Selective andppb level removal of Hg(ii) from water: synergistic role of graphene oxide and SnS2

Mercury (Hg) contamination can cause serious health issues like brain damage, skin diseases and birth defects. An upper limit of 2 ppb for Hg in drinking water has been allowed by the United States Environmental Protection Agency (EPA). Thus, the selective removal of Hg below 2 ppb is an important challenge in the treatment of wastewater. Herein, we report the tremendous selectivity and ppb level removal of Hg-(II) from water by using a graphene oxide and tin(iv) disulfide (SnS2) composite (GO@SnS2). The material can remove 99.1% of Hg-(II) from a concoction of Na-(I), K-(I), Cs-(I), Rb-(I), Ca-(II), Mg-(II), Co-(II), Cu-(II), Ni-(II), Zn-(II), Pb-(II), Cd-(II), Mn-(II), Fe-(III) and As-(III) with a high separation factor of the order 10(2) to 10(3). We have achieved a capacity of 342.02 +/- 8.02 mg g(-1) with a distribution coefficient (K-d) value of 8.68 x 10(5) mL g(-1) and GO@SnS2 is stable in the pH range of 0.5-11. The material can remove Hg-(II) from even 0.3 ppb Hg-(II) contaminated water. Furthermore, the mechanism behind the synergistic Hg-(II) adsorption is due to the interaction between Hg-(II) and -COOH of GO and the soft Lewis acid-base chemistry between S2- of SnS2 and Hg-(II). For convenient application, we have designed a tea bag filled with GO@SnS2 powder which can capture 99.9% of Hg-(II) from contaminated water economically.