Arsenic Removal From San Pedro de Atacama's Natural Waters Using a Sono-Electrocoagulation Technique

Arsenic contamination of water resources poses a major environmental and public health concern. This study evaluated a hybrid treatment process combining ultrasonication (US) and electrocoagulation (EC) for the batch removal of arsenic from complex natural water matrices using iron electrodes. Under the investigated conditions simultaneous US/EC achieved arsenic removal efficiencies exceeding 99.5%, at current densities as low as 10 A m^-2. The process remained highly effective when applied to untreated natural waters from Atacama Desert, Chile, containing naturally occurring geogenic arsenic concentrations of 285-2965 μg L^-1. Río Puritama, Socaire, and Camar Alto reached residual arsenic concentrations below the 10 μg L^-1 drinking-water guideline within 10 min, whereas Cruce Talabre, with the highest initial arsenic concentration (2965 μg L^-1), required 60 min to decrease arsenic to 2.33 μg L^-1. Kinetic analysis showed that the pseudo-second-order model provided a better empirical description of the Cruce Talabre data than the pseudo-first-order model; however, because more than 98% of the initial dissolved arsenic had already been removed by the first sampling point at 10 min, the fitted parameters should be regarded as apparent rather than intrinsic kinetic constants. Energy analysis showed that ultrasonication dominated the estimated laboratory-scale energy demand, primarily because the nominal 400 W ultrasonic power was applied to a batch volume of only 0.8 L. Overall, simultaneous US/EC showed high arsenic removal performance in chemically distinct natural waters, whereas future scale-up should prioritize optimization of ultrasonic energy input.