Applicability of solid process residues as sorbents for the treatment of industrial wastewaters

In the present work, four different geopolymers: PG (alkaline activated metakaolinite), PGA (aluminum oxide + PG), AG (alkaline activated analcime) and AAG (aluminum oxide + AG) and one commercially available MgO based sorbent: PM (PalPower M10) were compared on the basis of their copper adsorption capacity from aqueous solutions. It was observed that PM (PalPower 10) outperformed all the other adsorbents studied for copper removal efficiency and was consequently selected for further study. The effect of the main adsorption parameters such as pH (1 - 5), dosage (0.25 - 5 g/L) and contact time (15 - 1440 min) were systematically investigated with synthetic solutions of differing copper concentrations (100 - 500 mg/L). The results indicated that PM adsorbent removed all the copper ions at pH 4 with a dosage of 1 g/L and contact time of 24 h from solutions that contained only copper ions, whereas the presence of other ions - including Fe - significantly decreased the copper removal efficiency. Due to presence of other elements like As, Al, Zn in industrial wastewater, a higher dosage of PM adsorbent (~45 - 90 g/L) was required in order to remove all the metal ions after 24 h. The regeneration results suggested that the attached copper ions can be successfully stripped using a 2 M ammonia solution allowing the PM adsorbent to be regenerated. These findings demonstrate the potential of geopolymers to treat industrial wastewaters, especially for the removal of metal ions like copper.