Calcium sulfate dihydrate

Two different samples of process streams produced in an industrial manufacturing process were used in this experimental work. The samples were taken just before the PFHxA collecting facility that removed the contaminant before the general wastewater treatment was applied at the industrial plant. Table 1 displays the chemical characterization of the two samples, referred to as S1 and S2. The main difference lays in the content of PFHxA, which is about three times higher in S1 than in S2. Other components were common inorganic salts, which provided the samples the adequate conductivity for use as an electrolyte in the electrochemical experiments. It can be noticed that the values of total organic carbon (TOC) exceeded the theoretical TOC values calculated from the concentration of PFHxA. Therefore, the industrial waters contained other soluble organic compounds of unknown nature.
In additional to the real process waters described above, model solutions with salt contents equivalent to the real ones were prepared. All chemicals were of analytical grade and used as received without further purification. Perfluorohexanoic acid (≥ 97%) was supplied by Sigma-Aldrich. Calcium sulfate dihydrate (≥ 98%) was purchased from Scharlau. Sodium chloride (≥ 99%) was obtained from Panreac. Sodium carbonate (≥ 99.9%) was supplied by Merck Millipore.