Study on the stability, transport behavior and OH- release properties of colloidal Mg(OH)2

Mg(OH)(2) was considered as an environment-friendly material that has been received extensive attention on environmental remediation. It has low aqueous solubility that could slowly dissolve and provide a long-term source for alkalinity. However, the poor suspension stability and positive surface charge restrict its utilization in groundwater remediation. In this study, stable, negatively charged and cost effective colloidal Mg(OH)(2) was synthesized. Fourier infrared spectrum, surface charge and microscope photographs of colloidal Mg(OH)(2) were measured to analyze the modified mechanism of surfactant to Mg(OH)(2). Column tests were conducted to investigate the transport and slow OH- releasing properties of colloidal Mg(OH)(2). Experimental results indicated that sodium dodecyl sulfate (SDS) could significantly enhance the stability of Mg(OH)(2) suspension while needed large consumption (over its critical micellar concentrations(CMC)). Polyoxyethylene sorbitan fatty acid ester (Tween-80) could significantly decrease the CMC of SDS, leading to more aggregation of SDS around Mg(OH)(2) particle surface, increasing the utilization of SDS, and formulating relatively stabled double layer structure. Colloidal Mg(OH)(2) could both be intercepted by porous media and have certain mobility in aquifer, exhibiting a long pH buffering capacity after it was injected to aquifer.