Controlled Environment Potentionstat to Study Solid-Aqueous Systems

We designed a redox apparatus that controls electropotenial (Eh), pH, and temperature. The apparatus is full y automated and can be assembled from equipment found in most soil analytical laboratories. The reactor can maintain environmental conditions used to evaluate the chemical fate of contaminants under natural conditions (natural attenuation) or adjust them to a new steady state to evaluate the effect of engineered remediation on a subsurface system. It can oper­ ate within a wide range of redox potential va lues ( - 400 to 400 mV) and at any pH value. The stabilit y and accuracy of the instrument was tested by performing Eh-pH titrations on MnO, suspensions. Results indicated that Eh could be controlled wit hin 1 to 2 mV, pH within 0.05 to 0.1 unit, and temperature within O.l°C for weeks or months.