Highly Efficient Removal of Cr(VI) from Aqueous Solutions by Polypyrrole/Monodisperse Latex Spheres

Pyrrole (Py) is easily agglomerated during the polymerization process, affecting its performance. In this paper, polypyrrole/monodispersed latex sphere (PPy/MLS) composites were prepared using in-situ polymerization for the adsorption of hexavalent chromium (Cr­(VI)). The specific surface area of PPy/MLS (39.30 m²/g) was increased relative to that of PPy (24.82 m²/g), thus providing more effective adsorption sites. In addition, the adsorption properties of Cr­(VI) under different conditions, including Py content, pH of the aqueous solution, and PPy/MLS dosage, were investigated to reveal the adsorption mechanism. The results showed that PPy/MLS possessed high Cr­(VI) adsorption capacities when the Py content was 50 wt %. The maximum adsorption capacity was 343.64 mg/g at pH 2.0 and 25 °C. Remarkably, the adsorbents exhibited an excellent removal rate of Cr­(VI) after three cycles of adsorption–desorption (over 99%), suggesting that the adsorbents had exceptional recyclability. Furthermore, the adsorption process followed quasi-second-order kinetics and Langmuir isothermal adsorption model. The high adsorption performance, sustainability, and cost-efficiency make this adsorbent a promising candidate for large-scale Cr­(VI) contaminant removal.