PRETORIA (miningweekly.com) – The Council for Scientific and Industrial Research (CSIR) is developing low-cost polymer-based adsorbents for the removal of toxic pollutants such as heavy metals, anions and organics, from wastewater, that could be applied in the treatment of acid mine drainage (AMD).

AMD is the outflow of acidic water from mines which contains toxic metals and has a reduced pH, and has a detrimental impact on water quality and the environment.

“It’s an ecological disaster and many environmentalists are trying to treat this,” CSIR nanocomposite development student Athi Nogqwazi said at the CSIR Tech Day, in Pretoria, on Tuesday, adding that AMD diffuses into effluents, like drinking water and dams, and is absorbed by plants.

To address these challenges, the CSIR has developed a range of polymer composite adsorbents that serve as advanced and highly sensitive media for the active removal of pollutants such as heavy metals, ions, organics and oils from water.

The absorbent technology being developed by the CSIR, known as nanoclay, could lead to more feasible alternative treatment technologies to address water quality issues, such as AMD.

“We can de-absorb heavy metals found in AMD using an acid concentrate and sell off some of the heavy metals found in the contaminated water that have been absorbed by the clay, because those metals have commercial value,” he said.

Nogqwazi further stated that the main contributors to the deteriorating water quality in the country were intensive mining and industrial activity, which cause acidity and increased metals content.

Chemical precipitation is typically used for removing heavy metals and anions from water; however, this method involves handling large volumes of chemicals and it produces large volumes of sludge, he said.

He added that chemical precipitation was time-consuming and could be inconsistent and ineffective at low analyte concentrations.

Nogqwazi explained that nanoclay was a combination of natural and synthetic clays through which the AMD percolates, effectively absorbing heavy metals and toxins.

“We have a pilot plant in Carolina, in Mpumalanga, which was set up last year. We are currently in the process of collecting the effluent to check how many toxins have been removed by the nanoclay.”

According to laboratory studies, he said, elements such manganese, iron and lead have successfully been removed using this method.

“We have a provisional patent on this technology, which will be renewed in May,” he stated.