregnation and 171 m2 g− 1 and 0.168 cm3 g− 1 by Ag+ impregnation, while the values for Cu/Al-PILC were 209 m2 g− 1 and 0.184 cm3 g− 1. The micropore volume of all samples was about 20% of the total pore volume. The average Barrett–Joyner–Halenda (BJH) mesopore and Horvath–Kawazoe (HK) micropore dimensions were within 3.5–3.9 nm and 0.44–0.48 nm, respectively. Structural properties estimated from the Dubinin–Radushkevich (DR) method by using the nitrogen adsorption data were higher than those derived from the carbon dioxide adsorption data. SEM images indicated that Cu2+ incorporation increased the mesopore volume of the Al-PILC.

Research Highlights
► Structural properties estimated from different approaches were in agreement.
► Reflections of copper and silver oxides were observed in all incorporated samples.
► Structural properties were slightly affected by the metal ion incorporation.
► Calcination temperature increase resulted to a mesoporous structure for all PILCs.
► The micropore volume of all samples was about 20% of the total pore volume.