Bacterial cellulose‐modified castor oil‐based polyurethane sponge for hexavalent chromium removal

Abstract

Due to the multiple industrial applications of chromium compounds and their dangerous nature for the environment, the development of adsorbent materials has been investigated. In line with this reality, bacterial cellulose (BC) has become a potential filler in the polymeric matrix due to its ability to remove toxic metals; however, its performance is little explored. This research proposes a new approach for BC as a filler in castor oil‐based polyurethane, obtaining a sponge for Cr(VI) removal. The pure PU and PU + X%BC sponges (X stands for BC content between 5 and 20 wt%) were characterized by Fourier‐transform infrared spectroscopy, scanning electron microscopy, optical microscopy, density, contact angle (CA), and thermogravimetric analysis. Sorption capacity and efficiency were evaluated as a function of the fiber content, with tests performed in function of contact time (2.5 min to 3 h) at 50 mg L−1. The BC fillers of the sponges increased the density and influenced the morphological, chemical structural, thermal, and sorption properties. Thus, the sponge (PU + 20%BC) presented the highest CA (104.4°) and the best sorption capacity and efficiency (4.3 mg g−1 and 43.2%). The sorption mechanism was well‐defined by isotherm models, presenting a maximum adsorption capacity of 23.5 mg g−1 and best fit (R2 = 0.989) with the Freundlich isotherm. The sponge is an efficient material for Cr (VI) removal and provided a promising insight into an adsorption mechanism study.