One-pot preparation of P(TA-TEPA)-PAM-RGO ternary composite for high efficient Cr(VI) removal from aqueous solution

In this study, a novel poly(tannin-tetrathylenepentamine)-polyacrylamide-reduced graphene oxide (P(TA-TEPA)-PAM-RGO) ternary composite absorbent was prepared by a simple one-step method and used for the adsorption-reduction removal of Cr(VI). Several techniques, including scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy, were employed to analyze the morphology, thermal stability, and chemical composition of the as-prepared composite, as well as its adsorption mechanism toward Cr(VI). The adsorption studies indicate that the P(TA-TEPA)-PAM-RGO composite exhibits excellent Cr(VI) removal performance as evidenced by the synergistic effect between the adsorption component P(TA-TEPA), which contains rich phenolic hydroxyl and amine groups, and the supporting components PAM and RGO. The maximum removal capacity is 397.52 mg/g at 308 K, which is higher than that of most GO-and TA-based adsorbents. The fabricated composite displays excellent adsorption capacity in a short time and a favorable reduction to Cr(III). The adsorption process is endothermic and spontaneous and well fits the Langmuir isotherm and the pseudo-second-order kinetic models. In addition, the prepared composite exhibits efficient Cr(VI) competitive adsorption against heavy metal ions (e.g., Cu2+, Zn2+, and Cd2+) and anions (e.g., NO3- and SO42-). After three adsorption-desorption cycles, the composite maintains good adsorption capacity. Thus, the proposed P(TA-TEPA)-PAM-RGO composite could be a potential adsorbent for the removal of Cr(VI) from wastewater.