In a batch process, canola meal, pine bark and moss decreased the copper concentration in an industrial wastewater from a copper refining/smelting plant from 36.5 to 2.5, 4.1 and 5.2 ppm, respectively, when the concentration of each sorbent was 15 mg/mL. pH-controlled tests showed greater Cu2+ removal compared to those without pH control. The copper concentration was decreased to below its permissible upper limit for drinking water when the wastewater was treated with 9.2 mg/mL of bark at pH 5.2 followed by sorption with 2.3 mg/mL of activated carbon. This study also showed that the same total amount of sorbent used either in a single- or multistage sorption process resulted in the same level of copper removal. The removal of copper from the wastewater was also studied using columns packed with bark. After three sorption/desorption cycles, the copper concentration was decreased to 4 ppm.
This study also examined the mechanisms of metal biosorption by moss using analytical solutions. Scanning electron microscopy and energy-dispersive X-ray microanalyses revealed that metal ions were sorbed mainly at the cell wall of the moss and only a small amount of ions diffused into the cytoplasm. Both the energy dispersive X-ray analysis and the atomic absorption spectrophotometry measurements showed that ion exchange was an important mechanism in this sorption process.