Related Experiment Video
Updated: Jan 22, 2026

Removal of Arsenic Using a Cationic Polymer Gel Impregnated with Iron Hydroxide
Published on: June 28, 2019
The long-term stability of calcium arsenates: Implications for phase transformation and arsenic mobilization
Danni Zhang1, Shaofeng Wang1, Ying Wang1
1Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
Abstract:
It is well known that calcium arsenates may not be a good choice for arsenic removal and immobilization in hydrometallurgical practices. However, they are still produced at some plants in the world due to various reasons. Furthermore, calcium arsenates can also naturally precipitate under some specific environments. However, the transformation process of poorly crystalline calcium arsenates (PCCA) and the stability of these samples under atmospheric CO2 are not yet well understood. This work investigated the transformation process of PCCA produced by using different neutralization reagents (CaO vs. NaOH) with various Ca/As molar ratios at pH 7-12 in the presence of atmospheric CO2. After aging at room temperature for a period of time, for samples neutralized with NaOH and precipitated at pH 10 and 12, release of arsenic back into the liquid phase occurred. In contrast, for the samples precipitated at pH 8, the aqueous concentration of arsenic was observed to decrease. XRD, Raman, and SEM results suggested that the formation of various types of crystalline calcium carbonates and/or calcium arsenates controls the arsenic behavior. Moreover, the application of lime may enhance the stability of the generated PCCA. However, no matter what neutralization reagent is used, the stability of the generated PCCA is still of concern.
Related Concept Videos
RNA Stability
Long-term Depression
Phase Transitions
Nuclear Stability
To hold positively charged protons together...
Bacterial Transformation
Griffith made an unexpected discovery when he killed the pathogenic strain and mixed its remains with the live, non-pathogenic strain. Not only did the mixture kill host mice, but it also contained living pathogenic bacteria that...
Phase Transitions: Sublimation and Deposition

