Removal of dithioterethiol (DTT) from water by membranes of cellulose acetate (AC) and AC doped ZnO and TiO2 nanoparticles

Abstract

Dithioterethiol (DTT) is a typical example of substances that contain sulfur with adverse effects on human health. Membranes-based cellulose acetate is used for the separation processes of thiols after the addition of ZnO and TiO2 nanoparticles. The measurement of permeability allows us to estimate the efficiency of membrane cleaning. The permeability increases from 8.82 L.h−1.m−2.bar−1 for CA membrane to 20.77 L.h−1.m−2.bar−1 for CA-TiO2 and 21.96 L.h−1.m−2.bar−1 for CA-ZnO membranes. For the permeability values of DTT, we noted that the CA-ZnO membrane has the highest permeability (50.66 L.h−1.m−2.bar−1). The CA-ZnO membrane changes from nanofiltration to ultrafiltration membrane. On the other hand, for the CA-TiO2 modified membrane, the permeability decreases to 6.00 L.h−1.m−2.bar−1. The CA-TiO2 membrane is in the category of reverse osmosis membranes. This variation is explained by the interaction between nanoparticles and DTT. The contact angles of the incorporated membranes decrease progressively with the addition of TiO2 or ZnO-NPs. The low contact angle with water means high hydrophilicity, indicated that the addition of TiO2 and ZnO improved the hydrophilicity of the membranes. The CA membrane had the highest contact angle with water of 92.64 ± 1.5°. After the addition of 0.1 g of TiO2 or ZnO, the contact angle of CA-TiO2 and CA-ZnO was reduced to 86.7 ± 0.2° and 70.51 ± 1.5°, respectively. Both TiO2 and ZnO caused strong hydrophilicity of membranes. From the elimination rates of DTT, it is concluded that there are optimal conditions of (1) Pressure P = 2 bars, (2) pH = 10 and (3) DTT concentration = 2 mM.