The influence of silicic acid on aluminium hydroxide precipitation and flocculation by aluminium salts

被引:49
作者
Duan, JM [1 ]
Gregory, J [1 ]
机构
[1] UCL, Dept Civil & Environm Engn, London WC1E 6BT, England
关键词
D O I
10.1016/S0162-0134(97)10018-6
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Silic acid is always present in natural waters and interactions between silicic acid and aluminium have been reported over wide concentration ranges. Since aluminium sails are commonly used as coagulants in water treatment, it is possible that their effects may be modified by the presence of silicic acid. In many cases flocculation of particles in water is dependent on the formation of an amorphous precipitate of aluminium hydroxide and silicic acid may influence the precipitation process. Using a simple continuous optical technique, the influence of silicic acid on the precipitation process and on the flocculation of clay suspensions by aluminium sulphate has been examined. It has been found that silicic acic: can promote or prevent the aggregation of primary aluminium crystallites depending on solution pH and the concentration of silicic acid. These effects are closely matched by the effect of silicic acid on the flocculation process. At pH 7, with about 0.3 mM of silicic acid, the growth of precipitate and flocculation are enhanced; but with higher silicic acid concentrations these processes are hindered and eventually prevented altogether (at around 1.5 mM). The effects of silicic acid are more pronounced at pH 8. where less than 0.1 mM is sufficient to enhance precipitation and flocculation, and at 0.25 mM they are completely inhibited. These trends have been confirmed by determining the residual turbidity of suspensions after a standard stirring and sedimentation procedure and by electrophoretic mobility measurements on particles shortly after dosing of coagulant. It appears that the effects are closely connected with silicic acid-aluminium interactions, especially with regard to modifications in the charge of precipitated species. (C) 1998 Elsevier Science Inc. All rights reserved.
引用
收藏
页码:193 / 201
页数:9
相关论文
共 33 条
[1]  
[Anonymous], 1990, WATER RES
[2]  
Baes C.F., 1976, HYDROLYSIS CATIONS
[3]  
BIRCHALL JD, 1990, CHEM BRIT, V26, P141
[4]   Phosphate adsorption in flocculation processes of aluminium sulphate and poly-aluminium-silicate-sulphate [J].
Boisvert, JP ;
To, TC ;
Berrak, A ;
Jolicoeur, C .
WATER RESEARCH, 1997, 31 (08) :1939-1946
[5]   INVESTIGATION OF THE HYDROLYSIS OF AQUEOUS-SOLUTIONS OF ALUMINUM-CHLORIDE .2. NATURE AND STRUCTURE BY SMALL-ANGLE X-RAY-SCATTERING [J].
BOTTERO, JY ;
TCHOUBAR, D ;
CASES, JM ;
FLESSINGER, F .
JOURNAL OF PHYSICAL CHEMISTRY, 1982, 86 (18) :3667-3673
[6]   MECHANISM OF FORMATION OF ALUMINUM TRIHYDROXIDE FROM KEGGIN AL13 POLYMERS [J].
BOTTERO, JY ;
AXELOS, M ;
TCHOUBAR, D ;
CASES, JM ;
FRIPIAT, JJ ;
FIESSINGER, F .
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 1987, 117 (01) :47-57
[7]  
BRACE R, 1977, COLLOID POLYM SCI, V255, P153
[8]  
Clesceri L.S., 1989, STANDARD METHODS EXA, V17th
[9]   COAGULANT CONTROL IN WATER-TREATMENT [J].
DENTEL, SK .
CRITICAL REVIEWS IN ENVIRONMENTAL CONTROL, 1991, 21 (01) :41-135
[10]  
DUAN J, 1997, THESIS U COLL LONDON