Migration of viscosity modified colloidal Mg(OH)2 in heterogeneous porous media: experiment and model simulation

The uneven distribution of colloidal Mg(OH) 2 in heterogeneous porous media poses a significant challenge for its effective application in groundwater remediation. To address this issue, this study introduces a novel approach using xanthan gum (XG) as a viscosity modifier to enhance the migration of colloidal Mg(OH) 2 into low permeability zone. Results indicate that XG is highly compatible with colloidal Mg(OH) 2 , viscosity modified colloidal Mg(OH) 2 (VMC-Mg(OH) 2 ) exhibits significant shear thinning properties. The increased viscosity effectively reduces the deposition of colloidal Mg(OH) 2 and facilitates its return to groundwater. With the addition of XG to the system, the collision efficiency ( η ) between colloidal Mg(OH) 2 and porous media decreased from 0.00865 to 0.00142, while the attachment efficiency ( α ) was reduced from 0.4858 to 0.1038. These variations notably enhance the migration performance of colloidal Mg(OH) 2 , with C/C 0 increasing from 0.12 to 0.94. The incorporation of XG also leads to a substantial increase in colloidal Mg(OH) 2 sweep efficiency in low permeability zone, rising from 53.6 % to 92.5 % as the XG concentration increased from 0 mg/L to 200 mg/L. Moreover, the simulation of collision efficiency ( η ) and attachment efficiency ( α ) accurately predicts the migration of VMC-Mg(OH) 2 in heterogeneous porous media, with a maximum error of 5.39 %. These findings highlight the significant potential of VMC-Mg(OH) 2 as a reactive reagent for remediating contamination in low permeability zone