Extraction of copper from a simulated acid mine drainage environment using membrane technology

Submission note: A thesis submitted in total fulfilment of the requirements for the degree of Master of Science by Research (Chemistry) to the Department of Chemistry and Physics, La Trobe Institute for Molecular Science, College of Science, Health and Engineering, La Trobe University, Bundoora.

A complex-imprinted polymer inclusion membrane (CIPIM) was investigated and compared to a similar polymer inclusion membrane (PIM) for the extraction of copper from an acidic sulphate medium. The CIPIM used a bulky template of carrier-copper complex during preparation and the copper was subsequently removed before use to yield a working membrane. Improved extraction and transport performance for the CIPIM are hypothesised due to the imprinted complex that should result in a less entangled polymer structure and more open liquid channels in the membrane. Membranes were prepared using various formulations of PVC as polymer and combinations of some commercial copper extractants, plasticizers and modifiers. The membranes were tested to assess their optimal physical and chemical properties. The best CIPIM composition was 50% (w/w) Acorga P50-copper complex as carrier, 40% (w/w) PVC as polymer, and 10% (w/w) 1-dodecanol as modifier. Polymer inclusion membranes (PIMs) of similar composition using 50% (w/w) Acorga P50 as carrier were prepared for comparison. Preliminary experiments demonstrated a 10% improvement in copper extraction using a CIPIM compared to a similar PIM for a feed solution of 50 mg/L of copper at pH 2 and receiving solution of 2M H2SO4. Transport studies to assess permeability, stability and selectivity were also performed. The CIPIM demonstrated a superior copper flux of 2.6 x 10-10 mol.cm-2 .s-1 compared to 6.0 x 10-11 mol.cm-2 .s-1 with PIM. As well, the transport efficiency (%) was significantly better with 99% and 69% for CIPIM and PIM, respectively. The CIPIM also demonstrated a high selectivity for Cu(II) over Fe(III) and Zn(II) at pH 2 in a simulated acid mine drainage solution. During extended use experiments over six cycles, the CIPIM stability decreased significantly in the first four cycles. The transport efficiency (%) decreased from 99% to 80% for CIPIM from the 1st to 6th cycle, respectively. However, in comparison, a more significant decrease in transport efficiency (%) of 69% to 39% for PIM was determined. An improved extraction efficiency and better flux for copper using a CIPIM compared to a PIM of similar composition was demonstrated in the research.