Sorption and mechanism studies of Cu, Sr and Pb ions on mesoporous aluminosilicates/zeolite composite sorbents.

The research aimed to develop a novel mesoporous aluminosilicate/zeolite composite by the template co-precipitation method. The effect of aluminosilicate (AlSi) and zeolite (NaY) on the basic properties and adsorption capacity of the resultant composite was conducted at different mass ratios of AlSi/NaY (i.e., 5/90, 10/80, 15/85, 20/80, and 50/50). The adsorption characteristics of such composite and its feedstock materials (i.e., aluminosilicates and zeolite) towards radioactive Sr ions and toxic metals (Cu and Pb ions) in aqueous solutions were investigated. Results indicated that BET surface area (S), total pore volume (V), and mesopore volume (V) of prepared materials followed the decreasing order: aluminosilicate (890 m/g, 0.680 cm/g, and 0.644 cm/g) > zeolite (623 m/g, 0.352 cm/g, and 0.111 cm/g) > AlSi/NaY (20/80) composite (370 m/g, 0.254 cm/g, and 0.154 cm/g, respectively). The Langmuir maximum adsorption capacity (Q) of metal ions (Sr, Cu, and Pb) in single-component solution was 260 mg/g, 220 mg/g, and 161 mg/g (for zeolite), 153 mg/g, 37.9 mg/g, and 66.5 mg/g (for aluminosilicate), and 186 mg/g, 140 mg/g, and 77.8 mg/g for (AlSi/NaY (20/80) composite), respectively. Ion exchange was regarded as a domain adsorption mechanism of metal ions in solution by zeolite; meanwhile, inner-surface complexation was domain one for aluminosilicate. Ion exchange and inner-surface complexation might be mainly responsible for adsorbing metal ions onto the AlSi/NaY composite. Pore-filling mechanism was a less important contributor during the adsorption process. The results of competitive adsorption under binary-components (Cu and Sr) and ternary-components (Cu, Pb, and Sr) demonstrated that the removal efficacy of target metals by the aluminosilicate, zeolite, and their composite remarkably decreased. The synthesized AlSi/NaY composite might serve as a promising adsorbent for real water treatment.