Effect of Organic Ligands on Copper(II) Removal from Metal Plating Wastewater by Orange Peel-based Biosorbents
2013
Izquierdo, Marta | Marzal, Paula | Lens, P. N. L. (Piet N. L.)
Copper(II) biosorption in the presence of complexing agents (CA) onto orange peel (OP) and chemically modified OP (OPᴴ⁺, OPᴺᵃ⁺, and OP⁽ᴺᵃ⁺⁾⁽ᴴ⁺⁾) was studied. The study of the effect of pH showed that OPᴴ⁺ presented a copper(II) uptake similar to OP in the pH range 1.5–6.0, whereas OPᴺᵃ⁺ and OP⁽ᴺᵃ⁺⁾⁽ᴴ⁺⁾ showed the highest copper(II) uptake in the pH range 4–6. Copper(II) sorption isotherms were obtained with Cu(II)/CA mass ratios of 1:0 and 1:2 at pH 5. The Sips model fitted best the isotherms without CA, whereas the Freundlich and Brunauer-Emmett-Teller (BET) models fitted best the isotherms in the presence of ethylenediaminetetraacetic acid (EDTA) and citrate, respectively. The CA reduced the copper(II) uptake due to the presence of copper(II)-chelated species, though the interference of citrate was less important than that of EDTA. OPᴺᵃ⁺ and OP⁽ᴺᵃ⁺⁾⁽ᴴ⁺⁾ showed a higher copper(II) uptake capacity than OP, also in the presence of CA in solution. Copper(II) sorption mechanisms were studied using energy-dispersive X-ray and Fourier transform infrared spectroscopy and revealed ion exchange as one of the mechanisms. Biosorption reversibility and biosorbent reuse were evaluated in sorption/desorption cycles. Reversibility of copper(II) sorption was obtained (90 % metal recovery), though an important reduction of the metal uptake was observed in the second cycle.
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