Anodic sacrifice

Electrochemical technique (also electrocoagulation) is a simple and efficient method for the treatment of drinkable water. Recent results reported by Part-hasarathy and Yang [54,55] have demonstrated that electrocoagulation (EC) using aluminium anodes is effective in defluoridation. In the EC cell, the aluminium electrodes sacrifice themselves to form aluminium ions first. Afterwards the aluminium ions are transformed into AI(OH)3 before being polymerized to Aln(OH)3n. The AI(OH)3 floe is believed to adsorb F strongly as illustrated by the equation. 

Table 3.4 compares detection limits with secondary fluorescers to the results with the RMF method and 15-kV broadband excitation [16,17]. Four different fluorescence analyzers were tested (units A, B, C, and D), and the results were corrected for differences in performance for the energy-dispersive spectrometers employed on each unit. Unit A used a chromium anode tube, and unit B used a tungsten anode tube. Unit A was a commercial, general-purpose instrument. Unit B was specifically designed for atmospheric aerosol analysis, where closer coupling between the tube, fluorescer, sample, and detector could be employed with some sacrifice of insensitivity to specimen-positioning errors. Table 3.5 lists the x-ray tube operating conditions required for Table 3.4. For medium- to high-atomic-number elements, the secondary fluorescer method provides detection limits equivalent to the RMF element, but requires much higher x-ray tube power. For light elements.

Anode Materials. Highly electronegative aluminum alloys are routinely employed as sacrificial anodes, generally on steel structures or vessels such as pipelines, offshore construction, ships, and tank storage units. Most aluminum sacrifice anodes are pro-(foced from cast Al-Zn-Sn, Al-Zn-In, a Al-Zn-Hg alloys containing about 94 to 95% A1 and 3.5 to 5% Zn. 

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