Selective adsorption of Cu(II) from synthetic wastewater using melamine-formaldehyde- NTA resin

摘要

A new chelating resin was prepared by anchoring the chelating agent nitriloaminetriacetic acid (NTA) to melamine via an amide covalent bond during melamine-formaldehyde condensation reaction in an acidic medium. The effect of preparation conditions (temperature, acidity, and water content) on resin characteristics (water regain, rigidity, NTA functionality, and porosity) were monitored to specify the best preparation conditions. A pH of 1.3, temperature of 150°C and water content of 5 ml were found as the best conditions for resin preparation with stated amounts of reactants. This new resin was chemically characterized via infrared spectroscopy (FT-IR), CHNO elemental analysis, and morphologically characterized via nitrogen gas adsorption (BET) and field emission-scanning electron microscopy (FE-SEM). The best-produced resin sample has a surface area of 159 m~2/g. The content of NTA was about 1.24 mmole/g. Simultaneous adsorption of Co(II), Cd(II), Zn(II), and Cu(II) from synthetic wastewater solutions using a batch technique was quantitatively analysed using atomic absorption. Selective adsorption of the Cu(II) ion amongst Co(II), Cd(II), and Zn(II) ions by this resin was noted. It was found that Cu(II) adsorption is spontaneous (ΔG_(ads) < 0), exothermic (ΔH_(ads) < 0), and reversible (ΔS_(ads) < 0). Kinetically, it follows reversible and pseudo first-order. According to the Langmuir model, the capacity for Cu(II) adsorption is 52.6 mg/g (0.83 mmol/g). EDTA solution can regenerate the resin by stripping adsorbed metal ions. After regeneration, it was observed that the capacity decreased and this may be due to partial hydrolysis of NTA sites.