Novel triazine-based sulfur-containing polyamides: Preparation, adsorption efficiency and mechanism for mercury ions

The aminolysis of dimethyl 2,2′-(Propane-1,3-diyl-Bis(Sulfanediyl)) diacetate with Melamine in different ratio afforded two polyamides, namely, PBSM1 , PBSM2 . Similarly, using dimethyl 2,2′-(Ethane-1,2-diyl-Bis(Sulfanediyl))diacetate, EBSM1 and EBSM2 were obtained. Their adsorption performances for Hg 2+ in aqueous systems were examined. The factors that affect the adsorption effect are investigated, such as the dose of adsorbent, the adsorption time, the temperature of the solution, the original concentration of the solution, the pH, co-existence and repeated application. The pseudo-second-order kinetic model and Langmuir model are most suitable to describe the adsorption of Hg 2+ , and the saturation time of adsorption is 6 h. The maximum adsorption capacities were found to be 1273 mg g −1 ( PBSM1 ), 689 mg g −1 ( PBSM2 ), 1272 mg g −1 ( EBSM1 ) and 518 mg g −1 ( EBSM2 ), respectively. After 5 cycles of testing, there is no significant loss of original performance. Combining spectroscopic techniques, experimental results and DFT calculations, it is explained that S, N and, more interestingly, O on the polyamide are involved in the chemical sorption process of Hg 2+ .These results indicate that the polyamides can be used as efficient adsorbents for the adsorption of Hg 2+ in wastewater.