The CSIR has developed a novel process to reclaim high-quality precipitated calcium carbonate (PCC) from calcium-rich industrial solid waste.

High-quality calcium carbonate is useful for various specialised industrial applications such as gastric acid treatment, tablet filling in pharmaceuticals, plastics, paint, adhesives and in pulp and papermaking.

According to CSIR biochemical engineers Dr Mlawule Mashego and Jean Mulopo this technology, for which the CSIR has recently filed a patent application, can also be used as a waste management tool that creates new enterprises in the waste management sectors providing job opportunities and simultaneously reducing the amount of solid waste that could impact negatively on the environment.

Calcium-rich waste streams are generated by a number of industries in South Africa, including the power and energy utilities, steel-making industry, bulk water-treatment utilities, and the pulp and paper making industry. These industries dispose off large volumes of waste/s streams to on-surface waste disposal sites or landfills which are rapidly filling up.

Furthermore, legislative requirements for landfill disposal methods, such as the National Environmental Management Waste Act (NEMWA) 59 of 2008, are expected to be more stringent in the future, resulting in the need to adopt alternative and innovative waste management approaches.

According to the researchers the solid waste-producing industry, or new enterprises established to produce high-quality calcium carbonate, will be able to use such processes. “We also foresee an increase in demand for calcium carbonate for treating acid mine drainage,” Dr Mashego adds.

This research group at the CSIR in Pretoria focuses among others on the development of technologies for cost-effective production of high-quality effluent from various waste streams: “Some utilities responsible for waste treatment and management are moving away from regulatory compliance towards increased economic incentives in the process of recognising the value of waste and wastewater as a resource. Such an approach includes the recovery of energy, nutrients, metals and other chemicals as part of the wastewater treatment process. We also look at further beneficiation of recovered by-products to enhance waste utilisation,” Dr Mashego explains.

The newly-developed process involves three steps:

• Leaching of calcium from the solid waste using mineral acid;
• Neutralisation of the leachate using ammonium hydroxide; and
• Carbonation of the calcium-rich solution to produce high-quality calcium carbonate.