Unlocking Ash Secrets: A Better Way to Measure Metal Levels

Digging into solid waste incineration ash, scientists found that current methods to measure heavy metals and elements like calcium (Ca) and aluminum (Al) weren't cutting it. Why? Because the structure of the ash, especially the silicon dioxide (SiO2), was tough to break down. Using hydrofluoric acid (HF) created new problems, like the formation of compounds like aluminum fluoride (AlF3) and calcium fluoride (CaF2), which messed up the results. To fix this, a two-step digestion method was introduced. First, a mix of hydrochloric acid (HCl), nitric acid (HNO3), and HF was heated in a microwave at 240°C. This broke down most heavy metals, Ca, and Si, leaving a white residue. Next, a milder acid mix of 0. 5 mol/L HNO3 and 0. 5 mol/L HCl at 100°C dissolved the residue completely. This technique worked wonders on various ash types, including sewage sludge incinerated ash, incinerated bottom ash, and incinerated fly ash. Scientists even figured out how to handle unknown ash types.