goethite process, zinc chloride, waste sludge

This paper deals with the problem of waste sludge from the production of zinc chloride in the company Bochemie a.s. This sludge contains a high degree of zinc (therefore it cannot be used to charge a blast furnace) and a significant amount of dangerous waste is created. Waste sludge was treated under laboratory conditions, using the goethite precipitation process. Precipitation was carried out in a discontinuous reactor as well as in a continuous flow reactor. pH and the time of precipitation represented important factors. Both processes proved that the ideal pH was 2.5 and the ideal time of precipitation (?) was 4 hours. The speed of filtration of the first experiment EZ (pH = 2.5 and ? = 4 hours) was up to ten times higher than the time of all the other experiments. The content of zinc in this sediment was 1.4 wt %. All experiments using lower levels of pH resulted in a significant reduction of zinc in the sediment.