Leaching of heavy metals from wastewater sludge, using a thermostatted column

We have previously patented a process for the extraction of toxic and valuable metals from foundry sands using a thermostatted column. In this paper, we describe a similar device for the removal of toxic metals from wastewater sludge. The wastes were finely ground and suspended in an aqueous pulp, and 10-40 g of mineral acid or sodium hydroxide were added to reach a pH of 2, 5, 7 and 10, together with 4-10 g of a bisulphite and 0.3 - 1.5 g of sodium dodecyl sulfate. In some cases, this method can remove 100% of heavy metals from samples of various wastewater sludges. To study the removal efficiency of heavy metals, we used inductively coupled plasma atomic emission spectrometry (ICP-AES). The metallic alloys in the samples were studied by X-ray diffraction.