Extracellular Polymeric Substances Induced Porous Polyaniline for Enhanced Cr(VI) Removal from Wastewater

Extracellular polymeric substances (EPS) of bacteria were used as templates for synthesizing unique polyaniline nanocomposites, i.e., porous EPS-modified polyaniline (EPS@PANI). The proteins were responsible for forming porous structure, while polysaccharides for the fiber morphology of EPS@PANI. The specific surface area (53.2 m(2)/g) of these unique EPS@PANI with an optimal EPS loading of 2 wt % was similar to 2 times larger than that of pristine PANI. The PANI in EPS@PANI stayed as the emeraldine form and acted as the electron donor for reduction of Cr(VI) to Cr(III). Herein, 1.0 mg/L Cr(VI) was completely reduced to Cr(III) by 600 mg/L of EPS@PANI within 10 min, which was much faster than the pristine PANI (1 h). A maximum Cr(VI) removal capacity of 913.2 mg/g was achieved by these unique EPS@PANI nanocomposites and was similar to 4.7 times higher than the pristine PANI (193.8 mg/g). Moreover, the isoelectric point (pI) was decreased from pH 7.5 for pure PANI to similar to 4.5 for these porous EPS@PANI nanocomposites due to the low pI of polysaccharides remained in the composites. This lowered pI facilitated further Cr(III) removal on the surface of EPS@PANI from the wastewater.