The Significance of Polymeric Ligand Exchange (PLE) Technique for Arsenic Removal from Polluted Groundwater: A Review

Presently, the global concern over the toxic effects of arsenic and its wide distribution is particularly pronounced in India. This study adopts a specialized geochemical perspective to shed light on the issue. Groundwater in the northeastern states of India has been found to contain notably high concentrations of arsenic (ranging from 50 to 986 μg/l). This geographical region has come under scrutiny due to the escalating worldwide apprehension about arsenic toxicity and its pervasive presence of particular distress is the substantial disparity between the observed arsenic levels and the recommended limits defined by authoritative bodies such as the World Health Organization (WHO) and the Bureau of Indian Standards (BIS), which have set the acceptable arsenic levels in drinking water at 10 μg/l and 50 μg/l, respectively. In response to this critical situation, diverse techniques tailored for targeted removal of arsenic have emerged. These techniques encompass a range of processes including precipitation, adsorption, and modified iron-based and ligand exchange methods.

The inherent characteristics of various arsenic species further compound the challenge of selectively eliminating arsenic, especially when dealing with natural environmental contexts. Notably, hydrated Fe(III) oxides have played a vital role in most selective removal techniques through the mechanism of Lewis acid-base interaction. In this context, a pioneering approach known as Polymeric Ligand Exchange (PLE) has surfaced. This method has exhibited promising results by selectively extracting arsenic from drinking water, even in the presence of formidable competing anions such as sulfate. The efficacy of PLE in overcoming this complex chemical milieu marks a significant stride in the ongoing efforts to mitigate the arsenic contamination crisis.