A Study of Treatment of Industrial Acidic Wastewaters with Stainless Steel Slags Using Pilot Trials

Abstract

Different stainless steel slags have been successfully employed in previous experiments, for the treatment of industrial acidic wastewaters. Although, before this technology can be implemented on an industrial scale, upscaled pilot experiments need to be performed. In this study, the parameters of the upscale trials, such as the volume and mixing speeds, are firstly tested by dispersing a NaCl tracer in a water bath. Mixing time trials are used to maintain constant mixing conditions when the volumes are increased to 70, 80 and 90 L, compared to the 1 L laboratory trials. Subsequently, the parameters obtained are used in pH buffering trials, where stainless steel slags are used as reactants, replicating the methodology of previous studies. Compared to laboratory trials, the study found only a minor loss of efficiency. Specifically, in previous studies, 39 g/L of slag was needed to buffer the pH of the acidic wastewaters. To reach similar pH values within the same time span, upscaled trials found a ratio of 43 g/L and 44 g/L when 70 and 90 L are used, respectively. Therefore, when the kinetic conditions are controlled, the technology appears to be scalable to higher volumes. This is an important finding that hopefully promotes further investments in this technology.

Bioleaching Techniques for Sustainable Recovery of Metals from Solid Matrices

“…Metallurgical slag is among the most abundant by-products generated by such industries [3,9]. The production of this waste is used to recover iron [52].…”

“…Finally, depleted mines, although they increase the percentage of waste generated [9], contain a diversity of metals in low concentrations [57] that can be extracted by biological rather than chemical methods, as mentioned above.…”

“…Waste management is one of the critical steps to achieving sustainable development and a circular economy [8]. Governments are tightening restrictions on waste generation and opening new landfills, putting pressure on companies to produce more environmentally friendly and sustainable goods [9].…”

Recovery of Waste Materials: Technological Research and Industrial Scale-Up

“…Jarnerud T. et al [8], more or less in the same topic, have studied how CaO-containing waste from pulp and paper industries such as fly ash and calcined lime mud can be utilized to neutralize and purify wastewaters from the pickling processes in steel mills. De Colle M. et al [9] proposed the utilization of stainless steel slags for the pH buffering of acidic wastewaters.…”