Taiwan, from the early industrialization period until now, has produced enormous amounts of pollutions, especially, heavy metal pollution. Chromium is a common heavy metal pollutant and found to be human carcinogens.
Recently, many researches used zero-valent metals in groundwater pollution remediation. Moreover, nano-particle technology was also applied for producing zero-valent metals, which can increase the effective of zero-valent metals, reduce the amount of agents used, and reduce the impact on environment.
In this study, iron, copper and nickel were prepared by chemical reduction method.Sodium borohydride, which is a strong reducer agent, was then added into the solution for the reduction and synthesis of nanoscale zero-valent metal particals.This experiment aimed to study the ability of nanoscale zero-valent metal particals on the removal of hexavalent chromium in wastewater. Effects of fresh hexavalent chromium concentrations, fresh pH values and metal composition ratios were examined to identify the optimal condition for removing hexavalent chromium from wastewater. All experiments were carried out in batch mode.
Different combinations of nanoscale zero-valent metal particals (Fe0、Cu0、Ni0、Fe0/Cu0、Fe0/Ni0、Cu0/Ni0、Fe0/Cu0/Ni0) was compared on hexavalent chromium removal efficiency. Fresh pH values (3, 4, 5) were also identified and it was found that low pH value showed higher hexavalent chromium removal efficiency than high pH value. Moreover, results indicated that nanoscale zero-valent trimetallics have higher removal effieincy than nanoscale zero-valent bimetallics and nanoscale zero-valent metals, respectively.
For metal composition ratios, experiments revealed that nanoscale zero-valent bimetallics (Fe0/Cu0) at the optimum ratio of 95/5 yielded higher hexavalent chromium removal efficiency than other nanoscale zero-valent bimetallics. However, the highest removal efficiency of hexavalent chromium was found when nanoscale zero-valent trimetallics
(Fe0/ Cu0/ Ni0) at the optimum ratio 99/1/0.1 was applied.