DESOTEC QC laboratory: pH measurement

Steam activated or reactivated carbons can have pH and alkalinity spikes of significant duration when put into service. The pH increase and duration depend 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 lead to the leaching of aluminium from the activated carbon as well as the leaching of manganese and other transition metals from reactivated carbon in drinking water applications.

Desotec measures the effective pH and the contact pH (also called leaching pH) of activated carbon. The effective pH of activated carbon is determined by 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 certain period of 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 called 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. Upon request, DESOTEC can supply chemically activated carbons with a more neutral pH.

Feel free to contact us for advice or more info on this matter!