Optimization of tannin rigid foam as adsorbents for wastewater treatment

Tannin rigid foams are presented as novel adsorbents for wastewater remediation. Although these materials are known since long time ago, this is one of the newest applications in environmental technology. The efficiency of the different combinations of reagents in the foam synthesis were studied by using Response Surface Methodology, and the optimum category was subsequently tested on dye, surfactant and pharmaceutical removal. The results are promising for the three types of pollutant. Structural differences based on FTIR, Raman spectroscopy and other superficial characterization techniques confirmed the intrinsic adsorption benefits of this optimum category if compared with other tannin rigid foams. Optimum tannin rigid foam was obtained with 0.03 g of furfuryl alcohol, 0.11 g of formaldehyde, 0.25 g of diethyl ether and 0.20 g of p-toluensulfonic acid per g of Weibull Black tannin extract. With this combination of reagents, up to 250 mg g−1 of Methylene Blue removal was reached and a significant elimination of several dyes and surfactants was feasible.