Synergetic adsorption and electrochemical classified recycling of Cr(VI) and dyes in synthetic dyeing wastewater

Abstract

Heavy metal ions, dyes and high concentrations of salt are three kinds of representative compounds in the wastewater produced from dyeing processes. An integrated technical process with multifunctional adsorbents for the simultaneous removal of pollutants, e.g., inorganic heavy metal ions and organic dyes, is highly desired. Moreover, classification of the recycled adsorbates on the exhausted adsorbents is also important and necessary. Herein, we have developed a new strategy to synergistically remove and electrochemically classify the recycled Cr(VI) and dyes from synthetic dyeing wastewater. First, polyaniline (PANI) was used to decorate the spherical resin (PS) by one-step in situ polymerization, and the as-synthesized composite (PANI@PS) was used as an adsorbent for simultaneous removal of Cr(VI) and methylene blue (MB) in high saline medium mainly based on PANI and PS, respectively. The synergistic adsorption removal capacities of Cr(VI) and MB on PANI@PS reached 183.0 mg Cr(VI) g−1 PANI and 40.3 mg MB g−1 PANI@PS in a coexisting system, in contrast to 94.0 mg Cr(VI) g−1 PANI and 27.5 mg MB g−1 PANI@PS in a single-component system. These increases are attributed to the additional adsorption sites and electrostatic attractions between the adsorbed Cr(VI)(−) and MB(+). Noticeably, the adsorbed Cr(VI)(−) and MB(+) can be recovered and classified via electrochemically assisted desorption, with a maximum recovery ratio of 90.3% (Cr(VI)(−)) and 91.9% (MB(+)). This study is of great significance for introducing novel adsorbent composites for the simultaneous removal and classified recovery of specific coexisting pollutants.