Date seed activated carbon decorated with CaO and Fe_3O_4 nanoparticles as a reusable sorbent for removal of formaldehyde

摘要

Activated carbon (AC) was produced from date seeds by a calcination process at 700 degrees C for 2 h and then its surface was improved with CaO and magnetic nanoparticles. AC/CaO/Fe3O4 nanocomposite was then employed to remove formaldehyde ions from aqueous media. The structural characteristics of the materials were completely studied through FT-IR, XRD, SEM, EDX, Map, VSM, BET and TEM analyses. The results showed that the nanocomposite has a mesoporous structure (average pore diameter similar to 13 nm) with great sorption capability. Also, the utmost removal efficiency of formaldehyde using AC, AC/Fe3O4, CaO/Fe3O4 and AC/Fe3O4/CaO nanocomposite was 94.73, 95.67, 95.14 and 98.22, respectively, indicating that the removal efficiency increases by improving the surface properties of the AC. Moreover, the uptake of formaldehyde using AC/Fe3O4/CaO nanocomposite follows the Freundlich isotherm and pseudo-2(nd)-order kinetic models. Furthermore, the highest sorption capacity of AC, AC/Fe3O4, CaO/Fe3O4 and AC/Fe3O4/CaO nanocomposite using the Langmuir model was obtained 19.86, 24.21, 21.28 and 24.01 mg/g, respectively. The thermodynamic study showed that formaldehyde sorption using all four adsorbents is exothermic and spontaneous. The reusability of the adsorbents was also evaluated after ten reuse cycles and the outcomes indicated that these four adsorbents have significant reusability. Moreover, the impact of interfering ions (e.g., carbonate, sulfate, phosphate, nitrate and chloride) showed that all of these compounds, except nitrate, had little competition with formaldehyde ions for adsorption on the nanocomposite surface.