Al(III) speciation distribution and transformation in high concentration PACl solutions.
Effects of Al(III) concentration and pH on the speciation of Al(III) in polyaluminum chloride (PACl) solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the range of Al(III) concentration from 0.01 to 2.0 mol/L with the B (OH/Al ratio) value from 1.0 to 2.5 by forced hydrolysis of AlCl3. The samples were characterized by ferron assay, pH and 27Al NMR. It was shown that the Al(lIII) concentration had a dramatic effect on the hydrolysis processes and the species distribution of PACl was in relate to the decrease of pH. The fraction of Al species, Alb, (or A113) decreased and Al, increased with increase of total Al(III) concentration. Under the condition of AI(llI) 2.0 mol/L, B = 2.5, the pH value was 2.73 and no Al13 could be detected. During diluting and aging, the species distribution evolved. The Al13 could then be detected again and the amounts increased with time. If the diluted samples were concentrated by freeze dry at -35 degrees C or heating at 80 degrees C, the pH value and Al13 content would decrease with the increased concentration. It demonstrated that the key factor for formation of Al13 in concentrated PACl was pH value.
Huang
Li
L
State Key Lab of Environmental Aqueous Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Tang
Hong-xiao
HX
Wang
Dong-sheng
DS
Wang
Shui-feng
SF
Deng
Zai-jun
ZJ
D000535:Aluminum / Q000737:chemistry / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
D014874:Water Pollutants, Chemical; D000535:Aluminum