Low-temperature conversion of Fe-rich sludge to KFeS2 whisker: a new flocculant synthesis from laboratory scale to pilot scale

Herein, a KFeS 2 whisker was formed in mass production at a low temperature, with waste cold-rolling sludge as Fe source, which exhibited good performance in the removal of Zn/Ni from real electroplating effluent. At laboratory scale, KFeS 2 was generated at 80 °C by the hydrothermal method, and KFeS 2 whisker grew radially with the extension of the reaction time. This method was applied at pilot scale, where a similar KFeS 2 whisker was also produced with waste cold-rolling sludge as Fe source, and a residual brownish supernatant was observed after the reaction and then completely recycled in the next round for KFeS 2 synthesis. After recycling five times, the produced KFeS 2 whisker did not change. The drying and storage of KFeS 2 have also been verified. Freeze drying and vacuum drying were applicable, whereas air drying was not profitable. Moreover, the efficiency of Zn/Ni removal using undried KFeS 2 was similar to that of dried KFeS 2 . The efficiencies of Zn/Ni removal using KFeS 2 were apparently higher those of common reagents for wastewater treatment.