Highly efficient Cu-doped BTC aerogel for lead ions adsorption from aqueous solution: statistical modeling and optimization study using response surface methodology

Abstract

• Aerogel adsorbent were prepared with the incorporation of Cu-BTC and characterized. • The CCD-RSM design was used to optimize the removal of Pb(II) from an aqueous solution . • The adsorbent concentration, time, and pH were studied and optimized. • Aerogel adsorbent were found to have a high adsorption efficiency for the removal Pb(II) ions. • Adsorption mechanism proposed chemical bonding and electrostatic interaction phenomena. In this study, a new kind of Cu-doped BTC (Cu-BTC/CH) aerogel adsorbent is synthesized for the removal of Pb(II) ions from aqueous solutions. A Cu-BTC/CH aerogel was made by covalent crosslinking with a hierarchical structure. The prepared aerogel adsorbent material was characterized by scanning electron microscope (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS). The response surface methodology (RSM) was used to optimize the independent variables such as adsorbent concentration (0.2-1.2 g/L), time (20-180 min), and pH (3-7) respectively. The statistical techniques analysis of variance (ANOVA) indicated that the experimental results and the quadratic model were in good agreement (R 2 = 0.9882). The RSM model predicted that pH 6.5, adsorbent concentration of 1.15 g L −1 , and contact time of 170 minutes were the best experimental conditions for 99.96 % removal of Pb(II) ions. The highest Langmuir adsorption capacity for Pb(II) ions was found to be 204.08 mg g −1 with the correlation coefficient (R 2 = 0.99). The adsorption of Pb(II) ions on the aerogel adsorbent is an exothermic and spontaneous process with the negative ΔG°. The prepared adsorbent can be reusable for up to five consecutive regeneration cycles with the negligible effect of interfering ions. The mechanism of adsorption of Pb(II) ions was explained by XRD and XPS study and the adsorption phenomenon might be due to –OH, –NH 2 , and –COO − groups respectively. Considering all this, the proposed method is an effective and adaptable way to transform a huge amount of metal-organic framework (MOF) particles into a solid form and expand their use in water treatment. Graphical abstract