Stable concentrated polyaluminum chlorosilicate solutions
Novel polyaluminum chlorosilicates (PACSi) and sodium aluminum silicate (SAS) products having improved characteristics useful in the treatment of water and wastewater as compared with polyaluminum chlorides (PAC), are provided herein, as well as new processes for their manufacture, and methods of using PACSi as coagulants and flocculants in the treatment of water and/or wastewater.
1. A method for producing a sodium aluminum silicate (SAS) composition, the method comprising the steps of:
a) preparing a mixture containing: 30-60 wt % of a 50% NaOH, 1.7-6 wt% of a 30% sodium silicate solution, and 5-15 wt % water;
b) heating the mixture until the mixture is clear;
c) after the mixture is clear, adding 35-50 wt % aluminum oxide trihydrate to the mixture to form a liquid solution; and
d) heating the liquid solution until the aluminum oxide trihydrate is dissolved in order to produce the SAS composition having a molar ratio of Si:Al of 0.015-0.08 and a molar ratio of Na 2 O:Al 2 O 3 of 1.0-1.30.
2. The method of claim 1 , wherein the mixture is heated to a boiling temperature of the mixture.
3. The method of claim 1 , wherein the mixture is heated when adding the aluminum oxide trihydrate.
4. The method of claim 1 , wherein the solution is heated for 1 hour.
5. The method of claim 1 , wherein the aluminum oxide trihydrate is added to the mixture such that a resulting aluminum oxide concentration is 20% to 27% Al 2 O 3 .
6. The method of claim 1 , wherein the sodium silicate solution includes 0.9 to 4 wt % SiO 2 .
7. A SAS composition produced by the method of claim 1 having a formula:
(Na 2 O)a(Al 2 O 3 )(SiO 2 ) c (Formula III),
wherein:
a is 1-1.3 and c is 0.03 -0.15
and Si:Al has a molar ratio of 0.015-0.08 and Na 2 O:Al 2 O 3 has a molar ratio 1.8-1.30.
8. The SAS composition of claim 7 , comprising:
a) 20-32 wt % Al 2 O 3 ;
b) 12-22 wt % Na 2 O; and
c) 0.5-1.7 wt % SiO 2 .
9. The SAS composition of claim 7 , wherein Na 2 O:Al 2 O 3 has a molar ratio of 1.22-1.30.
10. A method of treating water to remove impurities, the method comprising:
producing the SAS composition according to claim 1 ; and
adding the SAS composition to water in order to remove turbidity and/or non-purgeable organic carbon (NPOC) from the water.
11. A method of treating water to remove impurities, the method comprising:
producing the SAS composition according to claim 1 ;
mixing a solution of 10 to 30 wt % of the SAS composition with a solution of 70 to 90 wt % comprising basic aluminum chloride (BAC) or aluminum chloride (ACL) to form a second solution; and
adding the second solution to water in order to remove turbidity and/or NPOC from the water.
12. The method of treating water according to claim 11 , wherein the mixing includes agitating the second solution for 1 hour to 12 hours.
13. The method of treating water according to claim 11 , further comprising
forming a silicated BAC or a silicated ACL before the mixing, wherein the second solution comprises the solution of 10 to 30 wt % of the SAS composition and the solution of 70 to 90 wt % of the silicated BAC or the silicated ACL.