Low-cost and high-efficiency metallurgical copper slag@polyaniline core–shell composite as an adsorbent for the removal of Cr(VI) from aqueous solution

Highlights: • ☻The maximum adsorption capacity of Cr (VI) on CS@PANI reached 452.5 mg g⁻¹.• ☻The Cr (VI) removal efficiency of CS@PANI was still above 90% after 5 cycles.• ☻CS@PANI adsorbed Cr (VI) could be easily separated from the solution by magnets.• ☻The work suggests an efficient approach for the recovery and utilization of CS. -- Abstract: Industrial heavy-metal waste water causes substantial harm to the environment and human health. Therefore, it is an essential and urgent task to develop an efficient adsorbent with a simple preparation technique, long service life, and easy solid–liquid separation, which can reduce the concentrations of heavy metals in wastewater to an acceptable threshold before discharge. In this study, a core–shell-structured copper slag@polyaniline (CS@PANI) composite was fabricated, which could effectively remove Cr(VI) from wastewater. The effects of the pH value, contact time, Cr(VI) concentration, and temperature on Cr(VI) adsorption were also investigated. The maximum adsorption capacity of CS@PANI for Cr(VI) was up to 452.54 mg/g, under applied experimental conditions. The adsorption kinetics followed the pseudo-second-order model. The Langmuir model was more consistent with the adsorption process between CS@PANI and Cr(VI) than the Freundlich model. After five cycles, the Cr(VI) removal efficiency of CS@PANI remains > 90%, which shows an outstanding stability and regenerability of the prepared composite. Meanwhile, the adsorption mechanism of Cr(VI) on CS@PANI was also investigated. The work suggests an efficient approach for recycling solid wastes in the metallurgical industry.