Preparation of rod-like γ-alumina/volcanic rock porous material and preliminary study on the adsorption property of Congo red

The porous materials of rod-like γ-alumina interlaced in pores of volcanic rock were prepared by in-situ growth using volcanic rock as matrix material, aluminum nitrate and ammonium bicarbonate as raw materials. The structure and properties of the materials were characterized by XRD, SEM, N₂ adsorption-desorption and TG-DSC technology. The adsorption performance of Congo red was also studied. It was found that the aluminum nitrate solution filled the pores of volcanic matrix materials by diffusion and adsorption, and amorphous alumina was formed after calcination. During hydrothermal treatment and calcination, the formed alumina was transformed into ammonium aluminum carbonate hydroxide and γ-alumina. The optimal reaction conditions for the preparation of rod-like γ-alumina/volcanic rock porous materials were as following: the concentration of ammonium bicarbonate solution was 0.8 mol/L, the reaction temperature was 140 ℃, and the reaction time was 4 h. The rod-like γ-alumina stacked in the channels of volcanic rock with a diameter of 50−150 nm and length of 3−10 μm. The specific surface area and pore volume of the porous material was 0.1 mL/g and 47 m²/g, respectively. When the concentration of Congo red solution was 500 mg/L and the dosage of porous material was 2 g/L, the removal rate was 96% with the adsorption amount of 243 mg/g.