ENCE 433 Dr. Alba Torrents

ENVIRONMENTAL ENGINEERING ANALYSIS Fall 1996

Homework Set #7 SOLUTION

SOLUBILITY

(A)

Log [Cd+2] = 13.5 - 2pH Log [Cu+2] = 7.7 - 2pH Log [Al+3] = 10.8 - 3pH

-Log [Al+3] = -10.8 + 3pH - Log [Al(OH)+2] = -5.8 + 2pH - Log [Al(OH)2+1] = -1.5 + pH - Log [Al(OH)3] = 4.2 = constant - Log [Al(OH)4-1] = 12.2 - pH - Log [Al2(OH)2+4] = -13.9 + 4 pH

Al_T is the addition of all dissolved species. At pH = 4.5, Al_T is mostly Al⁺³, at pH 6.5 is mostly Al(OH)₃ and Al(OH)₂⁺

As the pH decreases, the total dissolved concentration of Al increases.