Adsorption kinetics and isotherm modeling of arsenic removal from groundwater using electrocoagulation

The groundwater quality has undergone a change to such an extent that the use of it could be risky and hazardous due to arsenic contamination. The presence of excess arsenic (> 0.01 mg/L) is area-specific, and the sources of contamination are mostly natural and geogenic. Arsenic-free safe drinking water can be supplied in affected areas by applying the appropriate arsenic removal technologies to groundwater or by the conventional surface water treatment process. Arsenic removal from groundwater is commonly accomplished through co-precipitation and adsorption processes. However, the application of the electrocoagulation method for the removal of arsenic has emerged as an efficient and appropriate technology. In the present study, electrocoagulation experiments were performed in batch mode using three different electrode combinations, viz. mild steel (MS)-stainless steel (SS), MS-MS, and MS-aluminum (Al) electrodes (anode-cathode) of locally available materials with arsenic-contaminated natural groundwater. The arsenic removal efficiency is significantly higher than 99% for MS-SS, MS-MS, and about 67% for MS-Al, and the pH, total dissolved solids (TDS), and iron levels in effluent water are within desirable limits. The value of empirical constants and correlation coefficient (R-2) have been estimated for the Langmuir and Freundlich adsorption isotherm models. The R-2 value of the Langmuir isotherm fits well for MS-SS, and MS-MS, but MS-Al fitted with the Freundlich isotherm. The kinetic study has been described using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The pseudo-first-order rate of expression has been observed for MS-SS and MS-MS, whereas MS-Al has been followed the pseudo-second-order model. Finally, the intraparticle diffusion model confirms the equilibrium stage.

Automated summary

The groundwater quality has been affected by arsenic contamination, but the electrocoagulation method has emerged as an efficient technology for arsenic removal.