Effective removal of Cu2+ ions from polluted water using new bio-adsorbents

Sorbents derived from stem powders of Feronia limonia (FLSP), Amorphophallus paeoniifolius (APSP) and Pumpkin (Cucurbitapepo) (PSP) plants are investigated for the removal of Cu2+ ions from polluted water by adopting batch methods of extraction. Extraction conditions are optimized for the effective removal of Cu2+ ions. High sorption capacities are observed: 175.5 mg/g for FLSP; 140.4 mg/g for APSP; 130.0 mg/g for PSP. Effective pH ranges are: 5 to 10 for FLSP; 6 to 10 for APSP and 7 to 10 for PSP. The three spent adsorbents can be regenerated and used. Thermodynamic parameters indicate that the adsorption process is spontaneous, endothermic and have positive change in entropy values. As ΔH values are more than 25.0 kJ/mole, the adsorption may be due to surface complex formation between Cu2+ ions and functional groups of the adsorbents viz., -OH, -COOH etc. in the effective pH ranges. The good adsorption behaviour of FLSP even in acidic pHs may be due to the ion-exchange of Cu2+ ions for H+ ions of the functional groups of the adsorbent. The Langmuir adsorption isotherm and pseudo second-order model describe well the adsorption process. The sorbents are effectively applied to treat effluents from Cu-based industries and polluted lake water.