Interference of EDTA in the treatment of metal plating wastewater by biosorption

BACKGROUND: The applicability of biosorption for the treatment of metal plating wastewater is adversely affected by the presence of complexing agents. To investigate this limitation on the removal of copper(II) onto peat, batch and column experiments were carried out using EDTA as the model complexing agent. The influence of pH and copper(II):EDTA mass ratios were evaluated for copper(II) concentrations between 5 and 100 mg Cu(II) dm3. RESULTS: EDTA negatively affected the copper(II) uptake of peat for pH > 5. Batch and column experiments showed that copper(II)-EDTA complexes were not sorbed by peat. The leaks of copper(II) detected from the beginning of the column operation matched the copper(II)-EDTA concentration in the feed solutions. To overcome the interference of EDTA, a novel approach based on the combination of peat + activated carbon was proposed. Nearly complete removal of copper(II) was maintained over 70 h in the treatment of a solution containing 20 mg Cu(II) dm3 with 11% of copper(II)-EDTA complexes. CONCLUSION: A new mass transport model coupling copper(II) speciation in the feed and mass transfer rate-controlled process simulated the copper(II) breakthrough curves in the presence of EDTA and could be used to successfully predict the breakthrough point. This work demonstrated that biosorption can also be applied for the treatment of wastewater containing complexing agents with the proper combination of sorbent materials. (c) 2012 Society of Chemical Industry