Equilibrium, Kinetics, and Thermodynamics Studies on the Recovery of Rhenium(VII) and Molybdenum(VI) from Industrial Wastewater by Chemically Modified Waste Paper Gel

Waste paper was chemically modified with dimethylamine (DMA) to obtain a tertiary-amine-type gel, named WPD. By comparing with the adsorption of other coexisting metals, such as Pb(II), Ca(II), Zn(II), Mn(VII), and Ni(II), this novel gel exhibited selectivity only for Mo(VI) and Re(VII) with a remarkably high capacity 4.99 mol·kg–1 and 0.96 mol·kg–1, respectively. The adsorption mechanism of Mo(VI) and Re(VII) on the WPD gel was proposed as the anion exchange process. In addition, both the adsorption behavior obeys the Langmuir model, and the endothermic adsorption process followed pseudosecond-order kinetics. Also, the effectiveness of recovery and separation of Mo(VI) and Re(VII) from industrial wastewater was also tested using a column packed with the WPD gel, and it showed highly encouraging results with respect to the stability of the gel and selectivity for the targeted metal ions in the presence of excess of other metal ions.