Radial growth of polymeric Fe/S rods for improving removal of Cu/Zn from real electroplating wastewater

A mass production of one-dimensional polymeric Fe/S rod with 200 nm diameter and 300 nm length was developed under atmosphere conditions with FeCl3 and Na2S/NaOH. When such Na was partly/fully replaced by K, the polymeric Fe/S rod grow radially alongside the lattice planes of 020 and 221 from 300 nm to 1 µm and/or 5–10 µm, respectively, to form a long rod. In the long rod, such Na/K occupied the charged sites of Fe/S structure and can be replaced by each other in an alkaline solution with the retention of log-rod shape. The long rods showed superior efficiencies of Zn/Cu removal (nearly 100 %) from real electroplating wastewater, compared with short rods and other reagents, e.g., diethyldithiocarbamate and polymeric ferric sulfate. The processing method allows not only the development of a clean production to recycle the K and that used alkaline supernatant for preparing long rods without any secondary waste, but also posed the application prospect of long rods in wastewater treatment.