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 Pb2+, Zn2+, and Cu2+ were investigated in single-component and competitive systems. The strong RSDZ X-ray diffraction peaks at 2 theta = 12.47, 17.73, 21.65, 28.18, and 33.44 degrees, together with the results of scanning electron microscopy and Fourier transform-infrared spectroscopy (FT-IR) indicated that NaP1 zeolite (Na6Al6SiO32 center dot 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)center dot g(-1), 18.85 nm, and 0.12 meq center dot g(-1) to 47.77 m(2)center dot g(-1), 41.60 nm, and 0.61 meq center dot g(-1), respectively, after the fusion-hydrothermal process. The maximum Langmuir adsorption capacity of RSDZ for Zn2+, Pb2+, and Cu2+ in the unary systems was 0.37, 0.38, and 0.40 mmolg(-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 Pb2+ and Zn2+ than for Cu2+ due to the larger ionic radius and relative atomic weight of the former two cations. The relative affinity to Pb2+ and Zn2+ was related to their concentration, with more competitive adsorption of Pb2+ at concentrations higher than 0.4 mmolL-1 in binary systems and 0.25 mmolL-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.

Automated summary

RSDZ, derived from construction residual soil, was prepared through a fusion-hydrothermal process and showed promising adsorption performance for heavy metal ions. The competition studies revealed that RSDZ had higher affinity for Pb2+ and Zn2+ than for Cu2+, likely due to their larger ionic radius and relative atomic weight. Ion exchange was identified as the main mechanism for heavy metal ion adsorption by RSDZ.