Removal of metal ions on activated carbon from aqueous solutions in the presence of nitrilotri(methylphosphonic acid)

This work investigates the enhancing effect of nitrilotri(methylphosphonic acid) (NTMP) on the adsorption of metal ions onto unmodified, cheap, market activated carbon Norit made from coal. Different metal ion’s initial concentrations and molar ratios of NTMP to metal ions were tested. In single element system adsorption of 0.07–0.1 mg Cd/g (0.6–0.9 mmol Cd/kg), 0.11 mg Cu/g (1.7 mmol Cu/kg) and 0.01–0.09 mg Mn/g (0.2–1.6 mmol Mn/kg) were achieved. The addition of NTMP allowed for about a 10% increase in sorption capacity towards cadmium and about 140% towards copper. The 1:1 NTMP to metal ions molar ratio achieved about 2-times better performance than 1:2 molar ratio. Sorption capacity towards manganese was decreased by about 40% after applying NTMP to the system. The experiment with all three metal ions (cadmium, copper, and manganese) showed a correlation to the first part of the research. Adsorption of 0.004 to 0.01 mg Cd/g (0.03–0.09 mmol Cd/kg), 0.04 to 0.07 mg Cu/g (0.6–1.1 mmol Cu/kg) and 0.005 to 0.02 mg Mn/g (0.09–0.4 mmol Mn/kg) were achieved followed by 250%–300% increase towards cadmium, 150%–200% increase towards copper and 40%–70% decrease after applying NTMP.