Adsorption of Zn(II), Pb(II), and Cu(II) by Residual Soil-Derived Zeolite in Single-Component and Competitive Systems

Using construction residual soil (RS) as the raw material, RS-derived zeolite (RSDZ) was prepared through a fusion-hydrothermal process. The adsorption performance and mechanisms of RSDZ for Pb 2+ , Zn 2+ , and Cu 2+ were investigated in single-component and competitive systems. The strong RSDZ X-ray diffraction peaks at 2θ = 12.47, 17.73, 21.65, 28.18, and 33.44°, together with the results of scanning electron microscopy and Fourier transform-infrared spectroscopy (FT-IR) indicated that NaP1 zeolite (Na 6 Al 6 SiO 32 ∙12H 2 O) was successfully synthesised. The Brunauer–Emmett–Teller surface area, average pore size, and cation exchange capacity increased from 9.03 m 2 ∙g −1 , 18.85 nm, and 0.12 meq∙g −1 to 47.77 m 2 ∙g −1 , 41.60 nm, and 0.61 meq∙g −1 , respectively, after the fusion-hydrothermal process. The maximum Langmuir adsorption capacity of RSDZ for Zn 2+ , Pb 2+ , and Cu 2+ in the unary systems was 0.37, 0.38, and 0.40 mmol·g −1 , respectively. Increasing the initial solution pH facilitated the adsorption reaction, and the adsorption performance was stable when pH > 3. The distribution coefficients in the binary and ternary systems indicated that RSDZ had greater affinity for Pb 2+ and Zn 2+ than for Cu 2+ due to the larger ionic radius and relative atomic weight of the former two cations. The relative affinity to Pb 2+ and Zn 2+ was related to their concentration, with more competitive adsorption of Pb 2+ at concentrations higher than 0.4 mmol·L −1 in binary systems and 0.25 mmol·L −1 in ternary systems. X-ray photoelectron spectroscopy and FT-IR analyses indicated that ion exchange was the main mechanism involved in the adsorption of heavy metal ions by RSDZ, accompanied by ligand exchange.