Direct Arsenic Removal from Water Using Non-Membrane, Low Temperature Directional Solvent Extraction

Arsenic (As) poisoning in water due to natural minerals or industrial pollution is a critical global problem that threatens the health and life of billions. Current arsenic removal techniques involving chemical reaction, ion exchange, or membrane processes can be expensive, inaccessible or infeasible for underdeveloped regions or remote areas. Here, we demonstrate that using a so-called directional solvent extraction (DSE) process, arsenic ions in water can be effectively removed without the need of a membrane or chemical reaction, and this process promises to utilize very low temperature heat (as low as 45 oC). We have tested feed water with different arsenic concentrations and arsenic ions in different forms (As-III and As-V) commonly found in nature. It is demonstrated that DSE using decanoic acid as the directional solvent can purify contaminated water to meet the drinking water standard (arsenic concentration < 10 parts per billion, ppb), and the arsenic removal efficiencies are higher than 91% for As-III and 97% for As-V. Moreover, DSE can remove As-III directly without the need of pre-oxidation, which is required in most of the state of art techniques. DSE can potentially lead to effective arsenic removal technologies with low resource settings that are suitable for remote and underdeveloped regions, which are impacted by arsenic poisoning the most.