DESOTEC QC laboratory: pH measurement
Steam activated or reactivated carbons can have pH and alkalinity spikes of significant duration when placed into service. The pH increase and duration are dependent on the type of activated carbon and the chemical composition of the treated water. The pH of the effluent can rise to a value exceeding 9 or 10 for 200 to 500 bed volumes and can result in the leaching of aluminium from the activated carbon and, additionally, the leaching of manganese and other transition metals from reactivated carbon in drinking water applications.
Desotec Activated carbon measures the effective pH and the contact pH (also called leaching pH) of activated carbon. The effective pH of activated carbon is determined boiling the activated carbon in de-ionized water, while contact pH is determined by stirring carbon with de-ionized water at ambient temperature for a defined time.
The leaching pH (DSTM 11, based on ASTM 6851) allows activated carbon users and producers to predict the effect that an activated carbon will have on the initial pH of the treated water in contact with the activated carbon. Therefore contact pH is also mentioned as leaching pH.
pH test methods for activated carbon (ASTM D3838 - 05) are sensitive to the water quality or salt solution used during the measurement . When pH is critical to an application, it is important to compare test methods between customer and supplier.
Chemically activated carbons have an acid pH after activation. DESOTEC C-PURE® and C-PURE® Super are therefore post treated to obtain a pH of 3-6. DESOTEC can, upon request, supply chemically activated carbons with a more neutral pH.
Feel free to contact us for advice or more info on this matter!